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OVUFORNIAI
FISH- GAME
"CONSERVATION OF WILDLIFE THROUGH EDUCATION"
California Fish and Gome is a journal devoted to the conser- vation of wildlife. If its contents are reproduced elsewhere, the \juthors and the California Department of Fish and Game would appreciate being acknowledged.
The free mailing list is limited by budgetary considerations to persons who can make professional use of the material and to libraries, scientific institutions, and conservation agencies. Indi- viduals must state their affiliation and position when submitting their applications. Subscriptions must be renewed annually by returning the postcard enclosed with each October issue. Sub- scribers are asked to report changes in address without delay.
Please direct correspondence, except regarding paid subscrip- tions, to:
CAROL M. FERREL, Editor California Fish and Game 987 Jedsmith Drive Sacramento, California 95819
Individuals and organizations who do not qualify for the free mailing list may subscribe at a rate of $2 per year or obtain individual issues for $0.75 per copy by placing their orders with the Office of Procurement, Documents Section, P.O. Box 20191, Sacramento, California 95820. Money orders or checks should be made out to Office of Procurement, Documents Section. In- quiries regarding paid subscriptions should be directed to the Office of Procurement.
u
I
n
nnr
0
VOLUME bl
JANUARY 1971
NUMBER 1
Published Quarferly by
STATE OF CALIFORNIA
THE RESOURCES AGENCY
DEPARTMENT OF FISH AND GAME
STATE OF CALIFORNIA
RONALD REAGAN, Governor
THE RESOURCES AGENCY
NORMAN B. LIVERMORE, JR., Secretary for Resources
FISH AND GAME COMMISSION
C. RANS PEARMAN, President, San Gabriel
SHERMAN CHICKERING, Vice President PETER T. FLETCHER, Member
San Francisco Rancho Santa Fe
JOSEPH RUSS III, Member TIMOTHY M. DOHENY, Member
Ferndale Los Angeles
DEPARTMENT OF FISH AND GAME
G. RAY ARNETT, Director
1416 9th Street Sacramento 95814
CALIFORNIA FISH AND GAME Editorial Staff
CAROL M. FERREL, Editor-in-Chief Sacramento
STEPHEN J. NICOLA, Editor for Inland Fisheries Sacramento
MERTON N. ROSEN, Editor for Wildlife Sacramento
HERBERT W. FREY, Editor for Marine Resources Terminal Island
DONALD H. FRY, JR., Editor for Salmon and Steelhead Sacramento
HAROLD K. CHADWICK, Editor for Striped Bass, Sturgeon, and Shad Stockton
( 2 )
CONTENTS
The Striped Bass Party Boat Fishery : 1960-1968
Robert J. McKcclinic and Lee W. Miller 4
Upper Lethal Temperature and Thermal Shoek Tolerances of the Opossum Shrimp, Neomysis atvatschensis, from the Sacramento- San Joaquin Estuary, California James R. Hair 17
The Kokanee Salmon in Lake Tahoe Almo J. Corclone, Stephen J. Nicola, Phillip H. Baker, and
Ted C. Frantz 28
Tlie Carrying Capacity for Juvenile Salmonids in Some Northern California Streams James W. Burns 44
Some Influences of Temperature on the Development of the G run- ion, Lcurcsthes tenuis (Ay res)
Keirl F. Ehrlich and Davicl A. F arris 58
A Review of Possible Causes of Mortality of Oyster Larvae of the Genus Crassostrea in Tomales Bay, California Carl J. Berg, Jr. 69
Anguilla Recorded from California John E. Skinner 76
Book Reviews 80
( .{ )
Ciilij. F'ush (Did Game, 57(1) :4-lG. 1'M\.
THE STRIPED BASS PARTY BOAT FISHERY: 1960-1968^
ROBERT J. McKECHNIE and LEE W. MILLER ^
Anadromous Fisheries Branch
California Department of Fish and Game
Striped bass {Morone saxatilis) fuil-day party boat records are analyzed and compared with earlier trends in the fishery. Angler success reached an alS-time high for north San Francisco Bay during the 1960—63 period and then began to decline. Success in the other major areas generally declined throughout the study period. The average size of bass in the catch increased markedly. The data strongly suggest a decline in num- bers of bass, although the biomass caught per angler day has remained relatively stable during the period of decline.
INTRODUCTION
This report is a continuation of reports previously published on the catch of the striped bass {Morone saxatilis) party boat fishery. Calhoun (1949) published an analysis of party boat records for the years 1938 to 1948, and Chadwick (1962) analyzed records from 1949 through 1959. This report includes the years 1960 through 1968.
Party boat operators are required by law to keep a log of each trip made, although past studies have indicated that some trips are not reported (Johnson, 1951; Chadwick, 1962). These reports are sub- mitted monthly to the California Department of Fish and Game on forms supplied to the operators by the Department. The form used in northern California during most of the current period is shown in Figure 1.
Boot Namu
fish and Gam* No.
Town of Landing
Skipper: Please make a separate log for each trip of the day.
u^® Af®» «■'
|
KIND OF FISH CAUOHT | NUMUR { AVIKAOI WT. |
||
|
ROCKFISH (Cod) |
||
|
LINGCOD |
||
|
CABEZON |
||
|
SALMON |
||
|
STRIPED BASS |
||
|
AAACKEREL (Pacific) |
||
|
MACKEREL (Jack) |
||
|
HALIBUT |
||
|
OTHER FLATFISH |
||
|
NAME OTHER FISH |
||
Month Day Y»ar
No. of Hours Fished
(Hours Lines in Water)
Number of Anglers
Block Number Where Most Fish Caught
NS 13251
FIGURE 1. Daily log form used for party boat reports.
^- Accepted for publication May 1970. Tliis work was performed as part of Dingell- Johnson Projects California F-9-R, "A Study of Sturgeon and Striped Bass" supported by Federal Aid to Fish Restoration Funds.
2 Present address, 3900 North Wilson Wav, Stockton, California 95205.
(4)
STRIPED BASS FISHERY 0
GENERAL DISCUSSION OF PARTY BOAT OPERATIONS
The striped bass party boat fishery is concentrated in San Francisco and San Pablo Bays and Carqninez Strait. It also operates in the Pacific Ocean, Suisnn Bay, and Sacramento-San Joaquin Delta, though at a much lower level. The catch records are tabulated by the inland blocks delineated in Figure 2 and the ocean. Chadwick (1962) and Calhoun (1949) give detailed descriptions of the inland areas and the fishery.
FIGURE 2. Map of California striped bass party boat fishing areas. The numbers indicate the fishing blocks referred to in the text.
The party boats are placed in one of four categories determined by the time spent fishing on a trip. By far the most prevalent are the full-day boats which average 75% of the effort (reported angler hours) each year. Full-day boats are those boats fishing during the morning and afternoon for more than 4.5 hr or boats on which everyone took limits. Other boats fishing during the morning or afternoon are termed half -day boats. These account for an average of 23% of the effort and often make two trips a day. The other categories are one and one-half day boats and boats which offer evening trolling. They contribute the remaining 2% of the total effort recorded. Only records from full-day boats are included here.
CALIFORNIA FISH AND GAME
Tlio migratory nature; of the striped bass makes the fishery a sea- sonal one. Some fish are available in the lower bays all year and a number of boats operate continuously, but many boats fish only during l)eak seasons.
The 1960-1968 mean number of operators reporting declined 28% from the 1949-1959 mean. The mean reported full-daj^ boat angler days is up 13% over the 1949-1959 mean (Table 1). These statistics reflect the recent trend to larger but fewer boats in the fishery.
TABLE 1— Party Boat Fishing Effort and Catch 1960-1968
|
Year |
Number of* operators reporting |
Angler days reported on full-day boats for inland blocks |
Total bass causcht from full-day boats in inland blocks |
Full-day boat catch per angler day for all inland blocks |
|
1938-48 mean -- |
132 |
13,650 15,625 |
||
|
1949-59 mean |
||||
|
I960 . - - - |
105 (7) 105 (.5) 106 (.5) 99 (18) 87 (18) 81 (26) 81 (25) 81 (12) 84 (8) |
19,826 21.663 19,325 24,309 15,480 12.245 17,802 14,203 13,.581 |
38,597 45,087 39,728 48.435 21,397 11,363 23.2.59 15,331 14,977 |
1.95 |
|
1961 - - - --- |
2.08 |
|||
|
1962 |
2.05 |
|||
|
1963 |
1.99 |
|||
|
1964 . - |
1.38 |
|||
|
1965 |
0.93 |
|||
|
1966. |
1.31 |
|||
|
1967 |
1.08 |
|||
|
1968 |
1.10 |
|||
|
1960-68 mean |
95 (15) |
17,603 |
28.686 |
|
* Number of operators making one or more fishing trip in inland blocks. Figures in parentheses are operators reporting only ocean trips. Full-day, half-day, evening troU and 1.5-day boats are all included.
Limited evaluations of the usefulness of party boat reports were conducted by Chadwick (1962). He concluded that the reports pro- Anded a reliable index of fishing success, but they failed to provide ade- cjuate information on the striped bass population because all segments of the fishery were not covered and reliable information on the size composition of the catch was not available.
A problem developed in 1964 when the party boats operating in Blocks 301 and 308 (Figure 2) began enjoying some success catching sturgeon. This fishery rapidly gained in popularity and soon many of the party boats were devoting major portions of their effort toward sturgeon. This had the effect of increasing the effort recorded in these areas without the expected increase in catch of striped bass. To com- pensate for this, all effort expended on boat trips where sturgeon were caught was subtracted from the total party boat effort. Inherent defi- ciencies in this method of correction are: "(i) sturgeon may be caught incidental to striped bass and vice versa; (ii) information on effort expended for sturgeon when no sturgeon were caught is not available. At the present time, there is no way of assessing either of these defects.
BLOCK RECORDS Block 308 — The Carquinez Strait Region This area includes Carquinez Strait, the eastern quarter of San Pablo Bay, and a small portion of Suisun Bay (Figure 2).
STRIPED BASS FISHERY Y
Full-day party boat fishing effort dropped from a mean of 4,930 days per year for the 1949-59 period to 1,654 days from 1960-68. From 1960 to 1965 it remained relatively constant. Since 1965 effort has increased. This increase is probably partly due to including unsuccess- ful sturgeon trips.
Angler success as measured by catch per hour has been declining steadily since 1954 (Figure 3). The reported mean weight increased from a 1960-63 average of 5.0 lb. to a 1964-68 average of 9.5 lb. (Table 2, Figure 4). The most significant changes in weight occurred in 1963 and 1965. The mean weight lias declined since the 1965 high of 12.1 lb. The mean weight reported for full-day boats is based on fewer fish in recent years. Mean weights from half -day boats from 1964-1968 were 9.5, 6.7, 7.3, and 5.7 respectively. Except for 1964 these means are based on larger samples than the full-day boat means.
TABLE 2 — Summary of Full-Day Party Boat Reports from Corquinez Strait, Block 308
|
Angler days |
Striped bass |
||||||
|
Year |
Number |
Percentage of annual inland total |
Number* |
Percentage of annual inland total |
Catch/ angler day |
Catch/ angler hour |
Mean weight |
|
1938-48 mean. 1949-59 mean_ |
5,357 4,939 |
39 32 |
13,298 8,671 |
47 35 |
|
|
4.6 4.0 |
|
1960 ._- |
1,189 1,224 1,117 1,0.58 1,024 1,375 2,611 2,201 3,092 |
6 6 6 4 7 11 15 1.5 23 |
1,467 1,423 1,337 6.56 866 (140) .503 (3.58) 1,228 (317) 332 (166) 836 (361) |
4 3 3 1 4 4 5 2 6 |
1.23 1.16 1.20 0.62 0.85 0.37 0.47 0.15 0.27 |
0.16 0.16 0.16 0.09 0.12 0.05 0.07 0.02 0.04 |
6 0 |
|
1961 |
4 2 |
||||||
|
1962 |
3.8 |
||||||
|
1963 |
5 9 |
||||||
|
1964 ... - |
8 0 |
||||||
|
1965 |
12 1 |
||||||
|
1966 |
10.1 |
||||||
|
1967 .- -.. |
9 4 |
||||||
|
19G8 |
8.0 |
||||||
|
1960-68 mean- |
1,654 |
10 |
961 |
4 |
|
|
7.5 |
* Figures in parentheses are the numbers of additional bass caught along with sturgeon on full-day boats (mean weights are based on combined figures).
Catches per hour for months where 30 or more trips were made are shown in Figure 5. The effort in this block was too sparse to draw any conclusions about seasonal trends.
Block 301— San Pablo Bay
Effort in this area has declined since the ])eak period from 1958-60. However, the 1960-68 mean angler days reported for the area are above the 1949-59 average. Historically, effort in this area has fluctuated greatly. As in Block 308, effort increased here in 1965 and 1966 but declined since then.
Catch per hour declined steadily over the years of this report (Figure 3). Eeportecl mean weights increased considerably from 4.6 in 1960 to 12.6 in 1965 (Table 3, Figure 4). The 1968 mean dropped to 9.4 lbs. As in Block 308, the mean weights reported from half-day boats from 1964-68 are loAver than those from full day boats. Half-day
8
CALIFORNIA FISH AND GAME
0.60-
^ 0.50- O
0.40i
UJ
a.
0.30-
X
u
< 0.20-
u
O.IOH
BLOCK 301
BLOCK 308
BLOCK 488
55
— r~
56
~~1 — 57
58
— r~ 59
— r — 60
YEAR
61
— r- 62
— r— 63
— i — 64
— I — 65
66
— I — 67
FIGURE 3.
Three-year moving average of mean annual catch per hour of striped bass caught on full-day party boats fishing in Blocks 301, 308 and 488 (1955-1959 data from Chadwick, 1962).
I o
z <
1 6
15
14
1 3
1 2
1 1
1 0
9
8
7
6
5
A
3
2
1
BLOCK 301 •
BLOCK 308
BLOCK 488
OCEAN BLOCKS
J l_
39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67
YEAR
FIGURE 4. Three-year moving average of mean annual weights of striped bass caught on full-day party boats fishing in Blocks 301, 308, 488 and the Pacific Ocean (1939- 1959 data from Chadwick, 1962).
STRIPED BASS FISHERY
9
mean weights from 1964-68 are 5.3, 7.9, 9.4, 7.8 and 7.7. These means are based on about the same sample size recorded for full-day boats. Seasonal trends in angler success (Figure 6) point to an increasingly well defined season in this block, ruiniing from September through April. The summer and fall fisheries are similar to those prior to 1959 (Chadwick, 1962), but the November through February effort increased considerably during the current period. This winter effort corresponds to the peak of the sturgeon fishery and a portion of tho effort is prob- ably unsuccessful sturgeon effort.
|
I960 |
=30= |
= 44 = |
||||||||||
|
1961 |
= 49 = |
|||||||||||
|
1962 |
||||||||||||
|
1963 |
= 36 = |
|||||||||||
|
1964 |
M |
|||||||||||
|
1965 |
= 33- |
= 39 = |
= 37 = |
= 34 = |
= 52 = |
= 51 = |
= 47 = |
= 43= |
= 32 = |
|||
|
1966 |
= 31 = |
= 32 = |
= 35- |
= 38 = |
= 47= |
= 58E |
E50E |
^59^ |
= 52 = |
= 61 = |
= 53= |
|
|
1967 |
||||||||||||
|
1968 |
= 33 = |
= 32l |
= 36 = |
= 39 = |
= 4lE |
E35E |
||||||
JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC
Catch per hour 0.00-0.10
Catch per hour
0.32-0.42
0.11-0.20
0.4 3 -h
0.21-0.31
Less than 30 trips
FIGURE 5. Monthly catches per unit of efFort for striped bass by anglers fishing from full-day party boats in Block 308 (numbers in squares are the numbers of trips in that month).
10 CALIFORNIA FISH AND GAME
TABLE 3 — Summary of Full-Day Party Boat Reports from San Pablo Bay, Block 301
|
Angler days |
Striped bass |
||||||
|
Year |
Number |
Percentage of annual inland total |
Number* |
Percentage of annual inland total |
Catch ' angler day |
Catch/ angler hour |
Mean weight |
|
1938-48 mean. 1949-59 mean. |
3,803 3,338 |
28 21 |
7,156 6,288 |
25 25 |
|
6.2 3.9 |
|
|
1960 -- |
7,101 6,396 5,173 3,. 596 3,780 4,398 4.655 3,096 3,313 |
36 29 27 15 24 36 26 22 24 |
11, .391 9,381 7,.528 3,511 3,474 (96) 2,937 (242) 4,091 (423) 917 (782) 2,213 (413) |
30 21 19 16 20 18 6 15 |
1.60 1.47 1.46 0.98 0.92 0.67 0.88 0.30 0.67 |
0.23 0.21 0.20 0.14 0.13 0.10 0.13 0.04 0.10 |
4.6 |
|
1961 |
4.3 |
||||||
|
1962 |
4 8 |
||||||
|
1963 1964 |
6.6 7.8 |
||||||
|
1 965 |
12.6 |
||||||
|
1966 1967 |
11.8 12.5 |
||||||
|
1968 |
9.4 |
||||||
|
1960-68 mean. |
4,612 |
27 |
5,049 |
18 |
|
|
8.3 |
* Figures in parentheses are the numbers of additional bass caught along with sturgeon ou full-day boats (mean weights are based on combined figures).
TABLE 4 — Summary of Full-Day Party Boat Repoits fror Upper San Francisco Bay, Block 4S8
|
Angler days |
Striped bass |
||||||
|
Year |
Number |
Percentage of annual inland total |
Number |
Percentage of annual inland total |
Catch/ angler day |
Catch/ angler hour |
Mean weight |
|
1938-48 mean. 1949-59 mean. |
1,195 2,. 5.59 |
9 16 |
2,048 4,693 |
7 19 |
|
6.5 |
|
|
1960 |
10,566 12,933 12,147 19,172 10,079 5,718 9,264 7,816 6,629 |
53 60 63 79 65 47 52 55 49 |
24,633 32,469 29,471 43,776 16,666 7,234 17,016 12,696 11,549 |
64 72 74 90 78 64 73 83 77 |
2.33 2.51 2.43 2.28 1.65 1.27 1.85 1.62 1.74 |
0.49 0.59 0.55 0.49 0.32 0.22 0.38 0.31 0.34 |
6.0 |
|
1961 |
5.9 |
||||||
|
1962. |
6.4 |
||||||
|
1963 . - . |
7.5 |
||||||
|
1964 |
8.3 |
||||||
|
1965 |
9.9 |
||||||
|
1966 |
9.4 |
||||||
|
1967 |
10.0 |
||||||
|
1968 .... |
9 8 |
||||||
|
1960-68 mean. |
10,480 |
58 |
21,733 |
75 |
|
|
8.1 |
STRIPED BASS FISHERY
11
I960
196
1962 =31 ==38= =
963
964 E5I =E85= =
|
a\ |
— 51 ~ |
= 41 = |
=65 = |
mm |
<-:^St'y: |
^^Sh^ |
■■■'i(Sii:-: |
iiii |
|||
|
lli;;: |
WH^jjt^ |
=106= |
E58 = |
= 31 = |
M |
^Mm W^W!!<^W?!^ |
|||||
|
= 3,1 |
= 38= = 88 = |
=69 = |
= 106= |
^^M |
140 Illl |
= 41 = |
|||||
|
|
|||||||||||
|
= 42 = |
-70 — |
E6I E |
E34E |
= 75 = |
Hilil^i |
||||||
|
= 51 = |
E85l |
= 63 = |
E45E |
= 50 = |
-78--72- |
||||||
|
E36E |
E5I E |
=69 = |
E37E |
E124E |
353 = |
=134= |
|||||
|
=109= |
^2 = |
EII7Z |
= 48 = |
^eS |
= 34= |
=129= |
='251 |
= 80 = |
|||
|
E40= |
E35E |
E42E |
E65E |
=74E |
E38E |
||||||
|
= 41 = |
E54 = |
Esse |
=6e= |
= 85l |
E48E |
1965 E36EE5I EEP^-EEi^C^
966
1967
968 =41 = = 54 = =
JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC
Catch Per Hour
Catch Per Hour
0.00-0.10
0.32-0.42
0.11-0.20
0.21-0.31
0.43 +
Less than 30 trips
FIGURE 6. Monthly catches per unit of effort for striped bass by anglers fishing from full- day party boats in Block 301 (numbers in squares are the number of trips in that month).
Block 488 — Northern San Francisco Bay Fishing effort as measured by angler days continued the upward trend which started in 1957 (Chadwick, 1962). While effort dropped after 1964, it remained a fairly constant proportion of the total effort (Table 4). Several important factors led to tliis increase: a summer and fall fishery utilizing deepline trolling techniques developed in the mid 1950 's; and a winter fishery dependent on a spawning population of Pacific herring {Clupra pnllad) occurs in some years (Chadwick, 1962). In 1962, live bait fishing, including cliumming, attracted many people and was very successful. Only one boat was equipped for chum- ming in 1962 and 1963, and two boats in 1964. These boats dominated party boat fishing in this block from 1963 to 1965, and some incom- pleteness in reporting significantly affects apparent trends in effort.
12
CALIFORNIA FISH AND GAME
The catch per hour started declining in 1963 after increasing steadily since 1954. Prior to 1965, good fisliiiig was experienced in this block nearly year around (Figure 7). Subsequently the winter and spring fishery was almost nonexistent. Average weights increased significantly, although not to the extent reported in other areas.
Block 303— The Delta
Party boat effort in the Delta has dropped steadily and presently is of insignificant proportions. Tlie large number of skiffs and cruisers under private ownership contributed greatly to the decline (Chadwick, 1962). The 9-year mean number of angler days was 335, with 322 fish caught. In 1968 only 25 bass were landed on full-day boats in this block. Mean weight estimates in recent years are of little A'alue due to such small samples.
I960 1961 1962 1963
@- '-^^'j
^ ^ 1^ ;(^ j^ (^ (
(^ ^ ^ ^ :^ j|^ (^
^ @ ^ '^ ^ ^ ^
^% (^ (^ (^ ^
JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC Catch per hour Catch per hour
0.00-0.10
OJI-0.20
0.21-0.31
0.32-0.42
0.43 +
Less than 30 trips
FIGURE 7. Monthly catches per unit of effort for striped bass by anglers fishing from full- day boats in Block 488 (numbers in squares are the number of trips in that month).
STRIPED BASS FISHERY
13
Block 302— Suisun Bay The 9-year mean angler days reported in tliis block was 195 days with a range of 56 to 579. The mean number of striped bass caught during this period was 90. Tlic effort nearly doubled and the catch decreased from the 1948-59 mean. The mean catch per angler was 0.5 compared with 1.8 for the 1949-59 period. Part of this lower success is likely due to unsuccessful sturgeon effort reported in this block.
Block 489 — South San Francisco Bay A mean 319 angler days were expended to catch an annual average of 436 striped bass. Though effort was never very high, it fluctuated considerably, ranging from a low of 25 angler days in 1964 to a high of 795 angler days in 1967. Both the effort and catch are up from the 1949-59 mean of 252 angler days and 146 bass. The mean catch per angler day for 1960-68 was 1.4 compared witli 0.6 for the 1949-59 period.
THE OCEAN FISHERY
Prior reports by Calhoun (1949) and Chadwick (1962) dealt only with the inland blocks described here. Party boat fishing in the ocean previously has been of minor importance. Calhoun (1949) indicated that only occasional party boat forays were made in the Pacific Ocean. In the late 1950 's bass were reported from the ocean but an unknown portion of these were actually caught in San Francisco Bay while on the return to home port (Chadwick, pers. eomm.). To some extent this may be true for the period of this report. However, it does appear that the ocean party boat fishery has become relatively more important now than during the 40 's and early 50 's, especially since party boat effort has declined markedly in Blocks 302, 303 and 308. It is also likely that the ocean catch is underestimated significantly because some of the more successful operators did not report all their trips.
TABLE 5 — Summary of Full-Doy Party Boat Reports from the Pacific Ocean
|
♦Weight of |
|||||||
|
bass caught |
|||||||
|
in the |
|||||||
|
ocean as |
|||||||
|
Number of |
percent |
||||||
|
Number of |
Percentage |
striped |
Percentage |
Catch/ |
total |
||
|
anglers |
of |
bass |
of |
angler |
Mean |
weight |
|
|
Year |
reported |
total |
reported |
total |
day |
weight |
reported |
|
1960 |
3,446 |
14.8 |
1,760 |
4.4 |
.51 |
9.2 |
7.0 |
|
1961 |
355 |
1.6 |
557 |
1.2 |
1 . 56 |
6.2 |
1.4 |
|
1962 |
3,387 |
14.9 |
3,158 |
7.4 |
.93 |
9.9 |
11.5 |
|
1963 |
5,174 |
17.5 |
4,604 |
8.7 |
.89 |
11.5 |
12.9 |
|
1964 |
2,354 |
13.2 |
2,293 |
9.7 |
.97 |
10.6 |
9.8 |
|
1965 |
2,865 |
19.0 |
1,646 |
12.6 |
.57 |
14.6 |
15.3 |
|
1966 |
3,430 |
16.2 |
4,966 |
17.6 |
1.44 |
15.4 |
27.1 |
|
1967- |
3,290 |
18.8 |
2,962 |
16.2 |
.90 |
14.6 |
19.8 |
|
1968 |
1,221 |
7.4 |
1,211 |
7.5 |
.99 |
12.9 |
9.7 |
|
1960-68 |
|||||||
|
mean |
2,835 |
13.7 |
2,573 |
9.5 |
.91 |
11.6 |
|
|
* Includea |
weight of bass c |
aught with stur |
geon. |
||||
|
2—8] |
L136 |
li
CALIFORNIA FISH AND GAME
The data indicate that the nnmbcr of bass caught in the ocean as a percentage of tlie total increased from a low of 1.2% in 1961 to a high of 17.6 in 1966 (Table 5). The number of angler days reported in ocean blocks varied from 1.6 to 19.0% of the total but exhibited no definite trend. Many of the bass reported may have been caught incidental to the salmon fishery so that effort actually spent fishing for bass cannot be determined.
The mean weight reported was higher than for any of the inland blocks and show the same trend toward larger bass in recent years. The biggest change occurred in 1965 when the mean weight increased 1 lbs. from the previous year to 14.6 (Table 5). The ocean fishery con- tributes a higher percentage of total weight than of total numbers due to the larger average size (Table 5).
TABLE 6 — Agreement of Mean Weights Reported on Full-Day Party Boats in Block 488 and Estimates Made From Gill Net Length-Frequencies
|
Year |
Block 488 Daily boats x lbs |
Gill net X lbs* |
Difference (%) |
|
1958 - - |
5.1 5.5 6.0 5.9 9.9 9.4 |
5.7 5.4 6.0 6.4 8.5 9.6 |
-10.5 |
|
1959 |
+ 1.8 |
||
|
1960 - -- |
0 |
||
|
1961 1965 |
-7.8 + 16.5 |
||
|
1966 |
-2.1 |
||
* For a description of gill nets and their operation, see Chadwick (1967). Mean weight estimated by Robinson's (1960) length-weight relationship applied to each inch interval.
The inereasing importance of the ocean fishery is compatible with recent migration patterns. Chadwick (1967) found that striped bass tend to migrate farther seaward in recent years compared with the early 1950 's. This trend has probably been greater in the 63-68 pe- riod since the average size of bass has been increasing and the move- ment of bass seaward is correlated with bass size (Chadwick, 1967).
POPULATION TRENDS
Party boat catch rates may not reflect population trends accurately, so inferences about population trends should be drawn cautiously.
A major potential cause of error is changes in migration patterns. Striped bass tended to migrate farther downstream and remain there longer during the study period than they did in the early 1950 's (Chad- wick, 1967). The marked increase in party boat fishing in northern San Francisco Bay can be attributed partially to this migration change, so the changes in catch rates are not true reflections of population differences between the early 1950 's and the current period.
On the other hand, annual variations in migrations during the 1960- 68 period have been relatively small (Chadwick, 1967; Miller, unpub- lished data) in comparison to the differences between this period and the early 1950's. Hence, catch rates during the 1960 's have been af- fected less by migration changes, although fluctuations in availability in the Delta (Miller and McKechnie, 1969) suggest that such fluctua- tions cause indices based on catch rates to be imprecise throughout the fishery.
STRIPED BASS FISHERY
15
The changes in angling methods in San Francisco Bay have already been noted as a factor causing biases during the current period.
Calhoun (1949) and Chadwick (1962) used fall catches in Blocks 301 and 308 and yearly catches in Block 303 as measures of trends in population size. Effort in Block 303 has become so insignificant that it no longer provides a useful index. Catcli rates have declined through the current period in Blocks 301 and 308 in the fall (Figure 8), but the change in migration patterns and the initiation of a sizable sturgeon fishery undoubtedly have contributed to this decline.
>- <
O z <
UJ Q.
</)
Q
Z
o
OL
z <
15
lO
5 -
BLOCK 488 o-
ALL INLAND BLOCKS
57 58 59 60 61 62 63 64 65 66 67
YEAR
FIGURE 8. Three-year moving average of mean pounds per angler day for full-day party boats (based on 3-year moving average of mean weights reported and 3-year moving average of mean catch per angler day).
The size of bass in the fishery also provides information on popula- tion trends, although weights have to be used even more cautiously than numbers because they are estimates rather than counts. The differences in mean weights reported for half-day and full-day boats in Blocks 301 and 308 suggest biases in reporting. However, several sources indicate the general observed trend of increasing weight is real. One source is that mean weights of bass caught in gill nets during tagging operations in the Delta have increased and agree closel}^ with reported mean weights from Block 488 (Table 6).
Another source is the increase in size of fish in the party boat fishery has been paralleled by a similar increase in the Delta fishery from 1959 to 1965 (Miller and McKechnie, 1969). Tlie increase in the Delta was due to an increase in the average age of bass in the catch (Miller and McKechnie, 1969), and growth rates in tlie population have not changed (Miller and Orsi, 1969). There have been no changes in mi- gration or mortality rates (Chadwick, 1967 and 1968; Miller, unpub- lished data) which could cause this change in size independent of size
16 CALIFORNIA FISH AND GAME
changes in the population. Hence, the change undoubtedly reflects an ineroaso in the aA'erage age of bass in the population.
While several of the conditions discussed above make party boat catch rates an imprecise measure of population trends, the nearly steady decline in fishing success in all parts of the fishery after 1963 and the increase in average age are evidence that recruitment and population size have declined since 1963.
Although the catch per angler day for all inland blocks has de- clined since 1963 (Table 1), the overall trend in terms of weight per angler day has been upward since the late 1950 's and has been rela- tively stable since 1961 (Figure 8). The trend in north San Francisco Bay has generally paralleled the overall trend although the average size of bass was initiall.y greater.
These data suggest that while the numbers of bass in the population have decreased, there has been some compensation in terms of bio- mass due to the increase in the average weight of bass in the popula- tion.
REFERENCES
Calhoun, A. J. 1949. California striped bass catch records from the party boat
fishery : 1938-1948. Calif. Fish and Game 35(4) :211-253. Chadwick, Harold K. 19G2. Catch records from the striped bass sportfishery
in California. Calif. Fish and Game 48(3) :153-177. ■ — . 1967. Recent migrations of the Sacramento-San Joaquin River striped
bass population. Trans. Amer. Fish. Soc. 96(3) :327-342.
1968. Mortality rates in the California striped bass population. Calif.
Fish and Game 54(4) :228-246. Johnson, William C. 1951. The reliability of the striped bass party boat catch
records. Report to Bur. Fish. Cons., Calif. Div. of Fish and Game 51-1, Jan.
9, 1951, 14 p. (typewritten). Miller, Lee W. and Robert J. McKechnie. 1969. Trends in the striped bass fish- ery in the Sacramento-San Joaquin Delta from 1959 to 1965. Anad. Fish. Admin.
Rept. 69-5, 26 p. Miller, Lee W. and James J. Orsi. 1969. Growth of striped bass, Morone saxa-
tilis, in the Sacramento-San Joaquin Estuary, 1961—1965. Anad. Fish. Admin.
Rept. 69-6, 7 p. Robinson, John B. 1960. The age and growth of striped bass (Boccus saxatilis)
in California. Calif. Fish and Game 46(3) :279-290.
Calif. Pish and Game, 57(1) :17-27. 1971.
UPPER LETHAL TEMPERATURE AND THERMAL SHOCK
TOLERANCES OF THE OPOSSUM SHRIMP, NEOMYSIS
AWATSCHENSIS, FROM THE SACRAMENTO-SAN
JOAQUIN ESTUARY, CALIFORNIA^
JAMES R. HAIR
2
Anadromous Fisheries Branch California Department of Fish and Game
Temperature toSerance tests were performed on aduit opossum shrimp Neomysis awatschensis, collected in the Sacramento-Scan Joaquin Estuary from July 1968 to Octobes 1969.
The upper lethal temperature for adult N. awatschensis was between 75.6 F and 77.8 F as determined from 48-hr thermal bioassays.
The tolerance of adult N. awatschensis to rapid increases in tempera- ture decreased when the acclimation temperature increased. Rapid tem- perature rises of 25 F or less caused little or no mortality provided the test temperature did not reach 87 F. Survival was inversely related to temperature above 87 F. Rises of more than 25 F caused significant mor- talities even though the maximum temperature did not reach 87 F. Survival decreased rapidly with increased exposure time at Sethal tem- peratures.
INTRODUCTION
Neomysis awatschensis Briint is an important food for striped bass, Morone saxatilis, and other fishes in the Sacramento-San Joaquin Estu- ary (Heubacli, Toth and MeCreadv, 1963; Ganssle, 1966; Radtke, 1966; Stevens, 1966a, b; Turner, 1966a, b; Thomas, 1967).
The N. awatschensis popuhition in tlie estuary is centered much of the year in the Antioch-Pittsbnrs" area (Turner and Heubach, 1966; Heubach, 1969). Existing: and proposed power generating pLants are also in this area. In California tliermal power phmts, the condenser cooling water is raised a maximum of 15-25 F above the ambient water temperature in 4-9 seconds, and maintained at the elevated temperature for 1-6 minutes before discliarging into the receiving water (Adams, 1969a). The maximum temperature rise at existing and proposed pknts in the Delta is 18 F.
N. awatschensis near the plants might be affected in two ways: (i) exposure to the heated effluent and (ii) entrainment in the con- denser cooling water and exposure to a rapid temperature rise of as much as 18 F upon passage througli the steam condenser. Therefore, experiments were designed to test the upper lethal temperature and rapid temperature rise tolerances of N. awatschensis. Temperature tolerances were defined only for adults, because preliminary tests indi- cated that adults were not as hardy as juveniles. Hence, a(lult require- ments are controlling in defining suitable power plant operating criteria.
1 Accepted for publication September 1970. Funds for this investigation were provided by the Pacific Gas and Electric Company in cooperation with the Anadromous Fisheries Branch of the California Department of Fish and Game.
~ Presently assigned to Lake Almanor Fisheries Investigation, Region 2, California Department of Fish and Game.
(17)
IS CALIFORNIA FISH AND GAME
METHODS
Tlie slirimj) were collected from the Delta during all seasons. They ■were netted at salinities ranging from 0.02 to 1.9 ppt chloride. Delta "water was taken when the animals were collected and was used in all experiments.
The animals were placed into a 10 mesh/inch stainless steel screen basket in a plastic-lined ice chest two-thirds full of water for transport to the laboratory. Adults became separated from juveniles during trans- port because juveniles (less than 7 mm length) swam through the screen openings and the adults remained in the basket. Battery pow- ered aerators aerated the water.
The animals were held within 0.5 F of the capture temperature for 48 lir before testing began. The water was filtered and aerated continu- ously during this period.
The shrimp were siphoned through 3/16 inch ID Tygon tubing into 2-liter battery jars for the temperature tests. A small dip net was used to concentrate the animals in the holding tank to facilitate capture by the siphon. The animals were counted with a hand tally as they passed through a section of tubing laid across a white background. The speed of transfer was controlled by raising and lowering the battery jar. The shrimp were tested in groups of 100 with 3 replicates at each test con- dition.
The battery jars were filled only to about 5 cm from the top with water. This prevented the shrimp from jumping out. Shrimp that jumped and became stuck to the jar were eliminated from the original count. N. awatschensis are negatively phototrophic so the laboratory liglits were left on continuously to minimize jumping.
The water in each battery jar was aerated with compressed air delivered through an air stone. Temperatures under test conditions were normally maintained within 0.2 ¥ of the desired temperature.
The water in the test and control jars was changed once during the 48-hr test period of the upper lethal experiments. The water was re- moved by siphoning through ^ inch tubing screened at the intake to prevent loss of the animals. The jars were filled again with river water at the test temperature. Dead animals were removed once or twice a day to prevent fouling of the water.
Control groups were handled identical to the test groups. Test sur- vivals presented in this paper, except for true survivals in Tables 1 and 2 and as noted in the upper lethal temperature analysis, were adjusted by dividing the actual test survival by the control survival.
N. awatschensis were fed dried Daphnia during the holding and test periods. Cannibalism was prevented by making food available at all times.
DESCRIPTION OF TESTS
Upper Lethal Temperature
Fry, Brett and Clawson (1942) and Brett (1944) developed the tech- niciues used to derive the upper lethal temperature of N. awatschensis.
Battery jars of animals, at each acclimation temperature, were placed into 3 or 4 constant temperature baths at different test tempera- tures. The test temperatures varied between experiments. They ranged from 2 to 27 F above acclimation. The highest increases were in those
OPOSSUM SHRIMP TOLERANCES
19
tests witli the lowest acclimation temperature, and the lowest increases were in those tests with the higliest acclimation temporatui'e. Tlie period of t('ni])eratnre adjustment in the jars was approximately 1 hr for a 20 F rise with proportionally shorter times for lesser temperature rises and proportionally longer times for higher rises. Survival was measured after 48 hr.
For each acclimation group, tlie mean percentages surviving at each test condition were plotted against their respective test temperatures. A line was fitted to the points, by eye, and the LDr,o estimated by in- terpolation.
Experimental ld.-,o values were plotted against llicir correspond- ing acclimation temperatures and a line fitted to the points using the method of least squares. The upper letlial temperature is the point on the line where the acclimation temperature equals the lethal tempera- ture (Figure 1).
'50 52 54 56 58 60 62 64 66 68 70 72 74 76 78
Acclimation Temperature in T
FIGURE 1. Estimation of upper lethal temperature for N. awafschensis.
Rapid Temperature Rise For each test, 100 N. awafschensis and 775 ml of water at acclimation temperature were poured into a battery jar. An equal volume of warmer water was added over a 10-sec period. At the same time the
20
CALIFORNIA FISH AND GAME
mixture was rapidly stirred with a thermometer. The temperature of the water to be added was derived by multiplying the desired rise by 2 and adding- the product to the acclimation temperature. For ex- ample, if a 10 F rise was desired, the added water was 20 F warmer than the acclimation temperature. The elevated temperatures M^ere generally maintained for either 0, 2, 4 or 6 min. Animals in the zero minute exposure group were placed into a water bath at acclimation temperature to begin cooling iimnediately after the warm water was added. The other groups were held the required time in a water bath at the test temperature and then placed into the acclimation tempera- ture bath. Temperatures were measured immediately after mixing and at 2-niin intervals for the next 10 min. Thereafter temperatures were measured less frequently. Survival was measured at the end of 24 hr.
FIGURE
10 15 20 25 30
TRAVEL TIME IN MINUTES
35 40
2. The decay of temperature with time for a mass of wafer moving through the cooling water system of the Pittsburg Power Plant, California (Adams, 1969b).
10
15 20 25 TIME IN MINUTES
30
35 40
FIGURE 3.
Temperature decay for four laboratory experiments. Temperatures were main- tained 0, 2, 4, and 6 min before cooling.
OPOSSUM SHRIMP TOLERANCES
21
The temperature decay during the cooling period simulated very closely the actual thermal conditions at the Pittsburg power plant (Figures 2 and 3).
Some N. aivatsclicnsis "were held after the normal testing period to test the delayed effects of rapid temperature rise on survival and re])ro- duction. The animals observed for delayed effects were kept in 5-gallon aquaria at their acclimation temperature. The reproduction tests were on females cariying eyed embryos in the brood poucli.
RESULTS Preliminary Tests — Adult Survival vs. Juvenile Survival
Three rapid rise tests and two upper lethal tests were performed on both adult and juvenile N. awatscliensis during development of the experimental design. The true survival of adults was as low or lower than that of the juveniles in all tests (Tables 1 and 2). In two of the rapid rise experiments poor survival in the adult controls resulted in higher adjusted survival percentages for adults than for juveniles at elevated temperatures. In the other rapid rise test and in both upper lethal tests, the adjusted survival percentages were lower for adults than for juveniles.
These tests indicate that adults are probably not as resistant as juveniles to temperature changes. All subsequent testing was on adults.
TABLE 1 — PreSiminary Rapid Tsmpereiture Rise Experiments Performed on Adult and Juvenile N. awatsehensis ^
Acclimation
temperature (F)
68.5-
69.5.
70.0.
Temperature rise (F)
0 (control)
5 10 20
0 (control)
5
10 20
0 (control)
5 10 20
Survival percentages^
Juveniles
True survival
94.0 93.7 94.,'? 90.0
94.7 90.6 95.7 81.3
82.0 81.0 83.0 78.1
Survival
adjusted
for deaths
in controls
100.0 99.7
100.3 95.7
100.0
102.0
101.1
85.9
100.0
98.8 101.2
95.2
Adults
True survival
82.7 89.2 87.2 84.2
90.3 89.0 81.9 72.3
76.2 77.2 83.0 69.2
Survival
adjusted
for deaths
in controls
100.0
107.9
105.4
98.2
100.0 99.2 90.7 80.1
100.0
101.3
108.9
90.8
1 These tests were conducted while transportation, holding, feeding and temperature control methods were being developed. Results inconsistent with findings presented later in this paper are due to irregularities in the experimental technique. The period for which the shrimp were subjected to the maximum temperature varied between tests. The time interval ranged from a few seconds to one minute. Adult and juvenile shrimp were given equal treatment in all tests. Survival was measured after 24 hours.
" Mean of three groups of 100 animals each.
22
CALIFORNIA FISH AND GAME
TABLE 2 — Preliminary Upper Lethal Temperature Tolerance Experiments Performed on Adult and Juvenile N. awatschensis '
|
Test temperature (F) |
Survival percentages^ |
||||
|
Juveniles |
Adults |
||||
|
Acclimation temperature (F) |
True survival |
Survival adjusted for deatlis in controls |
True survival |
Survival adjusted for deatlis in controls |
|
|
69.0 66.5 |
69.0 (control) 74.0 79.0 84.0 89.0 66.5 (control) 71.5 76.5 81.5 86.5 |
94.7 86.6 58.3 0.0 0.0 93.6 95.0 85.3 0.0 0.0 |
100.0 91.4 61 . 5 0.0 0.0 100.0 101.5 91.1 0.0 0.0 |
81.7 68.0 19.3 0.0 0.0 90.3 87.9 72.5 0.0 0.0 |
100.0 83.2 23.6 0.0 0.0 100.0 97.3 80.3 0.0 0.0 |
'These tests were conducted while transportation, holding, feeding, and temperature control methods were being developed. Results inconsistent with findings presented later in this paper are due to irregularities in the experimental technique. Survival was measured after 24 hours. 'Mean of three groups of 100 animals each.
Upper Lethal Temperature test survival percentages were adjusted for mortality in the the lowest ld-.o temperature was 72.6 F at an acclimation ^ '^'' ° F. The highest ld-,,) temperature was 77.4 "^ "^
When
controls,
temperature of 51.8 i^'. The highest ld-,,)
an acclimation temperature of 71.6 F. The upper lethal temperature
of N. awatschensis was estimated to be 77.8 F (Figure 1) .
F at
54 56 58 60 62 64 66 68 70 72 74
Acclimation Temperature In "F
FIGURE 4. Effect of acclimation temperature on control survival in the upper lethal tempera- ture experiment.
OPOSSUM SHRIMP TOLERANCES
23
Survival in the controls ranged from 52 to 95%. Mean control sur- vival was 81%. Control survival was affected by temperature. It de- creased as the acclimation temperature increased. The rate of this de- crease intensified at 71 F (Figure 4). This relationship suggests that the upper letlial temperature is biased u])ward as some of the adverse effects of heat would have been cancelled when the actual test survival percentages were divided by tlie control survival percentages.
The upper lethal temperature M'as also estimated with no adjustment for mortality in the controls. This temperature is 75.6 F and probably biased downward because of mortjility not induced by heat. Some mor- tality was almost certainly caused by extraneous factors such as han- dling or disease. Therefore, the unbiased upper lethal temperature is between 75.6 F and 77.8 F.
Rapid Temperature Rise
Survival was tested at acclinuilioii tcmjieratures ranging from 46.4 F to 72.1 F. Adjusted survivals ranged from 0 to 102% (Table 3). Con- trol survivals ranged from 80% at the highest acclimation temperature of 72.1 F to 98% at the lowest acclimation temperature of 46.4 F. The mean control survival was 93%.
Control survival decreased as the acclimation temperature increased, but the results of these tests were not biased. The experiment was to
|
TABLE 3— Effects of a Ra |
pid Temperature increase on Survival of N. |
awcitschensis |
||||||
|
Percent survival in controls |
Temperature rise in F |
Percent survival' |
||||||
|
Acclimation |
Exposure period |
|||||||
|
temperature in F |
0 min |
0.5 min |
2 min |
4 min |
5 min |
6 min |
||
|
46.4 |
98.5 |
9 18 25 32 |
99.5 100.02 |
-- |
-- |
99.5 98.8 88.3 |
-- |
-- |
|
50.0 |
98.3 |
27 36 |
98.0 53.9' |
ll"2 |
94.9 2.3 |
91.2 1.0 |
__ |
87.5 |
|
57.0 |
96.0 |
10 15 19 25 |
100.7 100.0 100.0 100.6 |
-- |
;; |
98.6 98.2 96.1 |
98.2 |
_ — |
|
62.1 |
97.7 |
15 20 |
98.9 92.1 |
-- |
9.J.4 90.7 |
98.3 90.8 |
__ |
95.1 92.5 |
|
68.0 |
94.5 |
15 20 |
98.3 59.0 |
-- |
99.0 26.5 |
95.9 27.5 |
-- |
95.9 15.5 |
|
70.1 |
83.4 |
10 15 20 |
102.2 99.7 59.2 |
-- |
101.02 100.7 13.2 |
103.4 98.3 0.0 |
-- |
95.8 102.2 0.0 |
|
72.1 |
80.0 |
15 18 20 |
100.7 69.4 12.9 |
-- |
99.4 24.6 0.02 |
85.3 0.4 |
-- |
81.1 0.0 |
• All percentages represent survival for three test groups of 100 animals each, except where noted. Survivals are ex- pressed as a percentage of control survival. 2 Two test groups of 100 animals each. ^ One test group of 100 animals.
24
CALIFORNIA FISH AND GAME
determine effects of temperature increase so it was desirable to elim- inate effects of the base temperature. This was done by expressing survival as a percentage of control survival.
N. awatschcnsis at acclimation temperatures of 57.0 F to 72.1 F were exposed to rises of 10 to 25 F. Little or no mortality occurred until the maximum temperature reached 87 F. The survival of N. awatschensis at temperatures above this critical level decreased as the exposure time increased, and at each exposure interval there was a strong inverse relationship between survival and temperature (Figure 5).
'oo!
so-
so
70
- 60' o
>
W 50'
c a> o »- 40
Q-
30
20
10
0
-X-
o o ^^
X-0 Minutes Exposure •-2 Minutes Exposure 0-4 Minutes Exposure 0-6 Minutes Exposure
70
— I—
75
~i — ' 80
FIGURE 5.
Maxinnum Temperature F
Effect of maximum temperature attained during rapid temperature rise experi- ments on survival of N. owafschens/s acclimated at temperatures between 57.0 and 72.1 F.
OPOSSUM SHRIMP TOLERANCES
25
N. awatschensis acclimated at 46.4 and 50.0 F were exposed to tem- perature rises as high as 36 F. Significant mortalities occnrred witli temperature rises of 27 F to 36 F even tliougli tiie critical temperature of 87 F was not reached (Table 3) .
Survival declined as the temperature rise increased in nearly every experiment (Table 1). This decline was most pronounced at the high- est acclimation temperatures (Figure 6).
There was no delayed mortality attributable 1o the rapid tempera- ture rise when 173 slirimi) exposed for 6 min to a 27 F rise from a base temperature of 50.0 F were kept for 7 days. Eiglity-eight percent of tlie test animals survived the holding period while only 83% of the controls survived.
D
>
3
to
c a> o
^-
Q_
Temperature Rise In F
FIGURE 6. Effect of temperalure rise on survival of N. awafschensis from seven temperatures. Acclimation temperatures are circled. All data are fo exposure at the test temperature.
acclimation r a 4 min
Tests for delayed effects of rapid temperature rise on reproduction were inconclusive. In one experiment at a base temperature of 62.1 F I held for 5 days, 9 gravid females subjected to a 15 F rise, 9 gravid females subjected to a 20 F rise, and 9 control females. Eight females subjected to the 20 F rise survived Avhile only 6 control females and 3 females subjected to the 15 F rise survived. The control females pro-
26 CALIFORNIA FISH AXD GAME
diieed 101 j-oiiiig, which was greater tlian the 53 young produced by the females subjected to the 20 F rise, but less than the 116 young produced hy the females subjected to the 15 F rise. In another experi- ment at an acclimation temperature of 70.1 F I held 20 control females and 20 females exposed to a 15 F rise for 4 days. There was no hatch- ing in either group.
SUMMARY AND DISCUSSION
Tests made during the development of the experimental design in- dicated that adult N. awatsclicnsis are not as hardy as juvenile N. aicaischensis.
No studies on the effects of thermal shock on Neomysis have been previously reported. Wilson (1951) reported an upper lethal tempera- ture of 74.5 F for N. mcrccdis Holmes (now N. mvatschensis) from British Columbia. This was based on 48-hr experiments at 3 acclima- tion temperatures.
The difference between Wilson's value of 74.5 F and the upper lethal temperature reported here may reflect what Kinne (1963) termed "genetic adaptiition". N. awafficlirnsis in the Sacramento-San Joaquin Estuary are at the southern limit of their range (Banner, 1954) and have possibly adapted to warmer conditions than the shrimp studied by Wilson in British Colnmbia.
A closely related mysid, Neomysis americana, has a greater tolerance to higher temperatures. Mihursky (1969) reports 24-hr LD.-,n tempera- tures between 31 C (87.8 F) and 33 C (91.4 F) for N. americana in the Patuxent River estuary. In the summer, surface water temperatures approach these levels in that estuary.
The upper lethal temperature is obviously not a satisfactory environ- mental condition, and these experiments do not define with certainty how much lower temperatures in the environment must be to be satis- factory. N. awafschensis populations in the Sacramento-San Joaquin Estuary generally decrease when water temperatures exceed 72 F (Heubach, 1969). The calculated upper lethal temperature and the sharp decrease in survival of controls at acclimation temperatures over 71 F support the hypothesis that the decreased survival Heubach ob- served in the estuary is caused by temperature, with temperatures in the low 70 's unsatisfactory.
The most significant findings from my rapid temperature rise experi- ments were : (i) the tolerance of N. awatscliensis to a rapid temperature rise decreases with increasing acclimation temperatures, (ii) there is an inverse relationship between survival and exposure time at high temperatures, and (iii) adult N. awatscJiensis can withstand a rapid temperature rise up to 25 F above acclimation temperature provided the exposure time is short and the ultimate temperature does not reach the critical temperature of 87 F.
The lethal effects of a rapid temperature rise on N. awafschensis were immediate. Shrimp surviving the first few hours survived the entire 24-hr test period. There was no delayed mortality observed within 7 days.
ACKNOWLEDGMENTS
I wish to thank Jerry L. Turner and John E. Skinner for their guidance in the early part of this study. Special thanks are extended
.
OPOSSUM SHRIMP TOLERANCES 27
to Donald E. Stevens and Harold K. Chadwiek for directing the study, reviewing the manuscript and offering helpful suggestions. Mrs. Janet Boranian and Mrs. Marlene Oehler typed the manuscript. Financial support was provided by the Pacific Gas and Electric Company.
LITERATURE CITED
Adams. .T. R. lOGOa. Ecological invostis'atioiis nroniid somo tliornial powor stations ill California tidal waters. C'liesapoalve Science 10(8-4) :145-ir)4.
. lOGOb. Thermal power aquatic life, and kilowatts on the Pacific Coast.
Nuclear News 12(9) : 75-79.
Banner, A. H. 1954. New records of Mysidacea and Enphansiacea from the north- eastern Pacific and adjacent area.s. Pacific Sci. 8:125-139.
Brett, J. R. 1944. Some lethal temperature relations of Algonquin park fislies. I'uh. Ont. Fish. Res. Lab. 03 : 1-49.
Fry, F. E. J., J. R. Brett and G. II. Clawson. 1942. Lethal limits of temperature for young goldfish (Carrasius auratns L.). Rev. Can. de Biol. 1:50—56.
Ganssle, D. 19GG. Fishes and decapods of San Pablo and Suisun Bay, pages 64-94. In: D. W. Kelley (editor), Ecological studies of the Sacramento-San Joacpiin Estuary. Calif. Fish and Game, Fish Bull. 133.
Ileuliach, William. 19G9. Neomi/sis awatschensis in the Sacramento-San Joacpiin River estuary. Limnol. and Oceanog. 14(4) : 533-54G.
Ileubach, William, R. J. Toth and A. M. IMcCready. 19G3. Food of young-of-the- year striped bass (Rocciis saxatiUs) in the Sacramento-San Joaquin River sys- tem. Calif. Fish and Game 49(4) :224-239.
Kinne, O. 1963. The effects of temperature and salinity on marine and brackish water animals. I. Temperature. Oceanog. Mar. Biol. Ann. Rev. 1 : 301-340.
Mihursky, J. A. 1969. Patuxent thermal studies ; summary and recommendations. N.R.I. Spec. Rept. No. 1.
Radtke, L. D. 1966. Distribution of adult and subadult striped bass (Roccus saxa- tiUs) in the Sacramento-San Joaquin Delta, pages 44-58. In: J. L. Turner and D. W. Kelley (editors), Ecological studies of the Sacramento-San Joaquin Delta. Calif. Fish and Game, Fish Bull. 136.
Stevens, D. E. 1966a. Distribution and food habits of the American shad, Alosd sapidissima, in the Sacramento-San Joaquin Delta, page 97-107. In: J. L. Turner and D. W. Kelley (editors). Ecological studies of ihe Sacramento-San Joaquin Delta. Calif. Fish' and Game, Fish Bull. 136.
. 1966b. Food habits of striped bass, Roccus saxatili.s, in the Saeramonto-San
Joaquin Delta, pages 68-96. In: J. L. Turner and D. W. Kelley (editors). Ecological studies of the Sacramento-San Joaquin Delta. Calif. Fish and Game, Fish Bull. 136.
Thomas, J. L. 1967. The diet of juvenile and adult striped bass, Roccus saxatilis, in the Sacramento-San Joaquin River system. Calif. Fish and Game 53(1) : 49-62.
Turner, J. L. 1966a. Distribution and food habits of Ictalurid fishes in the Sacra- mento-San Joaquin Delta, page 130-143. In: J. L. Turner and D. W. Kelley (editors), Ecological studies of the Sacraniento-San Joaquin Delta. Calif. Fish and Game, Fish Bull. 136.
■ ■ — . 1966b. Distribution and food habits of Centrarchid fishes in the Sacramento- San Joaquin Delta, page 144—153. In: .T. L. Turner and I). W. Kelley (editors). Ecological studies of the Sacramento-San Joaquin Delta. Calif. Fish and Game, Fish Bull. 136.
Turner, J. L. and W. Heubaeh. 1966. Distribution and concentration of Neomysis aicatschensis in the Sacramento-San Joaquin Delta, pages 105-112. In: D. W. Kelley (editor), Ecological studies of the Sacramento-San Joaquin estuary. Calif. Fish and Game, Fish. Bull. 133.
Wilson, R. R. 1951. Distribution, growth, feeding habits, abundance, thermal and salinity relations of Neomysis mercedis (Holmes) from the Nicomekl and Ser- pentine rivers, British Columbia. Master of Arts Thesis. Univ. of British Co- lumbia, Vancouver.
Calif. Fi.^h and name, 57(1 ) : 2S-43. 1971.
THE KOKANEE SALMON IN LAKE TAHOE^
ALAAO J. CORDONE,^ STEPHEN J. NICOLA, and PHILLIP H. BAKER
Inland Fisheries Branch
California Department of Fish and Game
and
TED C. FRANTZ
Nevada Department of Fish and Game
Reno, Nevada 89510
Large numbers of kokanee ss^lmon (Oncorhynchus nerka) fry were stocked in Lske Tahoe from I?f49 through 1955. Kokanee became estab- lesihed but the popnilafion remained at a low Eevel until 1963 when a dramatic increase in the number ef spawners was observed. A fishery fiiiyl3y developed in 1967. Mst^or spawning conzentrfatsons occur in Taylor Creek send aloeig the sho/es of MeKinney Bay. In most years from 1960 through 1968 vir}usa!ly the entcre Taylor Creek run was composed of a single ege groap from eerJciiii strong year classes. Presence of strong year classes suggests high survival of naturaliy-speswned fish. There is some evEdeiice, however, of high egg retention. Lake Tahoe kokanee grow rapidly artd a trend toward increasing growSh rates since 1961 is suggested. Their length-weight relationship was log W i= — 3.26090 + 2.91063 log L. Their diet consisted mostly of cladoeerans. They are widely distributed in the limnetic zone and strongly surface oriented, except during the summer and early fall when large schools form off TayEor Creek at depths from 50 to 120 fi. Under these conditions fishing is feitsMe and an intensive deepline-troll fishery has developed. Efforts should be made to enlarge this fishery in space and time provided the average size of the kokanee does not decline below an acceptable level.
INTRODUCTION
The status of the kokanee sahiion in Lake Tahoe lias changed consid- erably in recent years. During the summers of 1967 and 1968, kokanee fisheries developed in Tahoe for the first time since the initial kokanee introductions in the 1940 's and 1950 's. Since the early 1960 's, more- over, kokanee spawning runs in Taylor Creek, the major spawning tributary, have increased substantially. Beach spawaiing during this period has also increased.
Fraser and Pollitt (1951), Richard (1954) and Corlett and Wood (1958) document the status of the kokanee in tlie first years following their introduction. They observed small runs in many tributaries but only in Taylor Creek did these runs persist after the early plantings ceased. No kokanee were observed in the sport fishery.
In 1960 the cooperative California and Nevada Lake Tahoe Fisheries Study was begun. From 1960 through 1966 we collected data on var- ious aspects of the life history of the kokanee in the lake. This report describes the development of the present fishery, and summarizes the information collected during the study on the spawning, age and growth, food habits and distribution of kokanee in Lake Tahoe.
1 Accepted for publication July 1970. This work was performed as part of Dingell-
Johnson Projects California F-21-R and Nevada P-15-R, "Lake Tahoe Fisheries Study", supported by Federal Aid to Fish Restoration funds.
2 Presently on leave of absence with the United Nations Food and Agriculture Organi-
zation, Jinja, Uganda.
(28)
KOKANEE IN TAHOE
29
STOCKING HISTORY
Kokanee first were introduced in 1944 when fry held at tlie Tahoe State Hatchery were released accidentally. From 1949 through 1955. fry were planted annually by the California Department of Fish and Game and/or the Neveda Fish and Game Commission at numerous points along the lake shore and in most of the major tributaries (Rich- ard, 1954; Corlett and Wood, 1958). Approximately 4.5 million kokanee were planted during this period. The eggs for these plants were ob-
NCLINE VILLAGE
Marlefte Lake
Spoon er Lake
v^^>SOUTH
•'"■lake tahoe
FIGURE 1. Map of Lake Tahoe showing Taylor Creek and areas referred to in text. 3—81136
30 CALIFORNIA FISH AND GAME
tained from A'arious sources in Idaho, Montana, and Washington. No kokanee were phmted by either state from 195G through 1963.
In 1964, 1965, and 1966 the Nevada Fish and Game Commission phmted 6.1 million fry on the Nevada side of the lake. Eggs for the 1961 and 1966 plants were obtained from Washington ; the egg source for 1965 was Taylor Creek. From 1967 through 1969 California planted over 6 million f rj^ from eggs obtained from the developing runs at Taylor Creek. Nearly all of the fish planted during the first 2 years were released in Taylor Creek or in Tahoe near Taylor Creek. A few, raised at the Tahoe Hatchery, were planted at the Wildlife Conserva- tion Board Boat Eamp near the hatchery, and in the hatchery creek. In 1969 the kokanee were planted off Kings Beach near Griff Creek, and at the Cave Kock Boat Kamp (Figure 1). They ranged in size from 350 to 47/oz.
NATURAL REPRODUCTION
Taylor Creek
The extensive tributary stocking program conducted from 1949 through 1955 produced spawning runs in most of the major Tahoe tributaries in the early 1950 's. Nearly all of these runs diminished after the cessation of the program, and currently only Taylor Creek has a naturally sustained run. A few fish are seen occasionally in several of the other tributaries but their contribution to the population is in- significant.
The tributaries to Lake Tahoe are not well suited for kokanee spawn- ing due to their small size, low flows, and poor condition. Taylor Creek, however, seems to be the exception. It has been the major kokanee spawning area at Lake Tahoe since 1960. This is probably the result of good equality spawning gravels and suitable flow patterns made possible by a regulatory dam on Fallen Leaf Lake (Figure 1), and perhaps some modification of typical stream temperatures by Fallen Leaf Lake water. It is only about 2 miles long, however.
Spawning runs in Taylor Creek generally start between the middle of October and the first week in November. They may begin much ear- lier as did the 1965 run which began in late September. The fish usu- ally complete spawning within 2 to 3 weeks. Stream temperatures during October and November decline rapidly from the mid-50 's F to the mid-30 's F, remaining at the lower level until April and May when they rise to the mid-50 's again. During these months, kokanee fry migrate downstream into Tahoe. Flows usually are allowed to reach low levels in summer and then are increased early in October to accom- modate spawning kokanee. brown trout (Salmo trutta), and mountain whitefish {Prosopium williamsoni). They remain at this level until spring when uncontrolled snowmelt runoff may create very high flows.
With the exception of the 1952 run of 474 fish (Eichard, 1954), the spawning runs in Taylor Creek before 1960 w'ere relatively small. In 1960 an estimated 1,800 to 2,000 kokanee ascended Taylor Creek to spawn. The Taylor Creek spawning runs have been surveyed each year since then to determine their size and composition (Table 1). In 1964 the spawning runs increased dramatically over that of previous years and continued at a similarly higher level through 1968. The average size of the run from 1965 through 1968 was about 18,000.
KOKANEE IN TAHOE
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32
CALIFORNIA FISH AND GAME
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— _ — ——___ — — rorororo(\jro(\j
po— — NrooJoi^b ^cnuicncn pj^^dootDtooo— — rorow
FORK LENGTH IN INCHES
FIGURE 2. Percentage size composition of spent female ( ) and male (-
salmon in Taylor Creek. Values less than 1.0% are not shown.
■ -) kokanee
KOKAlSTEE IN TAHOE 33
The size of kokanee spawning in Taylor Creek lias varied noticeably through the years since 1960. Mean lengtlis of males and females ranged from a low of 14.3 and 13.1 inches pl, respectively, in 1963 to a high in 1967 of 20.1 and 19.1 (Table 1). From analyses of the length frequencies and age and growth information, much of this vari- ation appears due to changes in age composition of the spawning run. Tlie progression in the length frequencies taken from 1963 through 1966, for example, suggests that a single year class dominated tlie run during the first 3 years, and contributed a small portion in the fourth year (Figure 2). Age and growth data from scales taken during this period indicate that 2-year-olds (2+) spawned in 1963, 3-year-olds (3+) in 1964, 4-year-olds (4+) in 1965, and a few 5-year-olds (5+) in 1966. These fish belonged to the .1961 year class and were the prog- eny of the 1960 Taylor Creek run. Similarly, tlie majority of the fish spawijing in 1966 and 1967 were 2- and 3-year-olds, respectivt'ly, be- longing to the 1964 year class.
There is some indication that tlie size of tlie kokanee population in the lake influences growth rate. For example, the average length of the 2-year-olds returning to spawn in 1963, which were part of the very large 1961 year class, averaged n])pr()ximately 2.5 inches smaller than fish of the same age returning in 1966. Also, the 3-year-olds re- turning in 1964 were smaller than those returning in 1967 or 1968.
Kokanee egg taking operations have been conducted at Taylor Creek in recent years. In 1964 California and Nevada collected eggs. Only those fry raised from eggs taken bv Nevada were returned to the lake. In 1966, 1967, and 1968 approximately 3.8, 2.0, and 2.3 million eggs, respectively, were taken at Taylor Creek by the California Department of Fish and Game. All of the resulting fry have been returned to Tahoe. Kokanee spawners have been transferred from Tay- lor Creek to other Tahoe tributaries : 479 in 1964 and 1,110 in 1966.
Lacustrine Spawning
Beach spawning in Tahoe first was observed in November 1954. At that time, two small schools of approximately 100 to 200 fish each spawned along the west shore between Homewood and Tahoe City. Since then numerous observations have been made of kokanee spawn- ing elsewhere along the shore. Most of the major established beach spawning areas are now known. The largest of these occurs along tlie west shore in the area of McKinney Bay. Some spawning also occurs at Rocky Point between Dollar Cove and Carnelian Bay.
Available data on beach spawning suggest that it contributes sizeably to the kokanee population in Tahoe. Surveys of the McKinney Bay area by boat in 1964 and 1968 produced estimates of approximately 1.600 kokanee spawners from south of Tahoma to Tahoe Pines in 1964, and over 2,000 in 1968, also including the Sunnyside area. Be- cause of the difficulties inherent in observing fish from a moving boat, these estimates are considered low.
Spawning Success
Internal examination of dead spawners commonly disclosed retained eggs. Of 103 dead kokanee examined in Taylor Creek in October 1965, 30% apparently had not spawned at all, 22% had retained about three-
34 CALIFORNIA FISH AND GAME
quarters of their eggs, 22% had retained about one-half of their eggs, 15% had retained about one-quarter of their eggs, and only 11% were completely spawned out or nearly so. During the 19G7 Taylor Creek run we dissected 43 dead kokanee and found that only 28% had spawned, while 26% were partially spent, and 46% had retained all their eggs (Frantz, 1968). The latter group included both green and ripe fish. We observed the same condition in lake spawners also. Ten dead kokanee examined at Lakeside Marina in 1967 had retained their eggs (Frantz, 1968).
In spite of the observed high egg retention, high survival at some or all stages of the kokanee life cycle in Lake Talioe is suggested by the development of strong year classes. For example, the 1961 year class that developed from the 1960 Taylor Creek run of 2,000 fish produced the runs in 1963, 1964, and 1965 'of between 33,000 and 48,000 fish. An estimated survival of 2% is indicated, assuming that all 2 million (1,000 females averaging 2,000 eggs each) of the potential eggs were deposited. Using the egg retention figures observed in 1965, it may have been that only 77,500 eggs were deposited. This would mean the survival of the 1961 year class was about 52% (assuming that this year class contributed about 40,000 spawners to the 1963-65 runs). This figure may not be unreasonable since kokanee spend little time in the creek after emergence, potential predators in the limnetic zone are few, growth is good, and no fishery existed in those years. These fac- tors will be discussed below.
Although no gravel samples have been taken, the spawning gravels of Taylor Creek, compared with otlier tributaries, appear relatively free of sand and silt. The short length of stream, below a natural sedi- ment settling basin (Fallen Leaf Lake), and a relatively undisturbed watershed contribute to this condition. Lakeshore spawning substrates, on the other hand, contain a relatively high proportion of fine ma- terial, and this may account for some low egg survivals found there. Eyed kokanee eggs were planted at nine locations around the Tahoe shoreline in the winter of 1962. At each site we buried two containers with 100 eggs each, plus local substrate material. Three of the sites were in areas where kokanee now spawn regularly in Carnelian and McKinuey bays. The containers were buried on January 16, 1962, and retrieved on March 13, 1962. Survival to the alevin stage occurred only at two of the three areas utilized by spawning kokanee. Percentage survival was about 25 at each of these locations and 0 at the remainder. In January and February of 1969, SCUBA divers sampled six redds located between Tahoma and Sunnyside. Of 97 eggs collected, 43% were alive and most were eyed. Percentage survival in individual redds ranged from 25 to 71.
^to'-
DISTRIBUTION
Kokanee are widely distributed in Lake Tahoe. We found them scat- tered throughout the limnetic zone and occasionally collected them near the bottom. Based on collections and fathometer traces, they appar- ently form schools only in the summer and fall off the southwestern end of the lake. These are mature fish which will later ripen and enter Taylor Creek to spawn.
KOKANEE IN TAHOE 35
Two years of intensive sampling with A'ariable-mesli multifilament gill nets set on the bottom captured only 25 kokanee. All but two were taken in September and October. Twenty-five bottom sets with mono- filament nets in May and June of 1963 caught 57 kokanee. Fifty-four were taken in a single set at a depth of 50 ft. These fish averaged 9.3 inches and ranged from 8.7 to 10.8 inches.
Kokanee were found in greatest abundance in the limnetic zone. Their distribution in the limnetic zone was determined in 1964 with monofilament gill nets. They were the most abundant species in this zone, comprising 143 (37%) of the total 387 fish caught. They ranged in length from 4.6 to 20.9 inches and averaged 14.1 inches. The re- mainder were wild rainbow trout (26%), tui chub (Gilalncolor) (18%), planted rainbow trout (16%), lake trout (Salvelinus namaijcush) (2%), and miscellaneous species (1%). Kokanee and wild rainbow were taken in 48% of all sets, planted rainbow in 38%, and tui chubs in 23%. Tui chubs, lake trout, and the miscellaneous species (brown trout, mountain whitefish, and Lahontan redside {Richardsonius egre- gius) were more abundant in nets set relatively close to shore, whereas kokanee and rainbow were more equally distributed between near shore and off shore catches.
Monofilament gill netting and fathometer readings indicated that mature kokanee are strongly surface oriented during all months of the year except July, August, and September. From November through June, 82% of all mature kokanee taken in the surface nets (22 ft deep) were caught in the top 10 ft of the net. Only one kokanee (from 103 ft) was taken in the deeper sets. During July through September, ko- kanee descend to deeper water. Of 31 kokanee caught in nets set at the surface and in the 50- to 72-ft zone on July 29 and August 25, 1964, only 3 were taken in the surface net and the remainder (90.3%) were scattered from 50 to 72 ft in the deeper net. What appeared to be fish schools were noted on fathometer tapes during August and September of 1964 at depths from about 50 to 120 ft. A mid-water trawl con- firmed that these were actually kokanee. In September 1963, our fathom- eter detected schools of kokanee concentrated at depths from 70 to ]00 ft. In October, the kokanee begin moving toward the surface in preparation for spawning. In October 1963 they were concentrated be- tween 15 and 50 ft. with lesser numbers between 0 and 15 and 50 and 90 ft.
The downward movement of kokanee in the summer montlis appears related to temperature. As temperature increases into the high 50 's and low 60 's dui'ing this period, they descend to the metalimnion where temperatures are 50 to 55 F. Their rise to the surface in October coin- cides with decreasing water temperature at the surface.
Although kokanee were relatively more abundant than other species in the limnetic zone in 1964, their actual density was quite low. The average catch per day (24 net-hours) in the surface sets from January through May was 0.4 fish, increasing to between 0.9 and 3.2 from June through November and then dropping to about 0.1 in December.
The limnetic zone of Lake Tahoe would seem to afford an excellent habitat for kokanee. The only species which could compete with them for food are the rainbow trout and tui chub, and these occur at lower densities. Piscivorous fishes such as the lake and brown trout rarely
36 CALIFORNIA FISH AND GAME
enter this region. Intraspecific competition would probably be the main factor limiting kokanee production.
Young-of-the-Year
The kokanee fry of the 1960 brood-year were sampled in Taylor Creek Avitli tAvo riffle fyke nets (Ilallock, Warner, and Fry, 1952) set overnight in April and May 1961. We modified the nets by adding a box at the cod end to capture fish alive. One was set about 100 yards upstream from the mouth and a second about 100 yards downstream from the State Highway 89 bridge crossing (about ^ mile from the mouth). The nets covered about one-fourth of the stream width. The downstream net captured all but a few of the fry collected. Twenty fry ranging from 0.9 to 1.1 inches were collected on April 28. Water temperature ranged from 45 to 48 F. The 0.!t-inch fry still retained a yolk sac. The kokanee were very secretive. We could not observe them during daylight hours and caught none with seines, dip nets, or electro- shocker. They moved downstream in large numbers only at night. On May 18 an overnight set of the two nets captured 212 fry which averaged about 1.0 inches (0.9 to 1.1 inches). Water temperature ranged from 48 to 54 F. Flow was about 25 cfs compared with about 2 cfs on April 28. TAventy-eight (13%) still had obvious yolk sacs. Ap- parently kokanee fry from Taylor Creek move doAvnstream to Tahoe just before and shortly after absorption of the yolk sac, possibly im- mediately upon emergence.
Our trap also took large numbers of fry and fingerling Lahontan speckled dace (IihinichtJiys oscnhis rohustus) and broAvn trout. Lesser numbers of rainboAV trout, Lahonton rcdside, Tahoe sucker (Catostomus i(ihocnsis) , and tui chub also Avere caught. Large broAvn trout are com- mon in the deep, loAver pools of this stream and probably prey heavily on fry moving through this area. Large rainboAV spaAvners are migrating upstream and actively spaAAaiing at tlie same time kokanee fry are emerging from the gravel and moving downstream. Their effect on sur- vival of kokanee fry is unknown.
Few young-of-the-year kokanee were collected from Lake Tahoe itself. On May 2, 1966, three kokanee fry (0.9 to 1.1 inches) AA^ere collected Avith a small sled trawl (Linn and Frantz, 1965) fished on the bottom in Avater 15 to 20 ft deep off the mouth of Taylor Creek. One 2.8-inch kokanee was collected in a 24-ft otter trawl in Agate Bay in November 1962 at a depth of about 150 ft. This Avas the only kokanee taken by this method, although 248, 10-minute traAvls were made from October 1962 through September 1964. Almost all trawling was done at depths from 100 to 500 ft in Agate Bay and at South Tahoe. Occasional sam- pling in August and September of the shalloAV littoral zone also failed to capture kokanee.
Twenty-seven surface and midwater traAA'ls, each of -^ hr duration, were made at widely scattered locations around the lake from July through November 1964. We traAAded at various depths from the sur- face to about 150 ft in Avater from 24 to 1,560 ft deep. Only four kokanee were collected: 3 fish, 1.3 to 1.6 inches, were taken on July 14 and one 2.5-inch fish on November 3. They were taken Avell offshore and below the surface at depths from 23 to 72 ft.
KOKANEE IN TAHOE
37
AGE AND GROWTH
We dctorminod gTOwtli I'iitcs i'roiii sciilcs tnkiMi from 242 kokanee captured in gill nets from 1!)(J1 tlii'ougli 1!JG5 and in tlie fishery in 1967 and 1968. No scale samples from the 1963 year class were collected.
The body length-anterior scale radius relationsliii) Avas dctci-mincd for 174 gill-netted kokanee (Figure 3). Since the body-scale relationshij) was apparently linear, at least for kokanee from 8 to 17 inches, the back calculations to various ages was based on the direct ])roportion formula of Lee (Lagler, 1956; p. 155). The adjustment for size at scale formation was based on an examination of hatchery-reared kokanee fry rather than extra]iolation of the body-scale regression line. The length at scale formation was 1.5 inches.
|
17 - |
|
|
in |
16 - |
|
UJ |
|
|
X |
|
|
o |
Ib- |
|
2 |
|
|
14- |
|
|
Z |
|
|
X |
13- |
|
1- |
|
|
2 |
12- |
|
bJ |
|
|
_l |
1 1 - |
|
•^ |
|
|
q: |
10- |
|
O |
|
|
h |
|
|
y^ |
|
|
8^ |
o - mean FL and scale radii for 5mm scale radius intervals
L=3.33 + 0.ll R r =0.9639
^^
45
FIGURE 3.
50 55 60 65 70 75 80 85 90 95 100 105 KO ENLARGED SCALE RADIUS IN MILLIMETERS (X52.5)
Body length-scale radius relationship of Lake Tahoe kokanee salmon. Upper graph represents data grouped by scale radius intervals, and lower graph data grouped by fork length intervals. N = 174.
The time of annulus formation could not be determined precisely from our data ; however, April was apparently the critical month. The scales of all fish collected in May or later showed new growth for the calendar year beyond the last annulus, whereas scales from eight fish taken in January, February, and March did not show any new growth. Of 22 fish collected in April, new growth was apparent on the scales of 15, or 68%.
Although sparse, the data suggest that the growth rates in recent years have been generally greater than those in the later 1950 's and early 1960 's (Table 2). This increase occurred in spite of a correspond- ing "increase in the kokanee population as indicated by the sizes of the Taylor Creek runs. However, growth data for several more years are needed to be certain of any definite trend.
38 CALIFORNIA FISH AND GAME
TABLE 2 — Summary of Growth of Five Year Classes of Lake Tahoe Kokanee *
|
Year of life |
||||
|
Year class |
1 |
2 |
3 |
4 |
|
1961 |
4.3 (153) 4.7 (21) 4.4 (13) 4.8 (44) 5.5 (8) |
8.6 (153) 9.1 (21) 10.8 (13) 8.9 (44) 12.2 (8) |
12.4 (83) 15.6 (13) 14.8 (43) |
15.2 |
|
1962 - - - |
(2) |
|||
|
1964 |
18.6 |
|||
|
1965 |
(1) |
|||
|
1966... _ . . |
||||
• Number of fish used in back calculations in parentheses.
LENGTH-WEIGHT RELATIONSHIP
The length-weight rehitionship was calculated for 256 kokanee sal- mon collected from 1961 tlirough 1965. Only fisli collected from the lake itself were used. Plots of observed lengths and weights of males and females indicated no real differences, so they were combined. Fish were also combined without regard to state of maturity, method of collec- tion, and time of collection. They were weighed to the nearest 0.01 lb.
TABLE 3 — Observed and Calculated Weights and Condition Factors of Lake Tahoe Kokanee Salmon
|
Observed |
Observed |
Condition |
Condition |
|||
|
Fork |
No. |
weight, |
weight, |
Calculated |
factor. |
factor, |
|
length* |
fish |
range |
mean |
weight |
range |
mean |
|
4.7 |
1 1 9 |
0.04 0.11 0.25 |
0.05 0.11 0.25 |
41.1 |
||
|
6.2 |
42.0 |
|||||
|
8.2 |
0.22-0.28 |
38.5-52.7 |
44.2 |
|||
|
8.7 |
10 |
0.26-0.33 |
0.30 |
0.30 |
40.9-48.6 |
44.8 |
|
9.2 |
35 |
0.30-0.41 |
0.34 |
0.35 |
39.0-52.7 |
43.8 |
|
9.7 |
20 |
0.33-0.44 |
0.38 |
0.41 |
37.3-45.7 |
43.1 |
|
10.2 |
3 |
0.48-0.53 |
0.50 |
0.47 |
41.1-46.6 |
44.8 |
|
10.7 |
3 |
0.51-0.61 |
0.56 |
0.55 |
42.8-49.8 |
45.9 |
|
11.2 |
3 |
0 . 08-0 . 86 |
0.75 |
0.62 |
51.2-64.6 |
54.3 |
|
11.7 |
5 |
0.70-0.84 |
0.76 |
0.71 |
43.7-52.6 |
48.1 |
|
12.2 |
11 |
0.80-1.00 |
0.88 |
0.80 |
44.1-52.4 |
48.2 |
|
12.7 |
13 |
0.84-1.10 |
0.95 |
0.90 |
40.1-52.5 |
47.3 |
|
13.2 |
21 |
0.94-1.27 |
1.09 |
1.00 |
41.8-52.9 |
47.5 |
|
13.7 |
11 |
1.00-1.39 |
1.20 |
1.11 |
39.8-51.8 |
45.3 |
|
14.2 |
12 |
1.04-1.43 |
1.26 |
1.24 |
37.9-52.1 |
44.4 |
|
14.7 |
18 |
1.20-1.46 |
1.35 |
1.37 |
38.6-46.9 |
42.8 |
|
15.2 |
13 |
1.28-1.67 |
1.49 |
1.51 |
.37.9-47.6 |
42.8 |
|
15.7 |
16 |
1.53-1.83 |
1.66 |
1.66 |
39.8-46.9 |
42.9 |
|
16.2 |
21 |
1.64-1.93 |
1.74 |
1.82 |
39.0-44.6 |
41.4 |
|
16.7 |
9 |
1.71-2.36 |
1.90 |
1.98 |
35.9-48.9 |
40.2 |
|
17.2 |
8 |
1.77-2.29 |
1.99 |
2.16 |
36.0-43.5 |
39.6 |
|
17.7 |
7 |
1.86-2.50 |
2.19 |
2.35 |
33.0-43.6 |
39.5 |
|
18.2 |
1 1 2 |
2.16 2.80 2.54 |
2.55 2.76 2.98 |
37.0 |
||
|
18.7 |
41.5 |
|||||
|
19.2 |
2.50-2.58 |
36.4-37.0 |
36.7 |
|||
|
19.7 |
1 1 |
3.47 3.23 |
3.21 3.71 |
46.1 |
||
|
20.7 |
35.4 |
|||||
• Midpomt of 0.5-inch intervals.
KOKANEE IN TAHOE
o = mean FL and scale radii for
1/2" FL intervals R = 6.80 + 5.97 L
39
1 1-
3 M 15 16 17
10 11 12 FORK LENGTH IN INCHES
5.0 4.5-
4.0
log W= -3 26090+2.91063 log L n= 256 r = 0.9928
1 1 1 1 1 r-
-1 1 1
9 10 II 12 13 14 15 16 17 18 19 20 21 22
FORK LENGTH IN INCHES
FIGURE 4. Length-weight relationship of Lake Tahoe kokanee salmon. Line fitted by the least squares method.
40
CATJFORNIA FISH AND GAME
'llw. Icii;4lli \\ci;^hl i-c|;i| idiisli ip is described b\' the e(|uation log W = — :{.2(i()!)n -I '2.'.n()C>'A log h, or W = 0.000548' L2-9io«-'5 (Figure 4), wliiiT W is Wright 1(1 ilic nearest 0.01 lb. and L is fl to the nearest 0.1 iiiclii'S. ( )|)Si'i-\'e(l weights averjiued I'oi- O.H-ineb length intervals cor- j-espoiided eh)Sely with culcLdaled weiglds (Table 3j.
/ W X 10"^ \ . . . 'I Im- (•(iiidirKiii t.'iclois I (J = YJi ^] of individual fish were grouped
by ()..") iiicli Icngih inlcixals and a-veraged (Table ;>). Condition factors Icndcd ((> incic.'isc wiMi size until lish reached about 13 inches and then dccUnetl. VirLually all of the (ish over 13 inches were mature or ripe.
FOOD HABITS
'\Vi> cxnmined llie sb)iii;i('li contents ol: 227 kokanee salmon ranging in h'nglh rroni "2S) lo b^.H inclies. Sixty-seven (29.5%) were empty and the i-einiiining KiO eontnined primarily zooplankton (Table 4). Clado- cefans, primarily Ihiphn'm pnlcx, were found in 00 to 100% of the stomachs. A single spccirs nf cop(^]K)d, Epischura 7icvadcnsis, was next in iiiipoi-t.ini'e, occuiTiiig in ;ibout 15''() of the stomachs. Midge larvae and pn|);ie .ind surface instu'ts occurrcnl infrequently.
TALUL 4 Prrcontage Frequency of Occurrence of Food in Stomachs of Lake Tahoe Kokcinec Salmon by Four Size Groups, 1963 and 1964 Combined
|
Size groups (inches) |
|||||
|
Itom |
Utuh>r 5.0 |
5.0-9.9 |
10.0-14.9 |
15.0-19.9 |
All fish 2.5-18.9 |
|
C^hvdooont .................. |
100.0 f.0.0 r>o.o ,■-0.0 |
93 . 2 15.9 i;?.6 o ■» |
S9.0 26.0 20.5 1.4 4.1 |
100.0 14.6 14.6 2.4 |
93 1 |
|
20 6 |
|||||
|
( 'l.i.l.H'oiiv iinii oopopodft _ ^U^lKO hvrvjvo ivtid pupao Smf.'H'o iiisoot.t Awphipodii |
17.5 1.9 8.5 0.6 |
||||
|
No. of stomaohs |
2 |
44 |
73 |
41 |
160 |
KOKANEE FISHERY
ICokanee sulmou rarely entered the creels of Lake Tahoe anglers be- fore 1JH>7 (Cordone and Frantz. 10(Uu?V In an intensive creel census by boat antl at the Cave Kock rublic Boat Ijauding from September 1960 through December 1903 we sampled only live kokanee (Cordone and Frantz, 1%(H>). These were all ripe fish taken oft" Taylor Creek. They reumined scarce in the catch through 19(>t».
In INlay and June 19t)7. we received reports that kokanee were being caught in increasing numbers. In August 19(57 au intensive kokanee tlshcry developed for the first time oft' the mouth of Taylor Creek (Figure r>\ Most of the tish were caught approximately SO to 100 ft below (lie surface. A few kokanee also were taken in "Rubicon and Meeks bays at similar depths. This tishery lasted through September and marked the first time that anglers actually tished specitlcally for ko- kanee in Lake Tahoe.
KOKANEE IN TAHOE
41
In 1968 the first intensive fishing for kokanee occurred in the Meeks Bay-Sngar Pine Point area during June. This fisliery remained rela- tively small throughout the summer, peaking in June and in early September. A much larger fishery again developed, in the Taylor Creek-Camp Richardson area late in June, with the greatest activity occurring during late July and early August. Both fisheries disap- peared about the end of Sp])t('mb(^r. A few kokanee v(m-p hiiided off
FIGURE 5. Successful kokanee anglers ofF Taylor Creek, August 22, 1967. Photograph by R. D. Beland.
Cave Rock in May and June (Frantz, 1969), but tliis fisliery was in- significant in relation to the other two. Also, a fishery of unknown magnitude occurred in October and November on kokanee spawning along the west shore between Sugar Pine Point and Sumiyside. In 1968, as in previous years, a downward movement of kokanee was observed as mid-summer approached. In May and June all of the kokanee were caught near the surface, but in July most were caught at depths of 50 to 75 feet ; and in August at about 100 ft.
"While at the surface, kokanee were caught with conventional topline gear, but later in the summer fishermen needed metal line to fish at the depths at which the kokanee occurred. Under both conditions the fishery was prosecuted entirely by trolling from boats.
From late June through September 1968, we conducted 22 creel sur- veys and/or use counts in the J\Ieeks Bay and Taylor Ci-eek areas. We estimated that 1,024 kokanee were caught from mid- July through Sep- tember (95% C.I. = ±1,386). This estimate is believed conservative as a disproportionately large number of days with bad weather were sampled. The small fishery on the Nevada side, and the Meeks Bay- Sugar Pine Point fishery in early June, were not sampled.
Although no creel censuses were conducted in 1967, we believe the fishing effort in 1968 was 5 to 10 times greater than in 1967, probably due to the late date (August) at which the fishing began in 1967. Suc- cess rates did not appear significantly different between the two years.
42 CALIFORNIA FISH AND GAME
Fish size, however, was different between the two years. Twenty-nine of the kokanee caught in Angust 1967 averaged 18.5 inches. Fifteen of these were weighed and averaged 3.0 lb. In August 1968, 37 kokanee averaged 16.7 inches and 2.1 lb. The 1968 sample contained a slightly larger number of 2-year-old fish than the previous year ; however, the difference in age composition was not great enough to account for dif- ference in the average sizes of the fish.
DISCUSSION
The major summer fisheries developed in 1967 and 1968 when the kokanee were concentrated in schools, largely in the south and western parts of the lake, in preparation for spawning. Here their densities permitted successful angling by those trolling deep with heavy terminal tackle. As our sampling data indicate, they are widely scattered and nonschooling at other times of the year. The basic question now is whether or not this restricted fishery can be enlarged to include a greater portion of Tahoe's large limnetic zone and to include more of the colder months of the year when the surface orientation of kokanee would allow their capture by more conventional, light tackle. This would require, we believe, a substantial increase in the kokanee popu- lation.
Unfortunatel}^, the sterility of Lake Tahoe (Goldman and Carter, 1965) miglit possibly limit the development of a kokanee fishery sub- stantially larger than the existing one. Attempts to significantly in- crease their numbers may intensify intraspecific competition for a lim- ited zooplankton supply (Lake Tahoe Fisheries Study, unpubl. data) and result in kokanee too small to be acceptable to the angler. How- ever, there are some compensating factors. Although the density of the zooplankton is low, they occur as deep as 300- to 500-ft (Lake Tahoe Fisheries Study, unpubl. data). In addition, the recent establishment of My sis r dicta in Lake Tahoe (Frantz, 1969) may insert a previously unavailable energy source into the kokanee food chain.
It is possible that natural reproduction alone would increase the kC'kanee population to the point where either the fishery would expand in time and space, or where a substantial reduction in the average size of kokanee would preclude such an expansion. Taylor Creek is the only tributary that appears suitable for kokanee reproduction, but it has a limited carrying capacity (probably between 3,000 and 6,000 spawn- ers). Lakeshore spawning is increasing, but again there may be definite limits imposed by available substrate type. Much of the littoral zone substrate is composed of sand and boulders. McKinney Bay may have the only suitable spawning grounds, although their precise extent and quality remain unknown.
RECOMMENDATIONS
Kokanee salmon are now thriving in Lake Tahoe and if managed properly should provide an important and large sport fishery. Hope- fully, their numbers can increase and become abundant enough to be caught by topline anglers, a type of angler whose success has been very low (Cordone and Frantz, 1966a). Surplus eggs, sometimes in consider- able numbers, can be collected from the Taylor Creek run. We recom-
KOKANEE IN TAHOE 43
mend that the egg take for Tahoe be limited to about 3 million. Sub- sequent growth, mortality, and contribution to the fishery of these fish and fish resulting from natural reproduction should be monitored care- fully. Any necessary adjustments should be made in the number stocked to provide the higliest possible sustained yield without depressing tlie growtli rate. In this regard, the slioreline spawning areas sliould be completely surveyed and the size of the beach spawning population (s), and its (tlieir) contribution to the fisliery should be determined. Intra- gravel survival in botli Taylor Creek and tlie beach spawning areas should be measured. The size composition of the si)awning gravels and the quality of the intragravel water should be measured also.
ACKNOWLEDGMENTS
Sterling P. Davis and AV. Donald Weidlein <issisted in various phases of the field activities. Mr. Wes Lane, a local fishing guide, did much to stimulate interest in the kokanee fishery and has generously assisted State biologists in collecting fisli and information on the fishery. Law- rence L. Chamberlain critically reviewed the manuscript.
REFERENCES
Cordone, Ahno J., and Ted C. Frantz. 1966a. The Lake Tahoe sport fishery. Calif.
Fish and Oame 52(4) :240-274. . ]966/<. The Lake Tahoe sport fishery — supplementary report. Calif. Dept.
Fish and Game, Inland Fish. Admin. Kept. (66-14) :94 p. (Mimeo. ) Corlett, Ray, and Norman Wood. 1958. Fisheries management report, July 1, 1954
to June 30, 1958, Tahoe and Topaz lakes. Nevada Fish and Game Comm., Dingell-
Johnson Job Completion Kept., Project No. FAF-l-R, 45 p. (Mimeo.) Frantz, Ted C. 1967. Job completion report, research project — January 1, 1966
through December 31, 1966. Nevada Fish and Game Comm. Rept. 41 p. (Mimeo.) . 1968. Job completion report, research project — January 1, 1967 through
December 31, 1967. Nevada Fish and Game Comm. Rept., 49 p. (Mimeo.)
1969. Job completion report, research project — January 1, 196S through
December 31, 1968. Nevada Fish and Game Comm. Rept., 72 p. (Mimeo.)
Fraser, J. C, and A. F. Pollitt. 1951. The introduction of kokanee red salmon (OucorJu/iicJiKs verka hennerhji) into Lake Tahoe, California and Nevada. Calif. Fish and Game 37(2) :125-127.
Goldman, Charles R., and Ralf C. Carter. 1965. An investigation by rapid carbon- 14 bioassay of factors affecting the cultural eutrophication of Lake Tahoe, Cali- fornia-Nevada. J. Water Pollution Control Federation 37(7) :1044-1059.
Hallock, Richard J., George H. Warner, and Donald II. Fry, Jr. 1952. California's part in a three-state salmon fingerling marking program. Calif. Fish and Game 38(3) :301-332.
Lagler, Karl F. 1956. Freshwater fishery biology. Wm. C. Brown Company, Dubuque, Iowa, xii -|- 421 p.
Linn, Jack D., and Ted C. Frantz. 1965. Introduction of the opposum shrimp (Mysis relicta Loven) into California and Nevada. Calif. Fish and Game 51(1) : 48-51.
Richard, James B. 1954. Obseravtions of kokanee salmon spawning in the tribu- taries of Lake Tahoe, October 1952 to February 1953. Calif. Dept. Fish and Game, Inland Fish. Admin. Rept., (54-3) : 14 p. (Mimeo.)
Seeley, Charles M., and George W. McCammon. 1963. A review of kokanee in Cali- fornia. Calif. Dept. Fish and Game, Inland Fish. Admin. Rept. (63-11) :35 p. (Mimeo.)
Weidlein, W. Donald, Ahno J. Cordone, and Ted C. Frantz. 1965. Trout catch and angler use at Lake Tahoe in 1962. Calif. Fish and Game 51(3) :187-201.
Calif. Fish and Game, 57(1) : 44-57. 1971.
THE CARRYING CAPACITY FOR JUVENILE SALMONIDS IN SOME NORTHERN CALIFORNIA STREAMS^
JAMES W. BURNS
Inland Fijiieries Branch
California Department of Fish and Gams
Standing crops of juvenile coho (silver) sa!mon [Oncorhynchus kisutch), steelhead rainbow trout (Salmo gaitdneri), and coest cutthroat trout (Salmo clarki) were examined in seven coastal streams to define the natural carrying capacity of these streams, and to develop methods of population comparison and prediction which could be used to determine the effects of road construction and logging on salmon end trout pro- duction.
Biomass per unit of surface area was the best method of expressing carrying capacity, because bicmass was better correlated with stream surface area than with other parameters tested. Volume of sfreambed sediments, total dissolved solids, eilkaiinity, and total phosphate in six streams were not satisfactory predictors of carrying capacity. Only living- space variables correlated significantly with biomass. Not all streams reached carrying capacity in the summer and salmonid biomass was highly variable. Even with 3 years of preloggircg study, it would be dif- fic'jlt to attribute a change in carrying capacity under 50% to any- thing but natural variation.
INTRODUCTION
Standing crops of juvenile colio (silver) salmon, steelhead rainbow trout, and coast cutthroat trout were examined in seven coastal streams. The goals of this investigation were to define the natural salmonid car- rying capacity of these streams, and to develop methods of population comparison and prediction which could be used to determine the effects of road construction and logging on salmon and trout production.
The most direct way to assess the impact of logging on anadromous salmonids is to compare numbers of juvenile outmigrants before and after logging. Tliis method is generally impractical in California, be- cause characteristic extreme seasonal fluctuations in streamflow make construction and maintenance costs of weirs and traps prohibitive (Burns, 1966). As an alternative, the juvenile carrying capacity of streams before and after logging was compared. Valid comparisons re- quired a reliable, standardized sampling method. I reasoned that dur- ing minimum streamflow in the summer, juvenile salmonids would be at tlieir greatest weight density (biomass per unit of living space), a density that would remain fairlv constant from vear to vear and would be regulated by available living space. Any adverse effects of logging should decrease the stream's salmonid carrying capacity and be indi- cated by a decrease in the weight density of salmonids during summer. However, before this method was used, I had to test two hypotheses : (i) salmonid carrying capacity' in coastal streams is attained during the summer, and (ii) the biomass of salmonids remains relatively con-
1 Accepted for publication Augvist 1970. This study was performed as part of Dingell- Johnson Project California F-IO-R. "Salmonid Stream Study", supported by Fed- eral Aid to Fish Restoration Funds.
(44)
CARRYING CAPACITY FOR SALMONIDS 45
stant from one summer to tlie next. The relationship of minimum streamflow and water quality to salmonid density was determined, since these variables also affect salmonid abundance and therefore carrying capacity.
Carrying capacity is defined as the greatest weight of fishes that a stream can naturally support during the period of least available habitat. It should be considered a mean value, around which popula- tions fluctuate (Moyle, 1949). Spawniug salmonids in coastal sti-cams are thought to produce enough progeny to fill streams to carrying ca- pacity. This assumption is supported by observations of high rates of emigration and mortality of fiy shortly after emergence from the spawning bed (Shapovalov and Taft, 1954). Since a section of sti-cain can accommodate only a limited number of territories, surplus fish are displaced (Allen, 1969). Displacement distributes fish to parts of the system remote from the spawning grounds, thus insuring that most of the area and productivity of the system is utilized. Even in the absence of excess fry production, receding summer streamflow limits habitat and practically insures that streams are filled to carrying capacity. Survival and growth of fishes in these streams are density dependent, or have densitj^ dependent components (McFaddeu, 19G9). The stream's carrying capacity limits the number and weight of salmonid smolts ul- timately produced,
METHODS
Sections of seven streams were studied during the summers of 1966 through 1969. The streams are located in the coastal redwood {Sequoia sempervirevs) belt between Crescent City and Fort Bragg, California. Three northern streams. Bummer Lake Creek, Godwood Creek, and South Fork Yager Creek, were in virgin, old growth forests (never logged) and four southern streams. North Fork James Creek, Little North Fork Noyo River, North Fork Caspar Creek and South Fork Caspar Creek, were in second-growth forests (logged about 100 years ago). Four of these streams (Bummer Lake Creek, South Fork Yager Creek, Little North Fork Noyo River, and South Fork Caspar Creek) were logged by 1968 (Burns, 1970) ; however, this report considers only prelogging conditions (Table 1). Postloggiiig conditions are the sub- ject of a future report (James W. Burns, MS). Only one stream had been recently logged (North Fork James Creek) and logging was com- pleted there in 1962. This stream was surveyed once. Unlogged streams (Godwood Creek, an upstream section of South Fork Yager Creek, and North Fork Caspar Creek) were studied for 3 years. More detailed descriptions of the streams are given by Burns (1970) and Fredric R. Kopperdahl, James W. Burns and Gary E. Smith (MS). Fishing pres- sure for juvenile salmonids on these streams was negligible.
Stream dimensions were determined by standard sampling procedures (Welch, 1948 and Lagler. 1956) using permanent transect stations. The number of transect stations ranged from 30 in stream sections less than 1 km long, to 101 in longer sections. Fish were captured Avith a battery-powered DC back-pack shocker, and populations estimated by the Petersen single census mark and recovery method (Davis, 1964) or by the removal method (Seber and LeCren, 1967). Age classes of trout were separated by length frequency methods. Fish less than 1 year
46
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Caerying capacity for salmonids 47
old were designated as 'Age +, and yearling and older fish Avere lumped as a single group, Age 1+. Coho salmon juveniles Avere also combined as a single group, Age -f , since few spend more than 1 year in stream residence. Biomass was determined by multiplying mean individual weight by the population estimate for each species. Population estimates were presented in two forms: (i) absolute, referring to the estimated population of fish in the stream section (e.g., kilograms or numbers), and (ii) relative, referring to the population of fisli per unit of living space (e.g., kilograms per hectare or number per square meter).
RESULTS AND DISCUSSION Methods of Expressing Carrying Capacity Carrying capacity is expressed either as the number of fish in the population, or more commonly, as the total weight of the population (biomass). Living space is also considered when measuring carrying capacity, since changes in biomass may be due to changes in available habitat. Living space parameters include stream surface area, volume, length, and flow. To determine which variables best expressed relative biomass, correlation coefficients for fish biomass and each of these living space parameters were calculated. Since these seven streams varied con- siderably in the length of stream surveyed and in their biomass (Table 1), I thought that some unmeasured factors could influence the correla- tions tested. Therefore, correlation coefficients for both the seven streams and a single stream were calculated (Table 2), thereby elim- inating some of the unmeasured factors. The best correlation for the seven streams was absolute biomass with surface area (Table 3). For North Fork Caspar Creek, biomass per surface area was also superior, with strcamflow also having a significant correlation with absolute bio- mass. These results pointed to kilograms per hectare or pounds per acre as superior to other expressions of biomass. Coho production in Oregon streams also correlated more strongly with available stream area than with other stream parameters (Mason and Chapman, 1965).
Changes in Biomass
Salmonid biomass in the unlogged streams changed considerably during the study. North Fork Caspar Creek's mean biomass of sal- monicls was 5.56' kg (Table 2). The 95% confidence limits were ±27.5% of the mean. The confidence limits of the mean kilogram per hectare were ±16.9% (y = 15.54). The mean in South Fork Yager Creek was 8.67 kg (Table 4), with 95% confidence limits of ±13.0%. The confidence limits of the mean kilograms per hectare were ±47.8% (y = 34.59). Changes in biomass in Godwood Creek were greater than in the other two streams (Table 5). The mean biomass of salmonids was 4.06 kg, with 95% confidence limits of ±75.2%. The confidence interval of the mean kilograms per hectare were ±81.2% (y = 12.54).
Weakness in the Biomass/Surface Area Expression
Density expressions of biomass (kg/ha) did not reflect well the real changes in total fish populations. They commonly increased in late summer when the total biomass actually decreased. Absolute biomass in North Fork Caspar Creek, for example, usually decreased as the stream's surface area decreased (Table 2). Relative biomass increased,
48
CALIFORNIA FISH AND GAME
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CAKRYING CAPACITY FOR SALMONIDS 49
TABLE 3 — Correlation CoefFicients for Living Space Parameters and Biomass
|
Variables tested |
Correlation coefficient |
Statistically significant at 5% level |
|
Seven northern California streams Stream surface area (ha) vs. salmonid biomass (kg) |
0.898 0.89.5 0.837 0.844 0.003 0.020 |
yes yes yes yes no |
|
Stream volume (m*^) vs. salmonid biomass (kg) _ - |
||
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Stream volume (ra') vs. teleost biomass (kg) |
||
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Streamfiow (m^/sec) vs. salmonid biomass (kg/km) . |
||
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Streamflow (m^/sec) vs. teleost biomass (kg /km) _ __ |
no |
|
|
North Fork Caspar Creek, Mendocino County Wetted stream lengtli (m) vs. salinoiiii.! biomass (kg) |
0.656 0.868 0 . 790 0.836 0.622 |
no |
|
Stream surface area (ha) vs. salmonid biomass (kg) |
yes |
|
|
Stream volume (m') vs. salmonid biomass (kg) |
no |
|
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Streamflow (m^/sec) vs. salmonid biomass (kg) . - _- |
yes |
|
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Streamflow (mVsec) vs. salmonid biomass (kg) . |
no |
|
however, because the fish were forced into a smaller area. Steelhead may have adjusted to greater population densities by reducing terri- tory size. Accommodation by steelhead has been reported from British Columbia streams (Ilartman, 1965). Another possible explanation for the increase is that the stream was not at carrying capacity in June because of low fry production resulting from small spawning escape- ments. Decreasing living space may have brought these fish to densities at or near the carrying capacity in October. To describe accurately changes in fish populations and carrying capacity it is best to present the absolute along with the relative values.
Carrying Capacity Studies
Salmonid biomass in Godwood Creek Mas exceptionally low, ranging from 1G.68 kg/lia in 1967 to 8.48 in 1969 (Table 5). Prairie Creek, to which Godwood Creek is a tributary, had a salmonid biomass of 21.95 kg/ha in 1969, suggesting that Godwood Creek probably wasn't at carrying capacity. Low population densities in Godwood Creek in 1968 and 1969 apparently reduced citmpetition, for fish attained greater average lengths than in 1967, when densities were greater (Tabic 6). Increased growth, however, apparently did not compensate for lowered density and carrying capacity was not reached in 1968 and 19()9. To test if Godwood Creek was at cari-ying capacity in 1969, I transplanted the salmonids captured in Prairie Creek in July into a 366-m section of Godwood Creek in sufficient numbers to increase the biomass to 27.98 kg/ha. Two months later the same section of Godwood Creek was con- sused to determine if the biomass had remained above the July 3 969 value of 7.36 kg/ha. It was 18.08 kg/ha at the second census. This experiment demonstrated that the stream had been below carrying ca- pacity before transplanting the Prairie Creek fish. There were no ob- vious reasons for the low number of salmonids in 1968 and 1969, except that young-of-the-year coho were exceptionally scarce then, suggesting that the spawning run had not seeded the stream to carrying capacity. There were no significant changes in spawning bed sediments (Burns, 1970) to explain reduced survival of incubating embryos and fry.
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CARRYING CAPACITY FOR SALMONIDS
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52 CALIFORNIA FISH AND GAME
Predation by oligoeliaete worms may have contributed to low survival, since Briggs (1953) found tliat the average mortality in Godwood Creek Avas about 56'/c and sometimes as high as 100% in salmon redds ijifested with oligochaetes. Oligochaetes were abundant in the benthos samples taken in July 1967 ; however, benthos was not examined in 1968 and 1969, when colio populations were lowest. Briggs also indi- cated that the spawning runs in Godwood Creek were usually small, with only about seven redds resulting from coho spawning in 3.2 km of stream. This experiment shows that artificially seeding streams with fry could bring them up to carrying capacity.
Yearling-and-older steelhead in South Fork Yager Creek were simi- lar in population density and average length in all years (Table 7). Age + steelhead, on the other hand, attained the greatest average length in 1968, when population density for this age group was great- est. In 1967 and 1969, densities were less and mean lengths were shorter, indicating that either carrying capacity changed or that the stream was not at carrying capacity in these 2 years.
Except for the seasonal increase that usually accompanies a decrease in surface area, the density of salmonids in North Fork Caspar Creek was similar in 1967 and 1968 (Table 8). In 1969, however, the density increased 22% over the 1967-68 average. Coho were scarce in 1967-68 and then became abundant in 1969. Apparently interspecific competi- tion was less influential than intraspecific competition in determining this stream's carrying capacity. These observations support the con- tentions of Nilsson (1956), Hartman (1965), and Fraser (1969) that two or more species use the habitat more efficiently than does one species alone. The similarity of biomasses in 1967 and 1968 suggests that the stream was at or near carrying capacity for the existing species combination. The change in species ratio apparently increased the carrying capacity in 1969. Territorially in stream salmonids is food-linked ; when food is abundant, aggression decreases and territories become smaller (Chapman, 1966). A higher population density could therefore result from an increased food supply. An increase in food did not occur in North Fork Caspar Creek, since the biomass of benthos was similar in all years of study (James W. Burns and Gary E. Smith, MS).
Young-of-the-year salmonids in North Fork Caspar Creek in June were largest when stock densities were lowest, suggesting a density dependent relationship (Table 8). Growth increments for salmonids in North Fork Caspar Creek from June to October, however, did not show any trend and therefore did not support a hypothesis of density dependent growth. Over-summer mortality did not indicate density de- pendence either. Decreasing availability of living space caused the greatest mortality, with total mortality highest in the summer of low- est streamflow. Mortality of Age -f- steelhead from June to October averaged 73% (range 71 to 80%). Mortality of Age I or older steel- head averaged 44% (range 6 to 66%). For Age -f coho, average mor- tality was 58% (range 46 to 61%).
North Fork Caspar Creek was relatively unproductive. Besides sup- porting a low biomass per surface area of salmonids, it had low sum- mer production (Table 9). Production of salmonids from June to October ranged from 0.29 to 0.38 g/mVmonth. This was considerably
CARRYING CAPACITY FOR SALMONIDS
53
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54
CALIFORNIA FISH AND GAME
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CARRYING CAPACITY FOR SALMONIDS
55
lower than tlie culio production of 0.56 g/m-/month reported for llie same season for Oregon's salmonid streams (Chapman, 1965).
Relationships of Physical-Chemical Factors to Carrying Capacities
The relationship of water eliemistry and morphoedaphic character- istics of lakes to fish production and standing crop have been investi- gated by Moyle (1946, 1956), Hayes and Anthony (1964), and Kyder (1965) ; however, little is known of the relationships of tliese factors to the carrying capacity of streams. A positive correlation between brown trout (S. friifta) biomass and conductivity in six Pennsylvania streams was reported by McFadden and Cooper (1962) ; however, tliis relationship was not statistically significant. LeCren (1969) found no apparent correlation betAveen Ijrown trout and Atlantic salmon (S. solar) production and calcium content of English streams. I failed to find any significant correlations between relative biomass and either total dissolved solids, total phosphate, or total alkalinity (Table 10). In addition, biomass was not significantly correlated with the volume of fine sediments in tlie streambed.
CONCLUSIONS
Biomass per unit of surface area was an acceptable method of ex- pressing carrj^ing capacity in small coastal streams. This expression did not always reflect trends in the absolute biomass, however. If lower surface area accompanied lower biomass, the kilograms per hectare of salmonids could remain the same or even increase, leading to erroneous conclusions about cJianges in fish populations. For this reason, it is nec- essary to include an absolute value when making such comparisons. The absolute value could be the number of fish in each age class for each species. The two values compliment each other; one considers changes in living space, while both reflect changes in fish abundance.
The hypotheses that streams reach carrying capacity in the summer, and that biomass per unit of living space is constant from 1 year to the next, must be rejected. Because of natural variation, comparing bio- mass from 1 summer month or year to the next was adequate for indi- cating gross changes only. In Godwood Creek the maximum change in relative biomass from the first to the tliird year was 49% and in North Fork Caspar Creek, the change from June to October of the same year
TABLE 1C — SaJmonid Biomasses and Some Physicctt and Chemical Parameters of Six Streams
|
Percentage |
|||||
|
mean volume |
|||||
|
of sediments |
|||||
|
Salmonid |
Total |
Total |
Total |
smaller than |
|
|
biomass, |
dissolved |
alkalinity, |
phospliatc, |
0.8 mm |
|
|
Stream |
kg/ha |
solids, ppm* |
ppm* |
ppm* |
diametert |
|
Bummer Lake Cr. |
41.13 16.67 43.90 |
57 80 109 |
26 30 56 |
0.30 0.45 0.43 |
10.2 |
|
Godwood Or |
17.3 |
||||
|
S. Fk. Yager Cr -. --- |
16.4 |
||||
|
Little N. Fk. Noyo R... - |
24.35 |
112 |
51 |
0.36 |
20.0 |
|
N. Fk. Caspar Cr. ... |
12.64 |
124 |
57 |
0.34 |
18.4 |
|
S. Fk. Caspar Cr. |
37.95 |
149 |
68 |
0.43 |
20.6 |
* Value from Fredric R. Kopperdahl, James W. Burns, and Gary E. Smith (MS), t Values from Burns (1970).
56 CALIFORNIA FISH AND GAME
was as luucli as 25%. The 95% confidence limits of the mean kilograms per hectare of salmonids in South Fork Yager Creek were ±48% of the mean. These results demonstrate that even with 3 years of prelog- ging measurements it would be ditficult to attribute a change in carry- ing capacity to anytliing but natural variation unless the change ex- ceeded about 50%. These extremes in natural variation are probably due to variable spawning escapement and, in the case of juvenile steel- head, to variable time spent in fresh water.
It does not appear that physical and chemical factors will prove to be useful factors for predicting carrying capacity, as only living space variables correlated significantly with biomass.
REFERENCES
Allen, K. Radway. 1969. Limitations on production in salmouid populations in
streams, p. 3-18. In T. G. Northcote (ed. ) Salmon and Trout in Streams. Univ.
British Columbia, Vancouver, Canada. Briggs. John C. 1953. The behavior and reproduction of salmonid fishes in a
small coastal stream. Calif. Dept. Fish and Game, Fish. Bull. Xo. 94, 62 p. Burns, James W. 1966. Fish screens, p. 156-161. In Alex Calhoun (ed.) Inland
Fisheries Management. Calif. Dept. Fish and Game. . 1970. Spawning bed sedimentation studies in northern California streams.
Calif. Fish and Game 06(4) :253-270. Chapman, D. W. 1962. Aggressive behavior in juvenile coho salmon as a cause of
emigration. J. Fish. Res. Bd. Can. 19(6) :1047-10S0. . 1965. Net production of juvenile coho salmon in three Oregon streams.
Trans. Amer. Fish. Soc. 94(1) :40-52.
1966. Food and space as regulators of salmonid populations in streams.
Amer. Naturalist 100 :345-357. . 1968. Production, p :182-196. In ^\. E. Bicker (ed.) Methods for assess- ment of fish production in fresh waters. IBP Handbook No. 3, Blackwell Sci.
Publications, Oxford. Davis, W. S. 1964. Graphic representation of confidence intervals for Petersen
population estimates. Trans. Amer. Fish. Soc. 93(3) :227-232. Fraser, F. J. 1969. Population density effects on survival and growth of juvenile
coho salmon and steelhead trout in experimental stream-channels, p. 253-266. In
T. G. Northcote (ed.) Salmon and Trout in Streams. Univ. British Columbia,
Vancouver, Canada. Hartman, G. F. 1965. The role of behavior in the ecology and interaction of
underyearling coho salmon and steelhead trout. J. Fish. Res. Bd. Can. 22(4) :
1035-1081. Hayes, F. R., and E. H. Anthony. 1964. Productive capacity of north American
lakes as related to the quantity and trophic level of fish, the lake dimensions and
the water chemistry. Trans. Amer. Fish. Soc. 93(1) :53-57. Lagler, Karl F. 1956. Freshwater fishery biology. 2nd ed. Dubuque, Iowa, Wm.
C. Brown Co., 260 p. LeCren, E. D. 1969. Estimates of fish populations and production in small streams
in England, p. 269-280. In T. G. Northcote (ed.) Salmon and Trout in Streams.
Univ. British Columbia, Vancouver, Canada. Mason, J. C, and D. W. Chapman. 1965. Significance of early emergence, environ- mental rearing capacity, and behavioral ecology of juvenile coho salmon in stream
channels. J. Fish. Res. Bd. Can. 22(1) :173-190. McFadden, James T. 1969. Dynamics and regulation of salmonid populations in
streams, p. 313-329. In T. G. Northcote (ed.) Salmon and Trout in Streams.
Univ. British Columbia, Vancouver, Canada. McFadden, James T., and Edwin L. Cooper. 1962. An ecological comparison of
six populations of brown trout. Trans. Amer. Fish. Soc, 91(1) :53-62. Moyle, John B. 1946. Some indices of lake productivity. Trans. Amer. Fish. Soc.
76 : 322-334. . 1949. Fish-population concepts and management of Minnesota lakes for
sport fishing. Trans. 14th N. Amer. Wildl. Conf. :283-294.
CARRTIXG CAPACITY FOR SALMOXIDS 57
. 1956. Relationships between the chemistry of ^Minnesota surface waters
and wildlife management. J. Wildl. Manage. 20(3) :303-320.
Xilsson, X. A. 1956. Interaction between trout and char in Scandinavia. Trans. Amer. Fish. Soc. 92(3) :2T6-2S5.
Ryder, R. A. 1965. A method of estimating the potential fish production of north- temperate lakes. Trans. Amer. Fish. Soc. 94(3) :214-218.
Seber, G. A. F., and E. D. LeCren. 1967. Estimating population parameters from catches large relative to the population. J. Anim. Ecol. 36(3) :631-643.
Shapovalov, Leo, and Alan C. Taft. 1954. The life histories of the steelhead rain- bow trout and silver salmon. Calif. Dept. Fish and Game, Fish Bull. X*o. 98, 375 p.
Welch, Paul S. 1948. Limnological methods. Philadelphia, the Blakiston Co., 381 p.
Calif. Fish and Game, 57(1) : 58-68. 1971.
SOME INFLUENCES OF TEMPERATURE ON THE
DEVELOPMENT OF THE GRUNION
LEURESTHES TENUIS (AYRES)^
KARL F. EHRLICH ^ and DAVID A. FARRIS
Biology Department
San Diego State College
San Diego, California 92115
The effect of temperature upon the deveSopment of the grunion, was studied throughout the spawning season of the fish. The viable range for hatching was determined to be 14.0—28.5 C. Developmental tempera- ture coefRcients were calculated for hatching, lens formation, eye pig- mentation, heart beating, and embryonic axis formation. These were equal for ell of the characteristics, but two distinct ones were found within the viable range, — 0.0613 from 14.0—23.0 C and — 0.0113 from 23.0—28.5 C. A temperature coefficient for maintenance of — 0.0221 was determined for the grunion during the period after it is ready to hatch but before it is freed from the sand. The maximum percentage of hatch- ing was close to 100 between 16.0—27.0 C but dropped off rapidly outside this thermal range. The average length at hatching was not influenced by the degree-hours incubated. The growth rate of larvae at 18.0 C post- hatching was not influenced by the temperature at which they were incubated.
INTRODUCTION
The reproductive habits of the grunion have been studied by Walker (1952). He found that in southern California grunion spawn on the beach just after high tide on descending spring tides from late Febru- ary or early March through late August or early September. The eggs remain in the sand until they are liberated by the next tide high enough to reach them ; this may require only 10 days or up to a month, depend- ing on the height of the tides and when the eggs were spawned. Walker also showed that eggs may develop to the point of hatching but will not do so until they are agitated (i.e. wave action).
If the grunion had a constant and continuous increase in its develop- mental rate with respect to temperature, the eggs would develop with increasing rapidity due to the increasing ambient temperature as the season progressed. The late spawned eggs then would have to spend a longer time maintaining themselves in the sand, until they could hatch. Furthermore, when summer spawned larvae entered the water, their metabolic rate would be higher than that of spring spawned individuals, but their yolk reserves would be lower. Since the larvae, after hatch- ing, are dependent upon their yolk reserves until they can capture food, it seems reasonable that a fish with a mechanism for conserving yolk to use during this critical period would have a selective advantage over one that did not have such a mechanism. One possible adaptation to this situation would have been for late-spawned eggs to have a slower rate of increase in developmental rate with respect to tempera-
1 Accepted for publication September 1970.
2 Present address : DunstafCnage Marine Research Laboratory, P.O. Box 3, Oban, Argyll,
Scotland.
(58)
GRUNION DEVELOPMENT
59
ture. To test this possibility, eggs were collected from various runs throughout the spawning season and incubated at different tempera- tures within their viable limits determined in tliis study.
METHODS AND MATERIALS
Grunion were collected on the beach at La Joila, California, during their bimonthly runs, from the middle of February to the end of Au- gust 1968. Gametes collected from the spawning fish were mixed in a half -liter plastic container holding 25 cc of sea water. After about 15 min the excess milt was poured off, and fresh sea water was added. Approximately 1 hr elapsed following the last egg collection before placing them in the appropriate incubation chambers. Eggs were in- cubated in fine gravel (1-2 mm diameter) with aerated sea water, which was changed every 2 or 3 days, dripping through it (Figure 1). No
PIASTIC SHEET
OPAOUE PLASTIC GLASS WOOL PLASTIC SHEET
AIR HOSE
GRAVEL AND EGGS
GLASS TUBE
-GLASS WOOL ■SEA WATER LEVEL -HOLES
RUBBER BAND PLASTIC CONTAINER
RUBBER TUBING STY80F0AM CUP
FIGURE 1. Chamber used to incubate grunion eggs.
attempt was made to simulate tidal changes. The incubation chamber was covered with a plastic sheet to diminish evaporation. All eggs were incubated in the dark in order to prevent any variability due to light. The incubation chambers were placed in thermostatically controlled water baths which maintained the following temperatures: (± 0.25 C) :
13.5, 14.5, 14.9, 15.5, 18.0, 20.0, 23.0, 24.0, 25.0, 26.0, 26.5, 26.7, 27.0,
27.6, 28.0, 28.5, and 29.0 C. Due to lack of equipment, eggs from each collection were not incubated at every temperature.
At about 24 hr intervals, samples of approximately 50 eggs were removed from each chamber and examined for their state of develop- ment. The criteria recorded were embryonic axis formation, heart beat- ing, eye pigmentation, lens formation, and hatching. A characteristic was considered to first appear when 50% of the sample showed it. Eggs
60
CALIFORNIA FISH AND GAME
Avere left in tlie incubation chambers beyond the time they were capable of liatcliiny in order to determine the length of time they could remain in the gravel, Avitli respect to temperature, and still be capable of hatching.
The temperature coefficient for maintenance "was calculated on the basis of the time from which 50% of the eggs first could hatch upon agitation, to when, after remaining in the sand for various periods, at least 50% of them could still hatch when agitated in sea water. The temperature coefficients for development and maintenance were deter- mined by calculating the least square lines. In this paper, the term temperature coefficient is used to describe these coefficients calculated in this manner. It does not apply to Qio values which were calculated differently.
The Qio values for development were determined at 2 degree intervals over the range of 14.0-22.0 C. The van't Hoff formula, as described by Giese (1962), was used for these calculations:
log Qio =
10
t2 - t:
1 ^2
log^^,
In this formula K2 is the rate at temperature t2, and Ki is the rate at ti.
In order to assess the effect of incubation temperature upon future larval growth rates, a group of larvae from incubation temperatures of 15.5, 16.0, 23.0, 26.0, and 28.0 C were reared for 45 days after hatching. This was done in five 15 gallon aquaria sitting in a parti- tioned water table. The water temperature was maintained at 18.0 C, to which the larvae were allowed to acclimate before release into the aquaria. Brine shrimp, Artemia salina, nauplii were used for food.
RESULTS
Temperature tolerance limits for hatching were 14.0-28.5 C. Two distinct developmental temperature coefficients were found (Figure 2) ; these were in the ranges of 14.0-23.0 and 23.0-28.5 C. The time re- quired for any of the examined characteristics (Table 1), to first occur or be detected at any one temperature, did not appreciably vary throughout the spawning season. The developmental temperature co- efficients of the different characteristics, when tested by means of a covariance analysis, were statistically indistinguishable (14.0-23.0 C, F(4, 49)df = 2.08, p<0.1; 23.0-28.5 C, F(4, 52)df = 2.09, p<0.1).
TABLE 1 — Temperature Coefficients Throughout the ViabSe Range for Development
|
Temperature coefficients for development |
||
|
Characteristic |
Temperature range 14.0-23.0 C |
Temperature range 23.0-28.5 C |
|
Hatching |
-0.0656 -0.0678 -0.0559 -0.0641 -0.0570 |
— 0 0199 |
|
Lens formation |
— 0 0010 |
|
|
Eye pigmentation |
— 0 0023 |
|
|
Heart beating |
— 0 0117 |
|
|
Embryonic axis formation |
— 0 0290 |
|
GRUNION DEVELOPMENT
61
z o o
|
o |
||
|
CN |
co C o c < c 5 u |
|
|
l\ |
o Q.CO |
|
|
CN |
ing difFerent s <0.1) below 2 |
|
|
lO |
= Q- |
|
|
CN |
me required, d (b=— 0.0613, |
|
|
CO |
u |
"*~ __ |
|
CN |
0 |
gainst log s are equa 0.4). |
|
LU |
° ^V |
|
|
oe: |
-□ o ^ |
|
|
— |
3 |
X. O O 0) >- |
|
CN |
< |
Q.-Z. N |
|
LU |
are II of from |
|
|
Q- |
a) ^ -a |
|
|
5 |
O 0) .-
1- U 3
m '^ D)
Q. O c
E c ■;=
<D ^
.2 o -^
o >- o
> D C
■ Q. c
^ D u
2 ^ ST
<D ci: -C Q- —
E o -
"- J3
S .= O
'- P =
> O X
01 <"
0
0) o
U)
<U
350. 0 Ji o
sy noH
o
62
CALIFORNIA FISH AND GAME
Tlic averafre temperature eoetScient in 14.0-23.0 C ranjre was — 0.0613, ■while tliat fr(nn 23.0-28.5 C could not statistically be distiiio'nished from zero it 6Udt' = 0.8340, p < 0.4). These coefficients show that althongh the time required for development decreases with increasing tempera- ture there appears to be a. minimum amount of time required for an event to occur or a structure to form irrespective of temperature. Ac- cording-ly, temperatures warmer than 23.0 C did not appreciably de- crease the time required for any of the examined characteristics to first appear or be noticed. The Qio values for development were all approximately equal to 5 (Table 2) ; these were not calculated above the range 14.0-22.0 C due to the leveling off of the developmental temperature coefficient (Figure 2).
2 75
2 70
^ 2 6 5
a:
Z>
O
X
o
2.60
2.55
21
23
25
27
29
TEMPERATURE C .
FIGURE 3. The effect of temperature upon the maintenance metabolic rote is estimated by plotting temperature against log hours from the time 50% of the eggs could first hatch, upon agitation, to when at least 50% could still hatch, after remain- ing in the sand for various periods, when agitated in sea water. Log hours = 3.2240 — 0.0221 Temperature C.
GRUNION DEVELOPMENT TABLE 2 — The Qio Values for Development
63
|
Incubation teniD. _ - |
C 14 |
16 |
18 |
20 |
22 |
|
Time in hours (II) until liatching |
536 |
387 |
280 |
202 |
146 |
|
1 Rate |
0.00186 |
0.002r)8 |
0.00357 |
0.00495 |
0.00084 |
|
H Qio _ . |
4.94 4.92 4.93 4.91 |
||||
o
z
X
u <
X
z
?
X
<
I 00
75
50
25
• : •
♦ t
1 3
1 5
1 7
19 2 1
TEMPE R AT URE
23
°C.
25
2 7
2 9
FIGURE 4.
Throughout most of the viable range, the maximum percentage of hatching was close to 100; however, as the lethal limits were approached, this percentage decreased rapidly.
Tlie temperature coefficient for maintenance Avas calculated ahoxc 21 C and was — 0.0221 (Figure 3). Tliis shows that at warmer tempera- tures tlie larvae could not maintain tlicmselves as long as under cooler conditions. The maximum hatching jiercentage was close to K)0 from 16.0-27.0 C, but on either side of tliis range it dropped off rapidly (Fig- ure 4). This should be ke])t in mind A\lien considering the events occur- ring near tlie end points; due to this phenomena tlie appearance of any of the developmental characters in this range was based on ob- servation of fewer individuals. The length of the grunion at hatching did not appear to vary with llic amount of time and tem])('rature (degree-hours) encountered during incubation (Figure 5). This sug- gests that little or no growth occurs in tlie period after the larvae are ready to hatch and while they are waiting for a tide high enough to reach and liberate them. In conjunction with this, no other gross mor- phological differences were observed between larvae from eggs that spent long or short durations in the sand after developing to a point of being ready to hatch. For these reasons, we call this period, the maintenance period. The temperature at which the eggs were incu- bated had no effect upon the post-hatching growth rate at 18 C during the first 45 days (Figure 6).
64
o
z
8 . 0
7 . 5
<
LLI
> 7. 0 <
CALIFORNIA FISH AND GAME
• •
i
• •
8
1 0
1 2
14
DEGRE E-HOURS x 1 0
FIGURE 5. The average length of larvae at hatching was not regularly influenced by the degree-hours spent in the incubation chambers.
0.35,
oj 0 <
X
io
a: O
|
3 0 |
• |
• |
|||
|
• |
• |
• |
|||
|
25 |
1 1 1 1 |
1 1 1 1 1 |
1 1 |
1 5
19 2 1 2 3 INCUBATION TEMPERATURE
2 5
27
FIGURE 6. The temperature during incubation did not regularly affect the grunion's grov/th rate at 1 8 C during the first 45 days after hatching.
DISCUSSION
The yolk in the egg can be considered as consisting of two portions: that which is required for development to the point of potential hatch- ing, and that which is for maintaining the larvae after it has com- pleted development to this point. Tlie latter portion is used by the larvae while it is in the egg and waiting to be freed from the sand, as well as supplying it with nutrients for growth and energy while it searches for food in the ocean.
The period after hatching and before the larvae capture food in sufficient quantities to maintain themselves is a critical period in the
GRUNION DEVELOPMENT
65
fe of fishes when mass mortalities are likely to occur (Hjort, 1926). urther studies (Shelbourne. 1957; Rosenthal and Hempel, 1968) have saown yolk-sac larvae to be relatively inefficient searchers and hunters (prey capture) as compared to older larvae. Considering this, it would seem reasonable tliat larvae Avitli larger yolk reserves would have a tetter chance of survival than tliose with smaller reserves. Further- nore, at any given temperature, a gr union which spends less time maintaining itself in the sand will have more j^olk left when it enters the water. With a developmental temperature coefficient of zero (or close to it) at temperatures above 23 C, the amount of sand mainte- nance time for the grunion is decreased from what it would liave been had the developmental tem]ierature coefficient displayed below 23 C been maintained (Figure 7). The maintenance temperature coefficient
1000
t/i
^ 100
CO
o
10
21
23
25
27
29
TEMPERATURE
FIGURE 7.
The maintenance advantage of the decrease in the developmental temperature coefficient at temperatures above 23 C. The solid lines represent the hours re- quired for maintenance with the decrease in the development rate above 23 C. The broken vertical lines indicate the additional hours that would have been required for maintenance had there been no decrease in rate. The broken horizontal line shows the approximate time required for the eggs to be freed from the sand by wave action.
(Figure 3) shows that the decrease in the effect of temperature on development — above 23 C — would have been of greatest advantage to those fish incubated at the warmest temperatures within their viable limits. The lack of influence of the physiological age (degree-hours)
66 CALIFORNIA FISH AND GA:ME
at hatching upon the hatching length is consistent with the statement of Blaxter and Hempel (1963) for herring from different areas, "... there is a very wide scatter of points and no consistent tendency for body size at hatcliing to be greater at either higher or lower tem- peratures."
The observed temperature tolerance range with respect to hatching (14.0-28.5 C) was broader than Hubbs (1965) reported (14.8-26.8 C). At least part of this difference might be explained by the fact that the eggs Hubbs used, were placed in the temperature gradient block (used for incubation) within 15 min after they were collected. In our study, approximately 1 hr elapsed before placing them in the ap- propriate incubation chambers. The eggs probably had enough time during tliis period to at least partially acclimate to the warmer incu- bation temperatures. This effect would have been accentuated even further due to the time required for the gravel, after the eggs were mixed into it, to warm up or cool down to the incubation water tem- perature. Kelley (1968) showed that the viable temperature range for largemouth bass, Micropterus salmoides, eggs was extended if the eggs were allowed to acclimate slowly to warmer or cooler temperatures. Another difference in incubation technique between this Avork and that of Hubbs was that we incubated many eggs together in fine gravel Avith aerated sea water dripping over them, while Hubbs incubated single eggs in test tubes of sea Avater. Although the temperature co- efficients for hatching were the same for both studies (t(16df) =: —0.5769, p < 0.6 in the temperature range 14.0-23.0C and t(14df r- — 0.2591, p < 0.8 in the temperature range above 23. OC, the time re- quired for hatching Avas different. (The temperature coefficient from the work done by Hubbs AA'as computed for this study by reading points off of his published graph.) The eggs in our study hatched about 120 hr sooner — throughout the temperature range 14.0-28. 5C — than those incubated by Hubbs. This difference might be explained on the basis of the variations in the experimental technique described above or possibly due to the eggs in the test tubes being under some sort of physiological stress.
As the lethal limits were approached, the development Avas altered before death set in. At 13. 5C, near the loAver temperature limit, the eggs developed through lens formation but did not hatch. At warm tempera- tures (28.0C), about one-third of the eggs developed normally, but others had stunted bodies, and the eyes Avere sometimes fused. The per- centage of hatching decreased sharply at these temperatures (Figure 4).
Giese (1962) stated that there are four different kinds of Qio values related to different mechanisms of action: "... those which are about tAvo, those Avhich are considerably higher than tAvo, those Avhich are considerably less than tAvo, and those which are about one." The Qio values for development obtained in this Avork (Table 2) would probably be classified as falling into the first category. Blaxter (1956) found for hatching and yolk-sac absorption of herring that Qio values of about two Avere obtained only throughout the temperature range the fish Avould encounter normally. The values decreased above these tempera- tures; while beloAv them, A'alues increased. In this study, the values of Qio did not vary throughout the range of 14-22C which suggests bio-
GRUNION DEVELOPMENT 67
chemical reactions occurring in griinion are more stable over a wider temperature range than those occurring in tlie liei-ring. This is under- standable considering that grunion eggs develop in beach sand, while those of the herring develop in open water.
No attempt was made to measure the bacterial count of incubation chambers at various temperatures. However, the effect of them on the po-gs — with respect to hatching — tlironghout most of the temperature range was probably minimal. Tliis statement is based on tlie fact that the percentage of eggs hatching was about 100 throughout the tempera- ture range, excluding the end points near the lethal limits. Although fungus developed on some eggs that were in the incubation chamber i'or over 2 weeks, it was not possible to determine Avliether tlie biiildu]) of fungus caused the eggs to weaken and die oi- wlidlicr fungus only grew on those eggs already weakened by some other factor.
SUMMARY
1. Grunion eggs were collected tln-oughout their spawning season and incubated at different temperatures.
2. The viable limit for hatching was 14.0-28. 5C.
3. During incubation, tlie development of these characteristics was followed: embryonic axis formation, lieart beating, eye pigmenta- tion, lens formation, and hatcliing. All of these displayed the same developmental temperature coefficients, but two distinct coefficients were found within the viable range (—0.0613 from 14. 0-23. OC, and — 0.0113 from 23.0— 28. 5C). The lower coefficient at liiglier tempera- tures could serve to conserve yolk for the larvae for use in the sea after hatching.
4. A temperature coefficient of —0.0221 was determined for the main- tenance of the grunion in the sand after it completed development to the point of being ready to hatch and while awaiting a tide high enough to reach and free it.
5. The maximum percentage of hatching was close to 100 in the range 16.0-27. OC but dropped off rapidly on either side.
6. The average hatching length of the grunion was not influenced by the degree-hours incubated.
7. The post-hatching growth rate of the larvae, at 18C, was not in- fluenced by the incubation temperature within the viable range.
ACKNOWLEDGMENTS
We wish to thank John H. S. Blaxter, Dunstaffnage Marine Research Laboratory, Oban, Argyll, Scotland, who reviewed the manuscript.
REFERENCES
Blaxter, John H. S. 1956. Herring rearing-II. The effect of temperature and other factors on development. Scottish Home Dept., Mar. Res. (5) :1-19.
Blaxter, John H. S., and G. Hempel. 1963. The influence of egg size on herring larvae (Clupca harengus L.). J. du Cons. 28(2) :211-240.
Giese, Arthur C. 1962. Cell physiology. W. B. Saunders Co., Philadelphia. 592 p.
Hubbs, Clark. 1965. Developmental temperature tolerance and rates of four South- ern Californian fishes, Finidulus parvivinnus, Atherinops affinis, Leuresthes tenuis, and HypsohlennUis sp. Calif. Fish and Game 51(2) :113-122.
68 CALIFORNIA FISH AND GAME
Hjort, Jolian. 192G. Fluctuations in the year classes of important food fishes. J. du Cons. 1(1) :5-3S.
Kelley, John. W. ]!)(iS. Effects of incubation temperature on survival of largemouth bass eggs. Prog. Fish-("ulturist 30(3) :ir)9-lC3.
Rosenthal, H., and G. Hempel. 19GS. Experimental studies in feeding and food requirements of herring larvae. ICES, FAO, ICNAF, UNESCO, and IBP Sym- posium on marine food chains. University of Aarhus, Denmark. 23-26 July, 19GS. Contribution Xo. 22.
Shelbourne, James E. 1957. The feeding and conditions of plaice larvae in good and bad plankton patches. J. Mar. Biol. Assoc. U.K., 3G(3) :539-552.
Walker, Boyd AY. 1952. A guide to the grunion. Calif. Fish and Game 38(3) : 409-420.
Calif. Fish and Game, 57(1) : G9-75. 1971.
A REVIEW OF POSSIBLE CAUSES OF MORTALITY OF
OYSTER LARVAE OF THE GENUS CRASSOSJREA
IN TOMALES BAY, CALIFORNIA^
CARL J. BERG, JR.^
Pacific Marine Station, Dillon Beach, California
Oysters of the genus Crassostrea do not produce successive genera- tions in TomcJes Say, California, because of the failure of the larvae to survive and set. Excessive turbidities, lack of proper food, and blooms of dinoflageilates ere probcbly the major causes of oyster larvae mor- tality, although there are other contributing factors.
INTRODUCTION
Recent work on the rcprodiietive eyclos of the p-iant Pacific oyster, Crassostrea gigas (Tlninberjj, 1798). nnd tlie eastern oyster, Crassosfrca virginica (Gmelin. 1791), siiowed tliat botli introduced s])ecies spawn in Tomales Bay, California. Failure of these oysters to produce successive peuerations in the bay Avas attributed to the inability of the larvae to survive and set (Berg, 1909). The great fecundity of the oysters and the occurrence of mass spawniug ensures a large number of larvae being produced even if only a small percent of tlie ova are fertilized. Tlie presence of a few Crasfiostrea spp. larvae in the waters over Tomales Bay Oyster Company beds demonstrated that at least some of the zygotes were viable. Therefore, conditions not inherent in the oysters themselves probably were responsible for larval loss.
Apparently, many environmental factors are involved, both singly and in combination, in the mortality of oyster larvae. This attempt to designate the factors probably responsible for the larval loss is based on the observations of both biological and physical factors ])revailing in Tomales Bay. Not all of these factors were examined at the time the larvae were preseut ffrom the end of June through September, 1907), but the hydrographic character of the area comprising Tomales Bay Oyster Company was well monitored during that period. Temperature, salinity, hydrogen-ion concentration, and turbidity measurements were recorded for both surface and bottom water at biweeklv intervals and more often at times. All samples and temperature readintj-s were taken at low oi- mid-1ides. This paper describes parameters wliicli a|iparcii1ly caused liigh hn'val mortality in Tomales Bay.
TEMPERATURE
Water temperature fluel nations in Tomales Bay were minimal while larvae were present, with tempei-atures ranging from 19.0 to 21.4 C. The fact that early morning temperatures Avere 19.0 C or higher, sug- gests the water seldom got mucli colder than 20.0 C during July and
1 Accepted for publication September 1970. Submitted in partial fulfillment of the re-
quirements for the degree of Master of Science at the University of the Pacific, Stockton, California.
2 Present address : Department of Zoology, University of Hawaii, Honolulu, Hawaii
96822.
(69)
70 CALIFORNIA FISH AND GAME
Auo-ust (Berg, lOGO"). If the water temperature had dropped, it would have 1)0011 quickly wanuod by the sun.
The elt'eet of temperature upon bivalve larvae has been reported by Seno. Ilori, and Kusfikabe (1926) ; Loosanoff and Davis (ir)63a) ; and by Davis and Calabrese (1964). The temperatures recorded at Tomales Bay Oyster Company during the study period were well Avithin the range of 17.5 to 35.0 C which is considered the approximate limits for normal development to the straight-hinge stage. Since Loosanoff and Davis (1963b) show that short periods of very low temperatures will not kill larvae, it is unlikely that temperature conditions were responsi- ble for the scarcity of oyster larvae in Tomales Bay. However, low temperature may affect the oyster larvae detrimentally by prolonging their pelagic stage, thus offering a greater chance for mortality, preda- tion, and dispersal. Jn tlieir natural environment in the waters of Long Island Sound, the larvae may take as long as 40 days to reach the setting stage at 20.0 C and at a salinity of 2T/(o (Davis and Cala- brese, 1964). In the colder waters of Tomales Bay, it is probable that larval development would take much longer, which in turn decreases the larvae's chances of survival.
SALINITY
Davis and Calabrese (1964) also show tlie effects of various combi- nations of tempcn-atiires and salinities on bivalve larvae. Unfavorable salinities reduce the number of larvae reaching metamor]">hosis and limit the range of temperature tolerances. Although Davis and Cala- brese dealt extensively with the range of salinities oysters miglit en- counter in Long Island Sound, little work lias been reported on larval tolerances to salinities as high as 35%o which are encountered during the summer at Tomales Bay Oyster Company. Loosanoff' and Davis (1963b) observed that some l-irvae from Lonu' Island Sound oysters may develop normally at 35%o, and Amemiya (1926) and Clark (1935) extended the salinity limits for normal development to 39%€. In a later paper, Amemiya (1928) states that between 31/^o and 34%o only a small proportion of oyster larvae attain normal develop- ment. Imai et al. (1950) report that giant Pacific oyster larvae suc- cessfully set in Japanese waters with salinities of 30%o to 32%o. W. W. Budge (Pacific Marieulture, Inc., pers. comm.) has noted that the larvae of eastern and giant Pacific oysters raised in California waters grow well at a salinity near 35%o. This supports Davis's (1958) statement that the salinity range for the development of straight-hinge larvae is, in part, governed by the salinity in which the parent oysters develop gonads. Salinity measurements for Tomales Bay ranged from 27.8 to 34.8%o. Therefore, I conclude that the salinity of Tomales Bay was probably not detrimental to the larvae of either species.
HYDROGEN-ION CONCENTRATION
The effect of hydrogen-ion concentration upon oyster gametes and larvae has been studied by Calabrese and Davis (1966, 1969). They found that at a salinity of 27%o the pH may range from 6.75 to 8.75 and still result in normal h;rval development, survival, and growth. During the study period, the pH of the water at Tomales Bay Oyster
OYSTER LARVAE MORTALITY 11
Compiniy was remarkably constant, raiiyiny between 7.04 and 7.96. This is the approximate midrange of values reported for normal de- velopment.
Calabrese and Davis (1960) also i-(»porled that lii.u'h concentrations of suspended silt can lower the pll below the limit for development. Excessive turbidities observed at Tomales Bay Oyster Comi)any may have reduced llie ])I1 temporarily and llius caused mass larval mor- tality, but while llie water was usually very turbid at the time of sampling, low pH readings were never recorded. Thus it is not likely that the hydrogen-ion concentration was a factor in larval mortalities.
TURBIDITY
Excessive turbidities may affect oyster larvae. Turbidity caused by suspended silt, detritus, or unicellular organisms harms oysters by clogging their gills (Loosanoff and Engie, 1947; Davis, 1953; Loos- anoff, 1954; 1958; 1962; Ukeles and Sweeny, 1969). At high tempera- tures (20.0 C), turbidity may cause rapid suffocation and starvation even in adult bivalves (Loosanotf, 1962). In solutions with as little as 0.5 g/liter of silt, only 81% of the oyster eggs developed to the straight-hinge larval stage, and growtli (if tlie snrviving larvae was seriously affected. Practically no eggs survived at greater concentra- tions (Davis and llidu, 1969). Extreme turbidities at Tomales Bay Oyster Company during the summer may be one of the major causes of larval mortalities.
These excessive turbidities had the greatest deleterious effect upon oyster propagation In' covering all ])Ossible ]ilaces for settlement with a layer of mud. Clean shells, on which si)at nornuilly set, were com- pletely covered by silt within 2 weeks. The only oyster spat found had set on the underside of the upper valve of a slightly gaping oyster. Because of tlie timely gaping and the narrow opening it formed, the spat found a clean area on which to settle. At times, mud on the oyster shells w^as as thick as 0.5 cm and was often infested with the amphipod Corophiwn sp. Even though clean shells were suspended from the oyster racks every 2 weeks, few spat were fonnd. nor did other animals settle on the shells. A few barnacles and liydroids wei-e found on the shells in early aiid late sunimer, ])ut (liirin;^' llie period of maximum oyster spawning even these forms did not settle on the mud covered shells. Witliout a place to set. the jx'lagic jieriod of the oyster larvae was probably prolonged until the lar\ae died or w'ere carried from the bay by tidal currents.
ORGANIC CHARACTER
Unfavorable changes in larval growth have been related to organic constituents of the water liberated from bottom sediments (Davis, 1953; Ito and Tmai, 1954; Tjoosanoff, 1958). Oysters are placed on a soft mud bottom in Tomales Bay. Because of the shallowness of the water, large waves and wakes of motorboats cause extensive bottom disturbances. With the great number of boats in the water during the summer months, large amounts of organic matter are released from bottom sediments. AVilson (1951) and Millar and Scott (1968) noticed differences in larval development which they attributed to a biological difference in sea waters. Loosanoff, Engle, and Nomejko (1955) dis-
72 CALIFORNIA FISH AND GAME
cussed a "water factor" consisting of certain dissolved substances needed for development of bivalve larvae. All organic chemical sub- stances that may aft'ect organisms via the external medium have been termed ''ectoerines" by Lucas (1947), and will be mentioned again in the section on metabolites. The bottom disturbances and the excessive turbidities in Tomales Bay may have contributed a "water factor" or "ectocrine" which caused oyster larval mortality. No attempts were made to test this hyjoothesis.
FOOD
In addition to the physical and chemical aspects of the environmentj biological aspects play a most decisive role in oyster development. Hav- ing the proper food available for larval consumption is one of the most important factors in larval development. In fact, Loosanoff (1950) attributes the variations in Long Island Sound oyster set to the ab- sence of proper food. Loosanoff and Davis (1963b) state tliat the larval pelagic period may be extended or larvae may never metamor- phose if specific food organisms are lacking or are uncommon in the environment. It has been demonstrated that larvae of Crassostrea spp. are able to utilize only a few of the many organisms available (Davis, 1953; Loosanoff, 1954; Loosanoff, Engle, and Nomejko, 1955). The thickness of the algal cell walls, the toxicity of algal metabolic prod- ucts, and water temperature are all important factors in determining the algal cells' value as larval food (Loosanoff, 1965). I did not use a phytoplankton net with mesh fine enougli to retain naked flagellates which are the best food for larval oysters (Loosanoff' and Davis, 1963b), therefore, I can not evaluate local forms. Since food requirements are very specific, larvae of introduced Crassostrea spp. may not have been able to find sufficient nutrients in Tomales Bay waters and hence starved to death.
METABOLITES
External metabolites of food organisms and other unicellular orga- nisms present in the water may be toxic to bivalve larvae. Blooms of dinoflagellates produce metabolic excreta which cause abnormal larval development, characterized by the scarcity or absence of early straight- hinge larvae (Davis and Chanley, 1956; Loosanoff, 1958). Excessive concentrations of metabolites may affect larvae directly or may kill the nannoplankton, starving the larvae or making them more susceptible to disease. Furthermore, the large numbers of organisms producing metabolites also may harm larvae by using up chemicals in the sea water that are essential to larval development (Loosanoff and Davis, 1963b). A large bloom of the dinoflagellate Gymnodinium sp. was ob- served by members of the Pacific Marine Station staff' in the summer of 1967 during the period of greatest spawning of both eastern and giant Pacific oysters. In addition to Gymnodinium, large concentrations of a unicellular ciliate of the family Tintinnidae were taken in planktoii samples throughout the summer. Both of these organisms may have produced toxic metabolites. Only straight-liinge larvae were found in plankton samples, and the disappearance of older oyster larvae may well be due to a cumulative effect of external metabolites in the water and the depletion of nutrients.
OYSTER LARVAE MORTALITY 73
PREDATION
The Tintinnidae may have liad another effect upon oyster larvae. Loosanoff (1959) reports that ciliates of; tlio families Condylostomidae and Follienlinidae may ingest bivalve larvae. Althongh no larvae were observed in the digestive tracts of any preserved specimens of Tintin- jiidae, the latter were present in snt^cieiit numbers to cause severe de- pletion of larvae if the ciliates did ingest them.
Large numbers of the scyphomedusae Avrclia aurita and Chrysaora mclanasfcr also were present during the oyster s]iawning season. Al- though Loosanoff (1966) could find no direct relation between numbers of ctenoiDhores and the oyster set in Long Island Sound, predation by ctenophores and coelenterates upon oyster larvae is well known (Tlior- son, 1946 ; Korringa, 1952).
A great number of herring and smelt were present in the bay during the summer. Thorson (1946), in his discussion of predation on pelagic larvae, considers fishes the principal enemies of larvae, but suggests that filter feeders such as barnacles, mussels, and the oysters them- selves also are important. It appears that the animals that w^ere in the greatest abundance during the summer were those that may have shown the greatest predation on bivalve larvae. Few bivalve larvae of any species were present during the summer and predation is suggested as one of the major reasons for lack of oyster spat in Tomales Bay.
DISEASE
The effect of bacterial and fungal diseases on oyster larvae has been described. Davis et al. (1954) and Loosanoff (1965) state that most larvae in culture chambers stopped growing and died soon after they were infected with the fungus SiroljykUnm zoophfhorum. Lethal effects of live bacteria and tlieir toxins have been simihirly discussed by Davis (1953), Walne (1958), Guillard (1959), and Tubiash, Chanley, and Leifson (1965). An infection of epidemic proportions among pelagic larvae in constantly mixing waters over Tomales Bay oyster beds is not likely.
CONCLUSIONS
The inability of oysters of the genus Crassostrea to produce succes- sive generations in Tomales Bay should be attributed to failure of lar- val survival and set, since the adults do spawn. No single factor can be held accountable for the absence of oyster spat. Many adverse condi- tions, such as low temperature, absence of proper food, and lack of suitable surfaces on which to set, while perhaps not lethal themselves, prolong the pelagic period and thus increase chance of larval loss due to predation, mortality, or dispersal by tidal currents. Apparently dis- persal is a relatively unimportant factor in Tomales Bay which has a low flushing rate, and spat were not found in other areas of the bay.
Lack of proper food and nutrients probably is a very important factor since the extreme irregularity of oyster set in Long Island Sound has been attributed to absence of proper food and not to physical environmental characters or predation (Loosanoff, 1950). In Tomales Bay, extreme turbidity is responsible for larval loss because all possible places where oyster larvae may settle are soon covered with a layer of
74 CALIFORNIA FISH AND GAME
mud. Blooms of dinoflagellates are the third major cause of larval mortality. Other causes are not likely as important as these three, but do contribute to generally unfavorable conditions for oyster larvae in Tomales Bay.
Even in their native environments, oysters, such as Ostrea edulis Avhieli liave a shorter pelagic period than the oviparous Crassostrca species, have as few as 5% of the larvae produced at 20.0 C, reaching metamorjihosis. Only 1% of these mature larvae are able to find sub- strates on which to settle (Korringa, 1952). Therefore, it is not sur- prising that so few oj^ster larvae set when so many factors are against them in the foreign environment of Tomales Bay.
REFERENCES
Amemiya, Ikusakii. 192(). Notes on experiments on the early developmental stages
of the Portuguese, American and English native oysters, with special reference
to the effect of varying salinity. .T. Mar. Biol. Assoc. U.K. 14(1) :161-175. . 1928. Ecological studies of Japanese oysters, -with special reference to the
salinity of their habitats. .7. Coll. Agric, Imp. Univ. Tokyo. 9(5) :333-382. Berg, Carl J., Jr. 19G9. Seasonal gonadal changes of adult oviparous oysters in
Tomales Bay, California. Veliger 12(1) :27-3G. Calabrese, Anthony, and Harry C. Davis. 1966. The pH tolerance of embryos and
larvae of Mercenaria mevccnaria and Crassosirea virginica. Biol. Bull. 131(3) :
427-436. . 1969. Spawning of the American oyster, Crassosirea virginica at extreme
pH levels. Veliger 11(3) :23.j-237. Clark, A. E. 1935. Effects of temperatur-e and salinity on the early development
of the oyster. Prog. Rcpt. Atl. Biol. Sta. 36:10. Davis, Harry C. 1953. On food and feeding of larvae of the American oyster, C.
virginica. Biol. Bull. 104(3) :334-350. . 1958. Survival and growth of clam and oyster larvae at different salinities.
Biol. Bull. 114(3) :296-307. Davis, Harry C, and Anthony Calabrese. 1964. Combined effects of temperature
and salinity on development of eggs and growth of larvae of M. mercenaria and
C. virginica. U. S. Fish. Bull. 63(3) :643-655. Davis, Harry C, and Paul E. Chanley. 1956. Effects of some dissolved substances
on bivalve larvae. Proc. Natl. Shellfish Assoc. 46 :.59-74. Davis, Harry C, and Herbert Hidu. 1969. Effects of turbidity -producing substances
in sea water on eggs and larvae of three genera of bivalve mollusks. Veliger
11(4) :316-323. Davis, Harry C, Victor L. Loosanoff, W. H. Weston, and G. Martin. 1954. A
fungus disease in clam and oyster larvae. Sci. 120(3105) :36-38. Guillard, Robert R. L. 39.59. Further evidence of the destruction of bivalve larvae
by bacteria. Biol. Bull. 117(2) :2.5S-266. Imai, Takeo, M. Hatanaka, R. Sato, S. Saki, and R. Yuki. 1950. Artificial breeding
of oysters in tanks. Tohoku J. Agric. Res. 1(1) :69-86. Ito, S., and T. Imai. 1954. Ecology of oyster bed. I. On the decline of productivity
due to repeated cultures. Tohoku J. Agric. Res. 5 :251-268. Koi-ringa, P. 1952. Recent advances in oyster biology. Quart. Rev. Biol. 27(4) :
339-365. Loosanoff, Victor L. 1950. Variations in Long Island oyster set. Atl. Fisherman
30 :15-16. . 1954. New advances in the study of bivalve larvae. Amer. Sci. 42(4) :
607-624.
1958. Challenging problems in shellfish biology. In Perspectives in Marine
Biology, A. A. Buzzati-Traverso (ed.), Univ. Calif. Press, Berkeley p. 483—495. — — . 19.59. Condylostoma — an enemy of bivalve larvae. Sci. 129(3342) :147. . 1962. Effects of turbidity on some larval and adult bivalves. Proc. Gulf.
Carib. Fish. Inst. 14th Sess. :80-95.
1965. The American or eastern oyster. U. S. Dept. Int., Fish. Wildlife
Ser., Bur. Comm. Fish., Circ. 205 :1-11.
1966. Time and intensity of setting the oyster, Crassosirea virginica in
Long Island Sound. Biol. Bull. 130(2) :211-227.
OYSTER LARVAE ISIORTALITY 75
Loosanoff, Victor L.. nnd Harry C. Davis. 19G3a. Slicllfisli Iialchcries and their
future. Comm. Fish. Rev. 25(1) :1-11. . . lOOiib. Rearing of bivalve molhisks. Ti\ Advances in Marine Bioln.ny. F. S.
Russell (ed.), Academic I'ress. New Yoi'k 1 :2-13G. Loosanoff, Victor L., and .Tames B. Enjile. 1!)47. Feeding of o.vslers in rdiilion to
density of microorganisms. Sci. 10") (2728) :2(iO-2Gl. Loosanoff, Victor L., .Tames B. Engle, and Charles A.. Nomejko. l!),j."). Differences
in intensity of setting of oysters and starfish. Biol. Bull. 109(1) :7.'j-81. Lucas, C. E.1017. The ecological effects of external metal)olites. Biol. Rev. 22(3) :
270-295. Millar, R. H.. and J. M. Scott. 19G8. An effect of water quality on the growth of
cultured larvae of the oyster Ostrea ediiUs L. J. Cons. Perm. Int. Explor. ]\Ier.
32(1) : 123-3 30. Seno, 13., J. Hori, and D. Kusakalte. 192G. Effects of temperature and salinily on
the development of the eggs of the common Japanese oyster Ostrea gi<jns Tlnin-
berg. J. Imp. Inst. Japan 22(3) :41-47. Thorson, Gunnar. 194G. Reproduction and larval development of Danish marine
bottom invertebrates, with special reference to the planktonic larvae in the
sound (0resund). Medd. Komm. Danmark's Fisk Havuud. Serie : I'lankton 4(1) :
1-523.
Tubiash, Haskell S., Paul E. Chanley, and Einar Leifson. 19G5. Bacillary Nec- rosis, a disease of larval and juvenile bivalve mollusks. J. Bacteriol. 90(4) : 103G-1044.
Ukeles, Ravenna, and Beatrice M. Sweeny. 19G9. Influence of dinoflagellate tricho- cysts and other fact<u's on the feeding of Criisso.strca virgiiiica larvae on Nono- chrysis lutheri. Limn. Oceanog. 14(3) :403-410.
Walne, P. R. 1958. The importance of bacteria in lalwratory experiments on rear- ing the larvae of Ostrea edulis (L.). J. Mar. Biol. Assoc. U. K. 87(2) :415-425.
Wilson, Douglas P. 1951. A l)iologieal difference between natural sea waters. J. Mar.' Biol. Assoc. U. K. 30(1) :l-20.
Calif. Fish and Game, 57(1) : 7G-79. 1971.
ANGUILLA RECORDED FROM CALIFORNIA^
JOHN E. SKINNER Colifornia Department of Fish and Game
Two specimens cf the Family Anguiilidae (true eels) have been taken alive in the Sacramento-San Joaquin Delta of California. The first was taken in 1964 by a local fisherman and was identified by Dr. Car! Hubbs of the Scripps Instituticn of Oceanography as Angu//;a rosirato 'Le Sueurj, The second was captured at a State-operated fish salvage facility on January 24, 1969 and was subsequently identified by Mr. W. I. FoUett, Curator of Fishes for the California Academy of Sciences, as Anguiila anguilla 'Linnaeus).
SPECIMENS TAKEN Anguilla anguilla (Linnaeus)
On January 24, 1969, a European eel, Anguilla anguilla (Linnaeus), was collected during routine fish salvage operations at the State's Delta Fish Protective Facilitj^ near B}-ron, Contra Costa County, Cali- fornia. This Facility is a louver fish screen located on an extension of Italian Slough, a natural deadend tidal reach. This slough connects directly with Old Eiver and thence with the San Joaquin Eiver. which flows westward to the Pacific Ocean. The capture site is approximately 65 airline miles east of San Francisco.
The fish, an adult female that initially measured 925 mm in total length, was captured at about 1900 hours at an ambient water tempera- ture of approximately 11 C. It was brought to the attention of the author b^' John Massie, an employee working at the Facility.
FIGURE i. Anguilla anguiila (Linnaeus; captured January 24, 1969.
The specimen under consideration was .submitted to Mr. W. I. FoUett, Curator of Fishes for the California Academy of Sciences. San Fran- cisco, who identified it as Anguilla anguilla (Linnaeus, 1758). In sup-
1 Accepted for publication October 1970.
(76)
ANGUILLA FROM CALIFORNIA
77
port of tlie identifieation the followino- is quoted from a letter fi-om Mr. Follett to the author (July 4, 1969) :
"In preservative, the speeimen now measures 91G mm total loimfli : tliis large size indicates that it is a female (Carl L. Ilubbs, personal (•(uiiniuni- cation).
"I have concluded that this specimen represents the European eel, Aiiniiilla angiiilla (Linnaeus, 1T5S).
"A radiograph shows the total number of vertebrae to be 114. According to Ege (1939, p. 132), this count eliminates AnguUla roKiraia. wliich has 103 to 111 vertebrae, but not Anguilla anijuilla (110-119) nor Anguilhi juiionlca (112-119) nor any of the following species of Anguilla (see Ege, on the pages indicated parenthetically, after the vertebral counts): mrgnxloma (110-114; p. 2G), nehitlosa lahiata (107-115; p. 72), dicffcnhachi (109-116; p. 133), aiistralis atistralis (111-115; p. ISS), aitstrolia schmidli (109-115: ]i. 1S9).
"The same radiograph shows (though not so clearly) the number of pre- caudal ('prehaemal' of Ege, 1939) vertebrae to be 4G. According to Ege (p. 130), this count is well within the range of AnguiUa anguilla (44--17), but is beyond that of Anguilla japo)iica (42-45). (The count of 4(! precaudal verte- brae eliminates Anguilla megastoma and Anguilla nebulosa lahiata; see Ege, pp. 26, 70.)
"Other characters of the present specimen that agree with tliose of Anguilla anguilla, but not with those of Anguilla japonica, are the following:
1. Preanal length without head, in hundredths of total length: 30.2 (tliis length is modal for A. anguilla; see Ege, p. 234).
2. Distance between verticals through anus and origin of dors:il liu, in hundredths of total length: 12.2 (see Ege, p. 100). (This distance eliminates Anguilla australis atistralis and Anguilla australis schmidti; see Ege, p. 163).
3. Distance from perpendicular through eyc-ccn(er on margin of upper jaw to angle of gape, in hundredths of length of gape: 12.5 (see Ege, pp. 110-111). (This distance eliminates Anguilla dicffcnhachi ; see Ege, p. 111).
"The foregoing are my reasons for concluding that your specimen represents the European eel. Anguilla anguilla (Linnaeus, 1758). We have so catalogued it, as California Academy of Sciences No. 27130.
"The paper that I have cited as Ege. 1939, is the following: Ege, Villi. 1939. A revision of the genus Anguilla Shaw. A systematic, phylogenetic and geo- graphical study. Dana-Report No. 16 :l-256."
Anguilla rostrafa (Le Sueur)
The week of June 1-5, 1961, Mr. Dennis Ivy, a Stockton resident, caught an eel in the vicinity of Honker Cut and Disappointment
■»M
i
.rp^
;; CALIFORNIA n.-.. AND GAME
Uough near Kin(r Islaml R<*sort, 15 mill's m.rtliwost of Stookt mgling. This spoi-imon )aited with "frosh v t was rope'-' '^ *■ ^' telly, olive '
The resort ovmor. Mr. Llnvi! < he attention of th«» lo<'aI ^ vy, only to fi- ' letter from II 'ortiinat«^ly. Ii- )flirtnipnt p«'rs<»niiol th«» - eached Dr. Carl V t tho lusti*:-- ■
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ANGUILLA from CALIFORNIA
79
1 believe the most logical explanation for the occurrene of both 3ls is that they were transported from abroad in the balM of com- lercial ships. The cities of Sacramento and Stockton haveboth been pened to ships of foreign commerce within the past twodecades or ). It is entirely plausible tliat sliips taking on ballast in foeign ports c at sea could have entrapped the eels and transported ttm to this rea and then expelled them with the ballast. The Japaese goby, canthogohius flavimanus (Temminch and Schlegel), now fimly estab- shed in the San Francisco Bay and estaurine system, isihought to we been introduced in a similar manner (Brittan, Albrech and IIop-
rk, 1963).
Tlic only prior records of eels in California date back t introduc- ons of the American eel, Anguilla rostrafa (Tjc Sueur) -hich were
ade in 1874, 1879 and 1882 '(Shebley 1917 and Everman, Warren id Clark, 1931). Of these introductions, Shapovalov, Dill ad Cordone
959) state only that, ''There are no authentic records olsurvival". 0 other introduction of eels in California has been docmented or
ported.
The ecological consequences of eels in the San Francisc( Bay-Delta
tuary are such that their occurrence should be documentd carefully.
r"%'^l^%\.»
ACKNOWLEDGMENTS
John Massie, formerly a Fish and Wildlife Assistant fi the Delta sh Protective Facility, deserves special commendation fr his alert- ss in recognizing and saving the eel taken at the fish fa<lity. I also sh to acknowledge the considerable efforts of W. I. Foll:t, Curator Fishes of the California Academy of Sciences, who icntified the ecimen of Anguilla anguilla and Dr. Carl Hubbs, wh identified iguilla rostrata.
REFERENCES
ittan, Martin R., Arnold B. Albrecht and John B. Ilopkirk. 196" An Oriental
)oby collected in the San .Toaquin River Delta, near Stockton, Cafornia. Cali-
ornia Fish and Game 49(4) :302-304.
'rmann, Barton Warren and Howard Walton Clark. 1931. A disiimlional list
'f the species of freshwater fishes known to occur in California, alif. Div. of
*'ish and Game, Fish Bnll. 35, p. 64.
ipovalov, Leo, William A. Dill and Almo J. Cordone. 1959. A rosed checklist
f the freshwater and anadromons fishes of California. Calif. Fh and Game
45(3) : 1.59-1 SO. ^bley, W. H. 1917. History of infroduclion of food and game dies into the v^aters of California. Calif. Fish and Game 3(1) :1-12.
78 CALIFORNIA FISH AND GAME
Slongli near King Island Resort, 15 miles northwest of Stockton while angling. Tliis specimen was canght at about 1700 houi's, on a hook baited willi "fresh water clam" while Mr. Ivy was fishing for catfish. It was reported to be approximately 30 inclies in length with "white belly, olive drab sides and back".
The resort owner, Mr. Lloyd Chelseth, called tlie strange catch to the attention of the local warden (Harold Hale) who contacted Mr. Ivy, only to find the fish had been skinned out and fed to his dog (letter from Harold Hale to Robert D. Montgomery, June 19, 1964). Fortunately, he had letained the skin. Through Fish and Game De- partment personnel the skin and a photograph of the fish eventually reached Dr. Carl Hubbs. The skin of this specimen has been retained at the Institution and is catalogued as SIO 64-219.
Dr. Hubbs identified the specimen at that time as Anguilla rostrata (Le Sueur) (letter to David Ganssle, June 16, 1964). Upon learning the specimen taken in January 1969 was Anguilla anrjiiilJa, Dr. Hubbs reexamined the photograph and skin of the 1964 specimen using tlie procedure outlined by Ege (op. cit.) for identification purposes. The following is quoted from Dr. Hubbs' letter to the author dated April 6, 1970.
"The nearest approximations I can make of critical parts ot the Ixxly. using Ege's methods of measuring, as specified on p. 7 and fig. 1 in the paper cited by Folh>tt :
"Length to vertical below dorsal origin, niinns head length measnres 16 or possibly 17 mm on the photograph, yielding the percentage valnes of 22 or possibly 24. Comparison ^Yith Ege's table 104 on p. 103 seems to eliminate japonica and almost certainly anguilla, but agrees with rostrata. Follett's meas- nrements yield a value of IS, by subtracting the percentage value for the interval between vertical through anus and origin of dorsal fin (12.2) from that for the preanal length without head (30.2) ; this value fits Ege's for either anguilla or japonica, but not for rostrata.
"Length to vertical above anus, minus head, seems to be 21.5 mm., yielding the percentage value of 30, apparently eliminating japonica, as I stated before, but agreeing with either rostrata or anguilla (Ijy comparison with Ege's table 97 on p. 97).
"Corresponding measurements including head seem to yield the same con- clusions.
"The prol)able proportionate value of 10 for the interval between verticals through anus and origin of dorsal fin seems to fit either japonica or rostrata better than anguilla (as tallied by Ege on table 100, p. 100). Follett's value of 12.2 fits only anguilla.
"Hence, I conclude that both A. rostrata and A. anguilla have somehow made their way into California in recent years."
DISCUSSION
It seems most probable that both specimens represent isolated cases of accidental origin, rather than representatives of a species in the process of becoming established in the area. Pursuing the former, the most probable sources are: (1) the aquarium trade, (2) the epicurean trade, (3) straying, (4) ship ballast.
Limited contact with personnel knowledgeable regarding the first two sources indicates that both are extremely unlikely. The larger public aquariums have denied importing European eels. Though sought fresh for food purposes, eels are rarely imported alive. The possibility that either eel reached the Delta by straying seems extremely remote but, if true, probably represents some kind of record for such an event.
ANGUILLA FROM CALIFORNIA 79
1 believe the most logical explanation for the occurrence of both eels is that they were transported from abroad in the ballast of com- mercial ships. The cities of Sacramento and Stockton have both been opened to ships of foreign commerce within the past two decades or so. It is entirely plausible that sliips taking on ballast in foreign ports or at sea could have entrapped tlie eels and transported them to this area and then expelled them with the ballast. The Japanese goby, Acanthogohins flavimanus (Temminch and Schlegel), now firmly estab- lished in the San Francisco Bay and osta urine system, is thought to have been introduced in a similar manner (Brittan, Albrecht and IIop- kirk, 1963).
The only prior records of eels in California date back to introduc- tions of the American eel, AnquiUa roftfrafa flje Sueur) whicli were made in 1874, 1879 and 1882 \Sheblcy 1917 and Evermann, Warren and Clark, 1931). Of these introductions, Shapovalov, Dill and Cordone (1959) state only that, ''There are no authentic records of survival". No other introduction of eels in California has been documented or reported.
The ecological consequences of eels in the San Francisco Bay-Delta estuary are such that their occurrence should be documented carefully.
ACKNOWLEDGMENTS
John Massie, formerly a Fish and Wildlife Assistant at the Delta Fish Protective Facility, deserves special commendation for his alert- ness in recognizing and saving the eel taken at tlie fish facility. I also wish to acknowledge the considerable efforts of AV. T. Follett, Curator of Fishes of the California Academy of Sciences, who identified the specimen of Anguilla anguilla and Dr. Carl Hubbs, who identified Anguilla rostrata.
REFERENCES
Brittan, Martin R., Arnold B. Alhrecht and John B. Hopkirk. 19GP>. An Oriental Goby collected in the San .Joaquin River Delta, near St<tckton, California. Cali- fornia Fish and Game 49(4) :302-304.
Evermann, Barton Warren and Howard Walton Clark. 1031. A distributional list of the species of freshwater fishes known to occur in California. Calif. Div. of Fish and Game, Fish Bull. 35, p. G4.
Shapovalov, Leo, William A. Dill and Almo J. Cordone. 1959. A revised checklist of the freshwater and anadromous fishes of California. Calif. Fish and Game 45(3) :159-1S0.
Shebley, W. H. 1917. History of introduction of food and game fishes into the waters of California. Calif. Fish and Game 3(1) :1-12.
BOOK REVIEWS
Trout Streams: Conditions That Determine Their Productivity and Suggestions for Stream and Lake Management
By Paul R. Needham; Annotated by Carl F. Bond; Holden-Day, Inc., San Francisco, 1969; X + 241 p., illustrated. $8.50.
The fii'st edition of Trout 8t7-eams, published in 1938, was written in response to a long felt need for information about the food, habitat, and management of trout in streams in a single volume.
INIuch additional knowledge about trout has been gathered and puldished in the following years, but not summarized under one cover. The need for an updating of Trout Streams was clearly evident.
The title page states that the book has been "revised", while the jacket says 'annotated". The latter is the more descriptive term. Dr. Bond has changed only a few words in the text, but has added a good foreword and a number of footnotes and literature citations to reflect new findings and developments. Unfortunately, the footnotes do not show whether they are Needham"s or Bond's. A comparison of the two editions reveals that in the first 100 pages 30 of the footnotes are by Bond, Avhile 21 are Needham's.
Dr. Bond has done a thoughtful and workmanlike job with his footnotes, but for meaningful updating some passages remain in need of revision.
The section on "Golden Trout", pages 42-43 is an example. The impression that golden trout are found only "at elevations around 10,000 feet", is perpetuated and also stated in many other publications. Actually, the native range extended down to around 6,400 feet. The California bag and size limits listed are obsolete. Golden trout are not now "limited to high mountain areas in Central California", but have been transplanted to many other waters in California and to several other states. It is true that within their native range golden trout seldom exceeded 10 inches, but in lakes to which they have been transplanted they reach a much larger size. The world's record golden trout, taken in Wyoming, weighed 11 pounds. A Di-pound golden was taken in California. Thus, the unitiated reader will be misinformed in his knowledge of golden trout. — Leo IShupovulov.
Olfaction in Fishes
By Herman Kleerekoper; Indiana University Press, Bloomington, 1969; Vill + 222 p., illus- trated. $12.50.
In this book, Mr. Kleerekoper reviews the literature of the past 100 years that deals with olfaction in fishes and summarizes the most significant contributions. He divides this information into two categories and devotes a chapter to each. The first chapter deals with the development, structure and function of olfactory organs in fishes, while the second discusses the role of olfaction in fish behavior.
The first chapter, on which the author places his emphasis, is, by the nature of its content and the manner in which it is written, likely to be of interest only to a few specialists or those particularly interested in olfaction. The second chapter, however, contains much information of concern to fishery biologists. It starts with a summarization of the old controversy as to whether or not aquatic animals actually have a sense of smell. This is followed by discussions on the followings topics : "Role of Olfaction in the Procurement of Food", "Olfaction and Social Behavior", "Olfac- tion and Defense Mechanisms", "Role of Olfaction in Parental Behavior", "Olfaction and Homing Orientation", and "Mechanisms of Orientation Through Olfaction",
An appendix entitled "Methods Used for the Observation and Recording of Some Locomotor Patterns in Fishes" follows the text and there is a 704 reference bibliog- rai)hy that reaches back to 1807.
This is a comprehensive review on the fields of olfaction and its influence in the life of fishes. It is clearly a must for anyone seriously interested in these subjects. — Franklin G. Hoover
( 80 )
REVIEWS 81
Fisheries Year Book and Directory 7968-69
Edited by Harry F. Tysser; British-Continental Trade Press Ltd., London, 1968; 444 p., illus- trated. £2. ,
The 196S-G0 ctlition of Fisheries Year Book and Dirertortj provides an interna- tional guide to tirms engaged in the fishery industry and iishing trades. Information on some 90 varieties of market fish and over 6,000 firms are presented in the edition.
A world fisheries stirvey of 33 nations provides the bacliground for the editorial and reference material that follows.
The editorial chapters present status reports on the cultivation of fish and shell- fish and other investigations and research being conducted in the United Kingdom.
Reference chapters cover a dictionary of fish names in 8 languages, a fish supply calendar, listings of organizations and trade associations, trade journals of interest to industry, reports on marketing, quick freezing, and oil and meal. A survey of new fishing vessels completed or on order and new equipment is also included.
In the directory section, listing of firms engaged in all facets of industrial sup- port allied to the fishing industry are indexed l)y national origin. Of particular interest to the industry is a classified buyers guide.
The wide range of information presented in this book makes it a valuable ref- erence to persons interested m all phases of the international fishing industry. — J. Gary Smith
1. Biometry: The Principles and Practice of Statistics in Biological Research
By Robert R. Sokal and F. James Rohlf; W. H. Freeman and Co., San Francisco, 1969; xxi -I- 776 p., illustrated. $15.00.
According to the authors, this book is aimed at academic biologists. It covers the subject of statistics from an elementary introduction up to advanced methods. It is designed to be used fur either a formal text with a course in statistics or for self- study.
The text represents the minimum required knowledge in statistics for a Ph.D. in biological sciences. The most important topics treated are simple statistical tests (including nonparametric tests), analysis of variance through factorial analysis, analysis of frequencies, regression and correlation.
The authors have found little correlation l)etween innate malhemalical ability and capability to understand biometrical methods. Statistical theory and mathe- matical derivations are therefore kept to a minimum, and emphasis is placed on teaching the students about which methods apply when, and how to apply them.
Special tables labeled "boxes" illustrate computational methods step-by-step, serv- ing later as quick summary reminders of techniques.
One chapter of the book deals with the application of digital computers to the solution of statistical problems. Several statistical programs are written in FOR- TRAN and included in an appendix.
Another appendix contains a key to statistical methods based on the purpose of research problems, by whether they are based on one or more samples, by whether the data are measurement variables or attributes, and other similar considerations. The key eventually leads the researcher to one of the "boxes" or other places in the book in which an appropriate method is featured.
The direct and personal style used by the authors and the wide but thonmgh coverage of the subject make this book a good prospect for biologists looking for a reference work on statistics. — Tiinot]iy C. Farley.
2. Statistical Tables
By F. James Rohlf and Robert R. Sokal; W. H. Freeman and Co., San Francisco, 1969; xi + 253 p., illustrated. $7.50 cloth, $2.75 paper.
The authors state that they included the statistical tables accompanying their text in a separate volume for ease of reference ; rather than searching through the text or thumbing to the back of the book to find a table referenced by the text, the reader can view both items simultaneously.
An introduction section on interpolation plus 83 tables and a list of mathematical constants make up the book. Each table has clear, concise instructions on its use. — ■ Timothy C. Farley.
82 CAIJFORNIA FISH AND GAME
Seashore Life of Southern California: An Introduction to the Animal Life of California Beaches South of Santa Barbara
By Sam Hinton; University of California Press; Berkeley and Los Angeles, 1969; 181 p., illustrated in color and black-and-white. $2.25 paper.
This informative and very reaclal>le booklet appears to be an expansion of Common Seashore Life of Southern California by Joel Hedgpeth and Sam Hinton (Natur- graph Company, 1061) and as such will be a welcome addition to many libraries.
Unfortunately, despite the author's efforts, there are many inaccuracies and inconsistencies in the text (e.s. the lack of required parentheses around certain authors' names, even though there is a lengthy discussion of this in the section on the Classification of Animals ; the incorrect statement that the solitary coral. Astrangia lajollaensis, is often found on the fronds of giant kelp; the failure to mention that the tube worm. Chaciopienis variopeclatus, is a typical inhabitant on marina floats, pilings, and the undersides of offshore rocks ; the use of Bryozoa rather than Ectoprocta to conform to the use of Endoprocta in listing phyla ; the failure to cite the California cone's small radula as the reason it has never been implicated in a human sting ; the many molluscan names which are not in keeping with recent literature; the fact that the poisonous sea urchin, Centrechinus maoci- caiuis, reported from Mission Bay, is proliably Cenfroslephanus coronatus. a com- monsubtidal inhabitant not mentioned in this book; etc.). These errors and omissions will not bother the casual lay reader, who will be unaware of them, nor will they seriously trouble the specialist, who will immediately recognize them. They will, however, cause trouble for the pseudo-specialist, those semi-learned and still learn- ing marine scientists employed by the numerous consulting and aero-space firms who have only recently discovered the ocean. Such workers all to frequently use booklets such as this as a panacea to answer their every inquiry regarding the ocean.
It is hoped that this book will be used as it is presumably intended, a general introduction to seashore life, and that a more thorough treatise will be sought for answers to specific questions concerning the nearshore marine environment and its ecologj-. — Charles H. Turner
Freshwater Fishes of Alabama
By William F. Smith — Vaniz; Exp. Sta., Auburn University, Auburn, Ala., 1968; V + 211 p., illustrated.
The last checklist of fishes in Alabama was written in 1865. The purpose of Freshicater Fishes of Alabama is to update that list, since some 50 new species have been reported. The author hopes this latest work will also serve as a research reference for future, more comprehensive work.
Species included are freshwater and a few marine species that occasionally occur during low flow periods of saline water intrusion.
The contents include a brief history of ichthyology in Alabama ; a discussion of common counts and measurements used and a glossary of key characteristics ; a key to families, and when two or more species common to a family are described, a key to species is presented. An annotated checklist following the key to species provides information on the known distribution in the State. An additional refer- ence to distribution is presented in several tables which relate the species to the 18 major river systems.
The author, in a rather "bare bones" fashion, has accomplished all of his goals, particularly in demonstrating the need for future, more comprehensive work. There was no stated or obvious logic in the sequence or composition of photographs pre- sented at the end of the book. The photographs are in black and white and often are poor in quality. I am certain they would be of little help in identifying species. The line illustrations of critical key characteristics in the keys would be helpful, how- ever.— Larry K. Puckett
Population, Resources, Environment
By Paul R. and Anne H. Ehrlich; W. H. Freeman and Co., Inc., San Francisco, California, 1970; 383 p., illustrated. $8.95.
Richard Goodwin of Connecticut College once said, "If I have any message for you it is only this, that the biologist has a higher duty than that of merely practicing his profession. He has special responsibilities because of his privileged position as an educated person, as a scientist and as a student of living organisms to play an active part in shaping human affairs ; to have his hands, so to speak,
KEVIEWS 83
on the space-ship controls. As a man he eats, drinks, pursues happiness, votes, reproduces and inflnonoos others. He is an integral part of tlie social system. As a leader he must be constantly mindful of the health of the entire enterprise."
This monumental work provides the first comprehensive, detailed analysis of the health of the entire enterprise and in particular the worldwide crisis of over- population and the resulting demands on food, resources, and the environment. The book covers a broad range of subjects from tlie destruction of the whale and sardine fisheries to a very readable section on pesticides and nitrojijcn poisoning.
If a fish and game liiologist is really concerned about saving the resources he works with, this book is a must in his library and as a guide to what actions he must take in life to slow down the extinction of many species including man himself. — Trd Woostrr.
The Marine Mammals of the North-western Coast of North America and the American Whale Fishery
By Charles M. Scammon; Manessier Publishing Company, Riverside, California, 1969; 319 p.. Illustrated. $29.00.
Long a collectors item, this classic of the literature on marine mammals is now available in a beautiful facsimile editi<m. First published in 1874, Scammon's book still remains a standard reference.
Scammon, with little schooling, was a remarkable observer and a consummate artist. In words and drawings, he captured with skill and beauty his mammalian subjects, from the 100 ft sulphurbottom (the whalers name for blue whah'l. the largest mammal which has ever lived, to the porpoise and sea otter. ITis drawings and descriptions of the hazardous occupation of whaling are of a spine-tingling quality. His whaling tales are as hard to put down as a good novel.
Young William Ilealey Dall. only 19 at the time, was stationed on Scammon's flagship as acting lieutenant on two trips to Alaska. Already a fine naturalist, Dall. later to reach eminence in his field, added kindling to Scammon's already awakened interest in whales and seals, and probably helped inspire Scammon to his eventual wi'iting of Marine Mammals. Dall called it the most important contri- bution to the life history of these animals.
In this year of heightened interest in the environment and conservation. Caiitain Scammon's description of the wholesale slaughter of whales and seals around the world is particularly timelJ^
Cambell Grant, detailing Scammon's biography in his introduction, brings out the little known facts of Scammon's contributions in the success of scientific explora- tion of Alaska and the important part he had in the plans to lay a cal)le across the Bering Sea l)etween Siberia and Russian America.
Victor B. Scheffer says of the whale in his Year of the Whale, "Moving through a dim dark, cool, watery world of its own. the whale is timeless and ancient ; part of our common heritage and yet remote, awful, prowling the ocean floor a half-mile down under the guidance of powers and senses we are only beginning to grasp." Charles Scammon brings these great animals to the surface for us to see and admire.
At a cost of $29.00 the purchase of this book will probably mean a sacrifice to most biologists who buy it, however, it will make a rewarding addition on any bookshelf. Here, over and al)Ove its scientific value, is a fitting companion to ^Melville for the lover of the sea. — John G. Carlisle, Jr.
The Central Desert of Baja California: Demography and Ecology
By Homer Aschmann; Manessier Publishing Company, Riverside, California, 1967; XIX -f- 282 p., illustrated. $12.00.
This book is leased on a doctoral dissertation : it is the result of 5 years of work, including two lengthy field trips in 1940 and use of the extensive resources of the Bancroft Library, Huntington Library, and the San Diego Presidio Museum.
Baja California once was inhabited by a large aboriginal population. Today few of these people live there ; this is especially true in the centi'al desert which is considered roughly as the area south of El Kosario and north of Comondu. The author describes, in some detail, the economy and social organization that enabled many Indians to wrest a living from this dry land, before they were "reduced" to Christianity.
In presenting his thesis, the authoi- also discusses the physical character of the central desert including climate, vegetation, soil, and other resources ; the Indians
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REVIEWS
85
ralist or beginning entomogy student will find it a valuable addition to his ry. — Ernest W. Lesh, Jr.
e Is the Desert
Ann Woodin, The MacMillaii ompany. New York, New York, 1970; 247 p., illustrated. $2.95 paperback.
lis book, written in a lis.t yet pbilosoidiii-al tone, deals prim.-irily with Ibc
, fauna and geology of th Arizona desert. Mrs. Woodin, the erudite wife of a
etologist, describes featun of this environment as it relates to the raising of
young family.
the course of her book s) recounts many humorous aiul dfligliirnl oxixM-ienccs
the wildlife of the area, iitersjiersed among tliese accounts, slie (h'livcu-s some
ted and perceptive conser^^;ion messages regarding the impact of man's activities
is world, and some fasciniing details in the life histories of des(!rt iidmbitanls.
account of a float trip (wn the Coloi-ado River prior to com|)letion of Cllcn
von Dam and inundation the area is a moving description of man's elTorl on
ire's works in (he name oprogress.
liis book's interesting mmre of ecology, nature study and philosophy makes h while reading for anyoi interested in our natural resources. — Jaiiicfi JTolvcn.
tming Fishes (Third Editioi
I George T. Baxter and Jami R. Simon; Bulletin No. 4, Wyoming Game and Fish Depart- ment, Cheyenne, Wyoming; i p., illustrated. $3.00 paper.
he third edition of this pai^rback book has been completely revised by the senior lor. Based on a recent suiey of Wyoming waters, the book di.scusses 78 species, luling native, introduced, ire and eiulangered, and possibly extinct species. The utilic names of all speciesiave been changed to conform with A irixt of Cohtmon Scientific ?\'(uiies of thch'ishcs From the United Hitiles (iiid (Uiniuhi, .second ion, special publication 1>. 2, American Fisheries Society. Distribution maps a been added for 44 specit.
he format of the book isogical and clear. There is a section entitled "(JenernI es on Fishes", which veryu'ielly discusses classilicatiou, scale fornuiti<ui, external tomy, and physiology. A sttion on "riiysiography and Ilydiograpliy of NVyomijig" •usses the major drainage and includes a map showing tlunr location, eys are included for ideutication to species. Information for each species includes hotograph, a distributiomuip (except for widely transplanted game species), a n'iption, life history inforation, current Wyoming hook ;nid line records, and an lanation of the scientific ame. A glossary is iucliuled.
'his is an excellent little lok, well worth $3 to any fisherman, conservationist, or inning fisheries student iio wishes to be better informed. — Kenneth A. llash- >i, Jr.
ir • p »^
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PrhliiHI C.-.LIFORNIA OFFICE OF STATE PKINTINC
L3t] — 800 10-70 5,300
84 CALIFORNIA FISH AND GAME
and their ecology and their contact with Europeans ; and finally, the decline of the Indians and its various causes.
The section concerned with Indian ecology (about J of the book) will especially interest those who love the desert, because it reveals how primitive people were able to live there. — Harold B. Clemens.
Lower California and Its Natural Resources
By Edward W. Nelson; Manessier Publishing Co., Riverside, California, 1966; XVI + 194 p., illustrations and maps. $12.50.
This is Volume XVI ; the Memoirs of the National Academy of Sciences. First published nearly 50 years ago, this classic has been out of print for a long time. However, because of its importance to scientists, students, and others interested in Lower California it has been reprinted in its entirety. In addition an introduction has been included, along with general biological information about the author who was former Chief of the U.S. Biological Survey.
In the early 1900's, personnel of the Biological Survey were engaged in detailed studies concerning the distribution of animal life and envir(jnmental relations, in the arid regions of the United States. It soon became apparent that similar infor- mation was needed about Lower California. Reliable data, however, was diiEcult to get so it was decided that the Biological Survey should undertake a recon- naissance of the peninsula.
Under the direction of E. W. Nelson, an expedition was started in March 1905 and ended in February 1906. It extended the entire length of lower California and crossed it eight times from coast to coast. The results are set forth in this volume.
The first part, about 35 pages, is devoted to a daily account of the expedition. It includes a general description of the country and the plants and animals that were encountered. The second part, about 59 pages, describes in more detail the mountains, plains and valleys, surface and underground water resources, and the climate of the peninsula. In the third part, about 31 pages, the author presents a general discussion of the plants and animals noted during the expedition ; then he divides Lower California into four major life zones (Arid Tropical, Lower Sonoran, Upper Sonoran, and Transition) and provides details about the plants, animals, and the environment in each zone. In the fourth section, about 8 pages, there is a brief discussion of the natural resources and the agriculture of Lower California. The fifth section, about 6 pages, is a brief summary of other significant expeditions into Lower California beginning with F. Deppe in 1S37 and ending in 1911 with an expedition by the American Museum of Natural History. The final portion of the volume is an excellent, 25-page bibliography of Lower Cali- fornia.— Harold B. Clemens.
A Field Guide to the Insects of America North of Mexico
By Donald J. Borror and Richard W. White; Houghton Mifflin Company, Boston, Mass., 1970; 404 p., illustrated. $5.95.
A Field Guide to the Insects of America North of Mexico is the 19th book in the growing list of field guides edited by Roger Tory Peterson. It is typical of the other guides in that the "Peterson System" of pictured keys with diagnostic arrows pointing out identifying characteristics is used. This system seems to Mork espe- cially well with insects since the structural details of insects may be more defini- tive than the field marks of larger animals.
Introductory chapters on the collection and preservation of in.sects, working w'itli living insects, the structure of insects, the growth and development of insects, and the classifying and naming of insects serve as a good introduction to the field of entomology. The systematic chapters discuss each order as to identification, similar orders, immature stages, habits, importance, classification, and number of species. Especially good are full colour plates illustrating the Odonata, Orthoptera, Hemip- tera, Homoptera, Coleoptera, Lepidoptera, Diptera, and Hymenoptera.
If any criticism can be made of this book it must be of the light treatment that the immature stages of insects receive. Immature stages are very briefly described in the general discussion of each order but only the adults are drawn. Man.v insects undergo radical changes in appearance and habit during their life cycle and may not be identifiable with the adult. More extensive treatment of this subject would have made this book more valuable than it already is.
In spite of this shortcoming A Field Guide to the Insects of Ame^-ica North of Mexico is an excellent guide to some 579 different families of insects. The amateur
REVIEWS 85
naturalist or beginning entomology student will find it a valuable addition to his library. — Ernest W. Lesh, Jr.
Home Is the Desert
By Ann Woodin, The MacMillan Company, New York, New York, 1970; 247 p., illustrated. $2.95 paperback.
This lidok. written in a liulit y<'t philosophical tone, deals primarily witli tlie flora, fauna and geology of the Arizona desert. Mrs. AVoodin, the erudite wife of a herpetologist, describes features of this environment as it relates to the raising of her young family.
In the course of her book she recounts many humorous and delightful experiences with the wildlife of the area. Interspersed among these accounts, she delivers some pointed and perceptive conservation messages regarding the impact of man's activities on his world, and some fascinating details in the life histories of desert inhabitants. Her account of a float trip down the Colorado River prior to completion of Glen Canyon Dam and imnidation of tlie area is a moving description of man's effort on nature's works in the name of progress.
This book's interesting mixture of ecology, nature study and philosophy makes worth while reading for anyone interested in our natural resources. — James Holven.
Wyoming Fishes (Third Edition)
By George T. Baxter and James R. Simon; Bulletin No. 4, Wyoming Game and Fish Depart- ment, Cheyenne, Wyoming; 168 p., illustrated. $3.00 paper.
The thii-d edition of this pai)erl)ack liof)k has been completely revised by the senior author. Based on a recent survey of Wyoming waters, the book discusses 78 species, including native, introduced, rare and endangered, and possibly extinct species. The scientific names of all species have been changed to conform with A I/ist of Common and Scientific Names of the Fishes From the United States and Canada, second edition, special publication No. 2, American Fisheries Society. Distribution nuips have been added for 44 species.
The format of the book is logical and clear. There is a section entitled "General Notes on Fhshes", which very briefly discusses classification, scale formation, external anatomy, and physiology. A section on "Physiography and Hydrography of Wyoming" discusses the major drainages, and includes a map showing tlieir location.
Keys are included for identification to species. Information for each species includes a photograph, a distribution map (except for widely transplanted game species), a description, life history information, current Wyoming hook and line records, and an explanation of the scientific name. A glossary is included.
This is an excellent little book, well worth $3 to any fisherman, conservationist, or beginning fisheries student who wishes to be better informed. — Kenneth A. Hash- agen, Jr.
printed in California office of state printing 81136—800 10-70 5,300
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