NOAA TR NMFS SSRF-655

NOAA Technical Report NMFS SSRF-655

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Immobilization of Fingerling Salmon and
Trout by Decompression

DOYLE F. SUTHERLAND

yfoods Hole, ^Aas*♦

SEATTLE, WA
March 1972

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^^O ftTMQSp,

'"''"^^F^src.o^

U.S. DEPARTMENT OF COMMERCE
Peter G. Peterson, Secretary

NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
Robert M. White, Administrator

NATIONAL MARINE FISHERIES SERVICE
Philip M. Roedel, Director

NOAA Technical Report NMFS SSRF-655

Immobilization of Fingerling Salmon and
Trout by Decompression

DOYLE F. SUTHERLAND

Marine Biological Laboratory

LIBRARY

SEP 1 3 1972

Woods Hole, Mass.

SEAHLE, WA
March 1972

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CONTENTS

Page

Introduction 1

Methods and materials 2

Laboratory study 2

Ice Harbor Dam study 3

Laboratory study of decompression 4

Immobilized fingerlings below Ice Harbor Dam 5

Literature cited 7

m

Immobilization of Fingerling Salmon and Trout
by Decompression

By

DOYLE F. SUTHERLAND, Fishery Biologist

National Marine Fisheries Service

Nortiiwest Fisheries Center

2725 Montlake Boulevard East

Seattle, Washington 98102

ABSTRACT

Laboratory experiments revealed that some chinook salmon {Oncorhynchiis tsh<v-
wytscha) and coho salmon (0. kisutch) fingerlings are immobilized when decompressed
from atmospheric pressure to high negative pressures. About 69 S^^ of the chinook salm-
on were partially or completely immobilized at 71 cm of mercury vacuum, 48% at 61 cm,
17% at 51 cm, and none at 41 cm. The effects developed rapidly, peaking 5 min after
exposure. The coho salmon, in comparison, were less severely affected. Only 9% were
immobilized at 71 and 61 cm of mercury vacuum (reached 10 min after exposure), 2%
at 51 cm (5 min after exposure), and none at 41 cm.

Studies (with coho salmon and rainbow trout [Salmo gairdneri] ) to determine the
effects of decompression within a turbine of a dam did not provide conclusive results.
However, some fingerlings caught in the tailrace immediately after their release in the
turbine intake were immobilized. Exposure to negative pressure below turbine runner
blades is one possible cause of immobilization.

INTRODUCTION

Many fingerling salmon and trout are injured
or killed by physical contact with turbines and
other structures within dams. Others are be-
lieved to suffer shock or death from severe pres-
sure changes encountered during passage
through dams (Schoeneman, Pressey, and Junge,
1961; Cramer and Oligher, 1964). Immobilized
fingerling salmon and trout have been observed
in turbine discharges of high and low dams on
the Columbia and Snake Rivers. The present
study, conducted in a laboratory and at Ice
Harbor Dam, was undertaken as a result of these

observations and examines the role of decom-
pression as a possible cause of immobilization.
The Kaplan turbines at Ice Harbor Dam have
an area of low negative pressure below the blades
that theoretically averages about one-half at-
mosphere (38 cm of mercury vacuum) when the
turbines are operated at rated capacity." The
actual level of negative pressure below the tur-
bine blades is not known but must be consider-
ably greater than the 38 cm theoretical average.

' Personal communication, S. Scott, U.S. Army Corps
of Engineers.

It is also known that decompression to levels
present in the turbines can be harmful to juvenile
Pacific salmon. In a study of the effects of neg-
ative pressure on fingerling chinook salmon,
Holmes and Donaldson' found that test fish suf-
fered an average of 3.5% mortality when de-
compressed from 18 psi to —2 psi. Muir (1959)
reported that fingerling coho salmon exposed to
negative pressures of 12.7-73.7 cm/Hg for 0.1-
2.3 sec appeared to be stunned momentarily but
concluded that decompression to partial vacuum
was not likely to kill the fish unless accompanied
by cavitation. Harvey (1963) concluded from
his studies and comprehensive review of the lit-
erature that the effects of decompression de-
pended on the condition of the fish and physical
factors in the environment as well as on the mag-
nitude of the vacuum.

Immobilized fingerling salmon and trout were
first observed at Ice Harbor Dam in 1966.
Marked juvenile coho salmon and rainbow trout
were released in a turbine intake and recovered
in a funnel net attached to the draft tube exit.
Some of the fish recovered swam normally;
others were dead or in distress. Either the
turbine or net could conceivably have produced
the effects observed. Therefore, laboratory ex-
periments were conducted to isolate and examine
the effects of pressure change alone. The present
paper reports the results of this research and
subsequent observations of immobilized fish at
Ice Harbor Dam.

METHODS AND MATERIALS

Laboratory Study

In this study chinook salmon fingerlings were
substituted for rainbow trout as the latter spe-
cies was not readily available. The chinook
salmon fingerlings were downstream migrants
caught in the gatewells of McNary Dam, Uma-
tilla, Oreg. The coho salmon were nonmigrants
taken from the White Salmon Federal Hatchery,
White Salmon, Wash. All fish were transported
to the test site by tank truck and held in a fish-
holding facility (described below) for at least
2 days before they were used in decompression

' Holmes, H. B., and I. J. Donaldson. A study of the
effect of pressure changes upon salmon fingerlings as
applied to passage through spillway at Mayfield Dam,
Cowlitz River, Wash. (Unpubl. manuscr., 18 p.)

tests. Fork lengths of the two lots of fish were
approximately the same; the chinook salmon
ranged from 119 to 180 mm and the coho salmon
from 135 to 190 mm. The slight size difference
is believed to have had little or no influence on
the comparative response of the two species to
negative pressure.

The experimental apparatus consisted of two
main components: (1) the fish-holding-recir-
culating system and (2) the pressure chamber-
vacuum system. The basic arrangement (except
for the vacuum pump and filter) is illustrated
in Figure 1. A round wooden tank served as
the holding facility. Water from the water main
of Pasco, Wash., treated with sodium thiosulfate
to neutralize the chlorinity, was continuously re-
circulated through a sand and charcoal filter and
aerated by a diaphragm compressor. The water
temperature was maintained at 9.0° C ± 0.5° C
by a portable refrigeration system.

The pressure chamber was built from a
129.4-cm length of heavy-duty iron pipe, 30.5 cm
in diameter. End plates of clear plastic, 2.5 cm
thick, permitted observation of the test fish.
Access to the chamber was gained through a
port made from a 10.2-cm pipe sleeve fitted with
a flange and cover plate. Additional sleeves pro-
vided plumbing attachments for water intake
and discharge lines, air exhaust port, pressure
gauge, and vacuum line. A 3,785-liter (1,000-
gallon) tank served as a vacuum reservoir and
was connected to the pressure chamber by a rub-
ber hose 1.9 cm thick. The vacuum was applied
by activating a hand-operated, 2.5-cm ball valve
on the chamber end of the hose.

The amount of negative pressure applied to
the chamber was controlled by evacuating the
reservoir to the desired level as indicated on a
gauge. A second gauge plumbed into the cham-
ber monitored the pressure change. The vac-
uum was relieved by closing the vacuum line
valve and venting the chamber by opening a
second .6-cm ball valve.

About 1 sec was required to obtain 61 cm of
mercury vacuum in the chamber when it was
filled with water; 21/2 sec were required to reach
71 cm of mercury vacuum because of the large
amount of dissolved gasses liberated by the low
negative pressure. At all negative pressures,
it took one-half second to relieve the vacuum by
opening the relief valve and closing the vacuum
line valve.

Discharge line

Vacuum gouge
Air exhaust X End plate a

-N \. ^P Plastic window

122 cm X 183cm
Fish holding tank

9

Aerator

Water pump

Chiller Cooling coils

Figure 1. — Fish holding-recirculating system and pressure chamber vacuum system.

All test fish were held in the laboratory hold-
ing facility for a minimum of 2 days and in the
pressure chamber for 1 hr before testing. After
exposure to negative pressure, the fish were held
in chambers for observation for as long as 1.5 hr,
then transferred to the holding facility for final
observation at the end of 24 hr. Water from
the holding facility was circulated through the
chamber at atmospheric pressure before and
after each test.

Counts were taken of the numbers of fish par-
tially immobilized, completely immobilized, and
dead during the following periods after expos-
ure: 5, 10, 20, 30, 40, 50, 60, and 90 min and
24 hr. Partially immobilized fish were recog-
nized by their feeble eflforts to swim; completely
immobilized fish were identified by spasmodic
movements or absence of movement other than
respiratory. Those fish showing no evidence of
opercular movement were considered dead, sub-
ject to later verification.

Each treatment was repeated three times on
different groups of each species, for a total of
six tests at each vacuum level. The number in
each test averaged 16 for wild chinook salmon
and 23 for the hatchery coho salmon for a total
of 151 chinook and 216 coho salmon. The re-
sponse of the test fish to decompression was com-
puted from the three tests at each negative pres-
sure and expressed as an average response. The
order in which the fish were tested was dictated
more by availability than by design. Generally
the testing proceeded from the highest vacuum
level to the next lower level.

Ice Harbor Dam Study

The coho salmon and rainbow trout tested in
the turbines at Ice Harbor Dam had been reared
in hatcheries to about 100-127 mm long. They
were transported to temporary holding tanks
near the dam a few days before the test to per-
mit them to acclimate to Snake River water.
Each fish was marked with a cryogenic brand
to identify it as to time and place of release. A
total of 5,408 coho salmon and 2,291 rainbow
trout were branded and released in the turbines
in 11 tests that began 11 October and ended 30
November 1966.

The test equipment used for studies of finger-
ling mortality in turbines was described by Long
and Marquette (1967). It consisted of three
basic components — a release hose extending from
the deck of the dam to the turbine intake, a fun-
nel net attached to the draft tube exit, and a
recovery barge secured to the cod end of the
net. A trough with several screened compart-
ments was placed on the barge to hold immo-
bilized fish for observation.

The test fish passed through a turbine that was
being operated at rated or overload capacity.
The first of the fish usually arrived at the barge
within 3 min and the majority within 20 min
after release. Those fish with characteristic
symptoms of immobilization associated with de-
compression, yet apparently free of net or tur-
bine injury, were immediately put into individual
holding compartments for further observation.
The times of release in the turbine intake, of

capture in the barge, and of recovery or death
were recorded for each fish. All live immobilized
fish were transferred at the end of the work day
to the holding tanks near the dam and held for
at least 3 days to evaluate delayed effects.

LABORATORY STUDY OF
DECOMPRESSION

Some fish were examined at the highest vac-
uum attainable with the system employed (71 cm
of mercury vacuum) . Other groups were then
tested at successively lower levels to the lowest
level of vacuum that produced immobility (61,
51, and 41 cm of mercury vacuum) . For valid
comparison of the laboratory results with those
in the field, it was desirable to simulate field
conditions by decompressing the fish as rapidly
as when passing a turbine (one-half second or
less). In exploratory trials with a small pres-
sure chamber (10.2 X 121.9 cm), a high level
of negative pressure could be achieved in a frac-
tion of a second. The test fish, however — par-
ticularly the wild Chinook salmon — did not ap-
pear to acclimate to the restricted environment.
Subsequently, a larger pressure chamber (30.5
X 144.8 cm) was used, although the time re-
quired to reach high negative pressures was in-
creased slightly.

The term "precondition" as used here means
allowing the fish time to readjust the gas volume
of the swim bladder to achieve neutral buoyancy
with respect to the water density at atmospheric
pressure in the excitement of being caught and
transferred to the pressure chamber. Harvey
(1963) described this behavior as a fright re-
action whereby fish force gas from the swim
bladder out through the pneumatic duct, de-
creasing buoyancy and facilitating escape by de-
scent to greater depths. In the tests this be-
havior was more pronounced among wild chinook
salmon than among hatchery coho salmon. Im-
mediately after being placed in the chamber,
the fish descended to the bottom where they re-
mained relatively motionless. The hardy indi-
viduals generally swam to the surface after about
5 min, gulped air, returned to the bottom, and
repeated the process until neutral buoyancy was
established. About 1 hr was required to re-
equilibrate all members of a test group; this
amount of time was subsequently adopted in the
standard test procedure.

Some chinook salmon fingerlings developed
partial immobility soon after decompression
(Fig. 2); peak levels of 17% at 51 cm, 43% at
61 cm, and 60% at 71 cm of mercury vacuum
were reached about 5 min after exposure. These
fish either recovered from partial immobility or
developed further complications leading to com-
plete immobility. The symptomatic transition
proceeded slowly but at a relatively uniform rate
of slightly less than 1% per min, although small
percentages were partially immobilized after
several hours.

Complete immobility occurred among some
chinook salmon fingerlings within a few seconds
after exposure to 61 and 71 cm of mercury vac-
uum. Others developed the condition after sev-
eral minutes of partial immobility (peak per-
centage 60 min after exposure to 61 cm and 30
min after exposure to 71 cm). None were com-
pletely immobilized by 51 cm of mercury vac-
uum. Most fish died that had developed complete
immobility after several minutes of partial im-
mobility. The percentages of deaths from expo-

PARTIAL IMMOBILITY

CENTIMETERS OF MERCURY VACUUM

51

61

71

5 10 20 30 ^O 50 60 70 80 90 1440
TIME AFTER EXPOSURE (MINUTES)

Figure 2. — Chinook salmon fingerlings partially immo-
bilized, completely immobilized, or dead after exposure
to various levels of negative pressure, by time after
exposure.

sure to the higher negative pressures were 24%
at 61 cm and 20% at 71 cm mercury vacuum.
The response of coho salmon fingerlings to
decompression is shown in Figure 3. Symptoms
of partial immobility developed in 2, 8, and 5%
of the fish decompressed at 51, 61, and 71 cm
of mercury vacuum, respectively. Ten minutes
were required for development of the symptoms,
compared to 5 min for the chinook salmon. No
fish were completely immobilized after exposure
to 51 cm of mercury vacuum ; peak percentages
were only 2% at 61 cm of mercury vacuum and
5% at 71 cm. Only 3% died from exposure to
71cm.

10

5

- 0

" 10
o:

UJ
Q.

- 5

o: 10

PARTIAL IMMOBILITY

CENTIMETERS OF MERCURY VACUUM
51

AH

COMPLETE IMMOBILITY

DEATH

5 10 20 30 40 50 60 70 80 90 1440
TIME AFTER EXPOSURE (MINUTES)

Figrure 3. — Coho salmon fingerlings partially immo-
bilized, completely immobilized, or dead after exposure
to various levels of negative pressure, by time after
exposure.

Wild chinook salmon were more susceptible to
the effects of decompression than were hatchery
coho salmon. The difference between species
varied with level of vacuum; the greatest dif-
ference occurred within 5 min after exposure
to 71 cm of mercury vacuum, when 69% of chi-
nook salmon were either partially or completely
immobilized as compared with 6% of the coho
salmon. At 41 cm of mercury vacuum, no re-
sponse to decompression was observed for either
species.

The duration of exposure to negative pressure,
or the rate at which fish subjected to reduction
from atmospheric pressure to a specific level of
negative pressure, probably influenced the ab-
solute if not the relative results. Holmes and
Rucker (cited by Holmes and Davidson, see foot-
note 2) found that chinook salmon fingerlings
lived if allowed 1 sec to adjust to decompression
from 40 psi to atmospheric pressure. In the
present tests, 2.5 sec were required to reach
71 cm of mercury vacuum from a.tmospheric
pressure and another 0.5 sec to relieve the vac-
uum. The test was executed in slightly less time
at 51 and 61 cm of mercury vacuum.

IMMOBILIZED FINGERLINGS BELOW

ICE HARBOR DAM

During the turbine studies at Ice Harbor Dam,
recovered test fish were closely observed for
symptoms of immobilization similar to those
manifested by fish decompressed in the labora-
tory. The first immobilized fish were seen on 4
November during the fourth test (Table 1). On

Table 1.— Duration of immobilization of individual coho salmon

and rainbow trout fingerlings recovered in the funnel

net at Ice Harbor Dam

, 4 November

- 6 December 1966.

Date
1966

Species

Time from release

in turbine to
capture in funnel net

Time
fish was immobilized

Observed Estimated

Time from release

in turbine

to recovery from

immobilization

Condition of fish
after 3 days

min

min

min

min

4 Nov.

Coho

6

4

9

10

Alive

Coho

6

62

67

68

Alive

16 Nov.

Rainbow

20

29

48

49

Alive

18 Nov.

Rainbow

22

1

I

1

Alive

22 Nov.

Rainbow

41

I

1

1

Dead

Rainbow

43

1

1

t

Dead

30 Nov.

Rainbow

18

77

94

95

Alive

2 Dec.

Rainbow

10

13

22

23

Alive

6 Dec.

Rainbow

6

14

19

20

Alive

' Remained immobilized for several hours.

that date two coho salmon that had behaved
identically to fish immobilized by decompression
were caught 6 min after release in the turbine.
They were quickly removed to individual holding
pens, where one recovered within 4 min and the
other within 62 min. The minimum travel time
from release point to the barge was about 3 min;
1 of the 3 min was required for travel from the
release point to the area of negative pressure
below the turbine blades. One of the coho salmon
was thus immobilized for a maximum of 9 min
and the other for 67 min after passing the tur-
bine blades. The recovery times of both fish were
within the range for recovery from immobiliza-
tion established in the laboratory. The two fish
were transferred later in the day to the shore
holding tank for observation of post immobiliza-
tion effects. Recovery was evidently complete,
for no adverse effects developed within 3 days.

Hatchery-reared rainbow trout were used in
the seven tests that followed (Nos. 5-11); immo-
bilized fish were found in six (Table 1). The
relatively high frequency of recovery of affected
fish suggests that either rainbow trout were more
easily immobilized than coho salmon or that sam-
pling efficiency increased with time. The former
appears more likely — the three completely immo-
bilized trout caught in tests 6 and 7 (November
18, 22) remained immobilized several hours. The
exact time of their recovery or death was not
determined. They were still immobilized when
transferred from the barge to the holding tank
late in the day. One recovered during the night
and was alive 3 days later; the other two died
during the night.

The four immobilized trout caught in tests 5,
9, 10, and 11 (16 and 30 November; 2 and 6
December) recovered on the barge while under
observation. At most, they were immobilized
from 19 (test 11) to 94 min (test 9) after pass-
ing the turbine blades. The minimum period of
immobilization ranged from 13 (test 10) to 77
min (test 9). The four fish survived a 3-day
holding period. The one caught in test 11 was
alive and evidently normal after 30 days of ob-
servation for possible development of latent
lethal effects.

Although few immobilized fish were caught in
the turbine discharge, the small catch assumes
greater significance when the methods of cap-
ture are considered. Of the total turbine dis-
charge screened by the funnel net, slightly less

than 1% entered the recovery barge; the rest
filtered through the meshes of the net. An esti-
rriated 18% of the test fish released in the turbine
were killed by impingement against the net and
a much higher percentage injured by physical
contact.

For immobilized fish to reach the recovery
barge uninjured (not lacerated, descaled, etc.),
they would have to be passively transported the
length of the net by that flow directed toward
the cod end.

Because the net may have caused immobiliza-
tion by impingement, it was highly desirable to
obtain samples of immobilized fish in the general
area occupied by the net in the 1966 tests. Field
parties with long-handed dip nets cruised the
area in boats just after releases in April and
May 1967 to search for fish in distress. Although
many such fish were seen to surface, most were
picked up by hovering gulls or pulled under the
surface by turbulence before they could be
reached. For the final test (10 May), a small
inclined-screen scoop trap (50.8 cm deep and
121.9 cm wide) was anchored in the turbine dis-
charge. It, too, proved of little value for col-
lecting distressed fish. The total catch by both
methods was only five immobilized fish. All of
them displayed the symptoms characteristic of
decompression, erratic motion followed by in-
activity and sinking. Observed immobilization
ranged from 2 to 6 min, and the computed max-
imum period of immobilization ranged from 6
to 18 min (Table 2).

Inherent in this study is the assumption that
immobilization was due to decompression. The
assumption is supported by laboratory experi-

Table 2. — Duration of immobilization of individual coho
salmon fingerlings caught by dip net and scoop trap
in the turbine discharge, 14 April - 10 May 1967.'

Time Time

from release u"^^ from release

Date in turbine to . "®^.^?^ , in turbine

1967 capture in immobilized to recovery

dip net and observed Estimated Jl^.'i?,™:
scoop trap — v,.i,,„*,„

mobilization

14 April

21 AprU
10 May

mm
3
5

14
7

11

mm
5
2
5
4
6

m.m

7

6

18

10

16

mm

8

7

19

11

17

All fish survived a 3-day holding period.

ments in which fingerling chinook and coho salm-
on were immobilized by exposure to negative
pressure and by two items of indirect evidence:
(1) regions of negative pressure within turbines
and (2) immobilization of some fingerling salm-
on and trout after passage through turbines.
The assumption, however, cannot be tested in
situ, and some (if not all) of the fish may have
been immobilized by factors other than decom-
pression.

Because of the limited sampling, the data are
of little analytical value but suggest that sig-
nificant numbers of fish passing through a tur-
bine are immobilized by physical forces in the
turbine. Those fish that experience sublethal
immobilization must surely contribute indirectly
to the total loss at dams. At a river velocity of
1 m per sec, 10 min of immobilization would
expose fish to predation for more than one-half
kilometer. An accurate measure of total mor-
tality due to turbines, then, requires an evalu-
ation of direct and indirect losses. It may best
be derived by determining the number of sur-
vivors passing a point several kilometers down-
stream from the dam.

LITERATURE CITED

CRAMER, F. K., and R. C. OLIGHER.

1964. Passing fish through hydraulic tur-
bines. Trans. Am. Fish. Soc. 93: 243-259.
HARVEY, H. H.

1963. Pressure in the early life history of
sockeye salmon. Ph.D. Thesis, Univ. Brit-
ish Columbia, Vancouver, Can., 222 p.
LONG, C. W., and W. M. MARQUETTE.

1967. Research on fingerling mortality in
Kaplan turbines. Proc. 6th Bienn. Hy-
draul. Conf., Moscow, Idaho, Oct. 18-19,
1967, p. 11-36. Wash. State Univ., Pull-
man. [Processed.]
MUIR, J. F.

1959. Passage of young fish through tur-
bines. Proc. Am. Soc. Civ. Eng., J. Power
Div. 80 (PO 1), Part 1: 23-46.
SCHOENEMAN, D. E., R. T. PRESSEY, and
C. 0. JUNGE, JR.

1961. Mortalities of downstream migrant
salmon at McNary Dam. Trans. Am.
Fish. Soc. 90: 58-72.

GPO 999-981

MBL WHOI Llbrai

ibrary ■

ii'iimiiii

SE 01835

621. Predation by sculpins on fall chinook salmon,
Oiicorhynchus tshnwptscha, fry of hatchery or-
igin. By Benjamin G. Patten. February 1971,
iii + 14 pp., 6 figs., 9 tables.

622. Number and lengths, by season, of fishes caught
with an otter trawl near Woods Hole, Massa-
chusetts, September 1961 to December 1962.
By F. E. Lux and F. E. Nichy. February 1971,
iii + 1.5 pp., 3 figs., 19 tables.

623. Apparent abundance, distribution, and migra-
tions of albacore, Thiinnus aluliniga, on the North
Pacific longline grounds. By Brian J. Roth.schild
and Marian Y. Y. Yong. September 1970, v +
37 pp., 19 figs., 5 tables.

624. Influence of mechanical processing on the quality
and yield of bay scallop meats. By N. B. Webb
and F. B. Thoma.s. April 1971, ii"i -|- 11 pp., 9
figs., 3 tables.

625. Distribution of salmon and related oceanographie
features in the North Pacific Ocean, spring 1968.
By Robert R. French, Richard G. Bakkala, Ma-
sanao Osako, and Jun Ito. March 1971, iii -|-
22 pp., 19 figs., 3 tables.

626. Commercial fishery and biology of the fresh-
water shrimp, Macrobrachiiim, in the Lower St.
Paul Riyer, Liberia, 1952-53. By George C. Mil-
ler. February 1971, iii -f 13 pp., 8 figs., 7 tables.

627. Calico scallops of the Southeastern United States,
1959-69. By Robert Cummins, Jr. June 1971,
iii -I- 22 pp., 23 figs., 3 tables.

628. Fur Seal Investigations, 1969. By NMFS, Ma-
rine Mammal Biological Laboratory. August
1971, 82 pp., 20 figs., 44 tables, 23 appendix A
tables, 10 appendix B tables.

629. Analysis of the operations of seyen Hawaiian
skipjack tuna fishing yessels, June-August 1967.
By Richard N. Uchida and Ray F. Sumida.
March 1971, y -|- 25 pp., 14 figs., 21 tables. For
sale by the Superintendent of Documents, U.S.
Goyernment Printing Office, Washington, D.C.
20402 - 35 cents.

630. Blue crab meat. I. Preservation by freezing.
July 1971, iii + 13 pp., 5 figs., 2 tables." II. Eflfect
of chemical treatments on acceptability. By
Jurgen H. Strasser, Jean S. Lennon, and Fred-
erick J. King. July 1971, iii -f 12 pp., 1 fig., 9
tables.

631. Occurrence of thiaminase in some common aquat-
ic animals of the United States and Canada. By
R. A. Greig and R. H. Gnaedinger. July 1971,
iii + 7 pp., 2 tables.

632. An annotated bibliography of attempts to rear
the larvae of marine fishes in the laboratory. By
Robert C. May. August 1971, iii + 24 pp.; 1 ap-
pendix I table, 1 appendi.K II table. For sale by
the Superintendent of Documents, U.S. Govern-
ment Printing Office, Washington, D.C. 20402 -
35 cents.

633. Blueing of processed crab meat. II. Identification
of some factors involved in the blue discoloration
of canned crab meat Callincctes sapidiis. By
Melvin E. Waters. May 1971, iii + 7 pp., 1 fig!,

3 tables.

634. Age composition, weight, length, and sex of her-
ring, CInpea pallasii, used for reduction in Alas-
ka, 1929-66. By Gerald M. Reid. July 1971,
iii + 25 pp., 4 figs., 18 tables.

635. A bibliography of the blackfin tuna, Thuniins
nthniticus (Lesson). By Grant L. Beardsley and
David C. Simmons. August 1971, 10 pp. For
sale by the Superintendent of Documents, U.S.
Goverhment Printing Office, Washington, D.C.
20402 - 25 cents.

636. Oil pollution on Wake Island from the tanker
R. C. Stoner. By Reginald M. Gooding. May
1971, iii + 12 pp., 8 figs., 2 tables. For sale by
the Superintendent of Documents, U.S. Govern-
ment Printing Office, Washington, D.C. 20402 -
Price 25 cents.

637. Occurrence of larval, juvenile, and mature crabs
in the vicinity of Beaufort Inlet, North Carolina.
By Donnie L. Dudley and I\Iayo H. Judy. August
1971, iii + 10 pp., 1 fig., 5 tables. For sale by
the Superintendent of Documents, U.S. Govern-
ment Printing Office, Washington, D.C. 20402 -
Price 25 cents.

638. Length-weight relations of haddock from com-
mercial landings in New England, 1931-55. By
Bradford E. Brown and Richard C. Hennemuth.
August 1971, V -f 13 pp., 16 fig., 6 tables, 10
appendix A tables. For sale by tlie Superintend-
ent of Documents, U.S. Government Printing
Office, Washington, D.C. 20402 - Price 25 cents.

B39. A hydrographic survey of the Galveston Bay
system, Texas 1963-66. By E. J. Pullen, W. L.
Trent, and G. B. Adams. October 1971, v +
13 pp., 15 figs., 12 tables. For sale by the .Super-
intendent of Documents, U.S. Government Print-
ing Oflftce, Washington, D.C. 20402 - Price 30
cents.

640. Annotated bibliography on the fishing industry
and biology of the blue crab, CnUincctes sapidus.
By Marlin E. Tagatz and Ann Bowman Hall.
August 1971, 94 pp. For sale by the Superinten-
dent of Documents, U.S. Government Printing
Oilice, Washington, D.C. 20402 - Price $1.00.

641. Use of threadfin shad, Dorosoma petenense, as
live bait during experimental pole-and-line fish-
ing for skipjack tuna, Katsiiwomis pelamis, in
Hawaii. By Robert T. B. Iversen. August 1971,
iii + 10 pp., 3 figs., 7 tables. For sale by the
Superintendent of Documents, U.S. Government
Printing Office, Washington, D.C. 20402 - Price
25 cents.

642. Atlantic menhaden Brevoortia tyrannus resource
and fishery — analysis of decline. By Kenneth
A. Henry. August 1971, v + 32 pp., 40 figs., 5
appendix figs., 3 tables, 2 appendix tables. For
sale by the Superintendent of Documents, U.S.
Government Printing Office, Washington, D.C.
20402 - Price 45 cents.

646. Dissolved nitrogen concentrations in the Colum-
bia and Snake Rivers in 1970 and their eff'ect on
chinook salmon and steelhead trout. By Wesley
J. Ebel. August 1971, iii + 7 pp., 2 figs., 6
tables. For sale by the Superintendent of Doc-
uments, U.S. Government Printing Office, Wash-
ington, D.C. 20402 - Price 20 cents.

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