CALIFORNIA FISH™ GAME "CONSERVATION OF WILDLIFE THROUGH EDUCATION" VOLUME 75 APRIL 1989 NUMBER 2 LrMJ c'~ " "1 ~^^\ Vl California Fish and Game is a journal devoted to the conservation and understanding of fish and wildlife. If its contents are reproduced elsewhere, the authors and the California Department of Fish and Game would appreciate being acknowledged. Subscriptions may be obtained at the rate of $10 per year by placing an order with the California Department of Fish and Game, 2201 Garden Road, Monte- rey, CA 93940. Money orders or checks should be made out to California Fish and Game. Inquiries regarding paid subscriptions should be directed to the Editor. Complimentary subscriptions are granted on an exchange basis. Please direct correspondence to: Robert N. Lea, Ph.D., Editor-in-Chief California Fish and Game 2201 Garden Road Monterey, CA 93940 u 1 0 V VOLUME 75 APRIL 1989 NUMBER 2 Published Quarterly by STATE OF CALIFORNIA THE RESOURCES AGENCY DEPARTMENT OF FISH AND GAME — LDA— STATE OF CALIFORNIA GEORGE DEUKMEJIAN, Governor THE RESOURCES AGENCY GORDON VAN VLECK, Secretary for Resources FISH AND GAME COMMISSION ROBERT A. BRYANT, President Yuba City JOHN A. MURDY III, Vice President E. M. McCRACKEN, JR., Member Newport Beach Carmichael ALBERT C. TAUCHER, Member BENJAMIN F. BIAGGINI, Member Long Beach San Francisco HAROLD C. CRIBBS Executive Secretary DEPARTMENT OF FISH AND GAME PETE BONTADELLI, Director 1416 9th Street Sacramento 95814 CALIFORNIA FISH AND GAME Editorial Staff Editorial staff for this issue: Editor-in-Chief Robert N. Lea, Ph.D. Editorial Assistant Lisa L. Smith Inland Fisheries Arthur C. Knutson, Jr. Marine Resources Peter L. Haaker and Robert N. Lea Wildlife Bruce E. Deuel 67 CONTENTS Page Ichthyoplankton of Lake Havasu, a Colorado River Impoundment, Arizona-California Paul C. Marsh and Diana Papoulias 68 Seasonal Abundance and Feeding Habits of Sharks of the Lower Gulf of California, Mexico Felipe Galvan-Magana, Henk J. Nienhuis, and A. Peter Klimley 74 Wetland Bird Seasonal Abundance and Habitat Use at Lake Earl and Lake Talawa, California Steven L. Funderburk and Paul F. Springer 85 Life History of the Sevengill Shark, Notorynchus cepedianus Peron, in Two Northern California Bays David A. Ebert 102 Rice Available to Waterfowl in Harvested Fields in the Sacramento Valley, California Michael R. Miller, David E. Sharp, David S. Gilmer, and William R. Mulvaney 113 NOTES Pacificogramma stepanenkoi Kharin, 1983 (Family Grammatidae), a Junior Synonym of Pronotogrammus multifasciatus Gill, 1863 (Family Serranidae) M. Eric Anderson and Richard H. Rosenblatt 124 Improved Self-Cleaning Screen for Processing Benthic Samples Ned H. Euliss, Jr. and George A. Swanson 126 58 CALIFORNIA FISH AND GAME Calif. Fish and Came 75(2): 68-73 1 989 ICHTHYOPLANKTON OF LAKE HAVASU, A COLORADO RIVER IMPOUNDMENT, ARIZONA-CALIFORNIA1 PAUL C. MARSH AND DIANA PAPOULIAS 2 Center for Environmental Studies and Department of Zoology Arizona State University Tempe, Arizona 85287 Eight fish species representing six families were identified among ichthyoplank- ton samples taken from Lake Havasu, Arizona-California, during springs of 1985 and 1986. Threadfin shad, Oorosoma petenense; common carp, Cyprinus carpio; and sunfishes, Lepomis spp., were predominant, with fewer numbers of razorback sucker, Xyrauchen texanus; black crapple, Pomoxis nigromaculatus; largemouth bass, Micropterus salmoldes; channel catfish, Ictalurus punctatus; and striped bass, Morone saxatilis. Although the razorback sucker reproduces upstream in Lake Mohave, larvae captured during this study constitutes the first evidence of spawning by this species in Lake Havasu since the 1950s. INTRODUCTION Mainstream impoundments on the lower Colorado River support important recreational fisheries for non-native fish species. Some, like rainbow trout, Sa/mo gairdneri, are maintained by hatchery plants while other species, such as largemouth bass, Micropterus salmoides, and channel catfish, ictalurus puncta- tus, rely largely on natural reproduction. Although knowledge of larval distribution, abundance, and ecology is important for assessing fish populations (e.g., Lagler 1956, Nikolsky 1963, Braum 1978), no larval fish reports have been published for the lower Colorado River since 1954 (Winn and Miller 1954). California Department of Fish and Game (CDFG) netting for larval striped bass, Morone saxatilis, in Lake Havasu, Arizona-California (Giusti and Milliron 1988), provided an opportunity to determine the occurrence of other fish species. STUDY AREA The study area (Figure 1 ) comprised two distinct sections: 1 ) a relatively cold ( <20°C), upstream river reach beginning 67 km downstream from Davis Dam and flowing 27 km through Topock Gorge; into 2) a warmer (to 24°C), downstream lentic portion (Lake Havasu). The river reach has current velocities exceeding 30 cm/s and averages less than 0.15 km wide and 5 m in depth. Lake Havasu is a storage and diversion reservoir impounded when Parker Dam was completed in 1938. It is 42 km long, 0.4 to 4.4 km wide and averages 9-10 m in depth; maximum depth rarely exceeds 18 m. MATERIALS AND METHODS Four and 16 sampling stations were established in the river and reservoir reaches, respectively (Figure 1) (Giusti and Milliron 1988). Larval fishes were collected with a 1.0-nrr, conical plankton net (1.13 m mouth diameter, 3.0 m long and 505 p.m mesh) towed diagonally at 0.76 m/s from bottom to surface ' Accepted for publication December 1988. -' Present address: 1100 High Point Lane, Columbia, Missouri 65203 ICHTHYOPLANKTON OF LAKE HAVASU 69 for 5 min at river stations and 10 min at reservoir stations from 5 March to 27 June 1985. Sampling was concentrated at six of the reservoir stations from 28 February to 12 June 1986; sampling at the four river stations was suspended in 1986 due to high flows. Samples were collected twice weekly at river and thrice weekly at reservoir stations, respectively; inclement weather or equipment malfunctions sometimes precluded sampling. Surface water temperature was measured at each station with a multiparameter probe. Specimens were fixed in 10% formalin and later stained with Rose Bengal, sorted and identified, and developmental stage of individual larva was deter- mined (Snyder 1981 ). Identifications were made by use of keys, descriptions, and illustrations in Winn and Miller (1954), Mansueti and Hardy (1967), May and Gasaway (1967), Lippson and Moran (1974), Conner (1979), Snyder ( 1 979, 1 981 ) , and Wang ( 1 981 ) . Mean monthly catch per unit effort ( CPE ) was calculated by dividing the number of larvae collected by the total number of tows for each month, and is expressed as the average number of larvae per tow. iLake Mohave iDavis Dam ARIZONA CALIFORNIA 0 5 10 k m FIGURE 1. Lower Colorado River and Lake Havasu study area, Arizona-California, and vicinity map (inset). Solid circles denote approximate locations of larval sampling stations. 70 CALIFORNIA FISH AND CAME RESULTS AND DISCUSSION Eight species representing six families were among the 6,617 larvae collected (Table 1); all Lepomis that could be positively identified were bluegill, L. macrochirus; however, other Lepomis were also present. Common carp, Cyprinus carpio, was the most abundant taxon in both years, 49% and 56% of total larvae, followed in 1985 by Lepomis spp. (29%, mostly bluegill, but also including other, undetermined species of Lepomis) , threadfin shad, Dorosoma petenense, largemouth bass and black crappie, Pomoxis nigromaculatus. In 1986, the second most numerous fish was threadfin shad (37%). Relative abundance of centrarchids was much lower in 1986 when they comprised only 3% of the total. Channel catfish, striped bass, and razorback sucker, Xyrauchen texanus, composed the remainder, with each accounting for < 2% of the total each year (Table 1 ). All species were found in both river and reservoir samples; however, all were notably more abundant in the latter. The strongly flowing, relatively cold, river reach was apparently not favored for spawning by many of these predominantly warm-water fishes. TABLE 1. Larval Fishes Sampled from the Colorado River at Lake Havasu, Arizona-California, March through June, 1985 and 1986. 1985 1986 Family Species No. (%) No. (%) Clupeidae Dorosoma petenense 964 (19) 553 (37) Cyprinidae Cyprinus carpio 2,524 (49) 831 (56) Catostomidae Xyrauchen texanus 8 ( 37 (2) Centrarchidae Lepomis spp. 1,475 (29) 33 (2) Micropterus salmoides 4 ( undetermined 12 (0.5 and supported at the 95% confidence interval were believed to indicate definite relationships between bird use and given environ- mental factors. RESULTS AND DISCUSSION Seasonal Species Abundance Ninety-five wetland birds were studied, and results on seasonal abundance are presented for the 76 more common species (Table 1 ). Uncommon species (<10 individuals observed) were Pacific Loon, Cavia pacifica, Red-necked Grebe, Podiceps grisegena, Leach's Storm-Petrel, Oceanodroma leucorhoa, Pelagic Cormorant, Phalacrocorax pelagicus, Black Scoter, Melanitta nigra, Common Goldeneye, Bucephala clangula, Cattle Egret, Bubulcus ibis, Green- backed Heron, Butorides striatus, Black-crowned Night-Heron, Nycticorax nycticorax, Parastitic Jaeger, Stercorarius parasiticus, Glaucous Gull, Larus hyperboreus, Black Tern, Chlidonias niger, Black-necked Stilt, Himantopus mexicanus, Solitary Sandpiper, Tringa solitaria, Spotted Sandpiper, Actitis macularia, Ruddy Turnstone, Arenaria interpres, Baird's Sandpiper, Calidris bairdii, Wilson's Phalarope, Phalaropus tricolor, and Red Phalarope, P. fulicaria. Most birds used the lakes from late September through April (Figure 1). Bird numbers peaked during October, and high numbers also occurred during April ( Figure 1 ) . Overall, an annual average of 3,092,300 bird-use days was calculated where one bird-use day is one bird observed on one day. Comparison of our results on particular groups or species with other findings is discussed only when unusual differences occurred. Waterfowl Twenty-seven species of waterfowl were observed; the numbers recorded during the study exceeded 10 for 25 species (Table 1). Waterfowl use-days averaged 1,467,800 annually (surface-feeders — 484,000; divers— 983,000). Wa- terfowl were most common from October through January (Figure 2). Four species — the Ruddy Duck, Oxyura jamaicensis, Northern Pintail, Anas acuta, American Wigeon, A. americana, and Canvasback, Aythya valisineria — made up 80% of all waterfowl observed. Tundra Swans, Cygnus columbianus, and geese were not common (Table 1 ). Peak numbers of swans were observed in December and January. Canada Geese, Branta canadensis, Greater White-fronted Geese, Anser albifrons, and Brant, Branta bernicla, occurred regularly but in small numbers (Table 1 ). Five subspecies of Canada geese were observed: Aleutian B.C. leucopareia, Cackling, WETLAND BIRD SEASONAL ABUNDANCE AND HABITAT 89 TABLE 1. Seasonal Abundance of Wetland Birds at Lakes Earl and Tala' wa, July 1974— February 1976. Season Winter Winter Summer74' Fall74 74/75 Spring75 Summer75 Fall75 75/76 Species Waterfowl Tundra Swan (17) + 10 for 12 species (Table 1). The Ruddy Duck was the most numerous of all waterfowl recorded. The Canvasback was the second most abundant diving duck and fourth most abundant waterfowl species (Table 1). Peters (op. cit. p.1) observed a high of 1,400 Ruddy Ducks, but we observed a high of 7,600. The highest number of Canvasbacks noted by Peters (op. cit. p. 85) was 900, whereas we observed a peak of 2,700. We never saw more than four Redheads, Aythya americana, at one time, but Dan Scott (Calif. Dept. of Parks and Recreation, pers. comm.) reported 127 in December 1984. Our results on Redheads do not agree with Yocum and Denson (1962) who state that this species is found in large numbers on Lake Earl. Our findings show the Greater Scaup, A. Marila, to be a common summer visitant and not rare as given by Yocom and Harris (1975). Species that regularly occurred but in small numbers were the Ring-necked Duck, A. collaris, Oldsquaw, Clangula hyemalis, Surf Scoter, Melanitta perspicillata, White-winged Scoter, M. fusca, Bufflehead, Bucephala albeola, Hooded Merganser, Mergus cucullatus, Common Mergan- ser, M. merganser, and Red-breasted Merganser, M. senator (Table 1). The Ruddy Duck was the only nesting diving duck recorded. A female and four downy young were seen on Lake Earl on 13 and 17 September 1974, the first breeding record for the area; other breeding records have been obtained since. Hehnke (op cit. p.85) reported three Common Merganser broods in his summer 1969 study, but none have been recorded since. A Ring-necked brood was observed on 19 July 1984 (Dan Scott, pers. comm.), followed by others subsequently, and a Redhead brood was reported on 14 June 1984 (Richard Erickson, pers. comm.). WETLAND BIRD SEASONAL ABUNDANCE AND HABITAT 93 Other Wetland Birds Thirty-seven species of wetland birds other than waterfowl and shorebirds (e.g., herons and gulls) were observed. The numbers recorded during the study exceeded 10 for 27 species (Table 1 ) . The average number of bird use-days per year was 1,203,600. The American Coot was the most abundant bird of any group found within the study area; peak numbers ( ^ 12,000) were noted during the fall (Figure 3). Species of other wetland birds commonly seen during the study area were the Western Gull, Laurus occidentalis, Pied-billed Grebe, Podilymbus podiceps, Western Grebe, Aechmophorus occidentalis, Horned Grebe, Podiceps auritus, Glaucous-winged Gull, Larus glaucescens, Eared Grebe, Podiceps nigricollis, and Double-crested Cormorant (Table 1). The Northern Harrier, Circus cyaneus, was the most common raptor observed (Table 1). Species that occurred regularly but in small numbers were Red-throated Loons, Gavia stellata, Common Loon, C. immer, American bittern, Great Blue Heron, Ardea herodias, Great Egret, Casmerodius albus, Snowy Egret, Egretta thula, Virginia Rail, Rallus limicola, Sora, Porzana Carolina, Bonaparte's Gull, Larus Philadelphia, Heermann's Gull, L. heermanni, Mew Gull, L. canus, Ring-billed Gull, L delawarensis, California Gull, L. Californicus, Herring Gull, L. argentatus, Caspian Tern Sterna caspia, Common Tern, 5. hirundo, and Belted Kingfisher, Ceryle alcyon (Table 1). Thousands 14 12 10 8 I.... ..ill J A 1974 S ONDJF MAM JJAS O N D JF 1975 1976 FIGURE 3. Seasonal abundance of American Coot on Lake Earl and Lake Talawa, July 1974-February 1976. 94 CALIFORNIA FISH AND CAME Our findings on Horned and Eared Grebes were much higher ( > 100) than the numbers ( < 15) observed by Peters (op. cit. ) . Hehnke (op. cit.) and Peters (op. cit.) observed fewer (1-60) Pied-billed Grebes than we did (^300). Our findings on this species also differ from Yocom and Harris (1975) who considered the species to be an uncommon resident. The highest number of Brown Pelicans we saw was 38, but Widrig (Widrig. R.S. 1977. Spring nesting and fall migration observations of shorebirds at Lake Talawa, Del Norte County, California. Unpubl. rep. on file Humboldt State Univ. Library, Areata, CA. 6 p. plus appendices) observed 100 on one occasion. Hehnke (op. cit.) and Peters (op. cit. p. 85) recorded substantially lower numbers of Western Gulls than we did; our higher numbers may have resulted from this species' attraction to seafood refuse spread on pastures adjacent to Lake Talawa by a rancher. In contrast to our findings, Peters (op. cit.) never observed more than four Bonaparte's Gulls. During summer 1974, coot broods were observed seven times and Pied- billed Grebe broods were observed 28 times. A previously unconfirmed nesting colony of over 40 pairs of Western Grebes was noted on the northeastern section of Lake Earl near a large stand of hardstem bulrush. Shorebirds Of the 31 species of shorebirds seen, the numbers noted during the study were >10 for 24 species (Table 1). The average annual number of bird-use days was 421,600. Highest numbers were seen during April (Figure 4). The principal species in our study, the Western Sandpiper, Calidris mauri, Dunlin, C. alpina, Least Sandpiper, C. minutilla, Long-billed Dowitchers, Limodromus scolopaceus, and Short-billed Dowitchers, L. griseus, made up 79% of the total number of shorebirds. These species were also the most abundant birds noted at Bolinas Lagoon, California from 1971-76 (Page and Stenzel 1975). Species regularly seen in small numbers were the Black-bellied Plover, Pluvialis squatarola, Lesser Golden-Plover, P. dominica, Snowy Plover, Charadrius alexandrinus, Semipalmated Plover, C. semipalmatus, Killdeer, C. vociferus, American Avocet, Recurvirostra americana, Greater Yellowlegs, Tringa melano- leuca, Lesser Yellowlegs, T. flavipes, Willet, Catoptrophorus semipalmatus, Long-billed Curlew, Numenius americanus, Whimbrel, N. phaeopus, Marbled Godwit, Limosa fedoa, Black Turnstone, Arenaria melanocephala, Red Knot, Calidris canutus, Sanderling, C. alba, Pectoral Sandpiper, C. melanotos, Stilt Sandpiper, C. himantopus, Common Snipe, Callinago gallinago, and Red- necked Phalarope, Lobipes lobatus (Table 1). Hehnke (op. cit.) and Peters (op. cit.) generally saw fewer shorebirds than we did, whereas Widrig (op. cit.) recorded more black-bellied Plovers, Ruddy turnstones, and Lesser Yellowlegs than we. We observed no Upland Sandpipers, Bart ram ia longicauda, or Wandering Tattlers, Heteroscelus incanus; however, one individual of the former species was observed on Lake Talawa by William Marshall (pers. comm.) on 13 September 1976 and single birds of the latter species were seen by Widrig (op. cit.) on 26 August 1977, and by Richard Erickson (pers. comm.) on 16 July 1981. Widrig (op. cit. p.85) did not see any Willets during his study. The highest number of Red Knots we saw was 12, but Widrig (op. cit.) recorded 46. Although we recorded no Sharp-tailed WETLAND BIRD SEASONAL ABUNDANCE AND HABITAT 95 TOTAL SHOREBIRDS OBSERVED IN THE LAKE EARL STUDY AREA 7/74-2/76 Thousands 0 II... 1.1 J A 1974 ..I lili II ONDJF MAM JJAS 1975 N D J F 1976 FIGURE 4. Seasonal abundance of shorebirds on Lake Earl and Lake Talawa, July 1974-February 1976. Sandpipers, Calidris acuminata, Widrig (op. cit.) recorded two to three individuals on Lake Talawa on four occasions. Widrig (op. cit.) saw many more Baird's Sandpipers than we did and recorded several hundred more Least Sandpipers in the fall than we. Peak numbers (2,825) of Western Sandpipers in the fall noted by Widrig (op. cit.) exceeded our fall peak of over 1,000 birds. Hehnke's (op. cit. p.1 ) counts of 1,300 to 2,100 Western Sandpipers in summer and early fall were also higher than our counts for the same seasons. No Hudsonian godwits, Limosa haemastica, or Ruffs, Philomachus pugnax, were noted by us, but Widrig (op. cit.) saw one of each on Lake Talawa on 12 September 1977. We did not record any breeding of shorebirds but suspected a nest of Snowy Plovers on Lake Talawa during spring 1976. Widrig (op. cit.), however, was successful in recording the breeding of Snowy Plovers, Killdeers, and a Wilson's Phalarope. 96 CALIFORNIA FISH AND GAME Habitat Use Data were summarized on habitat use of 73 species of wetland birds (Table 2). Twelve species, eight of which were surface-feeding ducks, were observed in six or more of the seven available habitats. The other birds used one to five habitats. TABLE 2. Percentage of Annual Habitat Use by Total Number of Wetland Birds at Lakes Earl and Talawa. Habitat types Fresh/ Mud/ Open brackish Salt sand Fresh- Sand Species water marsh marsh flats Pasture water shore Waterfowl Tundra Swan 32 <1 1 55 12 Crt. White-fronted Goose 27 73 Brant 24 5 5 24 5 37 Canada Goose 19 5 76 Swan/goose total 29 1 1 45 22 2 Wood Duck 76 12 2 10 Green-winged Teal 36 5 3 22 32 1 1 Mallard 45 29 4 15 4 3 Northern Pintail 84 1 2 9 3 1 <1 Blue-winged Teal 28 14 2 20 16 20 Cinnamon Teal 5 10 14 20 50 1 Teal species 36 18 27 11 8 Northern Shoveler 52 3 2 16 25 2 <1 Gadwall 63 3 14 8 2 10 American Wigeon 92 1 1 2 1 3 <1 Surface-feeding species 58 11 7 19 1 5 Surface-feeder total 75 4 3 9 6 3 <1 Canvasback 100 <1 Redhead 74 26 Ring-necked Duck 96 4 Greater Scaup 100 <1 <1 Oldsquaw 71 8 21 Surf Scoter 100 <1 White-winged Scoter 100 Bufflehead 99 1 <1 Hooded Merganser 80 16 4 Common Merganser 66 11 23 Red-breasted Merganser 98 1 1 Ruddy Duck 100 <1 <1 Diving duck species 100 <1 Diver duck total 99 <1 <1 <1 <1 <1 Waterfowl total 90 2 1 4 2 1 <1 Other Wetland Birds Red-throated Loon 100 Common Loon 100 Pied-billed Grebe 100 <1 <1 <1 Horned Grebe 100 <1 <1 <1 Eared Grebe 100 <1 Western Grebe 100 <1 <1 Brown Pelican 32 68 Dbl. -crested Cormorant 99 1 <1 Non-waterfowl diver total 99 <1 <1 <1 <1 <1 American Bittern 88 12 Great Blue Heron 31 11 35 13 <1 10 Great Egret 29 22 31 17 1 Heron/egret/bittern total 33 19 29 15 <1 4 Northern Harrier 75 10 1 13 <1 Virginia Rail 100 Sora Rail 100 American Coot 77 1 <1 3 17 2 Bonaparte's Gull 26 20 32 <1 22 Heerman's Gull <1 100 New Gull 13 12 75 WETLAND BIRD SEASONAL ABUNDANCE AND HABITAT 97 Ring-billed Cull 52 <1 <1 34 <1 13 California Gull 39 21 6 34 Herring Gull 3 48 49 Western Gull 7 <1 32 16 45 Glaucous-winged Cull 1 1 5 93 Gull species 16 16 6 62 Caspian Tern 12 74 14 Common Tern 55 4 3 19 19 Gull/tern total 12 <1 <1 15 15 58 Other wetland bird species 14 7 10 59 Shorebirds Black-bellied Plover 26 40 5 29 Lesser Golden-Plover 6 13 50 31 Snowy Plover 5 2 93 Semipalmated Plover 7 68 <1 25 Killdeer <1 5 21 69 5 American Avocet 79 21 Greater Yellowlegs 22 49 29 <1 Lesser Yellowlegs 1 95 4 Willet 47 53 Whimbrel 80 16 3 1 Marbled Codwit 4 90 <1 6 Black Turnstone 40 60 Red Knot 57 43 Sanderling 15 62 <1 23 Western Sandpiper <1 26 57 6 11 Least Sandpiper <1 30 43 22 5 Pectoral Sandpiper 22 73 5 Dunlin 20 45 26 9 Stilt Sandpiper 90 10 S.b./L/b. Dowitchers <1 22 63 9 6 Common Snipe 21 5 19 55 Red-necked Phalarope 92 3 5 < 1 Shorebird species 4 86 1 9 Shorebird total 1 <1 22 52 15 9 GRAND TOTAL 69 1 4 11 9 1 4 In decreasing order, habitats used most were open water (69%), flooded and non-flooded mud/sandflat (11%), flooded and non-flooded pasture (9%), sand shore and salt marsh (4% each), and freshwater marsh and fresh/ brackish marsh (1% each) (Table 2). Results of the habitat use vs. availability analysis showed that freshwater marsh, mud/sandflat, and sand shore were generally preferred over other habitat types by the four groups of birds (surface-feeding waterfowl; herons, egrets, and bitterns; gulls and terns; and shorebirds) and American coot that were analyzed (Figure 5). The principal areas of use of all species of waterfowl (except Cinnamon Teal) on Lake Earl and Lake Talawa were deep and shallow open water. Food analysis by Rodiack (Rodiack, J. C. 1976. Fall and winter flood habits of ducks at Lake Earl. Unpubl. rep., Wildl. Dept., Humboldt State Univ., Areata, CA. 4 p. plus figures and tables) showed that sago pondweed was the most important food item for waterfowl in this part of the lake. Surface-feeding ducks used all available habitats but relied primarily on open water (75%) and secondarily on mud/sandflats (9%). Habitat preference analysis (Figure 5) indicated that surface-feeding ducks showed significantly higher preference for freshwater marsh and mud/sandflat habitats than for the other habitats used by this group. The American Wigeon and Northern Pintail used open water predominantly (92% and 84%, respectively). The Tundra Swan, Green-winged Teal, and Blue-winged Teal frequently used this habitat as 98 CALIFORNIA FISH AND CAME well as shallow water mud or sandflats and pastures; most Cinnamon Teal used the last two types of habitat. Marshall (1953) determined that the American Wigeon was the second most abundant species of waterfowl on open water at Mission Bay, California. Romero (1976) found that surface-feeding waterfowl on Anaheim Bay, California, generally used tidal channels and mudflats. HABITAT PREFERENCE' Group Surface Feeding Waterfowl Most Preferred 5 -4 -3 -2 -1 Least Preferred 0 +1 +2 +3 +4 +5 Herons, Egrets and Bitterns American Coot Gulls and Terns Shorebirds f: :*''^-^ii';i'It-V-' ' LEGEND: mm Freshwater Marsh Mud or Sandllal Open Waler Fresh/Brackish Marsh Salt Marsh Sand Shore Pasture FIGURE 5. Bird use vs. habitat availability (* habitats shown for each group were the only ones the groups were observed in). Joined habitat types show no significant difference in preference between or among these habitats. Values show average difference between ranks of habitat type vs. availability; negative values show preference, positive show no preference. WETLAND BIRD SEASONAL ABUNDANCE AND HABITAT 99 All diving ducks recorded on Lake Earl and Lake Talawa used open water to a high degree (Table 2). The Canvasback, Greater Scaup, White-winged Scoter, Surf Scoter, and Ruddy Duck used open water almost exclusively. Almost all of the remaining species of diving ducks used other habitats to some extent, although they made primary use of open water. Buffleheads and Surf Scoters were recorded in large numbers on open water at Mission Bay, California (Marshall 1953). Loons, grebes, and cormorants used open water almost exclusively in every count (Table 2). The Horned, Pied-billed, and Eared Grebe were found commonly on open water at Mission Bay, California (Marshall 1953). Western Grebes used tidal channels and flooded mudflats on Anaheim Bay, California ( Romero 1 976) . At Lake Talawa the Brown Pelican was seen mostly on sand shore where they loafed; they used open water to a lesser extent (Table 2). Marshall (1953) and Romero (1976) found that Brown Pelicans used open water most at Mission Bay and Anaheim Bay, California, respectively. Highest numbers and densities of gulls and terns were found on sand shore and mud/sandflat, mostly on Lake Talawa (Table 2). These habitat types were also preferred over open water and pasture (Figure 5). Gulls and terns favored beach, land fill, and mudflat on Anaheim Bay, California (Romero 1976). At Mission Bay, California, Ring-billed Gulls were abundant on sand shores, and Western Gulls were common in this habitat and in open water ( Marshall 1 953 ) . As a group, herons, egrets and bitterns preferred mud/sandflat primarily and sand shore secondarily (Table 2). The most common species within this group, the Great Egret and Great Blue Heron, used mud/sandflats, fresh/brackish marsh, pastures, and salt marsh most heavily (Table 2). These two species were common on sand shore at Mission Bay, California (Marshall 1953). Most American Bitterns frequented fresh/brackish marsh containing moderately high to tall (0.5-2.0 m) vegetation. Virginia and Sora Rails were seen only in fresh/brackish marsh. The American Coot used open water 77% of the time and flooded pasture 17% of the time (Table 2). The only habitat not used by coots was sand shore. Habitat use vs. availability analysis indicates that the coot preferred freshwater marsh predom- inantly and mud/sandflat secondarily (Figure 5). Overall, shorebirds used mud/sandflat over twice as much as any other habitat type, followed by salt marsh, pasture, and sand shore (Table 2). Mud/sandflat was also more preferred by this group whereas sand shore was second in preference (Figure 5). Marshall (1953), Page and Stenzel (Page, G., and L. E. Stenzel. 1975. Aspects of the ecology of shorebirds on Bolinas Lagoon. Dept. of Parks and Recre., Co. of Marin, CA. 89 p.) and Romero (1976) also found that shorebirds favored mud/sandflat along coastal California. The Marsh Hawk used fresh/brackish marsh 75% of the time. Less frequently used habitats were pasture and salt marsh (Table 2). Correlation Analysis of Bird Use vs. Environmental Factors Bivariate correlation analysis showed no significant correlations between numbers of individual species and the four environmental factors studied (rainfall, temperature, water level, and salinity). Rapid changes in salinity and water level due to breaching the barrier beach, and occurrence of both high and 100 CALIFORNIA FISH AND CAME low numbers of migrating birds at both high or low water level periods may have accounted for the lack of correlations. Counts may not have been conducted frequently enough to adequately determine existing correlations. Page, Stenzel and Wolfe (1979) remarked that difficulties can be expected in determining factors affecting shorebird numbers because entire rather than parts of estuarine habitat complexes must be evaluated. Probably, daily changes in shorebird numbers on Lake Earl and Lake Talawa were also influenced by the large numbers of tidal mudflat and sandflat that became available during low tide at the nearby Smith River delta and Crescent City harbor. Many species were not affected by slight to moderate seasonal changes in the physical environment of Lake Earl and Lake Talawa because the changes did not disrupt the availability of the habitats they used. Observations indicated, however, that shorebirds, especially migrating and wintering individuals, occurred in large numbers when mudflats and sandflats were exposed. This was dramatically illustrated when breaching of the barrier beach allowed Lake Talawa to drain rapidly, making additional flats available to birds for varying periods of time. Widrig (op. cit. p.11 ) noted the same response. Three species, the Least Sandpiper, Dunlin, and Western Sandpiper, seemed to be most directly influenced by the drastic changes in the water level. The Green-winged Teal, Cinnamon Teal, American Coot, Greater Yellowlegs, Western Sandpiper, Dunlin, and the dowitchers, used pasture and mud/sandflat considerably more in winter and spring when these areas were flooded than at other times of the year. Gerstenburg (1972) noted that upland areas around Humboldt Bay, California, were used by shorebirds mostly during rainy periods. Even though seasonal changes in salinity showed no significant statistical correlation with changes in bird numbers, the degree of salinity and its effect on the types and amount of habitat generally determined the overall distribution of many birds on Lake Earl and Lake Talawa. CONCLUSIONS AND RECOMMENDATIONS Findings of this study show that Lake Earl and Lake Talawa serve as an important wetland area for a wide variety of migrating and wintering species of wetland birds. Three key elements are believed to be responsible for the heavy use of the lakes by wetland birds. First, the Lake Earl and Lake Talawa ecosystems provide a variety of habitats used by migrating birds. These habitats provide useful cover and contain valuable food items, especially sago pond- weed, widgeon-grass, and a variety of arthropods and fish. Second, because these lakes are located on the Pacific coast, they lie in the direct path of millions of migrating birds. Such a location, combined with the available habitat and food resources at the lakes, promotes heavy and extensive use by wetland birds. Third, the lakes are not heavily used by hunters during the hunting season. Consequently, human disturbance is minimized, and birds using the area are not pressured to move elsewhere. Like most wetlands, Lake Earl and Lake Talawa are vulnerable to human activities and developments. Fortunately, the lakes were purchased by the State of California and made part of its park and wildlife area systems. We believe the lakes should remain in public ownership so that they can be preserved WETLAND BIRD SEASONAL ABUNDANCE AND HABITAT 101 indefinitely for migrating birds. Efforts should be made to manage human use of the area so birds will continue to use this wetland in numbers similar to or greater than those found in this study. The seasonal entry of ocean water into the lakes exerts a profound favorable influence on the extent and variety of habitat and food types used by migrating birds. We recommend that the introduction of seawater be allowed to continue when winter flooding conditions exist so that the unique ecology of the lakes is maintained. ACKNOWLEDGMENTS Appreciation is extended to S. W. Harris and W. C. Vinyard, Humboldt State University, for help throughout the study and to C. J. Hoff and W. E. Rodstrom for assistance with field work. Special thanks goes to D. H. Johnson and A. M. Frank, Northern Prairie Wildlife Research Center, for conducting statistical analysis of habitat use/availability data, and to R. Howe and S. Spears, Louisiana Tech University, for their valuable help with the bivariate correlation analysis. M. Morrison, University of California, Berkeley, and M. Udvardy, California State University, Sacramento, reviewed the manuscript and provided helpful advice. LITERATURE CITED American Ornithologists' Union. 1983. Check-list of North American birds. Sixth ed. Amer. Ornith. Union, Wash., D. C 877 p. Barr, Goodnight, Sail, and Hedwig. 1977. Statistical analysis system (SAS). SAS Institute, Inc., Raleigh, NC Cerstenburg, R. H. 1972. A study of shorebirds (Charadrii) in Humboldt 8ay, California— 1968 to 1969. M. S. Thesis. Humboldt State College, Areata, CA. 207 p. Creeson, P. B„ J. R. Clark,a nd J. E. Clark (editors). 1979. Wetland functions and values: The state of our understanding. Proc. Natl. Symp. on Wetlands, November 7-10, 1978. Amer. Water Res. Assoc, Minneapolis, MN, 674 p. Hansen, H. A., and H. K. Nelson. 1964. Honkers large and small. Pages 109-124 in). P. Linduska, ed. Waterfowl Tomorrow. U.S. Fish and Wildl. Serv., Wash., DC. Johnson, D. H. 1980. The comparison of usage and availability measurements for evaluating resource preference. Ecology, 61(1): 65-71. Johnson, S. R , and C. F. Yocom. 1966. Breeding waterfowl in the Lake Earl-Lake Talawa area, Del Norte County, California. Murrelet, 47(1): 1-5. Marshall, W. F. 1953. Bird populations in representative habitats of Mission Bay, San Diego County, California, from September 27, 1950 to September 29, 1951. M. A. Thesis. San Diego State Coll. 43 p. plus appendices. Monroe, C. M., B. J. Mapes, P. L. McLaughlin, B. M. Browning, D. W. Rodgers, R. W. Warner, and J. W. Speth. 1975. Natural resources of Lake Earl and the Smith River Delta. Calif. Dept. Fish Came, Coast. West. Ser. No. 1. 114 p. Page, G., L. E. Stenzel, and C. M. Wolfe. 1979. Aspects of the occurrence of shorebirds on a central California, estuary. Pages 15-32 in F. A. Pitelka, ed. Shorebirds in marine environments. Cooper Ornith. Soc, Stud, in Avian Biol. 2. Reed, P. B. 1988. National list of plant species that occur in wetlands: 1988 California. U.S. Fish and Wildl. Serv. Biological Report 88 (26.10), 20 pp. plus list. Romero, P. E. 1976. Bird use of Anaheim Bay: A southern California salt marsh. M. A. Thesis. Calif. State Univ., Long Beach. 182 p. Tiner, R. W., Jr. 1984. Wetlands of the United States: Current status and recent trends. U.S. Fish and Wildl. Serv., Newton Corner, MA. 59 p. U.S. Fish and Wildlife Service. 1987. Endangered and threatened wildlife and plants. 50 CFR 17.11 and 17.12, Washington, D.C., 32 p. Yocom, C. F., and E. P. Denson. 1962. Importance of northwest coastal California to waterfowl. Calif. Fish and Game, 48(1): 65-76. Yocom, C. F., and W. A. Wooten. 1956. Blue-winged teal in Del Norte County, California. Calif. Fish and Game, 42(1): 81. Yocom, C. F., and S. W. Harris. 1975. Birds of northwestern California. Humboldt State Univ. Book Store, Areata, CA. 74 p. 102 CALIFORNIA FISH AND CAME Calif. Fish and Came 75 ( 2 ) : 1 02- 1 1 2 1 989 LIFE HISTORY OF THE SEVENGILL SHARK, NOTORYNCHUS CEPEDIANUS PERON, IN TWO NORTHERN CALIFORNIA BAYS 1 DAVID A. EBERT2 Moss Landing Marine Laboratories P.O. Box 450 Moss Landing, California 95039 Life history information was gathered on 128 sevengill sharks, Notorynchus cepedianus, from the coastal waters of California during a 20 month period from November 1981 through June 1983. The majority of sevengill sharks (96) were collected during the spring and summer in Humboldt and San Francisco bays. Gonad characteristics, egg size, embryo development, and scarring in adult sevengills captured in bays suggest a spring-summer breeding season. Cartilaginous and bony fishes were the major prey items of sevengill sharks captured in these bays. A distinct background color was observed for sevengills from different geographic regions. Several age determination techniques using vertebrae were tested. The ecosystem of several northern California bays plays an important role in the life history of the sevengill shark. INTRODUCTION Interest in elasmobranchs as a food resource has increased in California and among the more commonly marketed species is the sevengill shark, Notoryn- chus cepedianus Peron, 1807. This shark is known to frequent bays, including Humboldt and San Francisco bays where they support a small commercial fishery and are a popular target species of sportfishermen (Figure 1 ). Unfortu- nately, the elasmobranch assemblage of these bays is poorly understood and the importance of larger sharks, like the sevengill, to the bay environment is not well known. The sevengill shark is a member of the family Hexanchidae (cowsharks), which Compagno (1981) lists as having three genera and four or five living species. World-wide, several nominal species of the genus Notorynchus ( Ayres, 1855) have been described, with N. maculatus as the species representative from the eastern North Pacific. The distinguishing characteristic in these nominal species stem from the number of medial teeth (1 to 4) on the symphysis of the upper jaw (Kemp 1978). This difference is usually attributed to individual variation rather than as a distinctive characteristic (Bass, D'Aubrey, and Kistnasamy 1975, Kemp 1978, and Compagno 1984). Therefore, most recent authors have synonymized Notorynchus as a single species, N. cepedi- anus. Subsequent work I have conducted on this species confirms these author's opinion that Notorynchus is a monotypic genus. Notorynchus cepedianus is found predominantly in the temperate waters of both hemispheres, with no confirmed record of it from the tropics. In the eastern North Pacific sevengill sharks range form southeastern Alaska to the Gulf of California, with their distribution becoming sporadic south of San Fran- cisco Bay. 1 Accepted for publication January 1989. 2 Present Address: Dept. of Ichthyology, Rhodes University, P.O. Box 94, Crahamstown 6140, Republic of South Africa. LIFE HISTORY OF THE SEVENGILL SHARK 103 FIGURE 1. Commercial shark fisherman bringing aboard a 242 cm tl sevengill. Photograph by author. Since many elasmobranch species including the sevengill shark are mobile and reach a relatively large size, life history studies have been difficult. Members of the Hexanchidae are ovoviviparous (Gilbert 1981), but further information on their reproductive biology is limited. Herald and Ripley (1951 ) examined a number of sevengill sharks between 54 and 228 cm tl caught at shark derbies and reported that all sevengills examined were sexually immature. Herald (1961 ) estimated that sevengills reached maturity at a length of 306 cm tl. However, Herald (1968) revised this estimate after examination of a male (197.4 cm tl) and female (264 cm tl) sevengill that were both mature. Information on the feeding habits of the sevengill shark is rather incomplete. Hart (1973) reported that the sevengill's diet included smaller sharks. Herald and Ripley (1951 ) examined a few sevengill shark stomachs and found them to be either empty or to contain only bait. The objectives of this research were to investigate the life history of the sevengill shark in two northern California bays; this includes reproductive biology, length-weight relationships, food habits, age determination techniques, color variation, parasites, and movement patterns along the California coast. MATERIALS AND METHODS Sevengill shark data were obtained from field samples and reference collections. Most sevengill data were obtained from field collections made in Humboldt Bay (Iat40°52' N) and San Francisco Bay (Iat37°42' N). Additional data were obtained from the California Academy of Sciences, Moss Landing 104 CALIFORNIA FISH AND CAME Marine Laboratories, Natural History Museum of Los Angeles County, and the Tiburon Center for Environmental Studies. Shark samples were collected by several methods, including gill net, harpoon, long-line, and rod-and-reel. Sevengills in Humboldt Bay were captured using a gill net or harpooned during the spring and summer. Shark fishing in San Francisco Bay was conducted year-round using long-line gear and rod-and-reel. Gill nets were used in San Francisco Bay only during winter months. Measurements of shark alternate length (al, distance between the dorsal fin origin and caudal peduncle), girth (g), precaudal length (pel), and total length (tl) in millimeters, and weight (kg) were recorded. Weights were not taken in all cases because scales of sufficient capacity were not always available. The reproductive tracts of individuals of both sexes were examined to determine maturation. Male sharks were categorized as either juvenile or adult (Holden and Raitt 1974). Five indices were used to determine maturity in male sharks. These indices included (i) measuring and plotting the inner clasper length against total length. As the male sevengill approaches maturity, the claspers lengthen and stiffen. An increase in the clasper length versus total length indicates maturity (Chen and Mizue 1973), (ii) with the onset of maturity development of the clasper sac can be observed along the claspers of sevengills, (iii) the presence of a straight versus coiled wolffian duct. With the onset of maturation the wolffian ducts enlarge and coil (Cailliet et al. 1981 ), (iv) sperm smears were taken by applying pressure along the posterior end of the wolffian duct. Finally, (v) a field test for the presence of sperm was made by cross-sectioning the kidney and examining the wolffian duct, a test which Pratt (1979) used to indicate maturation in the blue shark, Prionace glauca. Length-weight relationships were plotted and combined with the information above to indicate approximate size at maturity. Sexual maturity of female sharks could only be determined by internal examination. Females were categorized as juvenile, adolescent, or adult. The developmental stage was determined by the condition of the ovaries (Holden and Raitt 1974). Females were considered adult when the ovaries contained large yellow eggs 22 to 75 mm in diameter. Pregnant females were those with eggs or embryos in the oviduct. The number and size of eggs ( > 18 mm in diameter) or embryos per female were recorded to determine fecundity and size at parturition. A graph depicting the length-weight relationship of females was plotted and combined with the information above to indicate approximate size at maturity. During the course of this investigation several sevengills were observed to bear scar and tooth marks that had been inflicted by other sharks. Total length, sex, and location of those wounds were noted. Stomachs were dissected and the contents identified. Food items not identified in the field were preserved in 10% formalin and returned to the laboratory. Empty stomachs or those containing only bait (squid or mackerel) were noted and discarded. Food items other than bait were identified to the lowest possible taxon, and an index of relative importance for ranking prey items (Pinkas et al. 1971) was calculated. Vertebral sections were collected for use in age determination. Vertebrae were removed from an area just posterior to the head region. Ageing techniques LIFE HISTORY OF THE SEVENGILL SHARK 105 currently in use for elasmobranch studies at Moss Landing Marine Laboratories (Cailliet et al. 1981, 1983) were tested. These techniques included the use of silver nitrate impregnation and ultra-violet light, x-ray spectrometry, and histology. Since the centra in Notorynchus, as with some hexanchids, can only be recognized by the presence of a transverse septum of fibro-cartilage (Ridewood 1921, Maisy and Wolfram 1984), vertebrae were cross-sectioned and examined for calcified rings. During this study I observed a distinct difference in background coloration of the dorsal region of sevengills from different geographic regions. Observations were made throughout the study to document the extent of this coloration and to describe these color patterns. Sevengill sharks were examined for visible ectoparasites. Parasite samples were collected and preserved in 10% formalin for later identification. Some sharks were tagged in order to obtain information on movement patterns and growth. RESULTS AND DISCUSSION Information on 128 sevengill sharks was gathered from November 1981 through June 1983. Of this total, 96 sevengills were taken in Humboldt (12) and San Francisco (84) bays. Additionally, information on 32 sevengills was obtained from several California institutions. Seasonality The occurrence of sevengill sharks in Humboldt and San Francisco bays during the spring and summer appears to suggest a seasonality. Some sevengills are caught year-round, however, the numbers caught in Humboldt and San Francisco bays was higher during the spring through early fall months. This observation is further supported by commercial fishermen in Humboldt and San Francisco bays who concentrate their efforts on sevengills during the spring and summer months due to their abundance at this time (K. Bates, Eureka and D. Kittredge, San Francisco, California, commercial fishermen, pers. comm.). Only a relatively small number of elasmobranchs, predominately the spiny dogfish, Squalus acanthias, were caught in San Francisco Bay during the winter period despite the use of several types of fishing gear. De Wit (1975) also reported the predominance of spiny dogfish during the winter months in San Francisco Bay. The seasonal occurrence of sevengills follows the appearance of other elasmobranch species in these bays suggesting a possible migration sequence. According to commercial shark fishermen in both Humboldt and San Francisco bays sevengills become prominent in the overall catch during the spring after several other elasmobranch species have appeared. The sevengill catch also decreases prior to a reduction in the catch of other elasmobranchs during the late summer, early fall periods. Future studies on the sevengill shark using tag and recapture or telemetry methods may reveal a complex movement pattern into and outside of these bays. Maturity My results indicate that all male sevengills over 150 cm tl are mature. Size at sexual maturity was determined by analysis of 71 specimens that ranged from 44 to 242 cm tl. Eighteen of 71 specimens were mature. The clasper length 106 CALIFORNIA FISH AND GAME increased abruptly at approximately 150 cm tl (Figure 2) and with develop- ment of the clasper sac mechanism indicated the onset of sexual maturity. E E c . 0) 4> Q. m 5 O c c 225- /* 200- Notorynchus cepvdianus A N = 60 • = Juvenile A 175 - A= Adult A\ 150- ▲ 125- A 100- ▲ 75- ▲ 50- 25- • # • • • • •• • • 0 -j I I I I i i I I I I 500 2000 25O0 Total Length Males (mm) FIGURE 2. The inner clasper length (mm) versus total length (mm) for 60 sevengill sharks. Coiling of the wolffian duct and expulsion of sperm through the genital papilla are conclusive indicators of maturity. Examination for the presence of sperm were negative except in those male sevengills with a fully coiled and enlarged wolffian duct. Sperm smears disclosed that sharks were fully mature when sperm could be expelled. Sperm smears collected at the genital papilla proved to be an easier method for determining maturity than taking a cross-section through the wolffian duct. The wolffian ducts of mature sevengills collected at various times of the year all contained viable sperm. Weights to the nearest 0.5 kg were obtained for 22 males ranging between 45 cm (0.5 kg) and 242 cm TL (79.5 kg). The length-weight curve for male sevengills began to more rapidly increase in weight at 150 cm tl (Figure 3). Male sevengills of 153 cm tl and weighing 13.5 kg were fully mature. Examination of the reproductive tract for 57 female sevengills, ranging between 78 cm and 291 cm tl, revealed that 48 were juveniles, three were maturing (adolescents), and six were adults. Those in the juvenile stage had ovaries that were small and contained no eggs or follicles. Juvenile females were recorded up to 186.5 cm tl. Two of the three adolescent females (219 and 221 cm tl) examined contained approximately 100 eggs per ovary, ranging from 0.5 to 18 mm in diameter. The third was smaller (164 cm tl) and contained only 75 eggs per ovary, ranging from 0.5 to 10 mm in diameter. Fecundity varied from 82 to 95 large ( > 22 mm in diameter) yellow vascularized eggs per female. The number of eggs per ovary in mature sevengill LIFE HISTORY OF THE SEVENCILL SHARK 107 sharks ranged from 39 to 55, with numerous smaller eggs ( < 18 mm in diameter) present. The left ovary contained 2 to 16 more eggs. A consistently unimodal distribution of egg size in individual specimens suggests that only one group of eggs develop at a time. Evidence for this came from a female examined during May that contained 82 near-term embryos but no large eggs in the ovaries. This is plausible since female sevengills carry between 82 and 95 eggs or embryos at a time and the size at parturition is quite large (approximately 45 cm tl). Egg size in adult females is approximately 75 mm in diameter prior to fertilization. Female sevengills with large eggs (55 to 75 mm diameter) present in their ovaries, but lacking embryos were caught during May and early June. These specimens also bore severe mating scars. Eggs from another female sevengill examined during June were small (22 to 41 mm diameter) and based on egg size, parturition had already occurred in this specimen. Therefore, it appears the next generation does not initiate develop- ment until after parturition. NotO'ynchus capeditnut "5? 100- N= 22 • = Juvenile (A ▲= Adult 0) to 75- (•)= Denote* two specimen* 5 O) '5 50- Ay ▲ o 25- ONE WAS MATURE ONE WAS IMMATURE t^^^ I 'I I I I I I I I I 500 1000 1500 2000 Total Length Males (mm) 2500 FIGURE 3. Total length (mm) versus weight (kg) for 22 male sevengill sharks. Developmental stages and their proposed timing for the sevengill shark is presented in Figure 4. Sevengills enter bays during the spring and females with developing eggs or embryos have been observed during this time. The length of time for large yellow eggs (approximately 75 mm in diameter) to develop is uncertain. However, assuming Herald and Ripley's (1951) speculation that sevengills enter San Francisco Bay for breeding is correct, then the time from parturition to fertilization may be from 6 to 12 months. Additionally, based on Holden's (1974) calculations for Hexanchus griseus, the time from fertilization to parturition (gestation) would extend another year. Therefore, after first parturition adult female sevengills would give birth every 18 to 24 months. Female sevengills mature at about 250 cm tl and weigh in excess of 91 kg (Figure 5). A sharp increase in the weight of females occurred after 200 cm tl as they approach adulthood. The smallest adult female I examined (268 cm tl, 127.3 kg) was slightly larger than a 264 cm tl specimen reported by Herald (1968). The largest female sevengill recorded was 291 cm tl and weighed in 108 CALIFORNIA FISH AND CAME excess of 182 kg. The largest previously reported sevengill was a 288 cm tl specimen caught in New Zealand (Phillips 1935). Newborn sevengil «■ 45-53 cm TL Adult: Age at reproductive / maturity unknown . / Birth Small white eggs < 18mm diameter Some evidence of time proposed No evidence of time proposed Development of eggs to fertilization 6 to 12 months Developing embryo Ovulation to birth 12 months Fertilization: Large yellow ( * 75mm diameter) highly vascularized eggs. 40 to 55 eggs per ovary FIGURE 4. A schematic diagram of the developmental stages and their proposed timing in the sevengill shark. Length of lines are not proportional to times proposed. Bite Injuries Two adult and two adolescent female sevengills were scarred. Both adults had three types of wounds that appeared specific to certain areas of the body. Fresh tooth slashes were observed on both of the adults and appeared as parallel straight or curved cuts. They were superficial and confined to the dorsum, anterior to the dorsal fin. Baldridge and Williams (1969) reported similar tooth slashes on the head of a dusky shark, Carcharinus obscurus, were from another shark, but they could offer no explanation for these scars. Fresh semi-circular jaw impressions showing continuous tooth marks were observed on both paired fins of one specimen. The other adult female had only a healed semi-circular jaw impression on its left pectoral fin. Single, straight, deep tooth cuts were observed laterally between both paired fins. Adolescent females had tooth slash marks similar to those seen in the adults. Fresh tooth cuts and semi-circular jaw impressions on gravid females caught in Humboldt Bay and San Francisco Bay during the spring and early summer suggest a possible breeding season. Breeding seasonality has been observed in several shark species (Olsen 1954, Jones and Geen 1977, and Parsons 1983) and it is well known that male sharks often bite their mates during copulation LIFE HISTORY OF THE SEVENCILL SHARK 109 * E A) CI 4) 5 (0 o 200- 175- 150- 125- 100- 75 50- 25- Nolorynchus cepeOianus N= 17 • = Juvenile 0= Adolescent A- Adult 500 1000 1500 2000 2500 3000 Total Length Females (mm) FIGURE 5. Total length (mm) versus weight (kg) for 17 female sevengill sharks. (Gilbert 1981). Also, adult females that presumably had recently given birth lacked fresh wounds suggesting these cuts are inflicted only when the female is ripe. Healed wounds, appearing as white patches of scar tissue, were observed on these specimens. Six mature male sevengills were observed to have slashes and tooth cuts laterally between the dorsal and tail fins. Occasionally, slashes were observed more anteriorly toward the head region. Parts of the dorsal and caudal fins were occasionally missing. No marks of any kind were observed on juveniles of either sex. Food Habits Sevengill sharks appear to be top predators in the bay ecosystem. Food items in sevengill stomachs included representatives of six groups: cartilaginous fishes, bony fishes, marine mammals, molluscs, lampreys and decapod crustaceans. The cartilaginous and bony fishes were the two major prey groups eaten by sevengills. Five species of elasmobranchs were found in sevengill shark stomachs, four of which were important prey items (Figure 6). The brown smoothhound, Mustelus henlei, represented the single most important prey species in the sevengill's diet; bat rays, Myliobatis californica, also ranked high. Bony fishes as a group were important in the sevengill's diet, but most were partially digested and could not be identified to species. Larger sevengills (>268 cm tl) consumed harbor seals, Phoca vitulina, on three separate occasions. According to fishermen (K. Bates and D. Kittredge, pers. comm.) marine mammal remains 110 CALIFORNIA FISH AND GAME in sevengill guts are not unusual. It is unknown whether the marine mammals were dead or alive before being ingested. Other prey items reported found in sevengills include the big skate, Raja binoculata, dolphin, human remains, jack smelt, Atherinopsis californiensis, and rats (K. Bates, pers. comm. and Compagno 1984). _ Unldantinad Oalakhmyat Ul CD 5 Z UJ 2 _l o > 50- 40- 30- 20- 10 0 10 20^ 30 40 -| 50 60- 70- 80 90 100 r- M henlel , — M calUomlca P vltuMna ^blllll »D S acanthlas T aamifasclata C magnter Cotlidae P nolatui M saiatllu9 Aclpan9«r ap N capadianut FREQUENCY OF OCCURRENCE (%) N= 38 r 0 n — i — r- 10 20 30 FIGURE 6. Index of relative importance for the prey items found in the stomachs of 38 sevengill sharks. Ageing None of the three methods tested to age sevengill sharks by using their vertebrae proved successful. The use of vertebral rings to age sevengills was not possible due to a lack of calcification in the vertebrae (Bass et al. 1975, Ridewood 1921). The use of other hard parts for ageing hexanchids seems unlikely since elasmobranchs continually replace teeth and scales tend to be variable (Applegate 1967). Unless new techniques are developed, the ageing of the sevengill shark may be dependent on tag and recapture studies. Color The dorsal background color of sevengill sharks collected from Humboldt Bay typically ranged from a pale silvery gray to reddish brown. These colors were consistent and were observed in both sexes. Although no observations were made on small specimens (210 cm tl), coloration did not appear to be related to size. Sevengills collected in San Francisco Bay had a dorsal LIFE HISTORY OF THE SEVENGILL SHARK 1 1 1 background color ranging from olive brown to muddy gray. These colors also did not appear to be related to size or sex and were consistent for all specimens examined from San Francisco Bay with the exception of one piebald colored sevengill caught off Hunter's Point (Ebert 1985). Parasites Three species of parasites were observed on sevengills. The copepod, Pandarus bicolor (Pandaridae), was observed on 56 specimens. Pandarus bicolor was recorded on both the paired and unpaired fins with some being observed on the dorsal and ventral body surfaces. Russo (1975) also noted the abundance of P. bicolor on sevengills, particularly on the trailing edges of the fins. The leech, Branchellion lobata (Piscolidae), was observed twice. Once in the oral cavity of a 164 cm female and another on the pelvic fins near the cloacal opening of a 268 cm female. Branchellion lobata, was reported by Russo (1975) on the claspers, fins, and buccal cavity of sevengill sharks. A parasite not mentioned by Russo (1975), the isopod Lironeca vulgaris (Cymothoidae), was observed in the gills of three sevengills. This is a common gill parasite found on many species of marine teleosts (Morris et al. 1980). The occurrence of L vulgaris may be difficult to measure as they were observed to quickly abandon their host upon capture. CONCLUSION Sevengill sharks are a seasonally abundant, poorly understood, apex predator in several northern California bay ecosystems. The seasonal occurrence of sevengills in these bays appears to correspond with their reproductive cycle, since adult females caught during the spring and summer had large eggs or embryos and mating scars. The importance of the sevengill shark to the bay environment and their activity outside of bays is for the most part unknown and more information is needed to confirm movement patterns within and outside of bays. ACKNOWLEDGMENTS I would like to thank the following persons for their time and consideration throughout this research. K. Bates, D. Kittredge, and B. Van Gorp for their fishing efforts in providing the numerous sevengills I examined. The following people provided additional specimens from their respective institutions, L.J.V. Compagno of the Tiburon Center for Environmental Studies, R.J. Lavenberg and J. Seigel of the Natural History Museum of Los Angeles County, and J.E. McCosker of the California Academy of Sciences. The members of my thesis committee G.M. Cailliet, M.S. Foster, and J.E. McCosker for their helpful suggestions and comments in reviewing this manuscript. L.J.V. Compagno, E.E. Ebert, R.N. Lea, and S. Smith provided many helpful ideas and suggestions. M. Moser identified the parasites. M. Kittridge for his fine work in illustrating the figures. General assistance in various portions of this study was given generously by T.B. Ebert, N.J. Hass, K. Hauge, K. Lohman, L.J. Natanson, and S. Willis. 112 CALIFORNIA FISH AND GAME LITERATURE CITED Applegate, S.P. 1967. A survey of shark hard parts. Pages 37-68 in P.W. Gilbert, R.F. Mathewson, and DP. Rail (eds.). Sharks, skates, and rays. )ohns Hopkins Press, Baltimore. Ayres, W.O. 1855. (Description of Notorynchus maculatus.] Proc. Calif. Acad. Sci., 1 (Pt. 1): 72-73. Bass, A. J., J.D. D'Aubrey, and N. Kistnasamy. 1975. Sharks of the east coast of southern Africa. V. The families hexanchidae, Chlamydoselachidae, Heterodontidae, Pristiophoridae, and Squatinidae. Invest. Rep. Ocean- ogr. Res. Inst., 43: 1-50. Baldridge, H.D. and |. Williams. 1969. Shark attack: feeding or fighting? Military medicine, 134(2): 130-133. Cailliet, CM., D. Kusher, L. Martin, and P. Wolf. 1981. A review of several methods for ageing elasmobranchs. Am. Fish. Soc, Cal-Neva Wildlife Transactions, 1981: 52-61. Cailliet, CM., L. Martin, D. Kusher, P. Wolf, and B. Welden. 1983. 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Fish and Game, 71(1): 58-59. Gilbert, P.W. 1981. Patterns of shark reproduction. Oceanus, 24(4): 30-39. Hart, J.L. 1973. Pacific fishes of Canada. Fish. Res. Bd. of Canada, Bull. 180: 740 p. Herald, E.S. and W.E. Ripley. 1951. The relative abundance of sharks and bat stingrays in San Francisco Bay. Calif. Fish and Game, 37(3): 315-329. Herald, E.S. 1961. Living fishes of the world. Double Day and Company Inc., Garden City, N.Y., 303 p. . 1968. Size and aggressiveness of the sevengill shark (Notorynchus maculatus). Copeia, 1968 (2): 412-414. Holden, M.J. and D.F.S. Raitt. 1974. Manual of fisheries science part 2 — Methods of resource investigation and their application. FAO Fisheries Technical Paper no. 115, revision 1. Holden, M.J. 1974. Problems in the rational exploitation of elasmobranch populations and some suggested solutions. 117-137. In F.R. Harden-Jones (eds.), Sea fisheries research, John Wiley and Sons, N.Y. Jones, D.S. and G.H. Geen. 1977. Reproduction and embryonic development of spiny dogfish {Squalus acanthias) in the Strait of Georgia, B.C. J. Fish. Res. Bd. Canada, 34: 1286-1292. Kemp, N.R. 1978. Detailed comparisons of the dentitions of extant hexanchoid sharks and Tertiary hexanchid teeth from South Australia and Victoria, Australia (Selachii: Hexanchidae). Mem. Nat. Mus. Victoria, 39: 61-83. Maisey, J.G. and K.E. Wolfram. 1984. Notidanus. Pages 170-180 in N. Eldredge and S. Stanley (eds.). Living Fossils. Springer Verlag. Morris, R.H., D.P. Abbott, and E.C. Haderlie. 1980. Intertidal invertebrates of California. Stanford University Press, Stanford, California, 690 p. Olsen, A.M. 1954. The biology, migration, and growth of the school shark, Galeorhinus australis (Macleay) (Carcharanidae) in southeastern Australian waters. Australian J. Mar. and Freshwater Res., 5(3): 353-410. Parsons, G.R. 1983. The reproductive biology of the Atlantic sharpnose shark, Rhizoprionodon terraenovae (Richardson). Fish. Bull., 81(1): 61-73. Phillips, W.J. 1935. Sharks of New Zealand: no. 4. New Zealand J. Sci. Technol., 16(4): 236-241. Pinkas, L., M.S. Oliphant, and I.L.K. Iverson. 1971. Food habits of the albacore, bluefin tuna, and bonito in California waters. Calif. Dept. Fish and Game, Fish Bull. 152: 1-105. Pratt, H.L. 1979. Reproduction in the blue shark, Prionace glauca. Fish. Bull., 77(2): 445-470. Ridewood, W.G. 1921. On the calcification of the vertebral centra in sharks and rays. Royal Soc. of London, Philosophical Transactions, Series B. 210: 348-404. Russo, R.A. 1975. Notes on the external parasites of inshore sharks. Calif. Fish and Game, 61 (4): 228-232. Stevens, J.D. 1974. The occurrence and significance of tooth cuts on the blue shark (Prionace glauca 1.) from British waters. J. Mar. Biol. Ass. U.K., 54: 373-378. RICE AVAILABLE TO WATERFOWL ] ] 3 Calif. Fish and Came 75 ( 2 ): 1 1 3-1 23 1 989 RICE AVAILABLE TO WATERFOWL IN HARVESTED FIELDS IN THE SACRAMENTO VALLEY, CALIFORNIA1 MICHAEL R. MILLER DAVID E. SHARP 2 DAVID S. GILMER and WILLIAM R. MULVANEY3 U.S. Fish and Wildlife Service Northern Prairie Wildlife Research Center Wildlife Research Field Station 6924 Tremont Road Dixon, California 95620 Rice fields in the Sacramento Valley, California were sampled in 1985 and 1986 to determine the weight of rice seed remaining in the fields immediately after harvest and again after the fields were burned. No significant differences were found between years (P>0.05). The pooled mean was 388 kg/ha in harvested fields and 276 kg/ha in burned fields. These values are less than estimates previously available. The values for harvested fields both years were no different (P -0.05) than values obtained by the U.S. Department of Agriculture (USDA). Surveys of rice fields in December both years showed that most fields were left either harvested (26-32%) or burned (37-40%) through the winter. Fields flooded for duck hunting made up <15% of the total. The proportion of fields plowed by December increased from 14% in 1985 to 22% in 1986. Sixty-three percent of all fields that had been flooded for hunting were drained within two weeks after the end of the hunting season. Harvest yield, field size, levee type (contour, lasered), straw status (spread, windrowed), harvest date, and rice variety did not affect the quantity of seeds remaining after harvest (P>0.05). One harvester model, the Hardy Harvester, left more rice in fields than did others we tested (P< 0.001). Specific management programs are recommended to mitigate annual variation in rice seed availability to waterfowl caused by differences in total hectares grown (15% less in 1986) and in the proportion of fields burned and plowed. INTRODUCTION Rice farms have displaced much of the original marshland in the Sacramento Valley, California (Gilmer et al. 1982). Rice seed left in fields after harvest sustains many waterfowl species during winter, including Northern Pintails, Anas acuta, Mallards, A. platyrhynchos, American Wigeon, A. americana, and geese, Branta and Anser spp. (Miller 1987; California Dept. Fish and Game, Sacramento and Sacramento National Wildlife Refuge, Willows, California, unpubl. data). Accurate estimates of rice availability are needed to determine the potential number of waterfowl that can be fed per hectare of harvested rice. However, no published information was available for California on the quantity of rice in harvested fields before and after burning. The USDA's Rice Objective Yield Survey (ROYS) (U.S. Dept. Agric. 1985) includes unpublished measures of loss after harvest. However, the program ' Accepted for publication March 1989. 2 Present address: Office of North Amer. Waterfowl Manage. Plan, Fed. Bldg., Fort Snelling Room 612, Twin Cities, MN 55111. 3 Present address: North. Prairie Wildl. Res. Cent., P.O. Box 2092, Jamestown, ND 58402. 114 CALIFORNIA FISH AND CAME wasn't operational in California in 1985, and data are not collected in burned fields. Other unpublished studies reported losses of 79-820 kg/ ha after harvest in California, but the studies sampled few fields, small sample plots ( <0.1 m 2), and only one plot/field (R.C. Curley and J. R. Goss, unpubl. rept., Dept. Agric. Eng., Univ. Calif., Davis, Feb 1964, 3pp - 1955 data; M. Dennis, U.S. Soil Conserv. Serv., Willows, Calif., Oct 1978), or supporting data were not provided (Sacramento Valley Waterfowl Habitat Management Committee, no date, p. 201). These California estimates are not adequate for waterfowl management. In the southeastern United States (Louisiana, Texas, Arkansas), investigators found 140-223 kg/ ha of rice in harvested fields (Harmon et al. 1960; Hobaugh 1984; K. J. Reinecke, U.S. Fish and Wildl. Serv., pers. comm.). However, these estimates are not applicable to California because the average yield of rice in California is up to 50% greater (U.S. Dept. Agric. 1987), specific rice varieties and seed sizes differ (Willson 1979, U.S. Dept. of Agric. 1987:A-33), and harvested fields are burned in California but not in the south (Huey 1971, K. J. Reinecke, U.S. Fish and Wildlife Service, pers. comm.). At present, a method is not available to monitor annual trends in harvest loss. Modern harvesters may improve harvest efficiency and leave fewer seeds for waterfowl (Gilmer et al. 1982). Also, rice land is less extensive during droughts and federal farm programs. Knowledge of carrying capacity of harvested rice may enable waterfowl managers to anticipate food shortages and take com- pensatory action. Decisions on food production on National Wildlife Refuges, State Wildlife Areas, and private hunting clubs would be facilitated with better knowledge of the amount of food available on farm lands. Our objectives were to: (i) estimate the mean weight of rice remaining in harvested fields in the Sacramento Valley before and after burning (and plowing if time allowed), and derive 95% confidence intervals that are within ±20% of these means; (ii) derive optimum sampling designs with various combinations of numbers of fields vs. number of plots/field to achieve objective precision and minimize time and cost; (iii) compare results from harvested, unburned fields with data obtained by the USDA ROYS program to determine if that survey can be used to monitor annual rice availability; (iv) document the status of rice fields at the beginning of the rainy season (harvested, burned, flooded for duck hunting, plowed); and (v) determine the rate at which flooded rice fields are drained after the duck hunting season ends. METHODS We conducted field work in the fall of 1985 and 1986 in Colusa, Butte, Sutter, Glenn, Yolo, Yuba, Sacramento, and Placer counties in the Sacramento Valley. These eight counties contributed > 92% of all rice grown in the Central Valley, and >99% of all rice in the Sacramento Valley (Calif. Agric. Stat. Serv. 1987). A list of > 300 rice growers was obtained for the eight counties. We randomly contacted growers, in the order selected, to participate in the study until the required number of fields was identified (100 in 1985); this was achieved with RICE AVAILABLE TO WATERFOWL ] ] 5 59 growers. We next obtained a map of each grower's rice fields, assigned a number to each field, and randomly selected study fields irrespective of rice variety and field size. We selected a maximum of two fields/grower, but we allowed up to four in large ( >725 ha) corporate farms where more than one farmer grew and harvested the rice. We initially selected sample fields among counties according to the percent of rice hectarage within each county. However, not all fields were burned, a few were burned before we could obtain a harvested sample, and some burned fields were flooded or plowed before we could obtain a burned sample. Therefore, as time allowed, we sampled additional harvested and burned fields. Ultimately, we obtained samples of long, medium, and short rice varieties from 111 harvested fields and 89 burned fields (Table 1). We only had time to sample four plowed fields. We used aircraft and ground vehicle surveys to check field status (harvested or burned) daily to assist in locating fields quickly. In 1985, we obtained samples within each field from two sites (plots) before burning, and two additional sites after burning. Each site was located at the intersection of two random coordinates. Sample plots measured 0.3 m by 5.5 m, the latter value the length of a standard harvester header, and were laid out perpendicular to the direction of harvester travel. We used pruning shears to cut straw and standing stubble from within the plots. The straw, containing seed heads, was saved in a labeled sample bag. We vacuumed the area within the sample plot with generator-powered shop vacuums and bagged the sample. We separated rice seeds from straw, other seeds, and dirt with a portable threshing machine and power seed cleaner. Final separation was done by hand before the seeds were dried (70° C) to constant weight. In 1 1 randomly selected fields, we separated the vacuumed (ground) and straw samples to determine what percentage rice in each contributed to the total. Analysis of 1985 data showed that desired precision could be attained by sampling more plots/field in fewer fields because variation within fields exceeded that among fields (SD = 45 vs. 17). Therefore, in 1986 we collected data from 15 randomly selected fields at a rate of eight plots/field (Colusa, Butte, Sutter, Glenn, Yuba, and Yolo counties). The total number of sample plots was reduced by about half from that in 1985 (Table 1). We located post-burn sample sites about 3 m away from pre-burn sample sites in the same harvester path. Not all fields were burned, so ultimately we sampled 15 harvested and 11 burned fields. In 1985, we had sampled 10 plots in one field before and after burning. We randomly deleted two of the plots and added this field to those sampled in 1986 to increase sample size for before and after burn comparisons (not for calculating mean weight). 1 1 6 CALIFORNIA FISH AND CAME TABLE 1. The Number and Proportion of Sample Fields of Short, Medium, and Long Grain Rice Varieties, and the Proportions of Each Variety Harvested in the Sacramento Valley, 1985-86. Variety County Short grain Medium grain Long grain Total Colusa 2 (1)* 24 (4) 3 29 (5) Butte 2 13 (3) 6 21 (3) Sutter 2 12 (3) 5 19 (3) Glenn 3 (1) 13 (1) 2 18 (2) Yolo 1 7 (1) 1 9 (1) Yuba 1 5 1 (1) 7 (1) Sacramento 12 14 Placer 3 1 4 Total Fields 12 (2) 79 (12) 20 (1) 111 (15) Sample % 10.8(13.3) 71.2(80.0) 18.0(6.7) 100.0 Statewide % 19.7 66.8 13.5 100.0 * 1986 data in parentheses. We derived regression equations to predict the weight of rice in harvested fields from data collected in burned fields (the latter are more easily obtained). We obtained the mean weight of burned and unburned samples of 10 groups of 1,000 seeds of each variety (long, medium, short), and derived regression equations for each variety to predict seed weight from the number of seeds. In December of both years, we visited 888 randomly located 32.4 ha rice fields distributed among counties proportionate to the amount of rice in each county. We recorded field status as: (i) not harvested; (ii) harvested (unburned, undisturbed stubble); (iii) burned (after harvest); (iv) plowed or disked (after burning); or (v) flooded for duck hunting (after burning). The flooded fields were surveyed beginning eight days after the close of the duck hunting season in January 1987 to determine what proportion had been drained and thereby potentially eliminated for use by ducks. For statistical analysis, we identified fields as the experimental units. Differ- ences in rice before and after burning were analyzed with a paired Mest. Differences between years and treatments (burned, unburned) were deter- mined through analysis of variance, with rice averaged over the plots. We assessed the effect of harvest yield, grain size, date sampled, harvester type, field size, levee type (laser leveled, contour), and straw status (windrowed, spread) on the availability of rice through a model-building approach (Draper and Smith 1981). Each model was evaluated by repeated measures (Milliken and Johnson 1984) with treatment types (burned, unburned) as the repeated measure, and plots as subsamples within each repeated measure. We used analysis of variance to test for differences in seed weights among rice varieties within and between treatments (Snedecor and Cochran 1980), and chi-square analysis for differences in field status between years (Siegel 1956). RESULTS We sampled harvested fields between 13 September and 9 November, and burned fields between 23 September and 22 November in 1985 (Figure 1 ). The mean time between harvest and burn dates and respective sample dates (sampling interval) was three days (SE = 0.2) for harvested fields and 3.1 days (SE = 0.3) for burned fields. In 1986, comparable dates were 2-28 October for RICE AVAILABLE TO WATERFOWL 117 harvested fields and 13 October to 17 November for burned fields (Figure 1 ). The sampling interval was 2.5 days (SE = 0.3) for harvested fields and 2.8 days (SE = 0.3) for burned fields. FIELD SAMPLING DATES: 1985/86 NUMBER OF HARVESTED FIELDS r u C' 5 a sees p. s CG ( , i eCBB AOS A Y S CGv , >Y YBCCBPOYS BS GBSB CCS3 OY> SBCCBA06S BO BS SG SBSB CGCCA0YGS8CCBGSSB G G C c BC G ca COY GB C GCS C CCB PC NUMBER OF BURNED FIELDS § OG p G 5 G G g yog sbog g sb g sb by sab a s c b y. >bco bcc aoy s acsb c b ssos g g sy s ccboybbco bcc xc c ocsb c s B OB YGB CGC CGC G G C c c c 1 0 II i 1 1 20 30 10 20 31 SEPTEMBER OCTOBER DATE SAMPLED I I 10 20 NOVEMBER C = COLUSA COUNTY B = BUTTE COUNTY S = SUTTER COUNTY G = GLENN COUNTY Y = YUBA COUNTY 0 = YOLO COUNTY A = SACRAMENTO COUNTY P = PLACER COUNTY C =1985 C=1986 FIGURE 1. Dates on which samples were obtained from harvested and burned fields in the Sacramento Valley during fall in 1985 and 1986. We detected no significant differences between years in the weight of rice in harvested (F = 0.01, P > 0.05) or burned fields (F = 0.01, P > 0.05). The pooled means were 388 kg/ha in harvested fields, and 276 kg/ha in burned fields (Table 2). This difference was significant {t = 6.78, P<0.001 ), and these values were respectively, 4.6% and 3.3% of the 1985-86 average harvest yield in California of 8,420 kg/ha (U.S. Dept. Agric. 1987). The 95% confidence intervals were ±10.6-10.9% of the mean for 1985 and pooled data, and ±25.9-27.8% of the mean for 1986 data (Table 2). TABLE 2. Annual and Pooled Mean Weights (kg/ha) of Rice in Harvested and Burned Fields in the Sacramento Valley, 1985 and 1986. Field Status Year N Weight £E 95% CI Harvested Burned 1985 1986 Pooled 1985 1986 Pooled 111 15 126 89 11 100 387 395 388 276 278 276 21 346, 427 51 285, 504 20 348, 427 15 246, 305 32 206, 350 16 244, 307 In a subsample of 11 harvested fields, nearly 75% of all the rice was found on the ground (254 kg/ha, SE = 37) compared to in the straw (91 kg/ha, SE = 17) (t = -4.98, P<0.001). We found only 22 kg/ha of rice in the four plowed fields, but larger samples were needed to obtain definitive data. The mean weights of rice in harvested fields as determined in this study were very 118 CALIFORNIA FISH AND CAME similar (identical in 1986) to values obtained by the USDA's ROYS program (375 kg/ha in 1985, N = 66, SE = 51.2; 395 kg/ha in 1986, N = 81, SE = 44.9). Obtaining pre-burn samples was more difficult than post-burn samples because of abundant straw. Therefore, we derived two predictor equations to estimate the weight of rice in harvested fields from weight in burned fields (kg/ha): (i) WEIGHT PRE-BURN = 186.9 + 0.83WEICHT POST-BURN (r = 0.41), for fields sampled with nonpaired plots; (ii) WEIGHT PRE- BURN = 28.0 + 1.19WEIGHT POST-BURN (r = 0.57) for fields sampled with paired plots. Two-way analysis of variance showed that long grain rice was lighter than medium and short grains in mean weight per 1000 kernels; this was true in harvested (long = 20.68 g, SE = 0.06; medium = 22.80 g, SE = 0.03; short = 22.43 g, SE - 0.05; F = 552, P< 0.001) and burned fields (long = 21.30 g, SE = 0.05; medium = 23.04 g, SE = 0.04; short = 23.23 g, SE = 0.08; F = 331, P< 0.001). Within varieties, the mean weight per 1000 kernels from burned fields exceeded that from unburned fields [F = 107, P< 0.001). This may have been an artifact of seed selection, in that some unburned seeds were not fully mature, so not completely representative. In the burned fields, immature seeds were consumed by fire, or seed coats were burned away, so fewer immature seeds were available for selection. Seed dry weight (g) may be estimated from seed numbers if the grain variety is known: (i) Harvested Fields: LONG GRAIN = 0.003 + 0.021X; MEDIUM GRAIN = -0.009 + 0.023X; SHORT GRAIN = -0.009 + 0.022X; (ii) Burned Fields: LONG GRAIN = -0.029 + 0.021X; MEDIUM GRAIN = 0.012 + 0.023X; SHORT GRAIN = -0.032 + 0.023X, where X = number of seeds, and in all equations, r 2 = 0.999. Analysis of variance showed that the weight of rice in harvested and burned fields was not explained by harvest yield, grain size, field size, straw status, levee type, or date sampled {P>0.05). Hardy Harvesters left more rice in fields after harvest, both as total rice and total rice as a ratio with yield, than did the others tested (F = 14.3, P< 0.01; F = 10.47, P< 0.01, respectively). There were no significant differences among the others (/?>0.05). The only factor that explained the weight of rice in burned fields was the weight of rice before burning (r2 = 0.50, /><0.01). The survey of field status in early December showed that no rice fields remained unharvested either year (Table 3). The largest proportion of the fields remained burned and there was no difference between years (X2 = 0.77, 1 df, P>0.05). The proportion of plowed fields increased markedly between 1985 and 1986 (X2 = 16.3, 1 df, P<0.05), and this increase occurred in all eight surveyed counties. Sutter County was most impacted by plowing (24% in 1985, 39% in 1986). In other counties, plowing varied from 0 to 30%, with Glenn (16 and 25%), Yolo (15 and 30%), Sacramento (25 and 28%), and Yuba (5 and 22%) most affected. Nearly 60% of Yuba County's rice was flooded, but the proportion of flooded fields varied from none in Sacramento County to 12-19% in Colusa and Butte Counties. Of fields flooded for duck hunting in 1986, 63% were drained within two weeks after the end of the duck hunting season (Table 3). Colusa and Glenn Counties retained the fewest flooded fields after the season with >85% drained, whereas in Yuba County, only 34% were drained. RICE AVAILABLE TO WATERFOWL 1 1 9 Drainage rates in the other counties ranged from 62-71%. The total hectares of rice grown and harvested in California declined 15% from 1985 to 1986 (Table 3). TABLE 3. Status of Rice Fields in the Sacramento Valley, California in December (Percent- ages of All Sampled Plots; N = 888), Percentages of Flooded Fields Drained Within 10 Days After the Hunting Season in January 1987 (N = 128), and total hectares harvested in the Sacramento Valley 1985-86. Total December January hectares Harvested Burned Plowed Flooded Drained harvested 1985 32 40 14 14 — 161,880 1986 26 37 22 15 DISCUSSION 63 137,600 The amount of rice we found in fields after harvest is markedly less than previous estimates for California. However, the absence of differences in mean weight of rice/ ha between years suggests that on a per hectare basis, the mean amount of rice is stable over the short term. The greatest effect annually on the amount of rice available to waterfowl depends on total hectares harvested, burned, and plowed. For example, we applied the status percentages to the hectares harvested (Table 3), and used the kg/ ha values for harvested, burned (used also for flooded), and plowed fields to derive a total of 44.5 million kg of rice in fields in 1985, and 34.0 million kg in 1986. To illustrate the potential impact of these annual differences on waterfowl populations, we arbitrarily assigned 60 g as a hypothetical daily intake of rice for waterfowl in the Sacramento Valley for October through February. We used this to determine a hypothetical number of birds fed: 44.5 million kg of rice/0.06 kg consumed per day/150 days (Oct-Feb) = 4.94 million ducks in 1985 and, with similar calculations, 3.78 million ducks in 1986. This theoretical 24% decline in carrying capacity resulted primarily from the reduced hectares and increased plowing in 1986. Not enough data are available from previous years in California to determine if there has been a downward trend in rice available to waterfowl. However, because our results closely matched those of the USDA ROYS program, their data may be used to monitor future trends. These data may be obtained from the Agricultural Statistics Board, South Agriculture Bldg., Room 4133, Washing- ton, D.C. 20250, or the Calif. Dept. of Food and Agriculture, Agricultural Statistics Service, 1220 N Street, Room 243, Sacramento, CA 95814. The quantity of rice left in fields after harvest in California was 1 .2 to 2.8 times more than in harvested fields in the southeastern United States (Harmon et al. 1960; Hobaugh 1984; K. J. Reinecke, U.S. Fish and Wildl. Serv, pers comm.). This disparity resulted from the markedly greater yields (1985-86 means, all varieties) obtained in California (8,420 kg/ha) compared with the southeast (5,895 kg/ha in Arkansas, 5,010 in Louisiana, 6,035 in Mississippi, and 6,590 in Texas) (U.S. Dept. Agric. 1987). In corn, losses increase with increasing yields because harvester efficiency cannot keep up with the increasing yields (Warner et ai. 1985). This probably occurs as well with major increases in rice yield. A new, more productive, long grain variety (Lemonte) has been developed for 120 CALIFORNIA FISH AND GAME use in the southeast that may eliminate the disparity in yields between the two regions (Anonymous 1985). There was 30% less rice in fields after burning. Some of this loss might be attributable to feeding by waterfowl and other birds. However, we were alert to evidence of waterfowl feeding in the vicinity of sample plots and avoided those locations. This, together with the short elapsed time between burning and sampling, leads us to conclude that the loss of rice resulted primarily from destruction during the burn. Most of this loss probably was in the portion of the rice still in the straw, because 26% of the rice in harvested fields was in the straw. The effect of burning on availability of rice resources for waterfowl feeding is not known because we do not know what percentage of rice in a harvested field is consumed by waterfowl. In a burned field, the seed is visible and, based on subjective evaluation of fields after waterfowl have fed in them, all seed may be available for consumption. Before the burn, the large quantity of straw obscures much of the rice, and an unknown portion of the seeds remain uneaten. In other studies, waterfowl have been found to consume 75-80% of grain present in harvested barley (Clark and Greenwood 1987) and corn (Baldassarre and Bolen 1984). Research is needed to determine depletion rates and feeding efficiency in rice fields. Because of the dry autumns, all fields in the Sacramento Valley were harvested each year. September and October 1986 were particularly dry, and this encouraged growers to plow more of their harvested /burned fields than in 1985. That nearly one fourth of all fields were plowed by December 1986 is cause for concern. In certain counties, especially Sutter, Glenn, Yolo, and Sacramento, the problem is severe. Our limited sampling in plowed fields suggests that little rice remains easily available to feeding waterfowl. We observed large flocks of ducks and geese feeding in plowed fields, but only after the fields were flooded. Development of a sampling scheme to determine available rice in such fields will be complicated by the absence of information on the depth to which feeding birds will probe in search of seeds. The problem of early draining of flooded rice fields after the hunting season ends is acute in all counties sampled except Yuba. Drainage of this habitat eliminates roosting space and productive feeding areas (Gilmer et al. 1982). Invertebrates, especially midge larvae, are common in flooded rice fields post-season (Miller 1987), but midges die within 10 days of drainage (Darby 1962). Also, most of these flooded fields have been hunted throughout the season. This probably prevents complete use of all rice, and perhaps other seeds, by waterfowl. If the fields were to remain flooded post-season, these foods could be used. Long grain rice was lighter in weight than were medium and short grains. Assuming all varieties contain similar metabolizable energy levels, feeding waterfowl would have to consume about 10% more seeds to obtain the same weight when feeding in fields of long grain compared to the other varieties. If market conditions in California change to cause an increase in the hectares of long grain rice (now about 6%) (Calif. Agric. Stat. Serv. 1986) at the expense of medium and short grains, feeding waterfowl will not benefit. RICE AVAILABLE TO WATERFOWL 121 Meteorological conditions affect the efficiency of harvest machinery (Willson 1979, Miller et al. 1985). The most active period of rice harvest in this study was October. Weather conditions then could affect rice availability later in winter. For example, above normal rainfall in October could decrease the rate at which fields are harvested and extend the period before harvested fields are burned and subsequently flooded or plowed. At the same time, harvest efficiency is reduced in wet conditions (Miller et al. 1985), so the amount of rice available to waterfowl ultimately would be increased. There are differences among harvesting machines in harvest efficiency (Miller et al. 1985), and of those available for testing in this study, Hardy Harvesters left more rice on the ground. This is important because Hardy's made up about 20% of the harvesters on our study fields. Thus, any changes in the proportion of Hardy's used may affect the amount of rice available for feeding waterfowl. In determining rice present after harvest, we did not differentiate between old and new Hardy Harvesters, and we found no significant differences between old and new models of the others. Large sampling variation, resulting from differences in rice variety, humidity and other weather parameters, harvest yield, operator skill, harvester speed settings, and the use of several different harvesters in a given field, masked any differences (Willson 1979, Miller et al. 1985). As a result, we couldn't conclude whether or not rice harvest is becoming more efficient, causing a concomitant reduction in rice available to waterfowl. Increased harvest efficiency does not necessarily result in increased farm income for rice growers (Miller et al. 1985) because income is based on the quality as well as quantity of rice delivered to buyers. Quality is measured by the amount of whole, unbroken, and uncracked milled seed (head rice). For example, for the M201 rice variety, (a medium grain that was the most commonly used variety during our study), Miller et al. (1985) found that total yield increased as the cylinder speed of the harvester increased. However, this procedure decreased the proportion of head rice. Thus, total income actually declined with increased harvest beyond a threshold level. Virtually all growers in our sample fields set harvester cylinder speed to maximize harvest. If rice growers harvested for income rather than for total yield, more rice could be available for waterfowl. When investigators plan rice field sampling schemes, consideration must be given to the time and money available as well as the sampling precision required. In general, sampling fewer fields at a higher rate will save time and money. We drove > 16,000 miles and recorded 25 hours of aircraft time with a crew of four to sample the 111 harvested and 89 burned fields in 1985. In 1986, we drove 4,500 miles with a crew of two to obtain our samples, and the sampling interval was reduced. Sampling 15 fields with eight plots/field theoretically should have yielded a confidence interval ±20% of the mean. However, we actually achieved only ±27% suggesting that variation within or among fields was greater in 1986 than anticipated with 1985 data. However, acceptable precision could have been attained by adding fields or plots/field. To plan an efficient sampling regime, relative to precision requirements and specific questions being asked, the number of fields and plots must be assigned based on known variation among (Sd2) and within (Sw2) fields. The general 122 CALIFORNIA FISH AND GAME sampling formula for harvested fields, to achieve a confidence interval that is ± 20% of the mean (X), is: F = 606/X2 (S „ 2 + S w 2/N), where F = number of fields required, X = 364 kg/ha, Sa2 = 1733, Sw2 = 12,362, and N = number of plots specified; for burned fields, X = 242 kg/ha, S a 2 = 0, and S w2 = 7339. MANAGEMENT IMPLICATIONS The amount of rice in harvested fields in the Sacramento Valley is less than previously estimated, and the amount of rice is annually variable and unpre- dictable. This unpredictability results from annual changes in hectares of rice grown in the Valley; the amount of rice lands burned, plowed, and flooded; and the rapid dewatering of flooded fields at the end of duck season. These facts present waterfowl managers with the need to develop management programs to compensate for this variation in the rice food supply. Restoration and development of marshes in the Sacramento Valley (State, Federal, private) would help to mitigate this variability by providing a more predictable food supply, and providing a hedge against future improvements in harvester efficiency. The quantity of foods in well managed wetlands exceeds that in harvested rice fields (Fredrickson and Taylor 1982). Rice fields in the Sacramento Valley are extensions of the managed wetlands. Much of the rice is grown on soils not suited for other crops (Willson 1979); therefore, restoration, where practical, should be promoted on lands that support crops of no value to waterfowl. Food production could be increased, in some instances, on existing wetlands through more intensive management. Incentives need to be developed to encourage rice growers to leave their harvested fields unplowed in the fall, while at the same time entering into hunting programs to increase the amount of fall flooding of harvested fields in certain areas. In addition, growers could be encouraged to manage set-aside lands as marshes. Duck club owners and operators should be encouraged to retain water on rice fields as long after the end of hunting season as practical. Research is needed to determine the relationship between post-season flooding and harvest yield the following fall. Growers should be encouraged to use harvesting techniques that maximize income, not necessarily total yield, thereby increasing the amount of rice for waterfowl. Mechanisms for accomplishing these goals by working with rice growers already exist through extension efforts of the U.S. Fish and Wildlife Service, University of California, Soil Conservation Service, California Department of Fish and Game, and the California Waterfowl Association (Heitmeyer 1988). Waterfowl managers should monitor annual trends in harvest losses with data from the USDA ROYS program. Managers need also to keep up with the latest developments in rice varieties and harvesters being used by growers. New varieties tend to be more early maturing; this allows harvest, burning, and plowing to be completed before the fall rains begin, thereby reducing waterfowl food. ACKNOWLEDGMENTS We are particularly grateful to the 59 Sacramento Valley rice growers who participated in this project by granting permission to collect samples on their land. The following people provided names of growers: University of California RICE AVAILABLE TO WATERFOWL 123 Farm Advisors S. Scardaci, C. Wick, J. Williams; U.S. Soil Conservation Service staff H. Cook, R. Rhondeau, R. Gray, C. Heitz, W. Cheechov, D. Simpson, W. Gilgert, E. Paschke; Agricultural Stabilization and Conservation Service staff C. Deaton, V. Gordon, B. Kataoka, C. Lauppe, and K. Marsh; and E. Collins and J. Miller of the U.S. Fish and Wildlife Service. We are grateful for the assistance of J. Day, J. Hicks, L. Reynolds, and T. Sharp in collecting and processing rice samples. We thank G. Miller and B. Petterson of the University of California at Davis for arranging our use of a portable threshing machine at the rice experiment station on campus, and G. Miller for advice in sampling methods. We thank A. Longshore, R. Radenz, and P. Stringer for assistance and allowing us to report USDA data from the ROYS program. C. Harvey performed statistical analyses. J. Takekawa provided many detailed comments helpful in improving the paper. LITERATURE CITED Anonymous. 1985. ).D. Woods: a believer in Lemonte, The Rice Journal, 88(1):8-9, 17, 20 Baldassarre, G.A., and E.G. Bolen. 1984. Field-feeding ecology of waterfowl wintering on the southern high plains of Texas. J. Wildl. Manage., 48:63-71. California Agricultural Statistics Service. 1986. Field Crops Statistics, California 1981-1985. 27p. . 1987. Field Crops Statistics, California 1982-1986. 27p. Clark, R.C., and H. Greenwood. 1987. A Circular "ring-angle" movement by field-feeding waterfowl. Wilson Bull., 99(4): 722-723. Darby, RE. 1962. Midges associated with California rice fields, with special reference to their ecology (Diptera: Chironomidae). Hilgardia, 32:1-206. Draper, N.R., and H. Smith. 1981. Applied regression analysis. 2nd ed. )ohn Wiley and Sons, New York, NY. 709p. Fredrickson, L.H., and T.S. Taylor. 1982. Management of seasonally flooded impoundments for wildlife. U.S. Fish and Wildl. Serv. Res. Publ. 148. 29p. Gilmer, D.S., M.R. Miller, R.D. Bauer, and J.R. LeDonne. 1982. California's Central Valley wintering waterfowl: concerns and challenges. Trans. North Am. Wildl. and Nat. Resourc. Conf., 47:441^152. Harmon, G.G., C.H. Thomas, and L. Glasgow. 1960. Waterfowl foods in Louisiana rice fields. Trans. North Am. Wildl. Conf., 25:153-161. Heitmeyer, ME. 1988. Farmers, duck clubs, and waterfowl — CWA's new outreach program. Calif. Waterfowl, 14(1):26-27. Hobaugh, W.C. 1984. Habitat use by snow geese wintering in southeast Texas. ). Wildl. Manage., 48:1085-1096. Huey, B.A. 1971. Rice production in Arkansas. Agric. Ext. Serv., Univ. of Arkansas Circ. 476 (Rev.). 46p. Miller, G.E., B.M. Jenkins, S. Upadhyaya, and ). Knutson. 1985. Comprehensive research on rice. Ann. Rep. Project No.RM-3. Univ. Calif., Davis, Dept. Agric. Eng. 4p with figures. Miller, MR. 1987. Fall and winter foods of northern pintails in the Sacramento Valley, California. |. Wildl. Manage., 51(2):405^H4. Milliken, G.A., and D.E. Johnson. 1984. Analysis of messy data, vol. I: designed experiments. Lifetime Learning Publ., Belmont, Calif. 473p. Sacramento Valley Waterfowl Habitat Management Committee. No date. Pacific Flyway waterfowl in California's Sacramento Valley wetlands: An analysis of habitat ... a plan for protection. Appendix A. 259p. Siegel, S. 1956. Nonparametric statistics for the behavioral sciences. McGraw-Hill, New York, N.Y. 312p. Snedecor, G.W., and W.G. Cochran. 1980. Statistical Methods. 7th ed. Iowa State Univ. Press, Ames. 507p. U.S. Department of Agriculture. 1985. Enumerator's Manual, 1985 Rice Objective Yield Survey. Crop Reporting Board, Stat. Rep. Serv., U.S. Dept. of Agric. Washington, DC. Pages not consecutively numbered. 1987. Annual crop summary, January 1987. Agric. Stat. Board, National Agric. Stats. Serv., U.S. Dept. of Agric. Pages A-33,34. Warner, R.E., S.P. Havera, and L.M. David. 1985. Effects of autumn tillage systems on corn and soybean harvest residues in Illinois. |. Wildl. Manage., 49(1 ):185-190. Willson, j.H. (ed). 1979. Rice in California. Butte County Rice Growers Assoc, Richvale. 254p. 124 CALIFORNIA FISH AND CAME Calif. Fish and Came 75 ( 2 ): 1 24-1 28 1 989 NOTES PACIFICOGRAMMA STEPANENKOI KHARIN, 1983 (FAMILY GRAMMATIDAE), A JUNIOR SYNONYM OF PRONOTOGRAMMUS MULTIFASCIATUS GILL, 1863 (FAMILY SERRANIDAE) Kharin (1983) described a new genus and species of grammatid fish, Pacificogramma stepanenkoi, from Uncle Sam Bank, Baja California Sur, Mexico. We refer the type and only known specimen of this species to the anthiine serranid species Pronotogrammus multifasciatus Gill 1863 (threadfin bass). This is the third new name (not in combination) proposed for this species since the original description. Previous synonyms are Anthias gordensis Wade, 1946 (or Holanthias gordensis; Hubbs et al., 1979: 21) and Holanthias sechurae Barton, 1947. Fitch (1982) gave a redescription and synonymy of the species including distributional notes, citing its range as off Portuguese Bend, California, to northern Peru in 40-205 m. Kharin (1983) placed his new genus in family Grammidae ( = Grammatidae), which he did not define. However, his inclusion of Pseudochromichthys riukiuanus Schmidt in the discussion indicates that he was using the previous, expanded definition of the family (Lindberg 1971, Nelson 1984). Johnson (1984) restricted the Grammatidae to the Caribbean region Gramma and Lipogramma. Kharin's discussion of the characters supposedly distinguishing the new genus within Grammatidae is irrelevant, since the generic type is an anthiine serranid, not a grammatid. The characters by which Pacificogramma is said to differ from its supposed relatives are exactly those characteristic of Pronotogrammus multifasciatus. These are: dorsal spines 10, arched and interrupted lateral line, incised caudal fin, dorsal soft rays 15, gill rakers 13, branchiostegal rays 7, spines on preopercle and maxilla scaled. Kharin's figure of the holotype of Pacificogramma stepanenkoi is an adequate rendition of Pronotogrammus multifasciatus, and agrees with the numerous specimens that we have examined deposited at the California Academy of Sciences, the Los Angeles County Museum of Natural History, and the Scripps Institution of Oceanography. The basis for Kharin's misidentification seems to be not only a lack of knowledge of the pertinent literature, but lack of familiarity with the eastern tropical Pacific ichthyofauna. The finding of a putative grammatid, although members of the grammatid-pseudochromid-plesiopid complex are limited to the tropical Atlantic and Indo-West Pacific, should have indicated that further research was necessary. Inexplicably, Kharin reported other specimens of the threadfin bass (as Holanthias gordensis) from the type locality of Pacifico- gramma stepanenkoi. Hobson (1975) recorded the first California specimen of the threadfin bass from Santa Catalina Island, and Jones et al. (1985) added two more records. Since then we have located six additional California and one Mexican specimen, bringing the total to ten (Table 1 ). On this basis we suggest that the threadfin bass should be considered a rare California species, after the criteria of Miller and Lea (1972), rather than an occasional stray. NOTES 125 TABLE 1. Southern California Bight Records of Pronotogrammus multifasciatus. Catalog No. Locality Depth m Date SIO 74-22 Santa Catalina Island a 40 Feb 1974 SIO 79-61 Off Oceanside b 66-73 19 Feb 1979 CBB 81.22.2 Off Pt. Fermin l> 80 18 Jan 1981 SIO 84-6 Off La Jolla 73 1 Mar 1984 SIO 84-35 Off Pt. La Jolla 68 10 Apr 1984 CAS 56964 Off Pt. La Jolla 68 10 Apr 1984 CAS 56855 Between Long Beach and Huntington Beach 84 23 Oct 1984 SIO 87-121 La Jolla Canyon 183 23 Jun 1987 SIO 89-4 14 Mile Bank off Dana Pt. 91 24 Jan 1989 SIO 89-3 North of North Coronado Isl. 122 29 Jan 1989 •'Hobson 1975 ''Jones et al. 1985 LITERATURE CITED Fitch, J. E. 1982. Revision of the eastern North Pacific anthiin basses (Pisces, Serranidae). Nat. Hist. Mus. Los Angeles Co., Contr. Sci. (339): 1-8. Hobson, E. S. 1975. First California record of the serranid fish Anthias gordensis Wade. Calif. Fish and Came 61 (2): 111-112. Hubbs, C. L., W. I. Follett, and L. J. Dempster, 1979. List of the fishes of California. Occ. Pap. Calif. Acad. Sci. (133): 1-51. Johnson, C. D. 1984. Percoidei: development and relationships, in, H. C. Moser et al. (eds.), Ontogeny and systematics of fishes. Amer. Soc. Ichthy. Herpet., Spec. Publ. 1: 464-498. Jones, L. L. C, R. R. Johnson, and Judith Hopkins. 1985. Additional records of Pronotogrammus multifasciatus and Gempylus serpens from California. Calif. Fish and Came 71 (2): 116-117. Kharin, V. E. 1983. Novyi rod i vid grammovykh okunei iz vod yuzhnoi KaF'ornii (Osteichthyes, Grammidae) (A new genus and species of grammid perch from the waters of southern (sic) California. Izvest. Tikh. Nauchno-lssled. Inst. Ryb. Khoz. Okeanogr. 107: 116-119. In Russian. Lindberg, G. U. 1971. Opredelitel' i kharakteristika cemeistv ryb mirovoi fauny (Families of the fishes of the world. A checklist and a key). Nauka, Leningrad. 480 p. In Russian. Miller, D. J. and R. N. Lea, 1972. Guide to the coastal marine fishes of California. Calif. Dept. Fish and Game, Fish Bull., 157: 1-235. Nelson, J. S. 1984. Fishes of the world, second ed. John Wiley and Sons, New York. 523 p. — M. Eric Anderson, Department of Ichthyology, California Academy of Sciences, Golden Gate Park, San Francisco, California 94118 and Richard H. Rosenblatt, Scripps Institution of Oceanography, La Jolla, California 92093. Accepted for publication February 1989. 126 CALIFORNIA FISH AND GAME IMPROVED SELF-CLEANING SCREEN FOR PROCESSING BENTHIC SAMPLES Aquatic invertebrates are important waterfowl foods during the breeding (Drobney and Fredrickson 1979, Swanson et al. 1979, Reinecke and Owen 1980) and nonbreeding season (Connelly and Chesemore 1980, Pederson and Pederson 1983, Heitmeyer 1985, Euliss and Harris 1987, Miller 1987). Therefore, waterfowl biologists attempt to quantify invertebrates in waterfowl habitats. Benthic habitats are among the most important micro-habitats sampled in waterfowl investigations. Processing benthic samples is time-consuming be- cause many samples are required, and samples collected with conventional sampling gear (Swanson 1978 and 1983) must be washed to remove small particles of soil and other debris. The transfer of sample residues to collection jars using current procedures is difficult and extreme care is required to avoid spilling samples. The self-cleaning screen described by Swanson (1977) has been used extensively by waterfowl biologists (Beam and Gruenhagen 1980, Pederson and Pederson 1983, Swanson 1983, Euliss 1984) and it is effective in concentrating sediment cores into sample residues. Samples are transferred from the original screen to a sample jar by placing a corner of the inverted screen on the inside edge of the jar and flushing the residue into the collection jar. The screen contains a 1.3-cm-thick lip that has to be carefully aligned on the lip of a sample jar to avoid spilling the sample. This method is unsatisfactory when samples are 25 CM FIGURE 1. Modified self-cleaning screen. NOTES 127 collected from an unstable platform such as a small boat. A modification of the self-cleaning screen described by Swanson (1977) reduces this problem and enables effective transfer of sample residues. The unit described (Figure 1) in this paper is similar to the initial design (Swanson 1977) with major modifications including an outside coat of fiberglass with an integral pour spout, galvanized hardware cloth to protect the screen and a small tract of fiberglass on an inside corner of the screen surface. The fiberglass tract provides a smooth surface that facilitates transfer of residue. Floatation foam can also be attached to the structure using fiberglass to eliminate the need to periodically replace worn styrofoam. A new coat of resin can restore damaged spouts. Because of the additional strength provided by the fiberglass laminate, the braces described for the original screen (Swanson 1977) are unnecessary. The improved self-cleaning screen is fabricated by applying fiberglass to the sides of 2 pieces of wood, 38 X 18 cm and 1.6-cm-thick, that have 2 rounded corners. Rigid polyvinyl foam can be used as a substitute if light weight or additional buoyancy is desired. A length of 25-cm-wide screen (0.5 mm) and an outer layer of galvanized hardware cloth is then pressed into resin applied to the bottom edges. Wooden handles are attached to the 2 sides and coated with fiberglass (Figure 1 ). The pour spout is fabricated separately using the edge of a board covered with wax paper as a mold. After the resin has hardened, the spout is trimmed, allowing a 2.5-cm overlap on the inside of the screen. It is attached with fiberglass. Additional resin is applied to smooth over uneven surfaces created by overlaying the spout. Polyurethane foam strips can be attached to the sides of wooden units using fiberglass to provide additional floatation. FIGURE 2. Core sample residue being emptied into a collection jar. 128 CALIFORNIA FISH AND CAME After the sediment core is deposited in the screen it is cleaned in the field by moving the apparatus back and forth horizontally just under the water's surface. The sample residue is positioned on the fiberglass tract inside the self-cleaning screen using directional water force with a sweeping action. The pour spout is then inserted into a specimen jar and the sample residue washed into the receptacle using spray from a syringe or wash bottle (Figure 2). This method facilitates transfer of sample residues into collection jars even when sampling from a boat when wave action is moderately severe. The original screen has proven to be an effective cleaning device and has held up to the rigors of sampling under a wide variety of conditions. The modified version has been used for 2 years. The fiberglass construction provides additional strength that should make the improved screen more durable than the original model. We thank D. A. Barnum, J. C. Bartonek, D. S. Gilmer, and H. R. Murkin for critical review of this manuscript and J. M. Hicks and R. D. Thielman for preparing figures. LITERATURE CITED Beam, )., and N. Cruenhagen. 1980. Feeding ecology of pintails {Anas acuta) wintering on the Los Banos Wildlife Area, Merced County, California. Calif. Dep. Fish and Game, Fed. Aid Wildl. Restor. Prog. Rep., Proj. W-40-D-1. 23p. Connelly, D. P., and D. L. Chesemore. 1980. Food habits of pintails, Anas acuta, wintering on seasonally flooded wetlands in the northern San Joaquin Valley, California. Calif. Fish and Came, 66(41:233-237. Drobney, R. D., and L. H. Fredrickson. 1979. Food selection by wood ducks in relation to breeding status. J. Wildl. Manage., 43:109-120. Euliss, N. H., )r. 1984. The feeding ecology of pintail and green-winged teal wintering on Kern National Wildlife Refuge. M.S. Thesis, Humboldt State Univ., Areata. 188p. , and S. W. Harris. 1987. Feeding ecology of northern pintails and green-winged teal wintering in California. |. Wildl. Manage., 51:724-732. Heitmeyer, M. E. 1985. Wintering strategies of female mallards related to dynamics of lowland hardwood wetlands in the Upper Mississippi Delta. Ph.D. Thesis, Univ. of Missouri, Columbia. 378p Miller, M. R. 1987. Fall and winter foods of northern pintails on three northern California Refuges. |. Wildl. Manage., 51:403-412. Pederson, G. B., and R. L. Pederson. 1983. Feeding ecology of pintails and mallards on Lower Klamath marshes. Final rep. on U.S. Fish and Wildl. Serv. contract 14-16-0001-79106. Humboldt State Univ. Foundation, Areata. 89p. Reinecke, K. )., and R. B. Owen, Jr. 1980. Food use and nutrition of black ducks nesting in Maine. |. Wildl Manage., 44:549-558. Swanson, G. A. 1977. Self-cleaning screen for processing benthic samples. Piog. Fish-Cult., 39:177-178. 1978. A simple lightweight core sampler for quantitating waterfowl foods. ]. Wildl. Manage., 42:426-428. 1983. Benthic sampling for waterfowl foods in emergent vegetation. |. Wildl. Manage., 47:821-823. G. L. Krapu, and ). R. Serie. 1979. Foods of laying female dabbling ducks on the breeding grounds Pages 47-57 in T. A. Bookhout, ed. Waterfowl and wetlands-an integrated review. Proc. Symp. North Cent. Sect., The Wildl. Soc. — Ned H. Euliss, Jr., U.S. Fish and Wildlife Service, Northern Prairie Wildlife Research Center, 6924 Tremont Road, Dixon, California 95620 and George A. Swanson, U.S. Fish and Wildlife Service, Northern Prairie Wildlife Research Center, P.O. Box 2096, Jamestown, North Dakota 58402. Accepted for publication March 1989. 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