摘要:

Phenotypes at 28 enzyme loci were analyzed by vertical starch gel electrophoresis for each of 90 populations of largemouth bass Micropterus salmoides. Allele frequencies at each locus, as well as the mean number of alleles at each locus, the average number of polymorphic loci, and the mean level of heterozygosity, were calculated for each population. Matrices of genetic identity and distance were used to assess interpopulational relationships. These analyses clearly reveal substantial genetic differences among populations in the United States. The northern subspecies M. s. salmoides and the Florida subspecies M. s. floridanus have fixed allelic differences at two loci, isocitrate dehydrogenase-B and aspartate aminotransferase-B, that can be used to determine contributions of each subspecies to the gene pool of any population. The intergrade zone between the subspecies consists of northern Florida, Mississippi, Alabama, Georgia, South Carolina, North Carolina, Virginia, and Maryland, as well as Texas, California, and perhaps a few other states in which largemouth bass with at least some of the genes of the Florida subspecies have been introduced. This increased intergrade zone is larger than previously proposed, and casts doubt upon the genetic identity of largemouth bass used in several studies of subspecific physiological properties and stocking success. Geographic distributions of the alleles encoded at four loci describe distinct latitudinal clines. This suggests a genetic influence on thermal tolerances and preferences of largemouth bass. This study demonstrates the need for incorporating genetic information and principles into current and future fisheries management programs.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<1:ABGEOT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Fish production was evaluated at three sites in Guys Run, Virginia, an 8-km, second-order Appalachian stream, from August 1979 through July 1980. Mean standing stock ranged from 21.4 kg˙hectare-1upstream to 47.4 kg˙hectare-1downstream. Annual production by the fish taxocene was estimated at 28.4, 31.6, and 39.6 kg˙hectare-1˙year-1in the upper, middle, and lower sections, respectively. Brook trout Salvelinus fontinalis, mottled sculpin Cottus bairdi, blacknose dace Rhinichthys atratulus, and bluehead chub Nocomis leptocephalus were the dominant species, accounting for 87 to 99% of total fish production in the stream. Annual production : biomass (P/B) ratios ranged from 0.6 to 1.6 and were consistent with previously determined values for the same or similar species in other small streams.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<21:AAPOFI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The resident brown trout Salmo trutta in Lake Myrkdalsvatnet utilized benthic and pelagic areas down to a depth of 40 m. Most 1- and 2-year-old fish were littoral; with increasing age, pelagic and deeper benthic habitats were utilized. It is hypothesized that the significant habitat segregation is caused by differential foraging profitabilities and social interactions among age groups. The proportion of females was significantly higher in pelagic than in benthic areas. Among mature fish, the males, but not the females, congregated in onshore areas in September before entering the tributaries to spawn in October-November. Age groups 1–2 fed mainly on littoral zoobenthos. In August, when zooplankton and surface insects were abundant, age-2 fish also were numerous offshore. Older benthic fish fed largely on chironomid larvae and pupae. Surface insects and zooplankton were important food for pelagic brown trout. Adult chironomids mainly were eaten during early summer, swarming ants during late summer. Holopedium gibberum and Bythotrephes longimanus were the selected zooplankton; smaller cladocerans were not eaten.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<27:AASSIH>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Differences in the age at first maturation, as well as timing and magnitude of growth (body and gonad) were examined for northern pike Esox lucius from three lakes in Michigan. The lakes varied in latitude (42 to 46°N), ice-free season (210 to 248 days), and total mortality (Z = 0.28 to 0.85). Body and gonad calorific equivalents were similar among all three lake populations. Male and female northern pike from all lakes and age classes 1–3 had significant accumulation of somatic energy during summer and winter and depletion of reserves over spawning. Testicular growth occurred entirely in the summer, whereas ovarian growth occurred mainly over winter. Females invested 6- to 18-fold more energy into gonads than did males. Total winter growth was significant in both sexes and all lakes. Individual body and gonad growth over the first 3 years of life for northern pike varied little among lakes. Age at first maturation varied significantly among lakes; the earliest maturation occurred in the lake of intermediate latitude, the latest in the southernmost lake. These differences did not correspond well with length of the growth season. However, there appears to be a relationship between total mortality (due to differences in fishing intensity) and proportion of fish mature at age 1. Increased fishing intensity may have induced higher total mortality rates, earlier ages at first reproduction, and higher total energy allocations to reproduction at earlier ages among these populations. Latitudinal differences in climate had little or no apparent effect on growth and reproductive characteristics of the populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<38:GMAPON>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Mortality of larval bluegills Lepomis macrochirus from predation was measured in 56 nests guarded by males and 21 nests from which the male guard was removed. Mortality was significantly greater in unguarded nests (median = 68%) than in guarded nests (median = 14%). Fish traps placed in unguarded nests captured significantly more predators than traps placed in guarded nests. Bluegills (3–12 cm total length) were the most abundant nest predators. Pumpkinseeds Lepomis gibbosus (7–11 cm), largemouth bass Micropterus salmoides (4–5 cm), and whitefin shiners Notropis niveus (5–6 cm) also were nest predators. Nest preparation by male bluegills exposed coarse gravel (8–32 mm diameter) and pebbles (32–64 mm) in nest substrate and removed particles smaller than 2 mm. Particles larger than 8 mm provided suitable interstitial space to accommodate bluegill larvae. Survival of larvae was directly correlated with the proportion of coarse substrate in the nest.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<47:ROMPCI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Changes in the catchability of yellow perch Perca flavescens in an otter trawl were examined by comparing annual catch per unit effort (CPUE) in Oneida Lake to mark-recapture population estimates over a series of years. Catchability was similar among age groups of adult yellow perch. Annual catchability was similar in 4 of 5 years, but threefold higher in the fifth, presumably due to lower water clarity in that year. Examination of within-season changes in CPUE indicate that other, undetermined environmental factors also affect catchability.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<53:VITCOY>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Five gear types were fished simultaneously to determine their efficacy at capturing premolt blue crabs Callinectes sapidus of commercial size (≥ 75 mm carapace width). Peeler pots, crab fykes, bush lines, habitat pots, and baited hard-crab pots deployed at each of nine stations (3 stations/area) in the Ashley River, South Carolina, were fished four consecutive days weekly from 18 April through 16 November 1979. Premolt crabs captured per gear-day (one unit of gear with a 24-hour soak time) were analyzed by 6-week intervals and area for each gear type. Hardcrab pots averaged more than 2.5 early premolt crabs per day during April and May, and habitat pots captured fewer, but consistent, numbers (0.7/day) of late premolt crabs from 18 April through 17 August. Modest peeler-pot success during April-May (over 0.5/gear-day) was attributed to the peak abundance of pubertal-molt females occurring prior to 18 April. Tidal amplitude (mean, 1.5 m) and current velocity (over 1.8 km/hour) limited the usefulness of bush lines and crab fykes throughout the study. Premolt male crabs outnumbered females 2.5:1, 1.6:1, and 1.3:1 in the habitat pot, peeler pot, and hard-crab pot, respectively. Overall, premolt crab catch rates declined from 1.0/gear-day during April-May to 0.4 in June-July, to 0.1 during October-November. Except for hard-crab pot catches during the first 6-week period, catch rates did not differ significantly among upper, middle, and lower river areas. Knowledgeable crabbers fishing habitat pots, peeler pots, and hard-crab pots in the most productive areas and seasons should capture premolt crabs at rates adequate to supply a shedding facility. A viable soft-shell crab industry in South Carolina would have little effect on the current fishery for hard crabs.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<60:COBCPI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

A roving creel survey was used to collect information on county of origin and fishing-trip expenses for anglers visiting West Point Reservoir, Georgia-Alabama, during the first five fishing seasons after impoundment, February-October, 1976–1980. Use-prediction models were developed to explain variation in attendance of various user-segments (bank, boat, bass, and crappie anglers) from participating counties on the basis of county population sizes and distances of counties from the reservoir. The models were used in conjunction with differential travel costs from the counties to the reservoir to estimate net economic benefit in the form of consumers' surplus. The average annual consumers' surplus for the fishery was estimated to be $1,913,000, which translates to $8.90 per angler-day. The percentage contribution of various user-segments to annual fishing effort was not, except for crappie anglers, an accurate indicator of relative contribution to annual consumers' surplus. Simple regression equations suggest that net economic value can be predicted by the use of more readily obtainable information acquired through statistically designed angler surveys.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<71:RBEBAS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Fifty-five-day-old gynogenetic grass carp Ctenopharyngodon idella, all females, were administered methyltestosterone through release from silicone elastomer (silastic) intraperitoneal implants during 460- to 656-day treatments in earthen ponds. Gonads of 27 implanted fish were examined; five had testes, nine had bisexual gonads, eight had gonads with no germ cells, and five had underdeveloped ovaries. No male germ cells were detected in the gonads of untreated gynogenetic fish. The successthl sex reversal of gynogenetic grass carp will permit testing of the hypothesis that breeding a functionally sex-reversed male with normal females will produce only female offspring.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<79:SROGGC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Spermatozoa of striped bass Morone saxatilis were successfully cryopreserved, retaining fertilizing capacity for up to 2 years. Spermatozoa in 14 extenders, in combination with three concentrations of four cryoprotectants at various sperm : medium ratios, were frozen at different rates and tested. Best results were obtained with extender “OH-189” (7.30 g NaCl, 0.38 g KCl, 0.23 g CaCl2˙2H2O, 5.00 g NaHCO3, 0.41 g NaH2PO4˙H2O, 0.23 g MgSO4˙7H2O, 5.00 g fructose, 7.50 g lecithin, and 5.00 g mannitol in 968.95 g distilled H2O) combined with 5.0% dimethylsulfoxide and mixed in a 1:4 sperm : medium volume ratio. The highest fertilization percentage obtained with cryopreserved semen was 87.7. No fertilization was obtained when glycerol, ethylene glycol, or propylene glycol were the cryoprotectants. Mean freezing rates faster than 5 C/minute were more effective than slower rates.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1983)112<86:CPOSFS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor