摘要:

The U.S. Fish and Wildlife Service and the New York Department of Environmental Conservation assessed the population of alewives Alosa pseudoharengus in U.S. waters of Lake Ontario during 1976–1982 with bottom trawls. Alewives were abundant in 1976 but a die-off greatly reduced their numbers during the winter of 1976–1977. The population quickly recovered, however, adult abundance increasing nearly sevenfold during 1978–1981. In spring 1981 the bottom population in southern Lake Ontario was estimated to be 5.25 × 109fish weighing 128,500 t. Estimated average alewife biomass per hectare during 1978–1982 far exceeded the estimates for either Lake Michigan during 1967–1982 or western Lake Huron during 1973–1982. Recruitment of age-II fish to the population was affected by abundance of adults in two ways: (1) the number of yearlings produced was directly related to adult abundance at low population levels but inversely related at high population levels; and (2) survival of yearlings to age II was inversely related to adult abundance. Growth in 1977 was exceptional, leaving a wide, unmistakable band on scales of the previously slow-growing adults. This wide growth zone served as a marker to identify survivors of the 1976–1977 die-off and to show that each year after 1978 a successively larger proportion of survivors was failing to grow in length or to form an annulus (54% in 1979, 96% in 1980, and 100% in 1981). There was no marker on scales of alewives recruited after the die-off, but the apparent age composition of our catches strongly suggested that most of them also failed to grow in 1981.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<1:DOAILO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A putative stock of largemouth bass Micropterus salmoides, characterized by small adult size and large condition factors, exists in the Mobile Bay or delta region of the Alabama River system. High salinity often occurs in this area of the river. Populations from the delta (mesosaline), Tombigbee River (fresh water), and Alabama River (fresh water), all in the Alabama River system, were electrophoretically compared to one another and to populations from other watersheds in Alabama. Largemouth bass from the Alabama River system were genetically distinct from those of other watersheds. Minimal allele-frequency differences were observed among delta, Tombigbee, and Alabama populations. Observed allele frequencies of delta and Tombigbee fish were more similar to each other than to those of Alabama River fish. Mean heterozygosity was 0.027, 0.019, and 0.004 for delta, Tombigbee, and Alabama River populations, respectively. Delta largemouth bass had a different (P = 0.05) allele frequency from Tombigbee and Alabama fish at the esterase-B locus. The smaller size and greater condition of delta largemouth bass relative to fish further upstream are probably due to environmental factors, because observed genetic differences were minimal. However, delta and upstream fish need to be grown in the same environment to determine the relative influences of environment and genetics on the body conformation of delta largemouth bass.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<15:BGOLBI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Changes in food habits of largemouth bass Micropterus salmoides were compared with seasonal and annual changes in size composition of a gizzard shad population Dorosoma cepedianum to better understand the temporal dynamics of this species as prey for largemouth bass. Stomachs of 5,283 largemouth bass were examined during spring, summer, and fall from 1978 to 1981. Gizzard shad was the most important species in the diet of age-I and older largemouth bass in all years. However, the age and size composition, as well as the percentage of the volume contributed by this species to the diet, varied substantially among years and seasonally within each year. Variation of gizzard shad in the diet of yearling and older largemouth bass reflected changes in availability caused by high winter mortality of young-of-the-year gizzard shad in some years as well as by annual variation in the summer growth of this age group. Seasonal gaps in the availability of important size classes of gizzard shad reduced its value as a forage species. Fish contributed a major portion of the diet of young-of-the-year largemouth bass in all years but gizzard shad were important only in 1981. Age-0 gizzard shad grew more slowly in 1981, a larger fraction remained vulnerable to predation, and more were eaten by age-0 largemouth bass than in any other year.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<21:IOGSIT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Otolith microstructure of chinook salmon Oncorhynchus tshawytscha from the Sixes River, Oregon, showed the effects of first-year growth rate on subsequent growth, mortality, and maturation. Although size-selective ocean mortality was not conclusively demonstrated, the results were consistent with the view that smaller fish were removed from the population at a greater rate during oceanic or late estuarine life. On average, fish that were large relative to the rest of the cohort at entry into the estuary remained so up to the formation of the first annulus. Male chinook salmon that grew quickly in the estuary and ocean up to the formation of the first annulus matured earlier, on average.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<28:FGROSR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Two methods are presented for estimating instantaneous daily mortality rates of larval fishes with otolith-increment data. The first involves construction of a histogram of the numbers of daily increments per larva from a sample of larvae, and estimation of mortality from the decline in the loge-transformed increment-frequency curve. The second approach is to convert larva lengths to number of increments with a growth curve derived from otolith data, and then to estimate mortality from the descending limb of a loge-transformed increment-frequency histogram. Counts of daily increments in otoliths of larval anadromous alewives Alosa pseudoharengus collected from a coastal Massachusetts pond were used to compare results from these two methods with results from a third method that uses the decline in catch per unit effort of larvae through time. The estimate of instantaneous daily mortality for larval alewives from otolith methods was 0.122, which was an average rate for larvae 6.0 to 13.9 mm total length over a 1-month sampling period. The three methods generally produced similar mortality estimates over large sampling periods; however, otolith-derived mortality estimates from single sampling dates were highly variable. Major advantages of otolith increment methods over traditional catch-curve methods for estimating larva mortality are elimination of the need for fitting a growth curve to estimate mortality and the ability to obtain better estimates of mortality for individual cohorts of larvae.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<34:MOELFM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Walleyes Stizostedion vitreum vitreum and white suckers Catostomus commersoni shared a common spawning ground in Apsley Creek. Their reproduction overlapped in time, but white suckers spawned mainly in the riffle zone (710 eggs/m2) and rarely in quiet water (0.5 eggs/m2) surrounding the riffle. In contrast, walleyes spawned more in quiet water (6,241 eggs/m2) than in the riffle (65 eggs/m2). Walleye egg survival was higher on a sand-gravel-rock substrate than it was on a mud-detritus bottom. Spottail shiners Notropis hudsonius and yellow perch Perca flavescens fed extensively on walleye eggs; predation on white sucker eggs was not detected. Larva drift of both species was passive, varying with stream velocity, and occurred during periods of decreasing light (2100–0100 hours). Although eggs of both species began hatching on May 7, white sucker larvae drifted 11–13 d after walleye larvae. There was no indication that walleyes and white suckers competed for spawning areas as adults or for food as larvae.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<41:SALDOS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Adenine nucleotide and glycogen concentrations were measured concurrently in white muscle of mummichogs Fundulus heteroclitus after the fish were exposed to stressors that either caused an increase in energy use (metabolic loading) or damaged metabolic function (toxic inhibition). When fish were exposed 4 h to 1% unbleached kraft mill effluent (which causes metabolic loading) in the presence of 6 mg/L dissolved oxygen, glycogen and AMP concentrations significantly (P ≤ 0.05) decreased below control values, whereas ATP, ADP, and total adenylate (TA) concentrations as well as the adenylate energy charge (AEC = [ATP + 1/2ADP]/TA) were unchanged. When dissolved oxygen was below 1 mg/L, the effluent caused significant decreases in glycogen, ATP, and TA, but not in ADP, AMP, or the AEC. The combined effect of effluent and hypoxia caused more significant drops in ATP or TA pool. When fish were exposed to 60 μg/L DDT (a toxic inhibitor) for 4 h, none of the measured energy variables changed even though this concentration was lethal after several days. At a concentration of 100 μg/L DDT, all variables except ADP decreased significantly from control values, which may have reflected energy depletion of the muscle in response to nerve spasms rather than a direct toxic effect on the muscle itself.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<47:COGAAN>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The effects of fluctuating diel temperature cycles on survival, growth, plasma cortisol and glucose concentrations, liver weight, and liver glycogen of juvenile coho salmon Oncorhynchus kisutch were determined. Temperature cycles (10–13°, 9–15°, 8–17°, and 6.5–20°C) were selected to simulate observed temperatures in clear-cuts of southeastern Alaska. Different levels of feeding, including starvation, were used in each of the tests. LT50s (peak temperature within a cycle producing 50% mortality) were 28°C for age-0 fish (350 mg) and 26°C for age-II fish (22-g presmolts). Cyclic temperatures for 40 d, averaging 11°C daily, did not influence growth of age-0 fish on any food ration as compared to controls held at a constant 11°C. Plasma cortisol and glucose concentrations were significantly greater in fish maintained for 20 d in the 6.5–20°C cycle but not different in fish in 10–13° and 9–15°C cycles or a constant 11°C. These elevated concentrations may be indicators of long-term stress. Plasma cortisol concentrations were lower in starved fish than in fed fish at all temperature regimes; however, fluctuating temperature did not enhance starvation effects on cortisol levels. Diel temperature cycles did not affect liver weights or liver glycogen concentrations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<52:EOFTOM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Enzyme allele frequencies at 28 loci were determined within nine lines of channel catfish Ictalurus punctatus selected for rapid growth and within their respective control lines. Thirteen of the 28 loci were polymorphic. There were differences among lines for frequencies of alternative alleles and for heterozygosity. Related lines had similar biochemical genetic character, but significant differences in allele frequencies were noted between control and select lines in as little as one generation. Lines derived by crossbreeding followed by selection had the least genetic variability. In general, selected lines had lower mean heterozygosity, lower percentages of polymorphic loci, and fewer alleles per locus than control lines. Heterogeneity of Wright's fixation indices, and the observed magnitude of change for allele frequencies compared to that expected from genetic drift, indicated selection for rapid growth caused the differences in enzyme allele frequencies between select and control lines at some loci. Actual measurement of drift by observing allele frequency changes between generations indicated selection within 9 of 13 polymorphic loci for at least one line of channel catfish per locus. Possession of certain allozymes partially explains growth differences between selected channel catfish and their randomly bred controls; such allozymes may have direct physiological effects on growth or their alleles may be linked to others affecting rate of growth.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<60:SODAFC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Pacific salmon Oncorhynchus spp. have been stocked in the Great Lakes where they accumulate body burdens of chlorinated hydrocarbons. The transport of these contaminants to resident communities in spawning streams was studied in two tributaries of Lake Michigan accessible to anadromous spawners and one control tributary blocked to them. No polychlorinated biphenyls (PCBs), DDT, or dieldrin were detected in the sediments or biota of the control stream, or in sediments of the test streams. However, trout Salmo spp. and, to a lesser extent, sculpins Cottus spp. accumulated PCBs and DDT as a result of eating contaminated salmon eggs. Eggs constituted as much as 87% (by weight) of the total stomach contents of trout collected during the salmon spawning season early October to early January. Salmon eggs contained 0.46–9.50 mg PCBs/kg, and 0.14–1.80 mg DDT/kg. Consumption of eggs varied greatly among individual trout, and there was a strong correlation between numbers of eggs in the stomachs and PCB and DDT concentrations in the fillets.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1986)115<69:COSFWC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor