摘要:

Daily length-frequency data were used to assess the effect of water temperature and salinity on the in situ summer growth of age-1 broad whitefishCoregonus nasuscollected in the Sagavanirktok River delta in arctic Alaska. Summer growth patterns for the years 1982 and 1985–1989 were approximated as piecewise linear functions whose slopes were regressed against mean surface water temperature and salinity in the delta for each designated period. Multiple-regression analysis indicated that growth rate was significantly correlated with water temperature (P< 0.01) but not with salinity (P= 0.28). The growth-temperature relationship was described by both a linear and a polynomial function. Both functions were used to generate growth patterns for each of the six study years, based upon water temperature, The linear function modeled the 6 years of growth data with a mean absolute error of 2.1 mm (SD, 1.5 mm) and the polynomial function with a mean absolute error of 3.8 mm (SD, 3.0 mm). If independent verification proves the model to be applicable to other coastal regions of northern Alaska and Canada, the model would have direct application in assessing impacts of oil and gas development in the Arctic.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0001:MOISTA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Intraspecific variation in nuclear DNA content (genome size) was measured for the Arctic ciscoCoregonus autumnalisby fluorescence flow cytometry with the fluorochrome 4′,6-diamidino-2-phenylindole (DAPI). Frozen erythrocytes from the domestic chickenGallus domesticuswere analyzed simultaneously with Arctic cisco samples, providing an internal reference standard. Mean DNA content for 140 Arctic ciscoes from seven sites along the Beaufort Sea coast of Alaska and Canada was 5.99 pg/cell. Sample variances and mean DNA content were significantly heterogeneous among coastal sites. A significant increasing linear trend in mean DNA content was found on a west-to-east cline along the Beaufort Sea coast. Intraspecific variation in genome size observed in this study was substantial, which indicates that genome size characterizations of species based on small samples from a single population may be grossly inadequate.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0013:GSIBSC>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Restriction fragment length polymorphism (RFLP) analysis was performed on the mitochondria) DNA (mtDNA) of 33 lake whitefishCoregonus clupeaformisfrom four spawning populations in north-central Minnesota. Diagnostic differences between the RFLP patterns of mtDNA from lake whitefish and ciscoC. artediwere useful in the identification of fresh fillets and fresh or frozen carcasses. However, mtDNA analysis was of little use for identification of lake whitefish populations because of the low diversity documented among study populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0021:MDVIFM>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Electrophoretic analysis of enzymes and proteins enables aquaculturists to distinguish among stocks of channel catfishIctalurus punctatusand blue catfishI. furcatus, and to monitor gene flow, hybridization, and inbreeding. Sixteen previously unreported genetic markers allow much more precise resolution of stock differences. Analysis of low-risk tissue samples (caudal fin, adipose fin, and barbels) enables investigators to obtain genetic data with little stress on individual fish. We have identified at least 69 enzyme locus products in populations of channel catfish (Kansas, Marion, “Auburn,” Mississippi, and Red River strains) and blue catfish by use of autopsied tissues. Polymorphic loci account for at least 36% of the loci examined. Allelic polymorphisms fixed between blue and channel catfish were observed at 13 loci. Genetic variation was observed at 17 loci among channel catfish populations and at 5 loci in the single blue catfish population. Analysis of species-specific genetic markers among approximately 400 sampled individuals resulted in detection of two blue catfish that had been misidentified in channel catfish populations as well as four interspecific hybrids. Low-risk tissue samples allowed adequate resolution of 54 (77%) of the gene products examined. The ability to resolve at least 50 enzyme locus products from barbel samples alone will facilitate future genetic studies of populations for which sacrifice of individual brood fish is undesirable.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0026:EIOGMI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Competitive interactions between white suckersCatostomus commersoniand yellow perchPerca flavescenswere evaluated in a whole-lake manipulation experiment with one treatment lake and one reference lake. After a 2-year pretreatment period, 80% of the adult white sucker population was removed from Douglas Lake, Michigan, with trap nets set during the spring spawning season of 1987. Following white sucker removal, the abundance of chironomid larvae and the mayflyCaenissp. increased 13–18-fold in Douglas Lake, In Little Bear Lake, the control lake,Caenissp. showed a 20% decline in abundance during the study period (1985–1989), and chironomid larvae showed a 2.2-fold increase over the same time period. Associated with the increase in benthic invertebrate abundance in Douglas Lake, the diet of adult (>age-0) yellow perch shifted from predominantly zooplankton to predominantly benthos. This shift was accompanied by an increase in mean stomach content weight and feeding rate, eventually becoming apparent as increased growth. Relatively small changes in feeding rate and no trend in the diet or growth rate of adult yellow perch were apparent in the reference lake. The size structure of the adult yellow perch population in Douglas Lake showed a small increase in the proportion of large (> 150 mm total length) individuals during the first 3 years following white sucker removal and a great increase during the fourth year. In the control lake, no significant change in the population size structure of yellow perch was observed. From these results, we suggest that removal of adult white suckers can be a useful management tool to improve yellow perch growth and the quality of yellow perch fisheries. Changes in yellow perch growth and size structure, however, did not occur immediately after white sucker removal and were relatively small in magnitude during the duration of this study.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0036:ROYPAT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We determined food of and habitat use by juvenile largemouth bassMicropterus salmoides, spotted bassMicropterus punctulatus, striped bassMorone saxatilis, and white bassMorone chrysopsover a 6-year period (1981–1986) in Lake Texoma, Oklahoma–Texas. Largemouth bass, spotted bass, and white bass are native to the river basin and reservoir, whereas striped bass are introduced. Diet overlap (based on numbers or weight) was highest between the two species ofMoroneand between the two species ofMicropterus, and was also substantial (if based on prey weight) between largemouth bass and striped bass and between largemouth bass and white bass. Diet overlap between field-caught striped bass and largemouth bass was sufficiently high to suggest potential trophic competition between juveniles, but the two species occupied substantially different habitats as juveniles. Spatial segregation seemed sufficient to ameliorate potential competition between the latter two species. A laboratory experiment to test for trophic shifts by coexisting juvenile largemouth bass and striped bass indicated nonsignificant or only marginally significant changes in diets of largemouth bass in the presence of striped bass. Juvenile striped bass overlapped more in habitat and foods with juvenile white bass than with largemouth bass, suggesting a greater potential for negative interactions between the two species ofMorone.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0054:FOAHUB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The delta smeltHypomesus transpacificusis endemic to the upper Sacramento-San Joaquin estuary. It is closely associated with the freshwater-saltwater mixing zone except when it spawns in fresh water, primarily during March, April, and May. The delta smelt feeds on zooplankton, principally copepods. Its dominant prey was the native copepodEurytemora affinisin 1972–1974 but the exotic copepodPseudodiaptomus forbesiin 1988. Because the delta smelt has a 1-year life cycle and low fecundity (mean, 1,907 eggs/female), it is particularly sensitive to changes in estuarine conditions. Tow-net and midwater trawl samples taken from 1959 through 1981 throughout the delta smelt's range showed wide year-to-year fluctuations in population densities. Surveys encompassing different areas showed declines in different years between 1980 and 1983. After 1983, however, all studies have shown that the populations remained at very low densities throughout most of the range, The recent decline of delta smelt coincides with an increase in the diversion of inflowing water during a period of extended drought. These conditions have restricted the mixing zone to a relatively small area of deep river channels and, presumably, have increased the entrainment of delta smelt into water diversions. Restoration of the delta smelt to a sustainable population size is likely to require maintenance of the mixing zone in Suisun Bay and maintenance of net seaward flows in the lower San Joaquin River during the period when larvae are present.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0067:LHASOD>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Juvenile chinook salmonOncorhynchus tshawytscha(40–50 mm total length, TL) and striped bassMorone saxatilis(30–40 mm TL) were exposed to serial dilutions (100, 50, 25, and 12.5%) of agricultural subsurface drainwater (WWD), reconstituted drainwater (RWWD), and reconstituted seawater (IO). Agricultural subsurface drainwater contained naturally elevated concentrations of major ions (such as sodium and sulfate) and trace elements (especially boron and selenium), RWWD contained concentrations of major ions that mimicked those in WWD but trace elements were not elevated, and IO contained concentrations of total dissolved salt that were similar to those in WWD and RWWD but chloride replaced sulfate as the dominant anion. After 28 d of static exposure, over 75% of the chinook salmon in 100% WWD had died, whereas none had died in other dilutions and water types. Growth of chinook salmon in WWD and RWWD, but not in IO, exhibited dilution responses. All striped bass died in 100% WWD within 23 d, whereas 19 of 20 striped bass had died in 100% RWWD after 28 d. In contrast, none died in 100% IO. Growth of striped bass was impaired only in WWD. Fish in WWD accumulated as much as 200 μg/g (dry-weight basis) of boron, whereas fish in control water accumulated less than 3.1 μg/g. Although potentially toxic concentrations of selenium occurred in WWD (geometric means, 158–218 μg/L), chinook salmon and striped bass exposed to this water type accumulated 5.7 μg Se/g or less. These findings indicate that WWD was toxic to chinook salmon and striped bass. Judging from available data, the toxicity of WWD was due primarily to high concentrations of major ions present in atypical ratios, to high concentrations of sulfate, or to both. High concentrations of boron and selenium also may have contributed to the toxicity of WWD, but their effects were not clearly delineated.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0078:TOASDF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Aquatic plants have been controlled in a series of relatively small public-use areas in Guntersville Reservoir on the Tennessee River in northern Alabama. We investigated the effects of herbicide use (2,4-dichlorophenoxyacetic acid, diquat dibromide, copper-ethylenediamine complex) and vegetation reduction on movements and population characteristics of largemouth bassMicropterus salmoidesat six sites (5–10 hectares) in this 27,479-hectare impoundment. Fish were sampled by electrofishing, and relative vegetation density was monitored periodically through a 100-d period in late summer and fall of 1989. The locations and movements of 29 largemouth bass were monitored at four study sites with radiotelemetry. Three sites were treated with herbicides applied from airboats, and three control sites were traversed by airboats to simulate herbicide application. Largemouth bass catch rates (catch/ 1,000 s of electrofishing) did not change in response to herbicide treatment; mean total length of largemouth bass did not differ by site or time relative to herbicide treatment. Largemouth bass condition declined during the study period, and the rate of decline did not differ among sites. Movements of radio-marked largemouth bass were limited (<300 m) and largely confined to the study sites. Differences among sites, herbicide treatments, and vegetation density had no measurable effect on the movements of largemouth bass. Overall, the results of this study provide no evidence that localized herbicide applications changed the abundance, size structure, condition, or movement of largemouth bass.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0094:EOAPCO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Variations in the feeding intensity of juvenile coho salmonOncorhynchus kisutchand chinook salmonO. tshawytschacollected in coastal waters of Washington and Oregon were examined with respect to year, month, and area of collection and to light intensity, chlorophyll concentration, zooplankton biomass, and salmon abundance measured at the location of capture. Although the absolute amount of food in stomachs increased with increasing predator length, there was not a significant relation between stomach contents (as percent body weight) and predator length for either salmon species. Variations by year and month (but not by area) of collection were significant when examined independently for coho salmon; area (but not year and month) of collection was a significant variable for chinook salmon. Chlorophyll concentration (for coho salmon) and light intensity (for chinook salmon) contributed somewhat to the variability in feeding intensity as determined by a multiple-regression analysis but the abundance of salmon at the location of capture did not. Feeding intensity of juvenile coho salmon was also positively related to the biomass of plankton in surface waters but not to the overall biomass throughout the water column. Feeding success was not adequately described by any one variable examined, apparently because of the interactions among the levels of each variable.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0104:FRTVIF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor