摘要:

Distributions of young-of-the-year and adult alewives (Alosa pseudoharengus) in Lake Michigan were determined by bottom trawling along isotherms at the intersection of the thermocline with the bottom near Grand Haven, Michigan over a 1-week period during September. Few alewives were caught on the bottom at night. During the day, adult alewives were caught primarily at 11–14 C. Young-of-the-year alewives on the bottom occurred only at temperatures greater than 15 C and primarily at 17–20 C. Bathymetric distributions of the two size groups of alewives shifted with oscillations in thermocline location. Young of the year and adults also differed in prey selection. Young-of-the-year alewives ate primarily cyclopoid copepods, calanoid copepods, and Daphnia sp. and these items were most common in stomachs during the day. Adult alewives fed mainly on Daphnia sp. and more were eaten during the day than night. Copepods, Bosmina sp., Pontoporeia hoyi, and Mysis relicta were also present in stomachs of adult alewives. It is suggested that behavioral thermoregulation can reduce the potential for food competition between adult and young-of-the-year alewives.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<469:SSOAAY>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Instantaneous total mortality rates for planktonic larval freshwater drums (Aplodinotus grunniens) in a channelized stretch of the Missouri River were estimated from analyses of cumulative catch curves. Mortality rates, which ranged from 0.11 to 0.21 per day, were significantly greater in 1976 than in 1974. Basing our interpretation on the underrepresentation of eggs and early larvae in the channelized river samples, we hypothesize that favorable environments upstream represent a more significant source of recruitment of larvae to the freshwater drum population than the channelized river.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<479:NMROFD>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Wild rainbow trout (Salmo gairdneri) were marked and released (N = 470) in Valley Creek, a small stream in east-central Minnesota. Subsequent sampling indicated no significant upstream or downstream movement over 2.5 years. A regression analysis of the transformed and weighted ratios of marked-to-total fish captured against time was used to determine if significant movement occurred. The lack of movement may be a feature of a genetically distinct nonmigratory race, individuals of which may occupy home territories throughout their lifetime.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<484:LORTMI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The performances of planted brook trout (Salvelinus fontinalis) and F1splake (Salvelinus namaycush x S. fontinalis) were studied in four Precambrian Shield lakes. Splake survived better than brook trout in three lakes; mean gill-net recoveries were 15.3, 13.2, and 8.5% of plantings of splake compared to 2.9, 1.2, and 7.2% for brook trout. The fourth lake showed a mean recovery rate of 28% for both splake and brook trout. Most brook trout were caught in the year of planting or the year following, whereas the splake recoveries were spread over 6–7 years. Each kilogram of planted yearling splake yielded 2.5–7.1 kg among lakes; each kilogram of yearling brook trout planted yielded 0.2–1.3 kg. Brook trout and splake planted in the same lake grew at approximately the same rate in the year following planting. There were, however, differences in growth rate of both brook trout and splake among lakes and for splake the differences were maintained for an additional 5–6 years. Diet of both species differed among the lakes but brook trout fed more on aquatic insects and fish while small splake utilized Entomostraca (chiefly Cladocera) and larger splake preyed heavily on Malacostraca (chiefly crayfish) and fish (chiefly yellow perch, Perca flavescens).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<491:SGAFHO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Four groups of age-I+ fall yearling Atlantic salmon (Salmo salar) were planted at Long Pond, Mount Desert Island, Maine between 1952 and 1969 to evaluate relationships between stocking rate, growth, and yield, the latter determined from randomly stratified creel censuses. There were significant inverse linear relationships between both stocking rate and growth and stocking rate and yield. Size at planting was not related to yield. Atlantic salmon recoveries averaged 6% for all plantings combined but ranged up to 45% for one lot. Mean size of Atlantic salmon caught from the different groups ranged from 41 to 45 cm and 0.6 to 0.9 kg. Mean annual effort expended in harvesting Atlantic salmon from the different cohorts ranged from 696 to 808 angler trips per year (summer and winter effort combined).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<502:SRATGA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The oscillatory properties of a striped bass (Morone saxatilis) population model controlled by a Ricker function were examined by plotting the value of the parameter alpha above which the population will oscillate with an amplitude equal to or greater than 1% of the equilibrium stock size. The value of alpha required for persistent oscillation was affected by the age distribution and the reproductive age structure of the model population. The most stable age structure was found to exist at an instantaneous mortality rate of about 1.0. The results support the notion that fluctuations in the abundance of striped bass stock are largely due to density-independent influences on survival.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<511:OBOASB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Mechanical harvesting of the submersed weed hydrilla, Hydrilla verticillata (L.F.) Royle, in Orange Lake, Florida entangled fish in the cut vegetation resulting in their disposal with the weeds on shore. Three block-net samples in dense hydrilla indicated fish standing crops (mean ± SD) of 205,000 ± 35,000 fish/hectare and 460 ± 30 kg/hectare. The estimated loss of fish to mechanical harvesting represented 32% of fish numbers and 18% of fish biomass. Fish most susceptible to mechanical removal with hydrilla were juvenile sportfish and smaller species. The monetary replacement value of the fish lost was estimated at over $6,000/hectare.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<517:FHRFMC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Coefficients of condition were calculated seasonally for largemouth bass (Micropterus salmoides), bluegill (Lepomis macrochirus), and redear sunfish (Lepomis microlophus) for three years from two hydrilla-infested Florida lakes, Baldwin and Wales. Hydrilla coverage was altered with aquatic herbicides and grass carp (Ctenopharyngodon idella) during the study period in both lakes. Bluegill and redear sunfish condition was not adversely affected until hydrilla occupied the majority of the water column. The reduction in condition which occurred with near total occupation of the water column by hydrilla was probably due to the elimination of a foraging gradient between the submersed macrophytes and open water. Harvestable (creelable) largemouth bass had low condition values once hydrilla coverage was above 30%; however, smaller largemouth bass were not as adversely affected until percent coverage exceeded 50%.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<521:COCFLB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The body conditions, K = 105(weight, g) ÷ (standard length)3, and various hematological characters were examined for largemouth bass (Micropterus salmoides) taken from Par Pond, a reservoir heated by effluent from a nuclear production reactor at the Savannah River Plant near Aiken, South Carolina. Largemouth bass with K less than 2.0 had significantly lower (P < 0.05) hematocrits, hemoglobin concentrations, total red blood cell counts, total white blood cell counts, and lymphocyte fractions, and significantly higher granulocyte fractions and cortisol concentrations, than those with K greater than 2.0; monocyte, thrombocyte, and reticulocyte fractions were not different between the two K-factor groupings. When data were pooled, all blood variables except the reticulocyte fraction were significantly correlated with K. Hematocrit, the lymphocyte fraction, and cortisol concentration account for 20.5% of the variation in K. These data support a previous hypothesis that elevated water temperature promotes stress. Stress within the Par Pond largemouth bass population may play an impotant role in the epizootiology of red-sore disease caused by the gram-negative bacterium, Aeromonas hydrophila.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<532:SABCIA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

We have detected significant reduction in genetic variation at isozyme loci in a hatchery stock of west-slope cutthroat trout (Salmo clarki) in comparison to the wild stock from which it was derived 14 years earlier. This conclusion is supported by (1) a 57% reduction in the proportion of polymorphic loci, (2) a 29% reduction in the average number of alleles per locus, (3) a 21% reduction in the average heterozygosity per individual, and (4) significant changes in allelic frequencies between age-classes. This loss of variation is attributed to both a limited number of founders of the hatchery stock and the effects of genetic drift in the maintenance of the hatchery stock.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<537:LOGVIA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor