摘要:

All species of suspension-feeding teleost fishes switch from particulate feeding to suspension feeding at a standard length of about 2–5 cm. Although this ontogenetic shift in feeding mode is suggestive of an energetic or biophysical constraint that restricts small fishes to particulate feeding, there have been no comparisons of the energetic costs of pump suspension feeding and particulate feeding based on oxygen consumption data. We found that the O2consumption (mg O2/[g body weights·h]) associated with the capture of prey by juvenile Sacramento blackfishOrthodon microlepidotus(Cyprinidae) during pump suspension feeding on small zooplankton did not differ significantly (P> 0.05) from that measured during particulate feeding on large zooplankton. The metabolic cost of energy acquisition (mg O2/[g body weights·103J prey consumed]) was approximately 2.5 times higher (P≤ 0.02) for pump suspension feeding than for particulate feeding. However, because the actual energy expenditure during the feeding period was only about 2% of the energetic content of theArtemianauplii consumed during suspension feeding and less than 1% of the energetic content of theArtemiaadults consumed during particulate feeding, the advantage of particulate feeding may be a potentially high rate of energy intake rather than a low energy expenditure. Because suspension feeding provides a lower rate of energy intake, small fishes may be unable to obtain the energy required for growth and maintenance by this feeding mode.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0149:ECOSFV>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

SteelheadOncorhynchus mykissfrom various sites between the Columbia River and the Mad River, California, were genetically characterized at 10 protein-coding loci or pairs of loci by starch gel electrophoresis. Fish from coastal streams differed from fish east of the Cascade Mountains and from fish of the Willamette River (a tributary of the Columbia River, west of the Cascade Mountains). Coastal steelhead from the northern part of the study area differed from those in the southern part. Genetic differentiation within and among drainages was not statistically significant; however, gene diversity analysis and the life history of steelhead suggested that fish from different drainages should be considered as separate populations. Genetic variation among fish in separate drainages was similar to that reported in northwestern Washington and less than that reported in British Columbia. Allele frequencies varied significantly among year-classes. Genetic variation within samples accounted for 98.3% of the total genetic variation observed in this study. Most hatchery populations differed from wild populations, suggesting that conservation of genetic diversity among and within wild populations could be facilitated by altering hatchery programs.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0158:GVISOO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Fish DNA was extracted from epithelial tissue covering a few scales and used as template for the polymerase chain reaction (PCR). Amplified segments of the mitochondrial DNA gene for 12S ribosomal RNA were subjected to restriction enzyme analysis. Restriction fragment length polymorphisms (RFLPs) are described for several fish species. Direct sequencing of amplified segments from largemouth bassMicropterus salmoidesand channel catfishIctalurus punctatuspermitted interspecific comparisons and the development of detailed microrestriction maps that reveal diagnostic allelic variations between the two species. The protocol outlined in this report is offered as an alternative to conventional DNA analysis, which usually requires the obligatory sacrifice offish. It may be particularly advantageous when genetic analysis of valuable brood stock or endangered species is necessary because it obviates the need for animal sacrifice.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0170:GAPMIA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We used 28–48 observations from 10 oligotrophic lakes and reservoirs to describe the influence offish density and relative aquatic productivity on growth of kokaneeOncorhynchus nerka. We found a positive relationship between length at age at all ages and an index of lake or reservoir productivity. We found evidence of strong density dependence for older fish (ages 2 and 3), but not for yearlings (90–210 mm total length). The density-dependent response in growth was of a decaying exponential form. We found a significant interaction (Secchi transparency × density) that indicated the general response of growth to density was more pronounced in waters of lower productivity. Density dependence may thus be more obvious in populations fluctuating at low density or in unproductive waters than in populations at higher densities. Intraspecific competition probably increases with age and size and probably is not important among age-0 or age-1 fish at the densities observed (< 1,000 fish/hectare). The form of the density-dependent growth response we observed for kokanee was different from that described for some populations of sockeye salmon, the anadromous form ofO. nerka. Mechanisms of population regulation for the two forms probably differ as well. Our empirical models of growth should be useful to managers interested in density-related changes in fisheries of oligotrophic waters.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0178:IOFDAR>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We evaluated nine commercially available tags to determine their suitability for marking yearling rainbow troutOncorhynchus mykissreared in raceways and circular tanks. The tags tested were Floy vinyl tubing tags FD-67 anchor, FT-2 dart, FT-4 cinch-up, and FT-4 lock-on; modified Carlin; modified Petersen disk; Monel strap 4-1005; Monel butt end 4-1242; and Stoffel fish seal. After 9 months, tag losses from raceway fish were lowest (8%) for the FT-4 lock-on tag; in tanks, none of the FT-2 dart, FT-4 cinch-up, FT-4 lock-on, or the Monel butt end tags were lost. At 90 d after tagging, raceway fish marked with the Monel strap or the modified Carlin tags showed significantly less growth than did fish marked with the FD-67 anchor tag; the converse was true for fish in tanks. After 9 months, raceway fish marked with the Monel butt end tag and tank fish marked with the FD-67 anchor tag were least injured. Injury was greater in raceways than in tanks for all tag types. Judged by overall performance, the FD-67 anchor was the most effective tag for fish maintained in raceways and the FT-4 cinch-up was a suitable alternative; the FT-2 dart, FT-4 cinch-up, and Monel butt end tags were equally suitable for fish in tank culture.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0192:PONETO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This study tested the hypothesis that thyroid hormone levels in wild juvenile coho salmonOncorhynchus kisutchare higher in fish beginning their seaward migration (smolts) than in lake-resident fish (parr). Average overall thyroxine (T4) levels were higher in wild smolts (3.5 ng/mL) than in wild parr (1.8 ng/mL); however, average overall triiodothyronine (T3) levels were similar in wild smolts (3.0 ng/mL) and parr (2.3 ng/mL). Whereas hormone levels in smolts varied between sampling dates (mean T4, 1.2–6.6 ng/mL; mean T3, 0.7–4.8 ng/mL;P< 0.05), hormone levels in parr remained fairly constant (mean T4, 1.3–2.6 ng/mL; mean T3, 1.8–2.8 ng/mL;P> 0.05). Partly because of these dissimilar patterns of variability, differences in thyroid hormone levels between smolts and parr tended to be subtle. Thus, wild coho smolts were more similar to wild parr than might have been predicted from studies of hatchery-reared fish. Furthermore, because hormone levels in migrants were sometimes similar to those in nonmigrants, predictions of the onset of the seaward migration by wild coho salmon probably should be based on more factors than thyroid hormone levels alone.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0199:PTHLIM>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Length of confinement in a dip net affected subsequent performance of 2–3-year-old striped bassMorone saxatilisin a swimming challenge. Fish that were not confined or were confined for only 5 min could consistently swim for 10 min at 100 cm/s, whereas fish confined for longer than 15 min often could not. Average swimming time was significantly less for striped bass confined for 15 min or longer than for unconfined controls. Plasma cortisol, glucose, and lactate concentrations were always higher in fish after a swimming challenge than in resting fish sampled from the holding tank, although length of net confinement before swimming had little effect on postchallenge plasma variables. Time of postchallenge blood sampling, however, had a significant effect on all three plasma variables: glucose and cortisol concentrations were higher in striped bass immediately after they were removed from the swimming chamber, whereas lactate concentration was higher after 45 min of recovery. Resting and stress levels of the plasma variables resembled those measured in other fishes, except for the extremely large and rapid rise in plasma cortisol concentration from less than 50 ng/mL in resting fish to over 500 ng/mL in fish that had swum for 10 min.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0206:RSPOSB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Fuzzy graph theory is applicable to any dynamical system where the values of all state variables are known for at least two points in time. This type of analysis is useful for detecting early trends in successional changes of assemblages of organisms. Seventeen successive years of research vessel trawl survey data from the Gulf of Thailand involving 38 species or species groups were amenable to this form of analysis. The compositional dynamics of the species were examined by using three fuzzy relations to describe succession from the same data set. Although fuzzy graphs resulting from these relations showed that successional trends depended somewhat upon the characteristics of the chosen relation, consistent succession to a relatively few short-lived opportunistic species occurred. After the initial perturbation, the system was not strongly time-varying and some prediction was possible from a short data set. This application of methods and algorithms of fuzzy graph theory to analysis of multispecies fishery dynamics suggests that preliminary interpretation of trends in such data can be made with them.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0211:AOFGTT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We evaluated the efficiency with which estuarine fishes were collected in a haul seine on 11 dates from 1984 to 1988. Comparisons between the catch in the first haul and the total population in a tidal creek pool demonstrated that species richness, species rank, and size distributions of dominant taxa were represented well in the first haul. However, abundance was not reliably estimated by a single collection. Collection efficiency for the six most common taxa ranged from 7 to 91%. A two-way analysis of variance, used to examine the efficiency of the first haul, indicated significant main effects for species and season. In general, efficiencies were significantly higher in summer and winter than in spring and autumn. Multiple-regression analyses, used to predict the efficiency of the first haul as a function of water temperature, salinity, total numbers, and modal length, only yielded significant relationships for some species. Collection efficiencies of striped mulletMugil cephaluswere related to water temperature and total number of striped mullet present, whereas water temperature and modal length were good predictors for the collection efficiency of spotLeiostomus xanthurus. Seasonal variations in efficiency among species and size-classes were consistent with our observations offish swimming behavior and avoidance responses. The application of rotenone after 15 consecutive seine hauls provided further evidence that differences among species and size-classes within species must be taken into account when seine collection data are interpreted. Because the degree to which a standard sampling effort underestimates estuarine fish abundance varies so greatly in time and space, we recommend that, in future studies, collection efficiency should be measured at least once each season.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0234:FITCEO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Declining growth and delayed age at maturity of walleyeStizostedion vitreumfrom 1965 to 1984 indicated that the species' large Lake Erie population was taxing the capacity of the prey fish community to support it. We examined the effects of prey and predator abundances on walleye diets and estimated the total predatory demand of age-0 through age-6 walleyes in western Lake Erie during 1986–1988. Walleye diets reflected prey fish abundances. Gizzard shad Dorosoma cepedianum and shiners (emerald shinerNotropis atherinoidesand spottail shinerN. hudsonius) were the major prey in years when they were abundant. In years when these prey species – especially gizzard shad – were not abundant, walleyes consumed more white perchMorone americanaand (to a lesser degree) yellow perchPerca flavescens. Total consumption by the walleye population was relatively constant, ranging from 83,700 tonnes in 1987 to 94,300 tonnes in 1986. Bioenergetics modeling showed that greater fishing mortality imposed on strong walleye year-classes could reduce competition among older cohorts; however, because diets of age-0 and age-1 walleyes differ from diets of older fish, few prey made available by greater harvests would be used by small walleyes to increase their growth. Walleye density and gizzard shad availability interact to influence prey consumption and walleye growth in western Lake Erie, High predatory demand and reduced growth of walleyes occur when large walleye year-classes predominate.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1992)121<0245:EOPAPA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor