摘要:

Stocks of pink salmonOncorhynchus gorbuschain British Columbia that were spawning from August through October 1982–1985 in rivers of different size were surveyed for variation in size, morphology, egg weight, and biochemical genetics. Fish that spawned in large rivers were longer and had proportionately larger heads, thicker caudal peduncles, and larger fins than those that spawned in small rivers. Differences in gill raker counts between the broodlines (i.e., fish spawned in even-numbered years versus those spawned in odd-numbered years) were greater than among stocks within broodlines. Differences in morphometric characters were greater among stocks within broodlines than between broodlines; this indicated morphometric adaptation to local conditions in the natal river. As the spawning season progressed, mean lengths of males and females and weight of eggs increased. Electrophoretic analysis indicated that in the odd-year broodline, pink salmon could be generally distinguished as originating from five regions; Skeena River, north and central coast (combined), south coast, Fraser River, and Puget Sound. In the even-year broodline, pink salmon could be distinguished from three regions: Queen Charlotte Islands, north and central coast (combined), and south coast. Variation in allelic frequencies between the broodlines was greater than among stocks within each broodline. Within stocks, allelic frequencies were generally stable over a 2-year period.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0109:VIBSME>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Young-of-year gizzard shadDorosoma cepedianum, the primary prey for piscivores in Ohio impoundments, are difficult to sample by conventional techniques. We developed a technique for sampling littoral zone quadrats with rotenone and compared this method to other gear. To sample, we isolated 0.15-hectare shoreline areas (N= 28 quadrats) with a plastic barrier, which confined the rotenone and even small fish, and applied rotenone at concentrations of 2–3 mg/L. To quantify densities of dead fish that sank, about 18% of the bottom within quadrats was covered with netting. These nets eliminated the need for species-specific recovery rates, which typically are highly variable, Tucker trawls and seines provided lower density and size estimates of gizzard shad than did our quadrat method. Despite difficulties associated with the quadrat rotenone technique such as site selection, variability, and personnel requirements, this method provided the best estimate of size structure and density of gizzard shad populations. To determine if prey size or density influenced stocking success of age-0 piscivores, we used our estimates of gizzard shad biomass and growth to calculate total production of prey (71.3 kg/hectare) during its first growing season. Five taxa of piscivorous fish were stocked and their growth and survival were monitored in conjunction with regular estimates of gizzard shad. Total consumption of prey by all predators, calculated from observed growth by bioenergetics models, was 14.5 kg/hectare, or only about 20% of total young-of-year gizzard shad production. Apparently, factors other than summer prey production, such as spatial and temporal overlap of predators and prey, the gizzard shad: predator size ratio at time of stocking, or availability of gizzard shad in winter, limited first-year growth and survival of stocked predators.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0127:UOAQRT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We documented differential vulnerability of fathead minnows Pimephales promelas, gizzard shadDorosoma cepedianum, and bluegillsLepomis macrochirusto predation by muskellunge Esox masquinongy, northern pikeE. lucius, and tiger muskellungeE. masquinongy×E. luciusin a 700-L tank. Individual esocids (150–225 mm in total length) were combined with singlespecies groups (N= 15) of optimal-sized prey (25–30% of predator length for bluegills, 37–43% for fathead minnows, and 30–36% for gizzard shad). Capture ability did not differ among esocids; however, mean captures per strike were higher for fathead minnow (0.67) and gizzard shad (0.78) than for bluegill (0A4). Morphology and antipredatory behavior, unique to each prey species, contributed to this differential vulnerability. In the field, we introduced equal numbers and similar sizes of these esocids into two systems, one with centrarchid prey and one with both centrarchid and gizzard shad prey. As predicted from laboratory work, esocids ate fewer prey and grew more slowly when centrarchids were the only prey than they did when gizzard were available, In a third reservoir, containing bluegills and gizzard shad, esocids strongly preferred gizzard shad over bluegills. To maximize growth and survival, esocids should be stocked in systems with soft-rayed or fusiform prey, such as cyprinids or shad, rather than in centrarchid-dominated systems.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0142:SPBTET>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Field surveys in the Pamunkey River, Virginia, indicated that numerous fish and invertebrate predators varied in their spatiotemporal coincidence with eggs and larvae of striped bassMorone saxatilison spawning grounds. In the laboratory, the cyclopoid copepod Acanthocyclops vernalis was observed to attack and kill striped bass larvae, In addition, juveniles or adults of satinfin shinerNotropis analostanus, spottail shinerN. hudsonius, tessellated darterEtheostoma olmstedi, white perchMorone americana, striped bass, bluegillLepomis macrochirus, pumpkinseedLepomis gibbosus, channel catfishIctalurus punctatus, and white catfishI. catusate yolk-sac larvae under laboratory conditions. Consumption of larvae by spottail shiners and satinfin shiners increased with increasing prey density to a maximum observed ingestion of 150 and 81 larvae per predator per hour, respectively. At prey concentrations simulating ambient Pamunkey River conditions (20–100 larvae/m3), consumption by both species ranged from 0 to 5 larvae/h, but these estimates were considered to be lower limits because prey densities were not maintained during the experiment. In contrast to these laboratory results, neither eggs nor larvae of striped bass were positively identified in guts of field-collected fishes, although various fish species consumed many eggs of the white perch.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0152:PPBFAI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

In Mack Creek, a third-order stream flowing through a 450-year-old coniferous forest in Oregon's Cascade Mountains, population size of young-of-the-year cutthroat troutSalmo clarkiwas positively correlated with length of stream edge and area of lateral habitat. Lateral habitats included backwaters and eddies at the margin of the channel that made up 10–15% of total stream area. Lateral habitat area was reduced at higher or lower streamflow, but the length of channel perimeter formed by lateral habitats was never less than twice the length of the reach. In an experimental manipulation of lateral habitat before the emergence of young fish from the redd, an increase in lateral habitat area of 2.4 times the area observed in control reaches resulted in a 2.2-times greater density of age-0 cutthroat trout. Young-of-the-year fish were virtually eliminated from stream sections with reduced area of lateral habitat. Growth was not affected by the greater density of fish in reaches with enhanced lateral habitat.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0162:ROYOTY>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We examined how interstice size in a structure influenced fish use of that structure. We determined preferences of bluegillsLepomis macrochirus(35–95 mm total length, TL) for small (40-mm), medium (150-mm), and large (350-mm) interstices within artificial structure units (2.5 m3) in three 0.16-hectare ponds both before and after largemouth bassMicropterus salmoides(255–454 mm TL) were added to study ponds. In the absence of predators, yearling bluegills preferred small- and medium-interstice structures over large interstices regardless of major differences in water clarity among ponds. In the presence of largemouth bass, bluegills preferred small interstices over medium and large interstices in all ponds; medium interstices were preferred over large interstices in turbid ponds but not in the clear pond. These preferences were most pronounced in the clear pond where bluegill use of medium- and large-interstice structures was halved after largemouth bass were stocked. The addition of largemouth bass reduced variability in numbers of bluegills using structures in all ponds; although, again, this reduction was most apparent in the clear pond. Largemouth bass preferred medium interstices over small- and large-interstice structures, although predator use of structures was low. Structures made up only 0.9% of the pond area, yet attracted about 5–10% of the bluegills. Structure may have a carrying capacity that limits the number of bluegills using that structure.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0171:SOHSIS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A biomass-based model for cohort analysis was examined for its performance in estimating total stock biomass over time. The model is based on the premise that a biomass-based analysis that incorporates growth can account for changes in population biomass resulting from changes in individual weight in addition to changes in number, and thereby give better estimates of population biomass over time. The biomass-based approach also facilitates the direct incorporation of data into the analysis in terms of biomass, bypassing the process of converting from biomass to numbers to do the calculations, and then converting the numbers back to biomass in order to make management decisions based on biomass. To incorporate growth into the analysis, we assumed that growth in weight occurs exponentially over the time increment of the analysis. Sensitivity of the analysis to the assumption of exponential growth was tested by examining its performance on three hypothetical data sets generated by simulations incorporating alternative representations of growth. The tests demonstrated that including growth enhanced the quality of the estimates. In addition, the model was extended to incorporate seasonal growth and seasonal catch. The model was applied to data on stocks of Alaska plaicePleuronectes quadrituberculatus, walleye pollockTheragra chalcogramma, and yellowfin soleLimanda asperafrom the eastern Bering Sea to demonstrate the features of the biomass-based analysis. Annual changes in growth rate were sometimes significant and influenced the results substantially, indicating that the inclusion of growth into this type of analysis may be important. The inclusion of seasonal growth and catch further improved the results of the analysis.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0180:BBCATI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Young channel catfishIctalurus punctatuswere incised through the peritoneal wall and the wounds were closed with a cyanoacrylate adhesive. Postoperative survival of test fish was 100% compared to 87% for control fish (fish that were handled like test fish but not incised). There was no difference in postoperative bacterial infection rates between test and control groups. Histological evaluation showed that wound healing was essentially complete within 14 d of surgery. Inflammatory responses were minor during this time and absent by day 14. Adhesions between incised tissue and the peritoneal viscera were observed in 60% of test fish; these adhesions slowed but did not alter the course of wound healing.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0190:WHOICW>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A simple behavioral test was devised to determine the effects of multiple acute stresses on the avoidance response time of fish. Groups of freshwater-adapted juvenile chinook salmonOncorhynchus tshawytschawere exposed to a sudden overhead light and the time it took each fish to reach cover was noted. Tests were done on fish stressed one, two, or three times with 3 h between stresses, and on fish 1, 3, 6, and 24 h after each level of stress; unstressed fish served as controls. All unstressed fish reached cover within 15 s. Stressed fish took longer to reach cover (often several minutes), with the greatest delay in response occurring immediately after the stress. There was a gradual decrease in response time with recovery from the stresses. Exposure to two or three consecutive stresses increased the delay in response time over that offish exposed to a single stress, indicating that the effects of the stresses were cumulative.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0196:CIARTO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Spatial and temporal variations in the abundance of young-of-the-year channel catfishIctalurus punctatuswere determined over 3 years based on 154 trawls taken from Navigation Pool 7 of the upper Mississippi River. No significant spatial patterns in abundance or length offish in the catch were found in seven poolwide surveys of the main channel. However, high variation among replicates existed. Temporal patterns in abundance and length-frequency distributions varied among the study years. Seasonal catch curves were similar in 1984 and 1986, although offset due to earlier spawning in 1986. Spawning appeared to have been protracted in both years, based on analyses of back-calculated dates of spawn and length-frequency patterns of young. Sixty to seventy percent more young were produced in 1985, when spawning occurred over a shorter period of time and a more uniformly sized year class was produced. These annual variations in year-class characteristics are hypothesized to have resulted in part from different river discharge patterns in the 3 years of the survey, with high discharge in 1984 and 1986 negatively affecting production of young.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0202:VIAOYO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor