摘要:

Lakes are like islands—isolated, small, and relatively young. These similarities suggest that the theory developed for species dynamics on islands by MacArthur and Wilson (1963) may be relevant to lakes. If so, the expectations are that the number of species in a lake is the result of an equilibrium between rates of immigration of new species and extinction of existing species. The number of species would be lower in small, isolated lakes with simple habitat than in large or complex lakes or those exposed to a source of new species. Instability in species structure would be higher in lakes with a continuous source of new species or “exotics.” The influence of immigrations on species structure would be greater in smaller or more simple habitats than in larger or more complex habitats. Man's activities increase both immigration and extinction rates and induce even greater instability to species structure and thus add greater uncertainty or “chance” into the results of fish management plans. Attempts to retain more “natural” rates of species exchange among lakes may reduce instability and increase predictability in fish management.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<1:MWEGOC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Hybridization, androgenesis, and gynogenesis were studied as potential methods for creating nonreproducing populations of fish. Hybrids from crosses of female grass carp (Ctenopharyngodon idella) X male carp (Cyprinus carpio, Israeli mirrow variety) died during embryonic development. Hybrids of the reciprocal cross hatched and were stocked in ponds, but most died within 3 months. Dimensions of the nuclei of erythrocytes from hybrids indicated that survivors were polyploid. Androgenetic grass carp and gynogenetic carp were both observed in this reciprocal cross. Gynogenesis occurred in 3% of the eggs from grass carp fertilized with UV-irradiated milt from carp. Nuclear dimensions of androgenetic and gynogenetic fish suggested a diploid karyotype. The yield of 7,862 gynogenetic grass carp is evidence that this method might be practical for production of monosex fish for experimentation.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<10:POHAAG>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Species associations among 48 fish species of the Kiamichi River, a large tributary of Red River in SE Oklahoma, were examined using factor analysis of abundance data for 131 collection localities. Collections with high scores for Factors II and III (Steelcolor Shiner and Brook Silverside Groups) were concentrated in upper portions of the drainage, although certain species of both groups were rather widely distributed over the drainage. Collections with high scores for Factor I (White Bass Group) were primarily restricted to the mainstream of the lower Kiamichi River; those with high scores for Factors V and VI (Silvery Minnow and Golden Shiner Groups) were concentrated in tributaries of the lower Kiamichi. Excepting two species restricted to the lower Kiamichi, the species of Factor IV (Green Sunfish Group) were widely distributed over the drainage. In general, occurrence in the lower Kiamichi was positively correlated with westward distribution of the species into prairie environments of Oklahoma. Apparently, this was due to the ability of many of these species to thrive in lentic waters and/or to their ecological flexibility. Brief consideration is given to factors influencing distributions of species and to possible impacts of reservoir construction on the ichthyofauna of the Kiamichi River.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<17:FAOSAA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Fish collections taken in the 1920's from the Au Sable River, Michigan, were replicated in 1972. The Au Sable system as a whole has remained a non-rigorous, predictable environment for fish species. Substantial changes in fish species lists have occurred at most stations. The percentage of cold-water species present in the cold-water, moderate flow areas has increased, while species diversity, evenness, and numbers of species have remained constant. The warm headwater areas remain unchanged. Below the impoundments and in the large river areas, water quality has changed with subsequent reductions in species diversity and evenness, and large changes in species lists.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<32:CIFSCI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Adult and juvenile red drum, Sciaenops ocellata (Linnaeus), confined to a saltwater marsh impoundment at South Island, Georgetown County, South Carolina, were studied to determine their length-weight relationship, age according to otoliths, and the time of annulus formation in the otoliths. The equation log W = −1.29596 + 2.74031 log L was determined for the relationship of length to weight. Sectioned otoliths revealed no annulus formed in fish up to 1,070 g and 38.5 cm in standard length, suggesting that no annulus was formed the first spring after hatching in September through November. Annuli were formed in spring (April-May). The largest fish belonged to the 1966 and 1967 year classes, which were in the marsh when the impoundment was formed in May 1968. Reading otoliths before they were cut produced erroneous results.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<41:AAGORD>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Five functional forms for the seasonal distribution of force of fishing mortality were used in determining expectations of death from fishing. Expectation of death from fishing calculated from E/F = A/Z was compared to the actual expectation of death from fishing determined by numerical integration. Bias results in the formula-calculated expectation of death from fishing if the force of fishing mortality is not a constant fraction of the force of total mortality. Bias is greater when the force of fishing mortality is more asymmetrical. Bias is positive when greater force of fishing mortality occurs early in the year; negative bias occurs when force of fishing mortality is greater later in the year. The magnitude of bias, for a given functional form of force of fishing mortality, is a function of the relative size of force of fishing mortality to force of total mortality.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<45:AAOTEO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Although strategies to meet most management objectives are relatively clearcut in single-species, catchable trout programs, strategies become much more complex when two or more species are involved. A difficult problem that must be faced in evaluating catchable trout fisheries management strategies is defining management objectives. One approach to testing alternative management strategies in complex resource systems, such as catchable trout fisheries, is systems simulation. A computer-implemented CAtchable Trout Fishery Simulator (CATS) was developed to evaluate fishery response under various management strategies in a multispecies stocking program. The user of CATS can select alternative management strategies and functions which generate predictions of fishing pressure in a particular fishery. To evaluate the effect of each system component, CATS was exercised over a wide range of potential, although entirely hypothetical, system component alternations. Predominant stocking of brook trout appreciably increased average catch per angler hour and percentage return to creel. Altering the stocking ratio to favor brown trout substantially increased the number of angler hours. Stocking predominantly rainbow trout produced results intermediate between those caused by stocking predominantly brook or brown trout. Estimates of expected angling pressure and catchability coefficients of each species stocked are of primary importance because of their considerable effect on other system components. A user must have a sound objective before deciding where, when, which species, and how many fish to plant. The primary utility of CATS is to enable the user to evaluate management strategies prior to implementation.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<48:AOCTFM>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Alevins of brook trout (Salvelinus fontinalis) were buried in laboratory troughs in spawning gravel containing 0 to 25% sand. Sand slowed emergence and reduced the number of fry emerging. Weight of fry was not related to proportion of sand in the gravel, but was related to time; the fry were heaviest near the time of peak emergence, and lighter before and after the peak. Survival was estimated to be 84% from egg deposition to hatching for brook trout in Lawrence Creek, Wisconsin, and 70% from hatching to emergence, providing a total estimate for survival from egg deposition to emergence of 59%.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<57:IOSIRO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

Forty-three adult sockeye salmon (Oncorhynchus nerka) fitted with ultrasonic transmitters were tracked in coastal waters near the Fraser River in July and August, 1967 and 1968. Movement patterns of individual fish were unpredictable. Some moved actively in appropriate directions, some drifted passively, still others travelled southward away from their presnmed destination. Fish released in pairs did not travel along similar paths. Active fish moved generally northward toward the Fraser River, keeping away from shore and following axes of tidal currents. There was little straying into bays and channnels with slow currents. Some fish remained active both during the day and at night, while others became inactive after sunset or when the sun was not visible behind clouds. Average ground speed was about 1 body length/s (61 cm/s). Orientation to geoelectric fields is postulated, along with a compass-related orientation northward.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<64:CMOAFR>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor

摘要:

The stomachs of juvenile chinook salmon, Oncorhynchus tshawytscha, taken in the Prescott-Kalama area of the Columbia River during July-November 1968 and March-December 1969 were examined to obtain information on their contents. Zooplankton, especially Daphnia, were the major item in the diet of the young salmon from July through October, whereas insects were the most important constitutents of the diet during spring and fall.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1976)105<72:OAUOZB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1976

数据来源: Taylor