摘要:

Ecological differences reflected in food and habitat preference and angling vulnerability were investigated between two introduced sympatric populations of cutthroat trout, Salmo clarki. The Pikes Peak cutthroat fed to a large extent on Daphnia (68% by volume), whereas the Snake River cutthroat fed primarily on terrestrial insects (68% by volume). Other food habit differences were observed in the brook trout, Salvelinus fontinalis, and rainbow trout, Salmo gairdneri, populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1974)103<423:MIOESB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The brook trout (Salvelinus fontinalis Mitchill) population in Valley Creek, Minnesota, recovered from heavy flood damage in 1965-66 in terms of standing crop, growth, and production rates over a period of 4 to 5 years. Standing crops of brook trout increased numerically by 20-fold from a low of 498/ha in 1966 to 10,882/ha in 1969, and in biomass by 6-fold from 25kg/ha in 1966 to a maximum of 148 kg/ha in 1970. Growth rate early in the recovery period was high due to the low density of trout but decreased in successive years as fish density increased. Annual production was about 50 kg/ha during the flood years but increased during the recovery years to a maximum of 167 kg/ha in 1969. Cohort production for the 1965 year class, the one most seriously affected by the floods, was about 15 kg/ha, whereas cohort production for the 1968 year class, the last one that could he completely followed in this study, was about 190 kg/ha. After the floods, rainbow trout (Salmo gairdneri Richardson) immigrated into the study section from downstream; although variable in year class strength, the rainbow contributed substantially to total salmonid standing crop and annual production in some years. It has apparently become permanently established, even after total recovery of the brook trout population.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1974)103<431:ROSCAP>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

In four northern Idaho streams I assessed availability of invertebrate drift in summer 1969. Brook and cutthroat trout inhabited two streams sympatrically and two allopatrically. I compared drift and diet components to assess proportion of drift cropped by trout and extent to which trout segregated into dietary niches.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1974)103<440:UOIDBB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Population dynamics of landlocked salmon, Salmo salar, were investigated at Love Lake, Washington County, Maine from 1959-71. Survival of one lot of hatchery-reared fish from age II-III was 14%; survival of three lots from age III-IV ranged from 20-49%; survival of one lot from age IV-V and one lot from age V to VI was 34% and 32%, respectively. The rates compared favorably with those from well known Maine salmon waters and also with those of naturally-reared fish. Those stocked in fall at age I+ survived much better than those stocked in spring at age I. There is a linear relationship (p < 0.01) between average weight of salmon stocked and their recoveries by trapnetting. Those that weighed less than 35 g when stocked survived poorly. Growth of salmon at Love Lake compared favorably with the average growth in 15 Maine salmon lakes. Mean standing crop of salmon age III and older from 1963-69 was 1.4 salmon/ha weighing 0.6 kg/ha. Spring standing crops can be predicted by the linear regression formula Y = 100 + 8.78 X where X is catch of salmon per net hour X 1,000 (p < 0.01). Both hatchery and naturally-reared salmon used the inlet of Love Lake for spawning rather than the outlet. Attempts to establish spawning runs to the outlet by stocking juveniles and relocating ripe adults there failed.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1974)103<448:PDOLSS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The numerical and biomass structures of the fish biofacies from a small stream were studied by means of diversity indices. Biweekly samples taken over a year's period showed temporal fluctuations within a narrow range of variation. Seasonal changes in species composition had very little effect on the overall numerical structure of the fish biofacies, as species richness and diversity indices based on numbers of individuals showed stability throughout the year. Contrastingly, the number of species per collection and diversity indices based on biomass exhibited seasonal variations in response to seasonal changes. In total, the numerical structure of the fish biofacies was controlled by the persistent dominance of a few resident species.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1974)103<457:DIATTF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Because adult yellow perch were known to be cannibalistic in Oneida Lake, New York, this species was studied in 1965-71 to identify factors affecting the intensity of cannibalism and to evaluate the effect of cannibalism on the abundance of young perch. Adult perch changed their food habits in response to changes in the availability of different food items from June through September. Although young-of-the-year perch were most abundant in adult stomachs in August of most years, wide variations occurred in the annual intensity of cannibalism. Length and abundance of young perch, abundance of large chironomids and amphipods, and the size of the adult predator were identified as important factors for explaining variations in the frequency of occurrence of young perch in stomachs of adults. Correlations between the annual intensity of perch cannibalism and length and abundance of young perch imply that cannibalism operates as a compensatory or possibly an extrapensatory mortality process.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1974)103<462:COYPCI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

A total of 295 juvenile ladyfish Elops saurus Linnaeus were collected with surface trawls from Louisiana coastal streams in June 1968 and June 1969. The fish ranged from 45 to 201 mm in fork length. Of the 295 ladyfish stomachs examined, 229 (77.6%) contained food. Fish constituted 94.5% by occurrence of the food organisms and decapod crustaceans 5.5%. Gulf menhaden comprised 72.0% of the fish identified. The calculated length-weight relationship for juvenile ladyfish in the size range 45-201 mm (fork length) was log10W = −5.3295 + 3.1123 log10L, and the mean condition coefficient was 8.1.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1974)103<472:SFLRAC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Cruises were made off Chesapeake Bight from December 1959 through April 1963 to determine species composition and distribution of fishes spawned on the Continental Shelf. Illustrations of young fish, herein provided, now complete figures from newly hatched larvae to juveniles. Verbal descriptions provide prominent features of young bluefish to aid in identification and osteological development and to compare similar appearing larvae. Bluefish larvae can be distinguished from similar appearing species (Peprilus triacanthus and Urophycis chuss) with which they were taken in Chesapeake Bight by myomere numbers and pigment patterns. Bluefish larvae closely resemble the larval scombrids, Scomber scombrus and S. japonicus, and larval carangids. They may be separated by myomere numbers or relative lengths of the preopercular spine.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1974)103<477:DOYBPS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The available data was evaluated to assess the impact of the Rhode Island Sound dredge spoil disposal area on the floating trap fishery. It is unlikely that a significant portion of the observed decline in landings has resulted from a decrease in fishing effort since no significant correlation was established between these variables. The mean levels of landings were not significantly different when comparisons were made between the period before the onset of dumping and the short post-dumping period. A review of other fisheries for scup (Stenotomus chrysops), the predominant species caught by Rhode Island floating traps, indicated that landings have declined throughout the species' range.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1974)103<498:RISDSD>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Stream drift and benthos were collected from five stream locations having different levels of domestic and industrial pollution. The drift organisms from 100 m3of water during the diel period of peak drifting was compared with the benthos from 1 m2of stream bottom. Numbers and weights of both drift and benthos followed similar quantitative relations with water quality, generally increasing with water degradation. The relative abundance of benthos greatly exceeded that of the drift at the most polluted station where tubificids, which infrequently drift, were abundant. A greater variety of organisms occurred in the drift than in the benthos. Drifting organisms came from a wider spectrum of habitats and were collected with less effort than benthic organisms but did not always include certain benthic forms that seldom leave the stream bottom.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1974)103<507:SDAAIO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor