摘要:

Twenty-nine species of fishes were collected in the middle and upper Colorado River basins in 1967-1973. The native suckers, Catostomus latipinnis and C. discobolus, were the dominant species in the study area. Introduced species outnumbered native species 19 to 10. The introduced Ictalurus punctatus and Notropis lutrensis were abundant throughout most of the upper basin. The abundance of introduced species has increased steadily since 1900 as has the introductions of new species. Four endemic species, Ptychocheilus lucius, Gila elegans, Gila cypha, and Xyrauchen texanus, are considered endangered. These rare forms reproduce in the lower Yampa River, Desolation Canyon of middle Green River, and the lower Green River in Canyon-lands National Park. The major reasons for the decline of native fishes are considered to be alterations of habitat by high dams and introductions of exotic species.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<217:DAAOMF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Breeding populations of Sacramento perch, Archoplites interruptus (Girard), were successfully established in four Colorado lakes of widely varied chemistries and differing fish faunas. Growth rates and length-weight relationships of A. interruptus in Colorado are comparable to those of the species in other states. Dipterans are the most prevalent summer food, although the Sacramento perch occasionally is cannibalistic on its young of the year.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<232:SRAGAF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Annual production by the slimy sculpin, Cottus cognatus Richardson, was estimated at 59.4 kg/hectare wet weight for the period July, 1970, to July, 1971, in Valley Creek, Minnesota. Mark-and-recapture population estimates made by electrofishing and aging with otoliths were the bases for determining mean biomass and instantaneous growth rates. Annual turnover ratio, i.e., ratio of annual production to mean standing crop, was 1.2. Unusual silt and turbidity conditions, occurring in 1971, reduced the 1971 year class drastically, but had less serious effects on total production by all age groups. Food of the sculpins was similar in most respects to that of the brook trout inhabiting the same stream. Young sculpins fed heavily on small dipterans, mainly chironomids; older sculpins fed mainly on Gammarus and Trichoptera larvae. Comparisons with annual production estimates for brook (Salvelinus fontinalis) and rainbow trout (Salmo gairdneri), made previously in Valley Creek for comparable time periods, suggested a normal total annual production for all fishes of about 200 kg/hectare, with sculpins contributing about 1/3 and trout about 2/3.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<237:APBTSS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A method of calculating indices of annual year class strength from abundance data only is introduced. It involves a mathematical technique based on difference equations. The method is applied to data for six commercially harvested species of Green Bay, Lake Michigan. Estimated year class strengths are then compared with relative abundance indices of the parental spawning populations. Only for smelt and perch was there a significant correlation between the two. The same species were also the only ones for which the exponential relation of Ricker between spawners and year class strengths could be established.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<245:AMFEYC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Research on stocking the New River with channel catfish (Ictalurus punctatus) following a partial fishkill showed restocking to be unsuccessful and of no measurable benefit to the fishery. Only an estimated 50 of the 3,000 channel catfish stocked were recovered by anglers. Cost of each recovered fish was $18.00, based on the initial stocking cost. Factors contributing to the failure of the restocking program probably include the considerable time between the fishkill and restocking (16 months), natural repopulation from unaffected areas, and the relatively small size of the “catchable” stocked fish. A survey of state fisheries agencies (43 replies) regarding restocking policy following a fishkill showed that: (1) twenty states do not restock as a normal policy; (2) fourteen states said they did not restock following fishkills; (3) twenty-seven state agencies replied that they had methods for economic evaluation of fishkills (ranging from a constant price per pound or number, regardless, of species, to the Southern Division, American Fisheries Society, method which gives costs per inch and/or per pound of a species or family); and (4) a consensus existed that no detailed evaluation of the effectiveness of restocking after fishkills has been made.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<256:RAFAAF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Brush shelters were placed along alternate 100-m shoreline sections in two coves, and examined underwater weekly, for 7 weeks during the spawning season, to compare the use of sheltered and unsheltered habitat for nesting by three species of bass-largemouth (Micropterus salmoides), spotted (M. punctulatus), and smallmouth (M. dolomieui).

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<264:UOBSAC>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

Harvests of 13 to 21%, mostly of larger, older fish, were imposed for two years on populations of smallmouth and largemouth bass (Micropterus dolomieui and M. salmoides) that previously had been virtually unfished. Another population of smallmouth bass served as a control. Using trap nets, estimates of the number of bass and their size were made for one year before and two years after initial harvest. From these data, annual natural mortality, growth, standing crop and production were computed. There were no strong and consistent changes in any parameter which could be attributed to reductions in numbers of fish. Changes in growth unrelated to population density apparently resulted in declines of ratios of production to biomass following harvest. Possible causes of the lack of compensatory responses to harvest include the relatively short period of study and time lag in changes in growth and mortality.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<270:TEOASA>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<277:PCSOLB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A blood smear from an immature goosefish (Lophius americanus Valenciennes) revealed an intraerythrocyte haematozoan infestation. The parasite resembles Haemogregarina platessae Lebailly, which has never been reported outside of the order Pleuronectiformes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<284:TOOHSI>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor

摘要:

A Streptococcus sp. isolated from moribund fish in a 1972 Alabama-Florida fish kill produced mortalities in five species of fish involved in the kill. Pathogenicity studies with six non-fish-related streptococci were also conducted on two of the fishes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1975)104<286:PSWASS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1975

数据来源: Taylor