摘要:

The toxicity of water from three rivers in the Santee–Cooper drainage of South Carolina was evaluated in a series of on-site studies with larval striped bassMorone saxatilis. Mortality and swimming behavior were assessed daily for larvae exposed to serial dilutions of water collected from the Santee, Congaree, and Wateree rivers. After 96 h, cumulative mortality was 90% in the Wateree River, and a dose–response pattern was evident in serial dilutions of the water. Larvae exposed to water from the Santee and Congaree rivers swam lethargically, but no appreciable mortality was observed. Acutely toxic concentrations of inorganic contaminants were not detected in the rivers; however, pentachloroanisole, a methylated by-product of pentachlorophenol, was twice as high in the Wateree River as it was in the other two rivers. Phenolic compounds may have contributed to larval mortality in the Wateree River and to lethargic activity of larvae in the Santee and Congaree rivers.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0521:TOWFTS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We made meristic and morphometric measurements on juveniles (25–100 mm total length) of hatchery-produced striped bassMorone saxatilis, white bassM. chrysops, original and reciprocal F1hybrids, original F2hybrids, and backcrosses with the original F1female. We compared both sets of measurements with published data and among themselves to delineate progeny differences. Meristic and morphometric values for all hybrids were generally intermediate between those of their parents, but exhibited considerable variation. We examined 11 meristic characters for detection of statistically significant differences (P< 0.05) between crosses that might be used for identification; of these, the numbers of lateral line scales, soft dorsal rays, and gill rakers differed among crosses. We examined 31 morphometric ratios with linear discriminant function tests for statistical differences between crosses. With the six best of these ratios, the overall discriminant analysis resulted in an 83% acceptable classification, and several crosses (16 out of 84 comparisons) were correctly segregated 100% of the time. After meristic differences were used to initially group samples of fish in a blind test, the discriminant function derived from the morphometric ratios allowed individual fish to be properly classified with a high degree of accuracy.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0529:IOJHOB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Even-year cohorts of northwestern Alaskan pink salmonOncorhynchus gorbuscha, sampled from 13 Aleutian islands, 1 Kodiak Island, and 4 eastern Bering Sea streams, were surveyed electrophoretically for 29 protein-coding loci. We observed no significant genetic heterogeneity among collections from the Aleutian Islands or within the Bering Sea regions of Bristol Bay and Norton Sound. The Bering Sea and Aleutian Island populations were more closely related to each other than to the Kodiak Island population. This similarity may reflect patterns of post-glacial colonization from the Bering Refuge. Genetic comparisons of northwestern Alaskan pink salmon with Asian populations from Sakhalin Island suggest that the Asian fish are most closely related to the northernmost North American populations that we collected, i.e., those of Norton Sound. Homogeneity among Aleutian Island populations is notable because the islands extend nearly 1,000 km, a distance over which pink salmon populations in other regions of Alaska exhibit genetic divergence. We propose that frequent straying, possibly a reflection of homing capabilities, may prevent genetic divergence of these populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0536:GROENA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Ten percent of the juvenile coho salmonOncorhynchus kisutchrearing in the main channel of Carnation Creek during the summer moved into intermittent tributaries and ephemeral swamps (off channel winter habitats) during the autumn of 1983. The number of juveniles residing within specific off channel sites during winter was governed by the magnitude of water levels associated with the first fall storms relative to the flooding levels required for adequate access to these sites (P< 0.05). Off channel habitats contributed 15.3% of the watershed's coho salmon smolts in 1983 and 23.1% in 1984. A 25-year flood event (65 m3/s) occurred in January 1984 and may have reduced the main-channel contribution for that year. The inability of coho salmon smolts to emigrate from off channel habitats and return to the main channel in spring may have reduced the off-channel contribution in 1983. April–May water levels were 37% below the 13-year mean water level in 1983 and 55% above it in 1984.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0546:COSFLA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

During the summers of 1981 and 1982, we studied resource partitioning by stocked lake troutSalvelinus namaycush, brown troutSalmo trutta, and chinook salmonOncorhynchus tshawytschaby fishing vertical gill nets at six distances from shore in south-central Lake Ontario. The nets were set at depths of approximately 15–45 m (nearshore stations, <4 km offshore) and more than 55 m (offshore stations, 4–24 km offshore). Salmonids were concentrated near shore, where they partitioned available habitat and, thus, food resources. Horizontal habitat was partitioned with respect to distance from shore; vertical habitat was partitioned in relation to temperature and the thermocline. Salmonids foraged for the most available prey items within their habitat. Overlaps in both food use and horizontal habitat use were inversely related to overlap in use of vertical habitat. There was increased habitat separation between sexes for those species caught farther from shore, At the salmonid stocking and prey density levels existing during our study, lake trout, brown trout, and chinook salmon appeared to partition resources and minimize deleterious trophic interactions during thermal stratification.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0552:RPISBS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The relationship between specific growth rate and fish size (weight) was influenced by temperature and genotype in two strains of rainbow troutOncorhyncus mykiss(formerlySalmo gairdneri) and their hybrid. Heterogeneity among the regression slopes for strains (genotype) as well as interaction with temperature invalidated the use of analysis of covariance to adjust for initial fish size differences. Regression slopes ranged from –0.74 ± 0.21 (SE) to –0.01 ± 0.16 among fish families reared at 7°C and from –0.41 ± 0.03 to –0.24 ± 0.09 among fish families reared at 15°C. The use of a particular slope value as a universal constant to compare specific growth rates offish is questionable.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0560:IOGATO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We assessed seasonal variations in endoparasite intensity (number per host) for six 1986 cohorts of age-0 bluegillLepomis macrochiruscollected from an overflow pond of the lower Mississippi River during March–December 1986.Allacanthochasmussp. (Trematoda) was the predominate endoparasitic taxon infecting bluegills. We noted peaked intensity curves and declines in variance-to-mean ratios for total endoparasites andAllacanthochasmussp. for three cohorts during pond flooding in October. Although changes in the distribution of parasite intensities during this period may have reflected bluegill mortality, declines in variance-to-mean ratios of parasite intensities were smaller than those predicted by theories of parasite-induced host mortality. We also examined bluegills of the previous (1985) year class in spring 1986; their endoparasite intensities and variance-to-mean ratios were substantially lower than those of 1986 cohorts in fall 1986. Because these data are from two year classes, they may not accurately reflect changes in the frequency distribution of endoparasites in age-0 bluegills during winter. However, there is little evidence of parasite mortality at low temperatures; if the pre- and postwinter intensity data are representative, overwintering mortality of parasitized bluegill may be substantial.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0565:PPMIAB>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Selection curves of encircling (run-around) and drifting (stab) gill nets used in the winter fishery for Spanish mackerelScomberomorus maculatusoff southern Florida were estimated by use of cumulative probability distributions of retention girth at length. Selection curves corresponded well with observed size frequencies obtained from each mesh size, Increasing differences between maximum and head girth perimeters as fish grew resulted in selection curves indicating increased selection range and efficiency. Selectivity of Spanish mackerel gill nets will change as the condition of the fish changes with the onset of the spawning season. Apparently, selectivity also changes with twine size.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0574:SOGNUI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We estimated the effects of gill-net mesh size regulations on the yield per recruit of Spanish mackerelScomberomorus maculatusin Florida. Yield per recruit was calculated with a simulation model that incorporated seasonal fishing rates by sectors (recreational and commercial) and size-varying availabilities of fish to the gear and retention probabilities once fish encountered the gear. Gains in yield (g) per recruit were always obtained by increasing mesh size, gill-net fishing mortality, or both. Adoption of a minimum length above the present enforced minimum 30.5 cm fork length may result in considerable gains in yield per recruit. This, however, depends on the assumption that there is no cryptic mortality of undersized fish in the recreational fishery. If such mortality is significant, the gains in yield per recruit will be much smaller.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0581:SYSFTF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Relationships of growth in weight to mantle length were examined for short-finned squidIllex illecebrosuscollected near Holyrood, Newfoundland, from 1964 to 1985. For lengths typically encountered in the commercial fishery, males generally were significantly heavier than females at a given length. Fish appeared to be the most suitable prey type for promoting growth of inshore short-finned squid, whereas crustaceans appeared to be the least suitable prey type in that respect. Relatively high weight at length during July in years of high short-finned squid abundance was related to a high level of predation on fish. Seasonal change in condition was also directly related to prominence offish in the diet. Incidence of cannibalism increased dramatically after July in years of high short-finned squid abundance as predation on fish declined sharply. In contrast, there were no seasonal changes in the diet during years of low abundance. In such years, the diet was mixed throughout the season and cannibalism remained at relatively low levels.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0591:LRFSSI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor