摘要:

We hypothesized that most recruitment of striped bassMorone saxatilisin the Santee–Cooper system, South Carolina, comes from river-spawn egg cohorts transported at the right time to high-quality nursery habitat, generally located in or near Lake Marion, a large reservoir within the system. Because striped bass produce a superabundance of eggs, only a small portion of the total egg production must develop in favorable nursery habitat to produce good recruitment in any year. In a 3-year study, we assessed temporal variability in egg mortality, compared the survival of progeny cohorts, and monitored abundance of juveniles and zooplankton in nursery areas. Growth rates and hatch dates of juveniles were estimated from otoliths. Mortality rates and hatching locations varied among egg cohorts. In the best recruitment years, 1988 and 1990, highest survival was associated with eggs hatched during the early half of the spawning season in Lake Marion. Zooplankton densities were higher in Lake Marion than in the spawning tributaries, suggesting that the lake was a superior nursery habitat. Growth rate of juveniles was highest in 1990. Water management at upstream dams in the Santee–Cooper system might increase recruitment by optimizing temperature and flow so that the maximum possible number of eggs hatch in upper Lake Marion.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0133:RDOSBI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

To assess mercury contamination of fish in Maine, fish were collected from 120 randomly selected lakes. The collection goal for each lake was five fish of the single most common sport fish species within the size range commonly harvested by anglers. Skinless, boneless fillets of fish from each lake were composited, homogenized, and analyzed for total mercury. The two most abundant species, brook troutSalvelinus fontinalisand smallmouth bassMicropterus dolomieu, were also analyzed individually. The composite fish analyses indicate high concentrations of mercury, particularly in large and long-lived nonsalmonid species. Chain pickerelEsox niger, smallmouth bass, largemouth bassMicropterus salmoides, and white perchMorone americanahad the highest average mercury concentrations, and brook trout and yellow perchPerca flavescenshad the lowest. The mean species composite mercury concentration was positively correlated with a factor incorporating the average size and age of the fish. Lakes containing fish with high mercury concentrations were not clustered near known industrial or population centers but were commonest in the area within 150 km of the seacoast, reflecting the geographical distribution of species that contained higher mercury concentrations. Stocked and wild brook trout were not different in length or weight, but wild fish were older and had higher mercury concentrations. Fish populations maintained by frequent introductions of hatchery-produced fish and subject to high angler exploitation rates may consist of younger fish with lower exposure to environmental mercury and thus contain lower concentrations than wild populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0144:MCIMSF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

We tested the hypothesis that larger individuals in a temperate fish population emerge from winter in better energetic condition than do smaller individuals. We sampled adult male bluegillsLepomis macrochirusin Lake Opinicon, Ontario, after spring ice break and just before active feeding began. By extracting neutral and membrane-bound polar lipids. we estimated the energetic condition of each individual. We found that both the mass of lipids and the lipids per gram of body weight were significantly and positively correlated with body size. These results are attributed to the allometric relationships between body size and energy reserves and between body size and metabolic rate. Body size, therefore, profoundly affects energetic state, which may explain why individuals of different size vary in their reproductive behavior and survivorship.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0153:NFELIE>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

I used a bioenergetics model to test whether overwinter starvation of age-0 smallmouth bassMicropterus dolomieu, a representative warmwater species, could account for their scarcity in coldwater streams of Wisconsin. I modeled 84 combinations of food consumption rate, maximum daily mean summer temperature, and winter duration that encompassed the range of conditions likely to be encountered in Wisconsin streams, and ran simulations for the specific thermal regimes in four coldwater, one coolwater, and two warmwater Wisconsin streams where smallmouth bass population status was known. The model predicted that starvation mortality was unlikely at the highest food consumption rates, the warmest summer temperatures, and the shortest winters. Mortality increased with decreasing food consumption rates, decreasing maximum summer temperatures, and increasing winter duration. Starvation mortality was predicted to be negligible in the two Wisconsin warmwater streams, which had self-sustaining smallmouth bass populations, and to be generally minor in the coolwater and three of the four coldwater streams, all of which lacked smallmouth bass. Only in the coldwater stream with the lowest maximum summer temperature and longest winter, a stream that also lacked smallmouth bass, was mean starvation mortality predicted to consistently exceed 30%. I conclude that, by itself, overwinter starvation of age-0 smallmouth bass is unlikely to limit the occurrence of smallmouth bass in most Wisconsin's coldwater streams. The model also predicted relatively slow growth of age-0 smallmouth bass in Wisconsin coldwater streams. Reduced growth could make age-0 smallmouth bass susceptible to other sources of mortality (e.g., predation, displacement) and might contribute to their scarcity in coldwater streams.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0157:IOWSOT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Populations of striped bassMorone saxatilisfrom six Atlantic coast locations and one Gulf of Mexico location were examined with polymerase chain reaction–restriction fragment length polymorphism assays at three independent, single-copy nuclear loci. Most alleles were present in all populations, and no allele was fixed in any population. Low levels of genetic divergence were observed among all populations. However, allele frequencies differed significantly between populations in the Gulf of Mexico and the Canadian maritime provinces. These results are consistent with those obtained previously with mitochondrial DNA markers.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0163:NDMRLL>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Limited information exists on the marine diet of the Atlantic sturgeonAcipenser oxyrinchus oxyrinchus. We examined the food habits of 275 Atlantic sturgeon (total length, 106–203 cm) caught in the commercial fishery off the coast of New Jersey. Stomachs were provided by fishermen. Significantly more stomachs were empty in the spring than in the fall. Sand and organic debris were a major component in the stomachs (26.3–75.4% by weight). Polycheates were the primary prey group consumed, although the isopodPolitolana concharumwas the most important individual prey eaten. Mollusks and fish contributed little to the diet. Some prey taxa (i.e., polychaetes, isopods, amphipods) exhibited seasonal variation in importance in the diet of Atlantic sturgeon. Identification of the offshore diet of Atlantic sturgeon is an important step in developing a better understanding of the life history requirements and marine ecology of this species.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0166:FHOASO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-126.1.171

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor