摘要:

The spawning and nursery area of striped bassMorone saxatilisin the Potomac River is located about 30 km downstream from the outfall of the Blue Plains sewage treatment plant in Washington, D.C. The area coincides with the fertile zone of the river that receives sewage from several treatment plants and has abundant phytoplankton and zooplankton. During the striped bass spawning season, April to June, there is a longitudinal downriver succession of sewage nutrients, phytoplankton, zooplankton, and striped bass larvae, suggesting the presence of a trophic link between sewage nutrients and larvae. We developed a transfer function-noise model of average daily biological oxygen demand loadings from sewage treatment plants and the total commercial landings of striped bass from 1938 to 1983. The model suggests a causal relationship between the sewage nutrients and the fishery. A multiplicative decomposition analysis of striped bass juvenile indices from 1958 to 1986 suggests that sewage nutrients play an important role in recruitment. We hypothesize that an increase in sewage raised the fertility of the spawning and nursery regions and was responsible for the abundance of striped bass from the 1940s through the 1960s. We hypothesize further that the improvements in sewage treatment processes since the early 1970s have greatly lowered sewage nutrient loading, lowered fertility in the spawning and nursery regions, and contributed to the recent decline of striped bass in the Potomac Estuary.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0001:RAFOTP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We investigated effects of starvation on acid tolerance of young-of-year smallmouth bassMicropterus dolomieuiin the laboratory. Juvenile smallmouth bass, held under simulated winter conditions for up to 5 months, experienced losses in ash-free dry weight of up to 30%. However, consecutive tests failed to demonstrate any decline in the short-term (≤7 d) tolerance of these fish for pH levels in the range from 3.0 to 4.5. We discuss the implications of these findings for northern populations where young-of-year fish experience significant winter starvation, followed by short-term exposure to low pH in spring. Calcium and sodium concentration of the water and fish body size (fork length) were all positively related to acid tolerance. A doubling of fork length increased survival time at any pH by 100%. At pH 3.0, a doubling of calcium concentration increased survival time by 13% and at pH 4.0 it increased survival time by 50%. Over the pH range 3.75 to 4.0, a doubling of sodium concentration increased survival time by 8%. The strong effect offish body size on acid tolerance should be recognized and controlled in future acid tolerance experiments. It should be taken into account when laboratory tolerance estimates are used to assess the susceptibility of wild populations to acid stress.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0023:CABFAA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The greenback cutthroat troutOncorhynchus clarki stomiasis a threatened subspecies native to the upper South Platte and Arkansas rivers between Denver and Fort Collins, Colorado, an area also susceptible to acid deposition. In laboratory studies, we exposed this subspecies to nominal pHs of 4.5–6.5 and to nominal aluminum concentrations of 0, 50, 100, and 300 μg/L; the control was pH 6.5 treatment without Al. We used soft water that contained 1.3 mg Ca/L. Exposures of 7 d each were made for four early life stages: fertilized egg, eyed embryo, alevin, and swim-up larva. Effects were measured at the end of exposure and again after a recovery period lasting until 40 d posthatch. The alevin stage was the most sensitive: at pH 5.0 with no Al, survival was reduced by 68% and swimming duration by 76%; at pH 6.0 and 50 μg Al/L, swimming duration was reduced by 62%, but survival was not affected. Reductions in whole-body concentrations of Na, K, and Ca indicated organism stress. Sodium was reduced most—about 50% in alevins exposed to pH 5.0 without Al and to pH 6.0 with 50 μg Al/L. Growth and the ratio of RNA to DNA were not affected by any exposure. All responses that were affected during exposure returned to normal by 40 d posthatch. Overall, it appeared that pH 6.0 and 50 μg Al/L might be detrimental to greenback cutthroat trout populations.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0034:SOGCTT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

I assessed the quality of salmonid hatchery effluents and receiving streams in Washington State during the 1988 summer low-flow period. Relative to hatchery influent waters, effluents showed significant increases in temperature, pH, suspended solids, ammonia, organic nitrogen, total phosphorus, and chemical oxygen demand. Wastewater discharges sometimes violated state water quality standards; effects were exacerbated by low dilution. Hatchery nutrient loads equalled or exceeded receiving water loads; effects of enrichment were most evident in oligotrophic waters. Benthic invertebrates sensitive to organic waste were often replaced by pollution-tolerant forms in the vicinity of hatchery outfalls. Survey findings necessitated revision of existing hatchery wastewater discharge permits in Washington.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0043:QOSHED>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Cellular temperature compensation of green sunfishLepomis cyanellus, a species active in cold water, was compared to that of the cofamilial smallmouth bassMicropterus dolomieui, a species quiescent in cold water. It was hypothesized that there would be a correlation between degree of cellular temperature compensation and degree of coldwater activity for these two centrarchids. Fishes were acclimated to 5, 15, or 25°C in the laboratory for 10 weeks. In both species, red muscle citrate synthase activity was elevated in fish acclimated to 5 and 15°C relative to those at 25°C. Red muscle area per body cross-sectional area was elevated in both species acclimated to 5°C relative to those at 25°C. Heart ventricle citrate synthase activity and ventricular weight showed temperature compensation in the smallmouth bass but not in the green sunfish. These data do not suggest a correlation between degree of cellular temperature compensation and degree of coldwater activity for these two centrarchids. Winter quiescence of smallmouth bass is almost certainly facultative, and cellular temperature compensation may commonly occur in facultatively quiescent ectotherms.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0052:TCITCF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Stocks of northern largemouth bassMicropterus salmoides salmoides, Florida largemouth bassM. s. floridanus, and both reciprocal F1hybrids were produced in Champaign, Illinois, with natural spawning techniques. The genetic composition of each of these stocks was confirmed electrophoretically. Overwinter survival of northern largemouth bass in central Illinois was significantly greater than that of Florida largemouth bass; the two reciprocal F1hybrids had intermediate survival. The absolute survival rate of all stocks decreased as the severity of the winter increased; however, the effects were most dramatic for the Florida subspecies. The northern largemouth bass also exhibited-greater second- and third-year growth than the Florida largemouth bass; again, the reciprocal F1hybrids were intermediate. Results of this study indicate the potential negative effects that may arise when Florida largemouth bass or hybrids between it and the northern subspecies are introduced into waters of the USA and Canada that are within or contiguous to the native range of the northern subspecies.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0058:SAGONF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We examined habitat-use patterns in a fish assemblage in a large warmwater stream in West Virginia. Fish species and life stage composition and densities differed among habitat types, and five habitat-use guilds (edge pool, middle pool, edge channel, riffle, and generalist) were proposed. Larger centrarchids used deep habitats with slow velocities, whereas young centrarchids used shallower habitat. Juvenile and adult smallmouth bassMicropterus dolomieuiwere nearly ubiquitous in the habitats of the study area, although densities were highest among snags. Minnows and darters used shallower areas, but the range of velocity used differed among species and life stages. Vegetated and channel edge habitats served as nursery areas. Total fish densities were highest in edge pool, backwaters, snags, edge riffles, and riffles. Nearshore, structurally complex habitats seem important in influencing the assemblage structure of fishes of large streams.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0065:HUBAAO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Age-0 Colorado squawfishPtychocheilus lucius(N= 11,379) were captured as larvae and postlarvae in drift nets and seines in the Green and Yampa rivers from 1979 to 1988. Larvae were captured in drift nets (N= 601) for 2–6 weeks in June and July. Small postlarvae (N= 3,079) were captured by seining shoreline habitats in July and August. In September and October, postlarvae were most abundant (N= 6,459) in low-gradient reaches of the Green River. Catch data indicated that the postlarvae moved from the Yampa and Green river spawning areas and were concentrated about 150 km downstream by autumn of each year. Spring sampling indicated that young fish (N= 1,240) overwintered in areas occupied the previous autumn. Postlarvae captured in the Green River (N= 5,043) most frequently occupied shoreline embayments (backwaters) that were relatively warm (mean, 17.0°C), deep (mean, 38 cm), large (mean, 826 m2), and turbid. Abundance and size of young Colorado squawfish in the Green River were inversely correlated with high summer and autumn flows, which inundated nursery habitats. Seine catches of young squawfish in 4 years of sampling the upper and lower Green River in autumn and the following spring were not reliable in assessing overwintering mortality of age-0 Colorado squawfish, presumably due to differences in capture vulnerability between seasons. Survival of small fish in spring indicated their tolerance of prevailing winter conditions.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0079:DHUAGO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

Brook silversideLabidesthes sicculusand inland silversideMenidia beryllinacoexisted in Lake Conroe, Texas, for at least 6 years before we began our field sampling in 1980. We hypothesized that an extensive infestation of aquatic vegetation was a critical factor allowing sympatry, because introduced inland silversides have rapidly displaced endemic brook silversides in other, less-vegetated, reservoir systems. We believe that an abundant invertebrate prey base associated with the aquatic vegetation was responsible for a low level of interspecific competition for food resources between the two silverside species in Lake Conroe. After removal of vegetation in 1981–1983 by grass carpCtenopharyngodon idella, the inland silverside population expanded and the brook silverside population declined. By 1986, brook silversides were rare in seine samples taken from, or near, the main basin of the reservoir and appeared to be restricted to tributaries and coves. Data suggest that food habits of the silverside species diverged after vegetation removal, coincident with declines in the limnetic and littoral invertebrate prey bases. The observed shifts in diets, abundances, and distributions of the two silverside populations were consistent with results predicted by studies on silverside feeding mechanics and the competitive exclusion principle.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0090:CITAOT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A spatially intensive survey in 1989 of 52 sites in the Red River drainage in southwest Oklahoma and surveys in all years from 1978 to 1987 on four sites in the drainage provided evidence that construction of Altus Dam on the North Fork of the Red River caused major changes in fish community structure in the river above the dam. Pre-impoundment data on the fish communities were scanty, but the inferences they allowed were similar to those obtained by comparing fish assemblages in the North Fork above the dam with assemblages elsewhere in the drainage, particularly along Salt Fork, which had similar habitat characteristics. Twenty-five species were collected in the North Fork above Altus Dam, compared to 33 in the Salt Fork and 34 in the North Fork below the dam. The speckled chubMacrhybopsis(formerlyHybopsis)aestivalisand the chub shinerNotropis potteriwere absent in the North Fork above Altus Dam but fairly common in similar streams elsewhere in the area. The plains minnowHybognathus placitusand the Red River shinerNotropis bairdiwere among the most common fish species found in southwest Oklahoma, but were not collected above Altus Dam in the 1989 survey and were collected only intermittently and in small numbers in the long-term survey. We speculate that these two species have repeatedly been extirpated and have been reestablished as bait-bucket introductions since the dam was closed. Upstream of the reservoir, the sand shinerNotropis stramineusand the emerald shinerNotropis atherinoidesreplaced the plains minnow and the Red River shiner as dominant species, and several reservoir species were more common. Significant negative association at two long-term sites suggested that the sand shiner and Red River shiner were filling similar niches.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1991)120<0098:UEOFMS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor