摘要:

We extended a bioenergetics model of growth for the average individual alewifeAlosa pseudoharengusto the Lake Michigan population of this species in the mid-1970s. We used the model to estimate patterns of total consumption of zooplankton by alewives. About 10% of total annual zooplankton consumption by Lake Michigan alewives could be attributed to larval fish feeding during the first 40 d of life. Young-of-year and larval fish together accounted for 50% of total annual consumption by alewives. Typical adult (age-3 and older) fish accounted for only 21% of total consumption. We evaluated the sensitivity of estimates of consumption by alewife larvae by using upper and lower bounds on metabolic rate and energy density of larvae. Total consumption estimates based on the low and high metabolic rates differed by a factor of 3. Consumption was relatively insensitive to energy density. Modeling a 29-d, normally distributed spawning period versus a single-day spawning period resulted in a 9% increase in total consumption from first-feeding larvae to fall young of the year. Predation by the alewife population was strongly seasonal: 45% of total annual consumption occurred in August and September, and 73% occurred during July through October. The mean daily population consumption (for each month), expressed as a percent of crustacean zooplankton biomass, peaked in August and September at about 8% of biomass per day. Similar estimates for the mid-1980s alewife population were greatest in August at 2.3% of zooplankton biomass consumed per day. We estimated potential consumption by the peak 1966 alewife population (ifsevere mortality had not occurred that year) at 20% of zooplankton biomass per day, which suggested that food limitation was one cause of the severe mortality that year.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0581:ZBAILM>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

We constructed a bioenergetics model for sockeye salmonOncorhynchus nerkaand evaluated its sensitivity to parameter error. When used to predict annual growth, the model was most sensitive, in declining order of importance. to changes in the intercept of the dependence of consumption on body weight, the proportion of maximum consumption, the energy density of prey, low temperature and its associated proportion of maximum consumption in the temperaturedependence function, the intercept of the energy density relationship to predator weight, and the intercept of the relationship between body weight and respiration. Estimates of consumption from the model, when consumption was constrained by fixed growth, were quite insensitive to perturbation of all parameters except the energy density of prey. We computed consumption rates and energy budgets with the model and compared these with independently derived estimates for populations in Lake Dalnee, USSR; Lake Washington, USA; and Babine Lake, Canada. The close agreement of estimates from the model to independent estimates of prey consumption and energy budgets for three different populations indicated that the model may be widely applicable to other populations. Performance of the model can be enhanced further if the frequency with which water temperature and mean body weight data are collected is increased for each cohort of interest.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0597:COABMF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Superposed epoch analysis, a nonparametric technique, can be used to test the statistical significance of associations between extreme environmental events and recruitment success. A test statistic, similar to a pairedt-statistic, is used to compare recruitment in years with extreme events to recruitment in the immediately surrounding years. Because statistical significance is determined by a randomization test, superposed epoch analysis does not rely on the usual assumptions (random sampling, normality, homogeneity of variance, independence of observations) of parametric testing. Thus, the method can be used when regression analysis, correlation, or at-test would be inappropriate. As an example, we tested the association between elevated sea level (often associated with El Nino events) and high recruitment success of chub mackerelScomber japonicusoff the coast of southern California. The association was statistically significant (P< 0.01) for the period preceding the collapse of the chub mackerel fishery in the late 1960s but not significant (P= 0.59) over the entire time series. This change may be due to statistical artifacts, a nonlinear relationship between sea level and recruitment, or biological causes. As with other statistical methods, a valid hypothesis test requires a priori formulation of the null hypothesis. Within this limitation, superposed epoch analysis is a useful method for conducting significance tests on autocorrelated time series, such as recruitment data.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0608:SEAART>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Simultaneous on-site and in situ studies of survival of prolarval and yearling striped bassMorone saxatiliswere conducted in the Potomac River during the 1988 spawning season. Various water quality and contaminant conditions were monitored during these experiments. In situ experiments on yearlings and monitoring of water quality and contaminants were also conducted in the Susquehanna, Elk, and Sassafras rivers of the upper Chesapeake Bay. Survival of striped bass prolarvae ranged from 1 to 20% in the Potomac River during three concurrent 96-h on-site and in situ experiments; survival of control fish was 78% or greater. Survival of striped bass yearlings was 15% or less during 28-d in situ tests at two Potomac River field locations; survival of control fish was 100%. Mortality of prolarvae in the Potomac River was likely caused by a combination of cadmium, lead, chlordane, and sudden drops in temperature. Mortality of yearlings was possibly caused by a combination of cadmium, lead, zinc, chlordane, and ammonia. Survivals of striped bass yearlings tested in 28-d tests in the Susquehanna, Elk, and Sassafras rivers were 57, 100, and 100%, respectively; survival of control fish was 100%. Mortality of striped bass in the Susquehanna River may have been partly caused by copper and lead concentrations; however, other nonidentified factors were likely more important. Water quality problems were not detected in the Elk or Sassafras rivers.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0619:SOCAWQ>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Acidic episodes in waters of the western USA, do not last as long and are not as intense as those in the eastern USA, but we found that the native western cutthroat troutOncorhynchus clarkiis sensitive to even brief reductions in pH. In laboratory studies, fish were exposed to acidity (pH 4.5–6.5) alone or in the presence of aluminum during the first 7 d of the freshly fertilized egg, eyed embryo, alevin, or swim-up larva stages of development. Following exposure to acidity and aluminum, eggs and fish were held under control water quality conditions to 40 d posthatch to assess effects of the exposure on subsequent development. Reductions in pH from 6.5 to 6.0 in low-calcium water (1.4 mg/L) did not affect survival, but reduced growth offish in the early life stages. The presence of as little as 50 μg A1/L at low pH further decreased growth and reduced survival. The most sensitive indicators of stress were loss of ions (determined from whole-body sampling) and reduced swimming in alevins, reduction in the ratio of RNA:DNA, feeding inhibition, and pathology of gill tissue in swim-up larvae. A pH of 6.0 and 50 μg Al/L reduced whole-body sodium by 72% and potassium by 50% in alevins. Reductions in the RNA: DNA ratio, correlated with lower growth rates, were observed in swim-up larvae exposed to pH 5.5 and 50 μg Al/L. Exposure to 50 μg Al/L at pH 6.0 reduced swimming activity of alevins by 68% and feeding rates of swim-up larvae by 67%. In the presence of 50 μg A1/L, pathological changes in gill tissue were observed in swim-up larvae exposed to pH 6.0 or less. Although acidification is not widespread in the western USA, cutthroat trout have a narrow margin of safety between conditions that currently exist and those at which pH and aluminum reduce survival and growth.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0630:SOESRC>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

We examined the behavioral and physiological responses of wild and hatchery-reared cutthroat troutOncorhynchus clarkisubjected to a single electroshock, electroshock plus marking, and multiple electroshocks in natural and artificial streams. In a natural stream, cutthroat trout released after capture by electrofishing and marking showed distinct behavioral changes: fish immediately sought cover, remained relatively inactive, did not feed, and were easily approached by a diver. An average of 3–4 h was required for 50% of the fish to return to a seemingly normal mode of behavior, although responses varied widely among collection sites. Using the depletion method, we observed little change in normal behavior offish remaining in the stream section (i.e., uncaptured fish) after successive passes with electrofishing gear. In an artificial stream, hatchery-reared and wild cutthroat trout immediately decreased their rates of feeding and aggression after they were electroshocked and marked. Hatchery fish generally recovered in 2–3 h; wild fish required at least 24 h to recover. Analysis of feeding and aggression data by hierarchical rank revealed no distinct recovery trends among hatchery fish of different ranks; among wild cutthroat trout, however, socially dominant fish seemed to recover faster than intermediate and subordinate fish. Physiological indicators of stress (plasma cortisol and blood lactic acid) increased significantly in cutthroat trout subjected to electroshock plus marking or single or multiple electroshocks. As judged by the magnitude of the greatest change in cortisol and lactate, multiple electroshocks elicited the most severe stress response; however, plasma concentrations of both substances had returned to unstressed control levels by 6 h after treatment. It was evident that electrofishing and the procedures involved with estimating fish population size elicited a general stress response that was manifested not only physiologically but also behaviorally. These responses may affect the accuracy of population size estimates by violating key assumptions of the methods, especially the assumption of equal catchability offish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0644:EMADME>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Witch flounderGlyptocephalus cynoglossusare distributed throughout Northwest Atlantic Fisheries Organization statistical subdivision 3Ps. However, the highest concentrations are found along the southwest edge of St. Pierre Bank and in the mouths of Hermitage and Fortune bays of Newfoundland. Witch flounder are most abundant at depths of 201–300 m, although substantial numbers have been caught down to 500 m. Beyond 500 m, abundance declines considerably. The preferred bottom temperature appears to be in the range of 3.1–7.0°C, and few fish are caught outside this range. I observed significant changes in mean size and age over varying depth and temperature ranges. There have been substantial changes in age composition, growth, and maturation since commercial exploitation began in the early 1950s.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0659:WFDOSN>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

The lower segments of tributary streams provide the only remaining backwater habitat for much of the lower Missouri River. We describe the movements of adult channel catfishIctalurus punctatusbetween a 13-km segment of the Missouri River and a tributary, Perche Creek, that enters the river in this segment to determine the extent to which river-dwelling fish use the tributary habitats. We used mark-recapture techniques to describe movements offish larger than 250 mm in total length between these habitats during a 22-month period. Most fish (59%) initially caught, recaptured, or both in the Missouri River moved into or out of Perche Creek, and most of these transient fish (72%) used the lower 8 km of the tributary. The tributary population was made up predominantly of resident fish (79%), which were initially caught and recaptured in Perche Creek. Channel catfish moved greater distances in the spring than in the fall and were more likely to move upstream in the spring and downstream in the fall. Fish shorter than 250 mm were more abundant in the river than in the creek and made up 45 and 35% of the catches in each area, respectively. Furthermore, of the fish longer than 280 mm, a greater proportion of the fish resident in the river (44%) than in the creek (33%) were longer than 380 mm. More fish longer than 380 mm moved from the creek to the river (44%) than from the river to the creek (26%). Thus, the tributary habitat was used most frequently by fish 280–380 mm long. Flathead catfishPylodictis olivariswere much less abundant in the creek than in the river and did not provide sufficient sample sizes to evaluate movement patterns. However, based on abundances in our catches, the proportion of river flathead catfish using the creek was much lower than for channel catfish. Most of the few flathead catfish found in the creek were longer than 280 mm.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0670:MOCAFC>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

I examined the diet of banded drumLarimus fasciatuscollected off North Carolina during September 1973–September 1976. Of the 42 food items ingested, the mysid shrimpNeomysis americanadominated the diet for all fish size-groups (19–182 mm standard length) across years and seasons. A sergestid shrimpAcetes arnericanus, calanoid copepods, fish remains, and chaetognaths were also important foods. Some diet changes occurred with increasing fish size; the smallest prey, calanoid copepods, were eaten more by smaller fish and were replaced in the diet of larger fish by the largerA. americanus. Data on stomach fullness indicated that banded drums fed maximally in summer and autumn. Copepods were eaten more during winter,N. americanain spring and summer,A. americanusin summer and autumn, and chaetognaths in autumn. Fish were eaten least during summer and about equally in other seasons. Banded drum appeared to be an opportunistic, perhaps nocturnal (or low light intensity), plankton feeder.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0680:DOTBDI>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

AlewivesAlosa pseudoharengusin the Great Lakes are thought to avoid extreme cold in winter by moving to deep water where the temperature is usually highest because of inverse thermal stratification. Information collected in Lake Ontario during autumn and winter 1981–1984 with an echo sounder and bottom and midwater trawls indicated that many alewives remained at depths above 110 m, regardless of water temperature. Alewives in the Great Lakes that did not descend to greater depths would be exposed to potentially lethal temperatures during cold winters.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1989)118<0687:DOAISL>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor