摘要:

The instream flow incremental methodology (IFIM) needs to be improved to more reliably predict the effects of altering fish habitat. Two-dimensional (2-D) hydrodynamic modeling with moving boundaries by the finite element approach overcomes may limitations related to classical physical habitat simulation modeling (mostly 1-D). Some of its most important properties are: the spatial resolution of the model can be adapted to the scale of individual fish habitats and to the spatial variability of field data; the areas frequently uncovered because of flow regime are correctly taken into account through the drying–wetting capability; and the flow resistance variables are more accurate in 2-D because they can be specified as functions of the local substrate conditions or lateral shear stresses. This approach is illustrated by a study of the habitat of juvenile Atlantic salmonSalmo salarof the Moisie River (Quebec) where a water diversion has been planned. The results of simulations carried out at two sites (a braided reach and a deep, narrow channel) over a wide range of discharges are presented. Average model error was about 10% for velocity and 2% for discharges. A finite element integration procedure allowed habitat suitability indexes (HSI) to be combined with the results of the hydrodynamic model. In this manner, detailed maps of the spatial distribution of the HSI as well as a “weighted usable area” were obtained for each discharge simulated. Atlantic salmon habitat did not appear to be very sensitive to projected flow alterations. The improved accuracy and resolution in predicting the effects of altering physical habitat variables by 2-D models would permit a better understanding of the shortcomings related to biological aspects of IFIM applications.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0645:TDHMAN>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In electrofishing, the form of size selectivity is unknown, so parametric models of selection have not been developed. Capture probability can be estimated as a continuous function of fish size for two-sample mark–recapture experiments such as those often made to describe stream fish populations. One approach is based on nonparametric regression by smoothing splines, in which general linear models are fitted to data by penalized maximum-likelihood methods. Capture probabilities modeled this way allow the data to reveal the form of size selectivity and can be used to estimate population size. A confidence band around the estimated capture probability function and confidence intervals for the population estimate are obtained by bootstrapping. A second approach is based on parametric regression models and requires some knowledge of the form of the selection function. A confidence interval for the population estimate is based on the variance estimated by the delta method. These approaches are illustrated by analysis of a mark–recapture experiment on brown troutSalmo truttain a Minnesota stream, and results are compared with those found in application of Chapman–Petersen estimates to size-groups. The biases of estimates of population sizeNand of SE (N) by these approaches were examined by using Monte Carlo simulations of known populations. For the size-group in which capture probability changed rapidly with size and for the total population, spline-based population estimates typically had less bias and better coverage than Chapman–Petersen estimates, and they typically had a smaller SE (N) and root mean squared error than parametric model estimates.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0663:MACFSS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The detrimental effect of oxygen depletion on fish is well known. Here a quantitative measure of anoxia is compared with the number of fish species in 52 south-central Ontario lakes. The anoxic factor (AF, days per year or per season) estimates the number of days that a sediment area equal to the lake surface area is overlain by anoxic water. It can be expressed separately as summer or winter AE Stepwise multiple-regression models were constructed with AF and common physical and chemical variables to predict fish species richness. Because some of the parametric regression assumptions were violated, the traditional statistics were evaluated with randomization tests to confirm significance. The best regression models included summer AF or lake surface area, or winter AF and mean depth, for subsets of acidic and circumneutral lakes; these models explained up to 75% of the variation in fish species richness. One of the models can be used to estimate the likelihood of winterkill. Anoxic factor was also correlated with the number of coldwater fish species present. The concept of AF can be used to model the distribution and number of fish species in stratified lakes and should be useful in the management of oxygen-dependent aquatic animals (e.g., finfish and shrimp) in freshwater and marine habitats.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0677:TAFAQM>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We examined relationships between lower Mississippi River physicochemistry and growth of young (≤age 2) blue catfishIctalurus furcatus, channel catfishI. punctatus, freshwater drumAplodinotus grunniens, and gizzard shadDorosoma cepedianumcollected from dike fields (river kilometers 669.0–883.2 upstream from the mouth) in September and October 1987–1990. Growth increments of the four fishes were determined from cross sections of otoliths (freshwater drum and gizzard shad) or spines (blue and channel catfishes), and we used regression analysis to assess the effects of annual variability in 15 physicochemical variables on growth. We hypothesized that growth of these fishes would be positively related to the extent and duration of the annual flood pulse, as it is in tropical floodplain systems. However, growth increments of age-0 blue catfish, channel catfish, and gizzard shad were related only to length of the growing season. Further, positive relationships between growth and total organic carbon levels (age-1 blue catfish), and negative relationships between growth and total hectares flooded (age-1 gizzard shad) and discharge (age-0 and age-1 freshwater drum) indicated that these fishes exhibited highest growth during years of limited floodplain inundation. These results suggest that for some fishes in large rivers with reduced floodplains, mainstem primary and secondary production may influence growth rates more than allochthonous inputs from seasonal flooding.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0687:IOPCOA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We developed a reference base of relative hypoxia and hyperthermia tolerance rankings for many of the common fish species that inhabit small streams in Missouri. We also investigated the influences of geographic variation and of fish size on these tolerances. Fish collected from the wild were acclimated to laboratory conditions over a 63–160-d period. They were then exposed to either progressively increasing temperatures or to decreasing dissolved oxygen concentrations over a 4–6-h period. The temperature at which a fish lost equilibrium or the oxygen concentration at which it ceased ventilating was recorded as the end point. No significant differences in critical maximum temperatures (hyperthermia tolerance) or critical minimum oxygen concentrations (hypoxia tolerance) occurred in any of the five comparisons between fish of the same species collected from different locations in Missouri. Neither the hypoxia nor hyperthermia tolerance values varied with fish size for any species. Among the 35 species tested, hypoxia tolerance means ranged from 0.49 to 1.59 mg/L. Among the 34 species tested, hyperthermia tolerance means ranged from 34.9 to 38.8°C. The mean hypoxia tolerances of species were significantly, but poorly, correlated with their mean hyperthermia tolerances.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0698:HAHTOH>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Indices of hypoxia and hyperthermia tolerance for Missouri fish assemblages were based on laboratory measurements of lethal dissolved oxygen concentrations and temperatures, combined with field measures of the relative abundances of tolerant and sensitive species. Fish assemblages and extreme physicochemical conditions were monitored over 3–4 years at 18 sites on headwater streams in the Prairie, Ozark Border, and Ozark regions of Missouri. Oxygen minima ranged from 0.8 to 6.0 mg/L, and temperature maxima ranged from 19.6 to 30.7°C; oxygen minima at study sites were not correlated with temperature maxima. Hypoxia tolerances of fish assemblages were strongly correlated with minimum stream oxygen concentrations and varied concordantly with regional, longitudinal, and temporal gradients in stream oxygen minima. Hyperthermia tolerances of fish assemblages were not correlated with maximum stream temperatures, nor were regional, longitudinal, or temporal differences in hyperthermia tolerances concordant with variation in temperature maxima. Axis scores from a detrended correspondence analysis of species frequencies were strongly correlated with dissolved oxygen minima for all 18 sites, but axis scores correlated with temperature maxima only at the four well-oxygenated sites. Low dissolved oxygen levels had a substantial effect on the composition of fish assemblages at most sites, but maximum temperatures influenced assemblages only at the few sites without severe levels of hypoxia.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0711:IOHAHO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We examined the influences of habitat, temperature, stream discharge, and the timing of spawning on the nesting success of smallmouth bassMicropterus dolomieu. Smallmouth bass began spawning when temperatures reached 15°C, and high flow disrupted spawning five times. Larger males spawned earlier than smaller males; a log-linear relation between male length and degree-days accumulated was significant (r= –0.63,P< 0.01). In all, 45 of 105 nests (43%) and 42 of 81 males (52%) produced free-swimming larvae. Production of free-swimming larvae was variable and lower than previously reported, ranging from 98 to 1,802 (mean, 608). Large males (>305 mm total length) accounted for the highest production of free-swimming larvae and also made the most renesting attempts, which suggests that large males can have a strong influence on year-class strength. Stepwise discriminant analysis distinguished successful nests from unsuccessful nests by higher flow at time of nest construction, higher mean temperatures, lower mean stream discharge during nest incubation, and shorter distance to shore. High flow (>10 m3/s) was responsible for most nest failures (85%). Increased water velocity at nest sites with increased stream discharge was the most likely cause of nest failures. The increase of mean velocity with increased stream discharge was significantly lower for successful nests than for unsuccessful nests, which showed that nest location determines the degree of exposure to high flows. The temporal pattern of streamflow fluctuation appears to be the most important abiotic factor determining nesting success or failure for smallmouth bass in this perennial stream.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0726:FANSOS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We evaluated the effects of prestocking handling and stocking site salinity on survival and stress response during the first 48 h after stocking for three size-classes of cultured striped bassMorone saxatilis(mean sizes: 20, 65, and 230 mm total length). Treatments were routine handling, tagging, and minimal handling. Routinely handled and tagged fish experienced normal hatchery procedures for a large-scale stocking program. Minimally handled fish were transported directly from rearing ponds to stocking sites at low densities. Fish were stocked at freshwater or brackish (salinity, 0–7‰) sites. Survival in cages was monitored for 48 h after stocking, and cortisol concentration was measured to indicate stress levels. Handling before stocking, stocking site salinity, and the interaction of these factors significantly affected survival and cortisol levels. For the two larger size-classes, minimally handled fish had high survival rates (>99%) and low cortisol levels (≤18 μg/dL) at both stocking sites. Routinely handled and tagged fish had intermediate survival (80–99%) and cortisol levels (15–18 μg/dL) at the brackish site and had low survival (6–48%) and high cortisol levels (26–36 μg/dL) at the freshwater site. For the smallest size-class, survival of minimally and routinely handled fish was 83–99% at the brackish site and 0–3% in freshwater. Brackish receiving waters appear to ameliorate the stress caused by routine handling and tagging procedures, which results in higher rates of short-term survival.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0736:IEOSSS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The influence of sampling protocol on estimation of mean lengths at age was evaluated by computer simulation of a population of red grouperEpinephelus morio. Variation in length at age was simulated with platoons of different lengths within each year-class. Mean length of each platoon was assigned with the normal distribution and mean size at age from a previous growth study. Natural mortality was assumed to be 0.2. Simulated samples were obtained at random or with length stratification from either the population or its fishery. Fishing mortality was assumed to be a function of either fish age or fish length. Estimates of mean length at age contrasted with known true mean lengths indicated that reliable estimates of mean size at age requires random sampling of lengths within ages. Stratification of samples by length biases the estimates of mean length at age. Similarly, samples drawn from size-selective gears or fisheries yield biased estimates of mean length at age. Growth models fitted to such data will not generally reflect the mean growth of individuals in the population, and even slight changes in sampling protocol can result in misleading temporal shifts of estimates of size at age.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0746:MSAAAE>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We compared juvenile walleyesStizostedion vitreumfed pellets (naive) with those fed minnows (experienced) to determine the effects of previous experience on feeding and growth. In aquarium experiments (72 L), foraging behaviors were compared for walleyes (115–180 mm total length;N= 57 each) feeding on golden shinersNotemigonus crysoleucas. Less than 60% of naive walleyes initially converted, and time to prey capture was higher than for experienced fish. In pool experiments, naive walleyes had high initial rates of conversion to minnows, but they captured and consumed fewer prey than experienced walleyes. Foraging behaviors improved with time in laboratory experiments, and naive walleyes learned to forage at rates comparable to experienced walleyes in less than 5 d. Experiments in ponds were designed to determine the effects that differences in conversion to minnows and foraging experience might have on growth and survival. Naive and experienced walleyes did not differ in growth and survival, indicating that differences in conversion rates between the two groups will not influence success in the field. Although we found no direct effects of feeding experience, indirect effects on behaviors influencing growth and survival, such as increased vulnerability to predation, must be investigated before final management recommendations can be made.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1995)124<0756:EOEWPO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor