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At least 613 records · Page 34Linked to original sources
USGS1984

Bias-elimination in fish population models with stochastic variation in survival of the young

The addition of random variation in survival to a single prereproductive age class in a Leslie matrix population model can alter population growth in the modeled system. Methods are presented to characterize the stochastic variation in survival and to determine a correction factor that, when included in the model, will eliminate the propensity for the modeled population to systematically deviate from the initial conditions. This ability is important for applications of fish population models that seek to evaluate probability distributions of population trends that are associated with stochastic variations in survival, and to forecast the effects of changes in fishing mortality rates in fluctuating environments.

Transactions of the American Fisheries Society↗
USGS1985

Toxic materials, fishing, and environmental variation: Simulated effects on striped bass population trends

Decreased survival of larval striped bass Morone saxatilis resulting from toxic chemicals in the environment and decreased survival of adults caused by fishing both are suspected as agents contributing to the decline in the Chesapeake Bay stock since the mid‐1970s. The relative power of each type of mortality to cause population declines was evaluated with simulation techniques. Equivalent levels of added mortality induced qualitatively identical and quantitatively similar trends in population simulations for all conditions examined except if strong density‐dependent mortality preceded the contaminant toxicity. In this case the contaminant effect caused a greater reduction in yield, but the population did not tend toward extinction. The results indicate that the observed downward trend in the Chesapeake Bay population can be halted or reversed by a reduction in fishing mortality, even if contaminant toxicity is the proximate cause for the decline.

Maryland↗
USGS1985

Maryland striped bass: Recruitment declining below replacement

A mathematical technique was developed to examine interrelationships among first‐year survival rates, adult fecundity, and adult survival of striped bass Morone saxatilis based on indices of year‐class strength. Application of this technique to striped bass in Maryland waters of the Chesapeake Bay provided evidence for reduced survival in the life cycle. If adult fecundity and survival have remained constant, first‐year survival declined significantly from 1969 to 1983, and averaged less than that needed for replacement for the last 10 years. Treatment of the individual spawning grounds separately indicated that the downward trend in survival for the pooled data was the result of declines in the upper bay and, to a lesser extent, in the Choptank River. Alternatively, if first‐year survival and adult fecundity were assumed to have remained constant, an annual decline of about 1.9% in adult survival would have been required to produce the observed trend in the pooled year‐class data. This would be consistent with increased fishing mortality and implies declining recruitment because of declining stock size. Continuing declines in first‐year or adult survival would eliminate the Maryland striped bass stock and the fishery it supports. Conversely, an increase in adult survival could offset the effect of the unknown factor or factors responsible for the apparent decline in first‐year survival.

Maryland↗
USGS1985

Use of otoliths to determine age and growth of largemouth bass in Florida

The annual formation of otolith annuli was validated through age 5 for Florida largemouth bass Micropterus salmoides floridanus. Sectioned otoliths (sagittae) gave more reliable ages than whole otoliths. Beginning at age 2, at least one annulus was obscure in some whole‐otolith mounts, a problem that worsened with fish age. By age 5, over 20% of the whole otoliths gave under‐estimates of true age; otoliths producing these errors came from fish with slower than average growth rates. Sectioned otoliths gave poorer regressions (lower coefficients of determination) of otolith radius on body length than intact structures because the sectioning plane varied slightly among otoliths. Nevertheless, back calculations of fish size and growth from sectioned and correctly aged whole otoliths were equally accurate. Otolith sectioning is the procedure of choice for age‐and‐growth analysis of Florida largemouth bass. Whole otoliths, however, require much less time for analysis than sectioned ones and may be used for rapidly growing fish and fish known to be age 3 or younger.

Florida↗
USGS1985

Lake trout reproductive behavior: influence of chemosensory cues from young-of-the-year by-products

Chemosensory cues, particularly those emanating from substrate areas occupied by previously hatched young, may play an important role in the reproductive behavior of lake trout Salvelinus namaycush. Support for this hypothesis was obtained in laboratory experiments. Adults were placed in a large circular pool with four experimental reefs. Egg membranes and feces obtained from young that had hatched earlier were placed in polyester fiber in screen envelopes and positioned on selected reefs. Females approached and males contacted ('cleaned') the treated reefs but not the untreated reefs. Of 6,858 eggs recovered, 92% were from treated reefs. Some of these eggs had been fertilized and provide the first record of volitional spawning by lake trout under artificial conditions. A second experiment was less definitive, because no spawning occurred, but visual observations and analysis of videotaped behavior sequences showed that, again, adults were attracted more to reefs treated with feces of young of the year than to untreated reefs.

Transactions of the American Fisheries Society↗
USGS1985

Gill lamellar dilations (Telangiectasis) related to sampling techniques

Among fish killed by concussion (a blow to the head), lake trout Salvelinus namaycush readily developed telangiectasis, lamellar edema, and hemorrhagic thymi; Atlantic salmon Salmo salar and rainbow trout Salmo gairdneri developed thymic hemorrhages but few or no gill lesions. This illustrates a potentially overlooked bias that sampling techniques can cause in histologic analyses.

Transactions of the American Fisheries Society↗
USGS1985

Relationship between reported commercial landings and abundance of young striped bass in Chesapeake Bay, Maryland

The ability to predict subsequent landings of striped bass Morone saxatilis from the indices of abundance of juveniles (young of the year) determined annually by the Maryland Department of Natural Resources was evaluated by multiple‐regression techniques. About 57% of the variation in reported landings could be accounted for by the juvenile indices 2, 3, 4, and 5 years prior to the year of the landings for the period 1959–1983. Elimination of the first 4 years of record (1959–1962) increased the R 2 to 0.83. The regressions of reported landings on the indices of ages 2–5 striped bass for the periods 1964–1973 and 1974–1983 indicated that mortality in the fishable stock increased between the two periods. These results support the use of the juvenile indices for monitoring recruitment into the population and as a basis for management decisions.

Maryland↗
USGS1986

Effects of barge traffic on distribution and survival of ichthyoplankton and small fishes in the upper Mississippi River

Short‐term impacts of commercial barge traffic on fish eggs, larvae, young‐of‐the‐year (age‐0) fishes, and small adults in the main channel of the upper Mississippi River were examined. Barge passages caused significant changes in the distribution of eggs and larvae in the study area. The mean catch of ichthyoplankton was reduced in both surface and bottom waters for 90 min after passage of vessels (generally loaded barges) downstream. The effects of upstream traffic (unloaded barges) on catch ranged from nil in surface or bottom samples to short‐term increases in surface samples immediately after passage. No consistent effect on the catch of age‐0 or small adult fishes in surface or bottom trawls was evident. Physical damage to eggs, but not to larvae or small fish, was significant.

upper Mississippi River↗
USGS1986

Dynamics of alewives in Lake Ontario following a mass mortality

The U.S. Fish and Wildlife Service and the New York Department of Environmental Conservation assessed the population of alewives Alosa pseudoharengus in U.S. waters of Lake Ontario during 1976–1982 with bottom trawls. Alewives were abundant in 1976 but a die-off greatly reduced their numbers during the winter of 1976–1977. The population quickly recovered, however, adult abundance increasing nearly sevenfold during 1978–1981. In spring 1981 the bottom population in southern Lake Ontario was estimated to be 5.25 × 10 9 fish weighing 128,500 t. Estimated average alewife biomass per hectare during 1978–1982 far exceeded the estimates for either Lake Michigan during 1967–1982 or western Lake Huron during 1973–1982. Recruitment of age-II fish to the population was affected by abundance of adults in two ways: (1) the number of yearlings produced was directly related to adult abundance at low population levels but inversely related at high population levels; and (2) survival of yearlings to age II was inversely related to adult abundance. Growth in 1977 was exceptional, leaving a wide, unmistakable band on scales of the previously slow-growing adults. This wide growth zone served as a marker to identify survivors of the 1976–1977 die-off and to show that each year after 1978 a successively larger proportion of survivors was failing to grow in length or to form an annulus (54% in 1979, 96% in 1980, and 100% in 1981). There was no marker on scales of alewives recruited after the die-off, but the apparent age composition of our catches strongly suggested that most of them also failed to grow in 1981.

Transactions of the American Fisheries Society↗
USGS1986

Effects of five metals on susceptibility of striped bass to Flexibacter columnaris

Exposure of young striped bass Morone saxatilis (weight, 8.5–34 g) to a mixture of arsenic, cadmium, copper, lead, and selenium at 4 and 10 times the average environmental concentrations of 1–3 μg/L protected the fish from experimental infection with Flexibacter columnaris, the causal organism of columnaris disease. In four trials, all striped bass died within 7 d after a 2‐min exposure to 5 × 10 6 F. columnaris cells in untreated water. In contrast, no fish died after a single dayˈs exposure to the metal mixture followed by infection with F. columnaris and a second exposure to the metals for seven more days. When striped bass were exposed 5 d to individual metals, copper protected against infection and cadmium offered marginal protection but was slightly toxic after 2 d exposure. Arsenic increased susceptibility to infection, and lead and selenium were without an apparent effect.

Transactions of the American Fisheries Society↗
USGS1986

Pathology caused by the bacterium Edwardsiella tarda in striped bass

Edwardsiella tarda was isolated from moribund age‐0 hatchery‐reared striped bass Morone saxatilis for the first time. Pathogenicity was confirmed by contact infection. Characteristic histopathology consisted of epithelial hyperplasia and necrosis associated with the lateral line canals, and abscess formation in the anterior kidney and other internal organs

Transactions of the American Fisheries Society↗
USGS1986

Does pH affect fish species richness when lake area is considered?

Numerous surveys have shown that fish species richness (number of species) is positively correlated with lake pH. However, species richness of fish communities is also correlated with lake size, and low‐pH lakes are often small. Thus, conclusions drawn from examination of fish community structure relative to spatial (among‐lake) variation in pH have been limited by uncertainties regarding the confounded effects of lake area. We used two statistical methods, analysis of covariance and a nonparametric blocked comparison test, to remove effects of lake area and compare fish species richness in low‐pH and high‐pH lakes. Data from six previous surveys of water chemistry and fish communities in lakes of Ontario and northern Wisconsin were examined. Lakes with low pH (≤6.0) contained significantly fewer fish species than lakes with high pH (>6.0) when the effect of lake area was considered. A simple probabilistic model showed that the ability to detect differences in species richness is low when lake areas and the pool of potential colonizing species are small. We recommend the blocked comparison test for separating the effects of lake area and pH on species richness and urge critical examination of inferences based on analyses of fish communities in small lakes.

Ontario, Wisconsin↗
USGS1986

Infectious pancreatic necrosis virus: Protocol for a standard challenge to brook trout

A protocol for experimental challenge with infectious pancreatic necrosis (IPN) virus was defined with brook trout Salvelinus fontinalis as the model species. Fish were exposed by immersion for 5 h in water containing IPN virus at a concentration of 10 5 plaque‐forming units per milliliter. We propose the protocol as a standard challenge based on our studies of exposure methods and host response to virulent virus. Immersion challenge induced higher and more consistent mortality than did challenge by hyperosmotic infiltration. Challenge virus should be sequentially transferred no more than five times in cell culture because further transfers reduced the virulence of the virus. At 12°C, mortalities due to primary infection occurred 6–12 d after immersion challenge and were highest (≥70%) in fish 27–56 d old. Susceptibility to lethal infection was enhanced by nutritional stress.

Transactions of the American Fisheries Society↗
USGS1986

Susceptibility of progeny from crosses among three stocks of coho salmon to infection by Ceratomyxa shasta

Crossbred coho salmon Oncorhynchus kisutch were produced from all possible crosses among three stocks. The relative susceptibility of the progeny to infection by the myxosporean parasite Ceratomyxa shasta was determined by exposure of juvenile fish to Willamette River water that contained the infective stage of the parasite. Susceptibility of coho salmon native to the Columbia River basin to the disease ceratomyxosis was relatively low whereas that of coho salmon from remote locations was relatively high. Susceptibility of crossbred progeny nearly always was intermediate between the susceptibilities of fish from the parental stocks.

Transactions of the American Fisheries Society↗
USGS1986

Plasma corticosteroid stress response of fourteen species of warmwater fish to transportation

Plasma corticosteroid concentrations were measured in 14 species of fish immediately after they were electrofished from reservoirs on the Alabama River and after they had been transported for 2 h. There was no corticosteroid response in spotted gars Lepisosteus oculatus. Bowfins Amia calva, longnose gars Lepisosteus osseus, and freshwater drums Aplodinotus grunniens had only small corticosteroid increases (14–39 ng/mL) during transportation. Corticosteroids increased by intermediate amounts (59–184 ng/mL) during transportation in blue catfish Ictalurus furcatus, paddlefish Polyodon spathula, largemouth bass Micropterus salmoides, channel catfish Ictalurus punctatus, river carpsuckers Carpiodes carpio, white bass Morone chrysops, striped bass Morone saxatilis, and crappies Pomoxis sp. The greatest increases were 223 ng/mL in gizzard shad Dorosoma cepedianum and 286 ng/mL in common carp Cyprinus carpio. Spotted and longnose gars, largemouth bass, and common carp also were held in tanks for about 2 months at 21°C and then stressed by confinement in a dip net for 30 min. The confinement caused significant increases (P < 0.01) of plasma corticosteroid concentration in all four species. Dip‐net confinement appears to be a useful method for comparing corticosteroid responses among species of warmwater fish.

Transactions of the American Fisheries Society↗
USGS1986

Parasite burdens in experimental families of coho salmon.

We examined the possibility that parasites affect survival rates of anadromous hatchery coho salmon Oncorhynchus kisutch during their period in the wild. Survival was estimated from the rates at which adults returned to the hatchery. The frequency of infection of heart tissue by metacercariae of Nanophyetus sp. was higher in individuals from families with relatively high survival. Various degrees of parasitic and bacterial infection were observed in all groups. We frequently saw extensive infection and tissue reaction to trophozoites of Ceratomyxa sp. (probably C. shasta) in the apparent absence of spores, suggesting that the clinical method now used to determine the presence of Ceratomyxa infection needs to be reassessed.

Transactions of the American Fisheries Society↗
USGS1986

Susceptibility of salmonids to furunculosis: Differences between serum and mucus responses against Aeromonas salmonicida

At the Reeds Creek (West Virginia) state hatchery, mortality from enzootic furunculosis is most severe among brown trout Salmo trutta, intermediate in brook trout Salvelinus fontinalis, and virtually nonexistent in rainbow trout Salmo gairdneri. In each species, survivors of epizootics had developed similar levels of protective antibodies in their sera as demonstrated by microtiter agglutination and passive immunization experiments. We concluded that serum antibodies were not related to graded differences in resistance to furunculosis. These same fishes, however, produced a mucus precipitin that reacted with cell‐free bacterial extracts in single‐radial immunodiffusion assays. The mucus precipitin activity correlated with the resistance of the three species to furunculosis. Breeding studies with brown trout also showed that fish selected for a high level of mucus precipitin activity against Aeromonas salmonicida, the cause of fish furunculosis, produced progeny that were more resistant to furunculosis than other progeny produced from random matings. The nonspecificity of the mucus precipitin reaction was also confirmed by reactions with cell‐free extracts from Vibrio anguillarum and Aeromonas hydrophila.

West Virginia↗
USGS1987

Comparison of five techniques for the detection of Renibacterium salmoninarum in adult coho salmon.

Samples of kidney, spleen, coelomic fluid, and blood from 56 sexually mature coho salmon Oncorhynchus kisutch were examined for infection by Renibacterium salmoninarum by five methods. The overall prevalence (all sample types combined) of R. salmoninarum in the fish was 100% by the enzyme-linked immunosorbent assay, 86% by the combined results of the direct fluorescent antibody and the direct filtration-fluorescent antibody techniques, 39% by culture, 11% by counterimmunoelectrophoresis, and 5% by agarose gel immunodiffusion. There was a significant positive correlation (P < 0.001) between the enzyme-linked immunosorbent assay absorbance levels and the counts by fluorescent antibody techniques for kidney, spleen, and coelomic fluid, and significant positive correlations (P < 0.001) in enzyme-linked immunosorbent assay absorbance levels for all four of the sample types.

Transactions of the American Fisheries Society↗