ISSN:0002-8487    

DOI:10.1577/1548-8659-117.4.321

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We monitored habitat use and summer production of stocked underyearling coho salmonOncorhynchus kisutchfrom 1983 to 1986 in three streams affected by the 1980 eruption of Mount St. Helens, Washington. Two streams were in the blast area and one was on a volcanic mudflow terrace, Midsummer water temperatures frequently exceeded presumed stressful thresholds and occasionally surpassed the incipient lethal limit. Temperatures at the study sites (up to 29.5°C) may have been the highest ever recorded in small streams in western Washington. In addition, there was relatively little submerged cover and limited pool habitat. Despite the severe conditions created by the eruption, production rates of stocked coho salmon at all sites ranged from 15.1 to 143.8 mg/m2·d (2.3–21.6 g/m2over an average 150-d summer period) and were equal to or greater than those measured in other streams of comparable size in the region. Coho salmon production in the streams was more strongly influenced by population biomass and density than by average individual growth rate. Production was also influenced by timing and average weight at stocking; larger fish stocked later in the summer had higher survival than smaller fish stocked earlier. Apparent summer mortality (true mortality plus emigration) may have been influenced by the presence of other salmonids. Coho salmon density at the end of summer was consistently lowest in the mudflow stream, the only site to have a large population of steelhead (anadromous rainbow troutOncorhynchus mykiss, formerlySalmo gairdneri). We suspected that an abundance of both terrestrial and aquatic food was partly responsible for the high summer production of stocked coho salmon in what was an otherwise hostile environment.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0322:SPOCSS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Induced peaking flows that increased discharge 4–100 times (up to 350 L·s–1) in a small stream did not displace brown troutSalmo trutta(mean total length ≥ 67 mm) downstream. Coarse substrate was thought to be essential by creating low-water-velocity microniches. In the available habitat, brown trout were significantly associated with certain depths, water velocities, substrate, and cover. Larger fish occupied areas with deeper water and more cover than did yearling brown trout. Short-term changes in flow did not influence habitat use. Fluctuating flows increased emigration slightly, especially at night.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0336:EOSFFO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Analysis of scales taken at the times of tagging and recapture from 74 Dover solesMicrostomus pacificuscollected off Oregon demonstrated that scales were inadequate aging structures for this species. This contradicted earlier work that used marginal growth of scales and age–length observations as indirect validation methods. Errors in scale-age determinations were found for fish assigned scale ages of 5 years and greater. For female Dover soles, the probability of increment (“annulus”) formation was greater for younger than for older fish. Relationships between expected scale age and actual age indicated that maximum longevity of this species off Oregon may be in the range of 48–52 years, in contrast to the maximum scale age of 28 observed for this species.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0345:AOSAAM>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

We estimated size-specific growth, maturation, yield, and egg production per recruit for an offshore population of American lobsterHomarus americanus. The yield and egg production model explicitly considered individual variability in growth. The model also incorporated the interaction between the growth and reproductive cycles of mature females and accommodated molt-related mortality for males and females. Growth rates of offshore American lobsters considerably exceeded estimates for inshore populations; yield and egg production per recruit were correspondingly higher. Simulations indicated that yield per recruit was maximized at low levels of fishing mortality for both males and females. Inclusion of molt-dependent mortality in these simulations resulted in lower levels of yield per recruit and less convex yield curves for both sexes. At high levels of fishing mortality, changes in the predicted mean size of the catch became small, indicating that detecting increases in mortality rates from size composition data would be difficult as fishing mortality increased.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0350:AOAYAE>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Recreation demand functions were estimated and economic values were derived for three geographic and fish species components of the private-boat fishery in Ohio's portion of Lake Erie. For two components, i.e., western basin walleyeStizostedion vitreumand yellow perchPerca flavescenssamples, gross economic value (willingness to pay) exceeded US$73.00/d when human time was valued at 25% of the wage rate, and consumer surplus (the excess of value over cost) exceeded $3.00/d. In contrast, central basin results showed a gross economic value of $44.00/d and a consumer surplus of $0.40/d. Public investments of $3.00/angler-day for the western basin and $0.40/angler-day for the central basin can be justified for maintenance and preservation of the respective fisheries for these uses. If an investment strategy to upgrade the central basin fishery to western basin quality could be developed, public investment of $3.00/angler-day would be justified to implement such a strategy.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0363:EVOGLS>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Four species of piscivorous fishes (coneyEpinephelus fulvus; schoolmasterLutjanus apodus; mahogany snapperL. mahogoni; and largemouth bassMicropterus salmoides) displayed distinct behavioral abnormalities after consumption of a ciguatoxic great barracudaSphyraena barracuda. Samples of the great barracuda were fed to experimental fishes as ether-soluble extracts or as ground flesh. Largemouth bass were also fed freeze-dried cells of the dinoflagellateGambierdiscus toxicusin a separate experiment and displayed a similar response, Signs of intoxication included skin color variations, inactivity, loss of equilibrium, erratic swimming, jerky feeding movements, and loss of orientation – and death, in the case of largemouth bass fed 1.0 g or more of great barracuda flesh or 7.1 mg·g–1or more of great barracuda extract. These abnormalities usually were observed within 24 h after the feeding of toxic materials, and were apparent in some cases for as long as 76 d.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0374:CTAAPF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The stress responses of migrating smolts of chinook salmonOncorhynchus tshawytschaand steelheadOncorhynchus mykiss(formerlySalmo gairdneri) to passage through three flumes (small baffled, large baffled, and unbaffled with corrugations) were determined by assaying plasma cortisol concentrations before and after fish passed through each flume. The flumes were tested under three conditions: nighttime, partly darkened in the daytime (400–900 lx at surface of water), and completely darkened in the daytime (1–4 lx). Flume design significantly affected post-passage cortisol concentrations in steelhead but not in chinook salmon smolts; concentrations were lowest in steelhead smolts that passed through the corrugated flume. In daytime tests, cortisol concentrations were significantly lower in chinook salmon smolts that passed through completely darkened flumes than in those that passed through partly darkened flumes. Cortisol concentrations did not, however, differ significantly in steelhead smolts that passed through partly and completely darkened flumes. Plasma cortisol concentrations followed a diel cycle in chinook salmon smolts held in both darkened (1–4 lx) and undarkened (3,800 lx) tanks and raceways for 40–60 h, being higher by day than by night. The cortisol response (postpassage minus prepassage concentration) of both species to passage through darkened flumes was smaller in day tests than in night tests.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0385:EOLIOP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Juvenile chinook salmonOncorhynchus tshawytschawere fed erythromycin thiocyanate for 21 d at a daily therapeutic dosage of either 0.05 or 0.1 g erythromycin/kg body weight. We analyzed samples of liver, spleen, kidney, red muscle, white muscle, and plasma removed from fish at intervals during and after drug administration to determine the concentration of erythromycin present. On all but one sampling date, the kidney had the highest mean concentration (weight of drug per unit of tissue weight) among the tissues sampled. The mean concentrations in all tissues and plasma offish fed at the daily dosage of 0.05 g/kg did not differ significantly over time while the drug was fed. However, erythromycin accumulated over time in the liver, spleen, kidney, red muscle, and white muscle offish fed at 0.1 g/kg; concentrations of the drug peaked on the last day of antibiotic administration. Doubling the dosage from 0.05 to 0.1 g/kg resulted in a 4–10-fold increase in erythromycin concentration in tissues, and a twofold increase in plasma on the last day of feeding. The patterns of depletion of erythromycin in tissues and plasma of chinook salmon fed either drug-treated ration were similar. Small quantities of erythromycin were detectable in the liver and kidney 19 d after drug administration ceased, but not in the muscle.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0394:AADOOA>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Channel catfishIctalurus punctatusencapsulated implanted dummy transmitters in fibrous granulation tissue, Thirteen to 23 d after surgery, the fibrous capsules, 0.1–2.0 mm thick, contained numerous elongate fibroblasts (myofibroblasts) and dense collagen fibers oriented parallel to the transmitter surface, Cell types in the fibrous capsule identified with light and electron microscopy included red blood cells, endothelial cells, vascular pericytes, tissue lymphocytes, tissue and circulating neutrophils, circulating eosinophils, macrophages with ingested red blood cells, and fibroblasts with numerous intermediate filaments. The high concentration of actin in the fibroblasts, demonstrated by immunoperoxidase techniques, identified these cells as myofibroblasts. Based upon differential cell counts, macrophage concentration was higher and myofibroblast concentration was lower in the capsule area adjacent to the transmitter than at the exterior of the fibrous capsule, When a transmitter was expelled through the original abdominal incision to the environment or through the intestinal wall to the intestinal lumen, significant changes in cell numbers occurred in the fibrous capsule but only in the portion newly exposed to the environment or lumen. Lymphocyte and macrophage concentration increased after exposure to intestinal contents, whereas exposure to the external environment resulted in the formation of multinucleate giant cells.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1988)117<0401:IROCCT>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor