摘要:

We used a stepwise linear discriminant analysis to investigate the population structure of summer flounder, Paralichthys dentatus (Linnaeus). Analysis was based on 18 morphometric and meristic variables taken from 1,214 specimens collected in coastal waters between Montauk Point, New York and Cape Canaveral, Florida. Two populations were identified: one in the Middle Atlantic Bight, or between New York and Cape Hatteras, North Carolina; the other in the South Atlantic Bight, or between Cape Hatteras and Florida. Discriminant analysis coefficients, based on five morphometric variables taken from specimens collected at geographic extremes of the survey area, provide a mathematical means for classifying summer flounder into either the northern or southern population with an accuracy of 93%.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<265:PSOSFB>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Factor analysis of attitudes held by steelhead (Salmo gairdneri) and salmon (Oncorhynchus spp.) anglers revealed at least five factors that determine the value of angling. While steelhead and salmon anglers differed, they generally negatively evaluated three factors dealing with the economic benefits from angling. These were personal economic well-being, professionalism, and general economic well-being. Two positively evaluated factors related to pleasure and identity. Angler pleasure and identity, however, were not associated strongly with the quantity caught. High catch-and-effort steelhead and salmon anglers did not differ significantly from low-catch anglers having comparable levels of effort on either pleasure or identity measures.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<272:AATVOS>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

An intensive ice-fishing creel census was operated at Eagle Lake, Bar Harbor, Maine, during February and March 1977 to evaluate angler catch from 5,400 age-I+ brook trout (Salvelinus fontinalis) stocked on 1 November 1976. A Leslie population estimate indicated 1,556 brook trout survived from stocking to the start of the season on 1 February. Between 1 and 6 February, an estimated 1,587 stocked fish were taken during 742 angler trips (4.2 trips per hectare). Only 121 brook trout were caught from 7 February to 31 March in 706 angler trips. Estimated total catch for the season was 1,708 trout, of which 92% were taken in 6 days during the first week of the season. Only 22 of these fish were caught in the open-water season of 1977. Near total exploitation early in the ice-fishing season is indicated. Stocking of hatchery-reared brook trout to provide winter recreation in special situations is feasible.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<282:REOHBT>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Steelheads (Salmo gairdneri) were vaccinated as juveniles against two serotypes of Vibrio anguillarum, marked, and allowed to migrate freely to the sea. A statistically significant (P ⩽ 0.01) 19.3% increase in return rate of adults to the hatchery occurred among the vaccinated group compared to the nonvaccinated control group. No difference between groups was found in the size or sex ratio of returning fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<287:IIOSOF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A mild state of bacterial kidney disease was induced in juvenile coho salmon (Oncorhynchus kisutch) via exposure to the infective agent in water from an adult sockeye salmon (O. nerka). As determined by toxicity tests, the susceptibility of the infected coho salmon to the toxic action of sodium pentachlorophenate was significantly greater than for uninfected coho salmon.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<290:EOABIO>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The effect of parasitism by glochidia of Anodonta oregonensis (a freshwater mussel) on the sensitivity of coho salmon fry, Oncorhynchus kisutch, to oil was determined by exposing fry with different levels of parasitism to several concentrations of either the water-soluble fraction of Prudhoe Bay crude oil or the aromatic hydrocarbons toluene and naphthalene. Fry infested with 20–35 glochidia were significantly (P < 0.05) more sensitive to each of the toxicants than uninfested fish. Sensitivity increased linearly with increased parasite numbers. Interpretation and application of results of toxicity tests should take into account the kinds and intensities of parasitism found both in the test animals and in the wild populations of fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<293:SOPCSF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Basal concentrations of plasma cortisol (near 50 ng/ml) and plasma glucose (near 0.50 mg/ml) were significantly greater in yearling channel catfish (Ictalurus punctatus) acclimated to 10 C than in fish adapted to 20 or 30 C; the latter groups had similar basal levels of cortisol (near 25 ng/ml) and glucose (near 0.30 mg/ml). Fish at 10 C had a slower and less marked increase in cortisol and glucose over minutes, hours, and days in response to the stress of severe confinement than fish at 20 or 30 C which were again similar. No mortality occurred in the fish stressed at 10 C during 3 days of confinement, while 89% died in the 20 C group by day 3 and all fish at 30 C were dead by day 2. Glucose concentrations initially rose more slowly than those of cortisol, but continued to increase between 3 and 12 hours after confinement. Also, glucose returned to near basal levels in dying fish while cortisol was at its highest then. Channel catfish, even at warm temperatures, have a slower and less extensive cortisol response to stress, taking 3 days to reach 225 ng/ml, than other fish that have been investigated.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<298:ATICAG>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The effects of hydrazine on bluegills, Lepomis macrochirus, were assessed in terms of acute toxicity and by examining the alterations hydrazine induced in the dorsal light response and aggressiveness. The static 96-hour median lethal concentration (LC50) of hydrazine was 1.08 mg/liter and the 96-hour continuous-flow no-lethal-effect concentration was 0.43 mg/liter. The dorsal light response in the presence of an artificial prey was significantly decreased within 15 minutes of exposure to hydrazine concentrations well below the 96-hour static LC50. This was true both in static and in continuous-flow conditions. In addition, aggressiveness, as measured by the number of attacks on the prey, was increased in a dose-related manner. Control fish made no attacks, but attacks increased as the hydrazine concentrations increased. These behavioral measurements offer some promise as monitors of subtle, sublethal effects of hydrazine and possibly other aquatic pollutants on fish.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<304:H>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Rainbow trout (Salmo gairdneri) were stocked at 3,700, 6,200, and 8,650 fish per hectare on November 16, 1977, in standing-water ponds at Auburn, Alabama. Each treatment was replicated four times. Fish were fed daily with commercial, floating trout feed. Average net production values, in order of increasing stocking rates, were 700, 1,130, and 1,640 kg/hectare at harvest on March 16, 1978. Feed conversion values (weight feed ÷ net production) ranged from 1.15 to 1.27. The winter was cooler than normal and water temperatures never exceeded 19 C (average, 9 C). Feed consumption by rainbow trout is reduced at water temperatures below 10 C. Other water quality variables were within desirable ranges for rainbow trout. Concentrations of dissolved oxygen (DO) at dawn were closely correlated with water temperatures. Nighttime DO budgets for ponds indicated that DO dynamics were dominated by diffusion.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<310:WQISPF>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Millipore (R) membrane filters (0.45 μm), Gelman glass fiber filters (Type A-E), and filter papers (Whatman No. 42 and No. 1) were all suitable for preparing pond water samples for orthophosphate determination. The stannous chloride method was just as accurate and precise, but more sensitive, than the ascorbic acid method for orthophosphate. However, the longer stability of the colored sol made the ascorbic acid method more suitable for analyzing pond waters for filtrable orthophosphate. Concentrations of filtrable orthophosphate changed rapidly during storage of unpreserved samples in polyethylene bottles. When a high degree of accuracy is necessary, samples should not be stored for more than 1 hour before analysis.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1980)109<314:DOFOIW>2.0.CO;2

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor