摘要:

Morphology, time of formation and deposition of the first increment, and rate of increment deposition were determined for sagittae, lapilli, and asterisci from Lost River suckerDeltistes luxatusand shortnose suckerChasmistes brevirostris. Sagittae and lapilli form on the day of hatch, and asterisci form after 41–52 d in Lost River sucker and after 14–25 d in shortnose sucker. Lapillus increments were validated by using known-age hatchery-raised larvae and wild-caught larvae and juveniles marked by immersion in water with an alizarin complexone concentration of 50 mg/L for 4 h and 18 h, respectively. A transition from relatively wide to relatively narrow increments was sometimes seen during the second week after hatch and appears to be associated with yolk absorption. Because of their readability and conservative growth, lapilli are the preferred otolith structure for age determination of larval and juvenile suckers, whereas sagittae are preferred for nonostariophysan fishes.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0488:NOMAIV>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Photoperiod and temperature are two environmental factors that have significant effects on fish physiology and behavior but few studies have investigated the effect of photoperiod on swimming performance. We studied the effects of five photoperiods, designated 24L:OD (24 h light:0 h dark), 16L:81), 12L: 12D, 8L: 16D, 0L:241), and three temperatures (5, 15, and 25°C) on the swimming performance of white crappiePomoxis annularis(5–11 cm in standard length) in a swim tunnel with propeller-driven flow. Two-factor analysis of variance (alpha = 0.05) indicated that both photoperiod and temperature significantly affected fish swimming performance but the interaction of photoperiod and temperature did not. At all temperatures, the 8L: 16D photoperiod resulted in the highest mean swimming speeds. In addition, the temperature effect was consistent at all photoperiods. The mean swimming speed at 5°C was significantly slower than at 15°C or 25°C; however there was no significant difference between swimming speeds at 15°C and 25°C. Our documentation of a photoperiod effect on fish provide further confirmation of the importance of this environmental variable on swimming performance.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0495:EOPATO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Tricaine methanesulfonate (MS-222) is an anesthetic commonly used to reduce fish stress during transport or sampling. The exposure of blacknose daceRhinichthys atratulusto MS-222 at concentrations of 300 mg/L or 500 mg/L for 9 min or less did not raise hematocrit levels above those of controls. Hematocrit levels tended to be somewhat lower in experimental groups than in controls; however the only significant difference (P= 0.044) among treatments occurred between the control fish (35% ± 2.3;N= 6) and fish exposed to 500 mg/L for 3 min (30% ± 1.8;N= 7). This difference suggests that initial exposure to MS-222 may cause stress or, less likely, that the anesthetic has some inherent hemodilution effect. Workers who monitor environmental acidification may be concerned with the hematocrit of the acid-sensitive blacknose dace because hematocrit increases during acid stress. The use of MS-222 to ease hematocrit sampling should not elevate measurements.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0500:EOTMMO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Until recently, human-induced perturbations other than fishing have received little attention in the stock assessment literature, Beginning in the late 1960s, environmental legislation in the United States has directed attention toward assessing the mortality of fish and other living aquatic resources caused by observed (or anticipated) changes in water quality or other habitat features that are related to ongoing (or proposed) human activity. Scientists are being requested not only to devise means to estimate the extent of aquatic impacts related to the causes, but also to devise means to reduce or avoid them. In this paper I review methods that can be used for comparing the population-level effects of mortality in fish populations induced by pollution (and sources with similar effects) to mortality induced by fishing. I also review the types of data needed to use the methods, limitations of the methods, and examples of method applications. Methods reviewed are the equivalent adult, production forgone, reproductive potential (eggs per recruit and spawning stock biomass per recruit), and individual-based. All of the methods reviewed share several common limitations, the foremost being inherent difficulties in estimating survival rates for early life stages of fish. Despite their shortcomings, the methods have been and continue to be useful tools for fishery management.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0506:MFCTIO>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Pollution in fish habitats can have economic effects on three groups: (1) commercial users and consumers; (2) recreationalists; and (3) nonusers. In commercial fisheries, the economic costs of pollution in the fishery habitats derive from lower production, or consumer perception of reduced fish quality, or both. The economic loss will depend on many factors, including the response of fish stocks to pollutants, the responsiveness of consumers to price changes, and the magnitude of the perceived change in quality of the fish products. Recreational losses due to pollution are manifest in the catch rates of recreational fishers. Additionally, the potential exists for anglers to value fish less if they are afraid to consume the fish they catch because of the quality of the habitat. For any given fishing trip, a decrease in catch rates or reduced take-home catch because of pollution results in fewer benefits to the angler from the experience. Also, people may substitute less pleasurable activities for trips to catch fish from polluted waters. Some individuals may be willing to pay something to avoid pollution in fishery habitats even if they do not intend to go recreational fishing or to consume the fish. The principle way to measure these “nonuse” values is through direct questioning (contingent valuation) rather than by observing market behavior.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0514:EEOPIF>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Puget Sound is a large marine and estuarine ecosystem in Washington State that serves as the habitat for a number of recreationally and commercially important species of groundfish and Pacific salmonOnchorhynchusspp. Over the past several decades, the human population of the Puget Sound drainage basin has increased substantially, resulting in increased habitat degradation and chemical pollution. There is now a body of evidence showing that groundfish and salmon in Puget Sound are experiencing a range of biological effects from chemical contaminant exposure, including impairment of several stages in the reproductive process, increased susceptibility to pathogens resulting from altered immune competence, and development of toxicopathic diseases. Preliminary studies suggest the potential for reduced survival of fish from urban areas of Puget Sound resulting from increased infectious and idiopathic diseases. The question that now must be addressed is whether contaminant-related reductions in reproductive and survival rates are sufficient to affect fish abundance in Puget Sound. In the current study, the potential impact of contaminant-related mortality and reproductive impairment on the population growth rate of English solePleuronectes vetuluswas examined by simulation modeling. An initial Leslie matrix population model was constructed for investigation of contaminant effects. The adult mortality rate for English sole in Puget Sound was estimated from recent historical data. Age-specific fecundity was determined from previously collected English sole ovary samples. Existing data on the effects of contaminants on reproduction, including impaired gonadal development, reduced spawning ability, and decreased egg and larval viability, were incorporated into the fecundity component of the model. The influence of density-dependent population regulation on model results was also examined. Results suggest that declines in the fecundity component of the model, like those observed in field studies of fish from contaminated sites such as the Duwamish Waterway and Eagle Harbor, could substantially decrease the population growth rate (r) if density dependence is weak or moderate, Estimated declines inrare comparable in magnitude to those associated with typical levels of commercial fishing pressure, However, a compensation for loss of recruits due to contaminant effects is observed if strong density-dependent population regulation is assumed.

ISSN:0002-8487    

DOI:10.1577/1548-8659(1997)126<0519:AFDEOP>2.3.CO;2

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-126.3.536

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-126.3.537

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-126.3.541

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0002-8487    

DOI:10.1577/1548-8659-126.3.543

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor