摘要:

Condition assessment is commonly practiced by fisheries personnel as one tool for evaluating fish populations and communities. Several noninvasive condition measures are available for use, including Fulton's condition factor (K), relative condition factor (Kn), and relative weight (Wr). The use of Wr as a condition measure has increased within several peer-reviewed journals. In 1995 to 1996, survey responses from agency personnel in 48 states indicated that 22 states used Wr as a standard technique, 18 states identified Wr use as occasional, whereas only eight states indicated no Wr use. The regression-line-percentile technique is recommended for developing standard weight (Ws) equations. There are currently Ws equations available for 52 species and three purposeful hybrids. Length-related trends in condition need to be evaluated prior to calculating a population mean Wr. Relative weight target ranges should be adjusted to meet specific management objectives. Relative weight values are influenced by seasonal dynamics. The uses of Wr may go beyond just a measure of fish “plumpness.” Relative weight can serve as a surrogate for estimating fish body composition, as a measure of fish health, and to assess prey abundance, fish stockings, and management actions.

ISSN:1064-1262    

DOI:10.1080/10641260091129161

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Foods produced in aquaculture are often more expensive than other sources of animal protein. To capture and maintain market share, they must therefore be of consistent, superior quality. This article reviews off-flavor problems in aquaculture that can adversely affect market demand, with emphasis on off-flavors acquired prior to harvest of the cultured animals. Odorous compounds responsible for preharvest off-flavors may be acquired from the water or diet, although flavor problems of dietary origin are uncommon in aquaculture. The most common preharvest off-flavors in aquaculture products are caused by geosmin and 2-methylisoborneol, two highly odorous, earthy-musty metabolites of aquatic microorganisms. Planktonic cyanobacteria in the order Hormogonales are principally responsible for synthesis of geosmin and 2-methylisoborneol in aquaculture ponds and other eutrophic aquatic ecosystems. The compounds are rapidly absorbed by fish and stored in lipid-rich tissues. Elimination of geosmin and 2-methylisoborneol is slower than uptake, and the rate of elimination is reduced as water temperature decreases and tissue lipid content increases. Management of off-flavors caused by aquatic microorganisms is difficult under commercial conditions. Abatement strategies have focused either on eliminating odor-producing cyanobacteria from culture systems or allowing the taints to depurate naturally by holding animals in clean water. Although flavor problems attributable to pollution are rare in aquaculture, accidental spills of petroleum products occasionally cause off-flavors. Odorous petroleum hydrocarbons are extremely lipophilic, so they are rapidly absorbed from the environment and then slowly eliminated. Management of pollution-related off-flavors is difficult because the accidents leading to flavor problems cannot be predicted.

ISSN:1064-1262    

DOI:10.1080/10641260091129170

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor