摘要:

This study examines life history patterns and correlations between traits related to body size, reproduction, age, and growth in sharks, using data from 230 populations representing 164 species, 19 families, and 7 orders. The analysis focused on interspecific life history variability, but intraspecific and intrapopulation variation were also considered. Interspecifically, body size correlated positively with litter size and offspring size, and a tradeoff between litter size and offspring size was found after factoring out the effects of body size. Offspring size correlated negatively with growth completion rate (K), but the correlation became positive after correcting for the effects of body size. Parental size for males and females was negatively correlated with K. Parental size and size at maturity exhibited a strong positive correlation, with sexual maturity occurring at about 75% of maximum size in both sexes. Males were 10% smaller than females and reached their maximum length 34% faster than females on average. Females tend to mature later and live longer than males, but age at maturity is reached at about 50% of maximum age in both sexes. Maximum size and empirical longevity were not significantly correlated in females, but were positively correlated in males. Size and age at maturity also exhibited a moderate positive correlation in males, especially after excluding data forSqualus acanthias. Principal component and cluster analyses were used to reflect similarities among life history traits of 40 populations from 34 species, and at least three separate life history strategies were identified.

ISSN:1064-1262    

DOI:10.1080/10408340308951115

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The gracilarioid red algae (Gracilaria, Gracilariopsis, andPolycavernosa) are the basis of a worldwide, multimillion-dollar industry, mainly associated with the production of agar, a commercially useful polysaccharide. Much of the current production comes from mariculture, and there have been numerous advances in research and cultivation in recent years. This review summarizes recent advances in the cultivation of gracilarioid algae in tanks, ponds, and in the sea (bottom planting and suspended cultivation) and compares those techniques. The main constraints to cultivation are discussed, including nutrient supply, epiphytes, grazers, and diseases. Further advances are predicted to depend on effective domestication of the wild plants, strain selection, and the commercialization of integrated cultivation with animals.

ISSN:1064-1262    

DOI:10.1080/10408340308951116

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Management of aquatic biodiversity and genetic resources, abbreviated here as FiGR (fish genetic resources), comprises both their conservation and sustainable use. Recognition of the need to manage FiGR has a much shorter history than that for plant and livestock genetic resources. Moreover, the adverse impacts of humans on FiGR have been and continue to be serious and inadequately addressed by countermeasures. FiGR are now higher than ever before on the agendas of the Convention on Biological Diversity and of other institutions and agencies; for example, FAO, ICLARM-The World Fish Center, IUCN, and the World Fisheries Trust. This paper examines the concept of management units for FiGR and suggests actions for more effective management including: adoption of an integrated ‘conservation and use’ approach; more systematic use of professional expertise on fish genetics by policymakers and developers; a balanced, intersectoral perspective; valuation of FiGR; and standardization of FiGR management terminology.

ISSN:1064-1262    

DOI:10.1080/10408340308951117

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor