974 resultados para Deep-water asymptotics


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Deep-sea resources have been increasingly exploited, and due to that, several ecosystems and species have been considerably affected. Deep-water sharks populations have been of the most disturbed by practices of unselected fisheries, bycatch and discard, mainly due to their low commercial value. Those practices make deep-water sharks very vulnerable to overfishing given their life-history traits, increasing their extinction risk. With the prohibition of the direct fishery, and implementation of quotas and TACs (Total Allowable Catches) regarding the deep-sea shark landings, the official landings have dramatically decreased after the 1990s. However, the IUU (Illegal, unreported and unregulated) catch has exponentially increased. With the analysis of catch per unit effort (CPUE), the depths, and the mean weight of the individuals over the years for each one of the nine most caught species in the Azores, we produced a descriptive analysis of the effect of fisheries in those species. The results show that some of these species have been suffering from a great fishing pressure, and their populations will be greatly affected in the near future if drastic measures are not taken when it comes to managing their long term sustainability.

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The present study deals with a general introduction which outlines the objective of the study providing an exhaustive review of works on crabs with particular reference to deep-sea forms. In the first section, Taxonomy and Geographical disribution of the crab are dealt with. The species is described in detail based on several male and female specimens obtained from the pelagic and bottom collections, and its identity in Indian waters is established. It is also distinguished from a closely allied species so far not reported from Indian waters. The second section comprises the biology of the species and it is dealt with under four subheading, namely Habit and Habitats, Reproduction, Food and feeding and Proximate composition. The different habitats occupied by juveniles, subadults and adults of the species have been described and discussed in the light of available information on differential distribution of other related species. The reproductive biology is described in various details touching on gross anatomy and histology of the reproductive systems, spermatogenesis, oogenesis, size at maturity, ovarian maturation process, fecundity, egg carriage and breeding. The food and feeding habits of the species have been studied with reference to the different life stages such as juveniles, subadults and adults during the different phases of life based on stomach content analysis. The percentage of meat recovery and protein, carbohydrate and lipid content of meat have been described in the section dealing with proximate composition. In section three the distribution and abundance of the crab for the entire Indian EEZ and some contiguous ares have been described and illustrated in detail separately for pelagic and benthic realms. The size frequency disrtibution, sex ratios, length weight relationship and relative abundance of breeding population in the experimental catches have been dealt with in detail and discussed.