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Biology, population dynamics, management and conservation of deep water lantern sharks, Etmopterus spinax and Etmopterus pusillus (Chondrichthyes: Etmopteridae) in southern Portugal (northeast Atlantic).

 

 

 

I have delivered my PhD thesis to the University of the Algarve in June 2007 and it is currently being read by the selected Jury. Oral presentation is expected in September / October 2007.

 

 

 

 

Abstract

Deep water sharks are particularly vulnerable to fishing mortality with population collapses occurring even at low levels of fishing. Two lantern sharks species, Etmopterus spinax and E. pusillus, are commonly caught as by-catch in commercial fisheries that operate in southern Portuguese waters. Little is known of the fisheries biology of these two species that have low or null commercial value and are usually discarded. The present study focused on several aspects of these two species, including fisheries, morphology, life history, distribution patterns and population dynamics. Commercial fisheries are having an impact on these species, with different gears affecting different components of the populations, as well as critical areas such as mating and nursery areas. Multivariate analysis was used to efficiently separate these two very similar and easily mistakable species, and models were created for future studies to more easily discriminate these species. Life history parameters, specifically age, growth, fecundity, maturity and reproductive seasonality, were determined and incorporated in mortality and demographic models. The results indicate that the current fishing pressures in the south of Portugal are not sustainable and the populations are declining. Urgent conservation measurements are therefore needed.

 

Key-words

 

Deep-water; fisheries; life-history; management; population dynamics; sharks.

 

 


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