Open AccessThe horizontal migration of hammerhead sharks along the southern Brazilian coast, based on their exploitation pattern and considerations about the impact of anchored gillnets activities on these species
Author(s) -
Jorge Eduardo Kotas,
Miguel Petrere,
Roberta Aguiar dos Santos,
Ajax Bustamante,
Celso Fernandes Lin,
Antônio Alberto da Silveira Menezes,
Elizabethe Lobão Veras Micheletti
Publication year - 2014
Publication title -
revista cepsul
Language(s) - English
Resource type - Journals
ISSN - 2177-9392
DOI - 10.37002/revistacepsul.vol3.32245-68
Subject(s) - fishing , fishery , geography , submarine pipeline , latitude , longitude , oceanography , population , reproduction , biology , ecology , geology , demography , geodesy , sociology
Between 1995-2009 hammerhead sharks were sampled from the landings ofthe industrial fleets based in the harbours of Itajaí and Navegantes, SC State,and Ubatuba, SP State, Brazil. In this case, fishing boats which operated with gillnetslonglines and trawls along the southern Brazilian Economic Exclusive Zone and internationaladjacent waters were targeted. A total of 2483 and 353 S. lewini and S. zygaena carcasses respectively were sexed, measured and converted to total lengths (LT). Additionallyinformation about, year, season, latitude/longitude and local depth (m) from the catches,by fishing category, were obtained. During the considered period, intense fishing mortalityover pups was caused by gillnets and trawls operating on shallow waters (≤20m) and overjuveniles along the continental shelf (>20m and ≤200m). Additionally, adults were exploitedby driftnets and longlines along the shelf border and slope (>200m). Therefore,both hammerhead species are exploited at all life-stages and throughout their migratory circuit.This includes during their inshore-offshore migration while they are growing from pupsto juveniles and as the offshore-inshore migration of pregnant females to pupping areas inshallower waters. This apparently unsustainable exploitation pattern, over different sizeclasses (newborns-juveniles-adults), and the economic pressure caused by the internationalfin market, is one of the reasons for population declining of these two species in southernBrazil. Non fishing zones for the hammerheads, protecting their migratory circuit, which isdriven by their growth pattern and reproduction, are necessary. Additionally, fishing effortreduction and a control over the international fin market are recommended.