Fisheries capture impact on metabolic rate of a commercially exploited species, Mustelus antarcticus

LICIA FINOTTO; JUAN MANUEL MOLINA; TERENCE WALKER; RICHARD REINA

João Pessoa

Conferencia; Sharks International Conference (2018 : João Pessoa-PB).; 2018

SBEEL ? Sociedade Brasileira para o Estudo de Elasmobrânquios AES ? American Elasmobranch Society Squalus - Fundación colombiana para la investigación y conservación de tiburones y rayas

Overfishing is the main cause of the alarmingdecline in chondrichthyan populations. e e ectsof sheries capture extend well beyond immediatedeath; bycatch species (unwanted capture) arereleased back into the environment to an unknownfate, as injuries and long-term physiological, physicaland behavioural consequences can ultimatelylead to delayed mortality. Metabolic rates (MR) area measure of the amount of energy animals invest indi erent biological process and determine the ratesof almost all these activities, such as growth andreproduction. Research on sheries stress e ectson MR would be highly relevant for the assessmentof the sustainability and the effects of fisheries.Nevertheless, few studies have investigated baselineMRs in Chondrichthyans and, to our knowledge, nostudy exists on the impact caused by sheries practiceson MRs. In this study, we use MR assessment,measured using respirometry, to compare the e ectof simulated gillnet capture on Mustelus antarcticus.This species is an active, demersal, facultativeram ventilator and is quite sensitive to stress. M.antarcticus is commercially exploited, but due toexisting management measures, a large number ofindividuals are released back after capture, makingit relevant to study the e ect of sheries stress. InM. antarcticus simulated gillnet capture produceddelayed mortality of up to 60%; MRs betweensurvivors and dead individuals was not found to besigni cantly di erent, suggesting that other variables,not related to respiratory performances, areresponsible for delayed mortality. Contrary to whatwas expected, the MR of stressed animals were ingeneral signi cantly lower than their baseline MR.Up to date, reduction of the MR in response to acutestress has not been reported for chondrichthyans,and it is probably caused by an underlying secondarystress-related change. is suggests that gillnettinge ects are highly energetically demanding and thatthe only way these shes can cope with them andavoid immediate death is to shut down unnecessarybiological activities, such as growth and reproduction.Ultimately, this energy relocation can seriously