Productivity and susceptibility analysis for species caught in Atlantic tuna fisheries

Abstract

-Ecological risk assessment is a useful methodology for assisting the management of fisheries from an ecosystem perspective. Atlantic tuna fisheries, managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT), are economically important and interact with several bycatch species. In spite of these interactions, no comprehensive ecological risk assessment has been conducted for bycatch species caught in ICCAT fisheries. In this paper, we followed a two stage approach with the objective of assessing the relative risk of species being negatively impacted by Atlantic tuna fisheries. An analysis of the ICCAT bycatch species list (which includes all species reported to have interacted with different tuna fishing gears operating in the Atlantic) revealed that most of these species are caught in longline fisheries, followed by gillnets and purse seines. According to the IUCN red list, 7 species of the ICCAT bycatch list (3 coastal sharks, 3 sea turtles and one seabird) are categorized as critically endangered. In our study, and based on their life history characteristics, marine mammals and coastal sharks caught in ICCAT fisheries showed the highest intrinsic vulnerability values. A productivity susceptibility analysis for the European Union (EU) tropical tuna purse seine fleet and the United States (US) pelagic longline fleet revealed two groups with high relative risk scores. The first one included pelagic and coastal sharks, characterized by relatively low productivities, and the second one included teleosts, characterized by higher productivities but high susceptibility to purse seine and longline gears. Some alternative approaches to conduct productivity susceptibility analyses in the context of ecological risk assessments are discussed.

Global spatio-temporal patterns in tropical tuna purse seine fisheries on drifting fish aggregating devices (DFADs): Taking a historical perspective to inform current challenges

“…Bycatch ratios observed in some fisheries suggest that globally, the bycatch by longlines of bony fish and shark species is much higher than by DFAD purse seine fisheries (Stevens 1992;Harrington et al 2005;Kelleher 2005;Mejuto et al 2006). While the potential ecological dangers arising from the use of DFADs in purse seine fisheries are more visible because of observer programs implemented in all tuna-RFMOs, they are surely much lower than the environmental risks exerted by longliners (Arrizabalaga et al 2011). The same conclusion stands for some unobserved fisheries, such as the large-scale driftnet fisheries of the Indian Ocean that annually catch ∼500 000 t of tuna and likely produce large undeclared bycatch of sharks, turtles, and marine mammals (IOTC 2012).…”

Summer distribution and abundance of the giant devil ray (<em>Mobula mobular</em>) in the Adriatic Sea: Baseline data for an iterative management framework

“…One approach to move towards quantitative assessments with limited data is the use of ecological risk assessments (ERAs) (see Cortés et al 2010, Arrizabalaga et al 2011, Hobday et al 2011 to identify populations at risk and fisheries of concern. ERAs combine biological productivity analysis with susceptibility analysis to assess the likelihood of a population being impacted by threats such as direct or incidental capture.…”

An overview of the hooking mortality of elasmobranchs caught in a swordfish pelagic longline fishery in the Atlantic Ocean

“…Cortés et al (2010) conducted an Ecological Risk Assessment (ERA) for eleven pelagic elasmobranch species in the Atlantic Ocean, and determined their relative productivity/susceptibility in order to rank and compare the vulnerability of the species caught in the fishery. More recently, Arrizabalaga et al (2011) carried out an ERA analysis that included all bycatch groups captured in pelagic longline tuna fisheries in the Atlantic Ocean. One parameter that can be used and included in such types of assessment (in the susceptibility component of the analysis) is the probability of survival after capture, which can be partially inferred from the proportions of species-specific hooking mortality.…”