Aquat. Living Resour.
Volume 24, Number 4, October-December 2011
|Page(s)||337 - 350|
|Published online||12 October 2011|
Effects of time-area closure on tropical tuna purse-seine fleet dynamics through some fishery indicators
Institut de Recherche pour le Développement, UMR EME 212 (IRD,
Ifremer et Université Montpellier 2), avenue Jean Monnet, BP 171, 34200
2 IEO, Centro Oceanográfico de Canarias, Apdo. de Correos 1373, 38080 Santa Cruz de Tenerife, Islas Canarias, España
a Corresponding author: Daniel.Gaertner@ird.fr
Received: 27 February 2011
Accepted: 29 August 2011
Time-area closures have become a frequently used tool to control fishing effort and protect feeding and spawning areas. However, because time-area closure strata are mainly based on biological and ecological considerations, and do not accounts for fishermen’s behavior-at-sea, this type of regulation tool may not entirely achieve its objectives. With the aim of comparing the impact of two different time-area regulations: (1) a moratorium on Fish Aggregating Devices (FAD) sets (1997–2005) and (2) a no-take area for surface fleets (2005–2010) on the dynamics of the European (EU) tuna purse seine fleet operating in the eastern tropical Atlantic, several fishery indicators were evaluated through a Before-After, Control-Impact (BACI) approach. The results showed that prior to any regulation, the fleet used to be concentrated within the Gulf of Guinea area. During the first years of the moratorium on FAD (from November to January within a large region in the eastern Atlantic) there was a movement towards outside the protected area, increasing the total sets on FAD (restricted fishing activity). In general, this moratorium fulfilled its objectives; however, it was not respected during the last years of this regulation. The no-take time-area closure restricted all tuna catches for the surface fisheries but only in November and within a small area (i.e., the Picolo zone). As a result, there was an increase in activities on free schools outside the no-take area. Our findings suggest the use of some simple fishery indicators to understand fleet dynamics as a complement of ecological information before implementing new time area closures. Furthermore, since tunas are highly mobile species, anticipating the possible re-allocation of effort of purse seiners to adjacent areas in response to the spatial regulation is required to design different candidate time-area closures and to evaluate their effectiveness to protect juvenile tunas.
Key words: Time-area closure / Fleet dynamics / Tropical tuna / Fishery indicators
© EDP Sciences, IFREMER, IRD 2011
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