Furthermore, in the month following the closure the fleet moved

back into the area and reported higher catch rates on floating objects than usual for December (15.8 versus 11.0 t fishing day−1 for the same period in 2008–2011; IOTC data). There is insufficient data available to evaluate the effect of this closure in terms of a reduction in bycatch, although the closure area is a hotspot for bycatch of silky sharks [38]. The displacement of effort around the boundaries of closed areas, often termed ‘fishing the line’, is a common harvesting tactic in many fisheries (e.g. [39] and [40]) and in this instance the purse seine fleet could still access much of the seasonal fishing ground. As such the closure appeared to simply displace the issues associated with FAD fishing. In order to produce meaningful reductions in the catches of juvenile

yellowfin R428 and bigeye tunas using an area closure, it would probably be necessary to implement closures considerably larger (and longer) than those that have been implemented selleck inhibitor to date [41]. The creation of a massive closure in the main FAD fishing region is likely to have a disproportionate effect on catches, as it is unlikely that the fleet would be able to recoup its losses through the reallocation of effort elsewhere due to the relatively poor fishing in other regions during this season. Whilst this conservation measure would be expected to reduce overall catches of small yellowfin and bigeye tunas, it would also result in a significant reduction in catches of skipjack tuna. This loss in catches of what is currently a healthy stock would probably be an unacceptable penalty to the purse seine industry and would also have a major impact on the processing industry in Indian Ocean states, realistically limiting the possibility of such a dramatic conservation measure ever being adopted by the IOTC. The known location of FADs is an important information in determining where

a skipper will choose to fish and in general a larger number of monitored FADs improves both search efficiency and the fishing capacity [2]. A limit on the number of deployed 3-mercaptopyruvate sulfurtransferase or monitored FADs would thus curb search efficiency and decrease (or maintain, depending on where limits are set) the total number of sets made, although it is important to note the distinction between the number of FADs deployed and the number monitored; the former is relevant to modification of the pelagic habitat (and issues related to their effect on tuna biology) whereas the latter is relevant to fishing capacity and efficiency. A challenge for implementing both the measures is setting an appropriate limit without a well defined reference point, which is yet to be calculated by the IOTC.