Comparison of bycatch species captured during daytime and nightime: preliminarily results of longline experiments carried out in Seychelles waters

Bycatch and mitigation measures are a keystone issue to assure a sustainable use of marine
resources. Many studies focus on gear configuration and not on fishing strategy when fish habitat is
a major question in term of gear selectivity. The objective of this study is to compare bycatch that
occurred during night sets and day sets.
For that purpose, 69 fishing experiments using an instrumented longline (hook timer, temperature
depth recorder) were carried out in Seychelles waters from December 2004 to May 2006 on board
small scale research longliner. Two types of sets were done: some during night (setting at dusk and
hauling at dawn) with shallow basket to principally target swordfish and some during day (inverse
cycle of night set) with shallow and deep basket to target tuna. Each time, bycatch species were
identified (species, basket and hook number) and the depth of capture calculated.
Results show difference between the two strategies in terms of species composition, quantity, and
depth of catch. Day sets induce more bycatch than night sets.