Feeding ecology of larvae of southern bluefin, albacore and skipjack tunas (Pisces: Scombridae) in the eastern Indian Ocean

Abstract

Copepod naupl~i, calanolds, cyclopolds and cladocerans (all Crustacea) were the maln prey of the larvae of southern bluefin Thunnus macco)w and albacore tuna T alalunga In the eastern Indlan Ocean, although the importance of each prey type differed between the 2 specles Cannibalism was found in post-flexion T m a c c o p Sklplack tuna K a t s u ~v o n u s p e l a m ~s larvae fed malnly on appendlcularlans and flsh larvae T maccoyij selected for copepod nauplli and corycaeids and a g a ~n s t calanoids T alalunga selected for corycaelds and agalnst calano~ds K pelamjs selected for appendlcular~ans The 2 Thunnusspecies fed only by day, wlth peaks in feedlng In the early mornlng and late afternoon The gut evacuation tlme of T alalunga was e s l n ~a t e d at ca 4 h Indexes of feedlng success ~n T maccoy11 were posihvely correlated with zooplankton bion~ass, whlch suggests food was lim~ted Estimates of the dally ratlon and abundance of larval tuna and the abundance of rnlcrozooplankton In the study area ~n d ~c a t e that l a ~v a l T m a c c o p can affect the abundance of thelr mlcrozooplankton prey