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

Vertical distributions of larvae of 3 tuna species were investigated in the East Indian Ocean. In the presence of a strong pycnocline, the entire depth range of tuna larvae could be covered by sampling the mixed layer by both day and night. A small proportion of tuna larvae were found below the mixed layer when the pycnocline was weak. Thunnus maccoyii and T. alalunga larvae moved into the surface layers durlng the day. Katsuwonuspelamis, however, moved into deeper water during the day. All species of tuna were more evenly dispersed in the mixed layer at night. Greater numbers and larger larvae of T rnaccoyli and K pelanijs were captured at night, indicating marked differences in net avoidance between day and night. No evldence of increased avoidance during the day was found in T alalunga. The relative abundance of T m a c c o j~~i larvae could be predicted from surface tows; however, the relationship between surface and obllque tows showed regional and diel variability. To reduce blas and increase preclslon, estimates of tuna larvae abundance should be based on oblique tows made at night from the surface to just below the mixed layer.

The southern bluefin tuna (SBT) supports a seasonal fishery off the east coast of Tasmania, Australia. The distribution of zooplankton biomass in this region was examined a s a means of finding out why the SBT are attracted to this area. We examined whether there was a particular area or depth stratum that supported significantly greater amounts of potential feed, directly or indirectly, for SBT Samples of zooplankton and micronekton were collected during the winter SBT fishery seasons in 1992-94. Five net types (mouth opening 0 25 to -80 m') w~t h codend mesh sizes ranging from 100 to 1000 pm were used. Samples were collected from 4 main hydrographic areas: warm East Australian Current water, cool subantarctic water, the front separating them (the subtrop~cal convergence), and the adjacent shelf. Four depth strata (50, 150, 250 and 350 m) were also sampled. In contrast to our expectations, the biomass in the subtropical convergence was no greater than that in the 3 other areas. Rather, it was the shelf, albeit with some inconsistencies, that generally had the greatest biomass of both zooplankton and micronekton. Offshore, there was no s~gnificant difference in the biomass of the depth strata sampled, although the biomass of gelatinous zooplankton in the surface waters increased during the study period. We suggest that the higher bionlass on the shelf is the result of increased nutrients derived from a mixture of subantarctic water and upwelling along the shelf break. This biomass is converted via krill and gelatinous zooplankton to small pelagics such as jack mackerel, and finally to top predators, amongst which is SBT The SBT, particularly sub-adults, may time their migration eastward to take advantage of the concentrations of prey present at this tune of year

Hyperiid amphipods were sampled from a warm-core eddy in the Tasman Sea in August, September and October 1979. Samples were taken at night to a depth of 400 m using a midwater trawl (RMT-8). In all, 22 798 hyperiids representing 38 species and 10 families were identified, adding 13 new records for eastern Australian waters. For each species, synoptic information is given on taxonomy, life history, vertical distribution, geographic range and associations with gelatinous zooplankton. Hyperiids were confined mainly to the upper 100 m of water at night. Evidence for a summer breeding season was found in three abundant species (Scina crassicornis, Primno johnsoni and Brachyscelus crusculum). Tropical hyperiid species may be transported into the Tasman Sea by the southward movement of eddies from their origin in the Coral Sea.

Densities of the brittle star O. fidelis at a site on the upper continental slope (420-580 m) off eastern Tasmania, Australia, were calculated from underwater photographs. Their beds covered 61% of the substratum, with a mean density of 348 animals m-2 (52.2 g m-2). The starfish Mediaster australiensis, which was restricted to O. fidelis beds, had a mean density of 0.09 animals m-2 (5.5 g m-2). Gut analyses of trawled M. australiensis confirmed that they are predators of 0. fidelis, as were several common benthic fish species.