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Summer and winter larval fish assemblages around oil/gas platforms in Bass Strait, south-eastern Australia – what’s the attraction?
Faculty of Fisheries & Marine Environment, Australian Maritime College, PO Box 21 – Beaconsfield, Tasmania 7270, Australia
Email: f.neira@fme.amc.edu.au
Opportunistic larval fish surveys were conducted around nine oil and gas platforms in Bass Strait, south-eastern Australia, in February 98 and 99 (summer) and August 98 (winter). The 108 samples collected in vertical, surface and oblique, day-night tows yielded 1,526 larval fishes from 45 families and 55 taxa. Larvae of pelagic/mesopelagic species dominated the catches, whereas abundances of larvae of reef-associated species normally observed amongst platform structures in the area were unexpectedly low. Carangids, scomberesocids and berycids were dominant in summer, myctophids and bovichtids in winter. Carangids, myctophids and Scomberesox saurus accounted for 80% of all larvae caught, with jack mackerel (Trachurus declivis) being the most abundant species (55.6%). Bovichtus angustifrons and Centroberyx affinis accounted for 3.0 and 2.8% of the total caught, respectively, whereas triglids, Australian salmon (Arripis trutta), bothids and pomacentrids each contributed <2.0%. A large proportion of jack mackerel were late postflexion/transforming larvae (>12 mm BL), whereas those of Australian salmon were all transforming (11.9-30.2 mm BL). Concentrations of all larval fishes combined (nos. per 100 m3) in vertical tows adjacent to platforms did not vary significantly between day and night in all surveys. Likewise, time of day and tow type (surface vs. oblique), as well as the interaction, were not significant for either all larvae or jack mackerel in February 99. Despite similar sampling efforts during the summer surveys, both species diversity and concentrations of some species were greater in February 99, when a distinct upwelling was observed in the area. The role of platforms as artificial reefs in Bass Strait, including their likely function as “giant light traps” to larval and juvenile fishes, is discussed.
Room 1 Friday 3.40 pm
