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Larval fish assemblages along the south-eastern Australian shelf: linking mesoscale non-depth-discriminate structure and water masses

journal contribution
posted on 2023-05-26, 10:41 authored by John KeaneJohn Keane, Neira, FJ
We present findings of the first mesoscale study linking larval fish assemblages and water masses along shelf waters off south-eastern Australia (southern Queensland- New South Wales), based on vertical, non-depth discriminate data from surveys in October 2002 and 2003 (spring) and July 2004 (winter). Clustering and ordination were employed to discriminate between larval assemblages and, for the first time, to define water masses from water column temperature frequencies. Surveys yielded 18 128 larval fishes comprising 143 taxa from 96 identifiable families, with small pelagics accounting for 53% of the total. Three major recurrent larval assemblages were identified during the study, each of which matched one of three water masses, namely East Australian Current to the north (EAC; 20.5‚Äö-23.4oC), Tasman Sea to the south (TAS; 14.8‚Äö-17.5oC), and mixed EAC‚Äö-TAS water in between (MIX; 18.3‚Äö-19.9oC). All three assemblages were present in spring, whereas only EAC and MIX occurred in the more northerly constrained winter survey. Furthermore, boundaries between the EAC, MIX and TAS assemblages were found to be dynamic, with locations shifting temporally and spatially depending on EAC extent. Assemblage composition differed significantly between water masses across surveys, with EAC‚Äö-TAS being most dissimilar. Such contrast was due to the presence of tropical‚ÄövÖvëtemperate taxa in EAC, primarily temperate-associated taxa in TAS, and a combination of EAC‚Äö-TAS taxa within MIX consistent with the convergence of both waters. Results highlight the strength of employing larval assemblages as indicators of water masses, particularly in view of the potential effect of climate change on spawning habitats of shelf fishes.


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Fisheries Oceanography





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