Natural variability of macro-zooplankton and larval fishes off the Kimberley, north-western Australia: preliminary findings

During the austral autumn, spatial (regional cross-shelf) and temporal (tidal cycle and spring-neap cycle) variability of macro-zooplankton and larval fishes off the Kimberley coast were examined in conjunction with the physical oceanography. Though surface waters were isothermal across the study area, strong stratification was evident and warm, high salinity surface waters overlaid a cooler, less saline water mass. There was no evidence of frontal features over the shelf or at the shelf break. Variability of macro-zooplankton, particularly krill and larval fishes, was defined by significant cross-shelf structuring in relation to isobath; higher concentrations were recorded for coastal waters, compared to shelf and oceanic waters. Pseudeuphausia latifrons was the dominant krill species in shelf waters, whereas the more speciose oceanic assemblages were dominated by species of the genus Stylocheiron. The greater diversity and concentrations of larvae of neritic teleost families for assemblages at the 50 m isobath distinguished coastal waters from those further offshore and within the more turbid waters of King Sound. Assemblages in proximity to the Lacepede Islands were also taxonomically distinct. The occurrence of larvae of commercially valuable teleost fishes, such as the Lutjanidae, Serranidae and Scombridae, in the study region is an important consideration for environmental and fisheries management. This study provides a baseline which can be used to evaluate anthropogenic disturbance to the Kimberley pelagic ecosystem.