Where are the little ones: distribution and abundance of the threatened serranid Epinephelus daemelii (Günther, 1876) in intertidal habitats in New South Wales, Australia

Abstract

Summary A survey of intertidal habitats, including coastal rock pools, was undertaken across New South Wales (NSW), Australia, February to May 2012, to test the hypothesis that the distribution and abundance of threatened juvenile black cod Epinephelus daemelii (Gunther, 1876) does not differ across marine bioregions. An assessment was also provided on their habitat use and site fidelity. Various methods were trialled to determine the best method for detecting juvenile E. daemelii, with the most suitable method being the deployment of small baited underwater high definition video cameras for a period of 30 min. Using these baited video cameras, sampling occurred across four bioregions in NSW, covering approximately 800 km of coastline. Within each bioregion, a minimum of nine locations was selected, and at each location a minimum of six intertidal habitats was surveyed for the presence of E. daemelii. Of 412 sites surveyed, a total of 20 juveniles (mean size = 16.7 cm ± 1.1 cm SE) were found in intertidal habitats along approx. 420 km of coastline. The smallest juvenile was LT 3 cm and the largest fish was stereo measured at LT 26.5 cm. E. daemelii were found to tolerate a large range of water quality parameters, particularly temperature (mean 21.7°C ± 0.7 SE, min = 16.8°C and max = 31.2°C) and dissolved oxygen (mean 11.2 mg L−1 ± 1.3 SE, min = 5.7 mg L−1 and max = 19.2 mg L−1). E. daemelii were found in habitats dominated by boulders and overhangs, indicating a preference for structural features that provide solid cover. No E. daemelii were recorded at sites that had algae as the dominant habitat type. Juvenile E. daemelii were found to display site fidelity to rock pool habitats, with two individuals recorded as remaining at their same sites for a period of 471 days, even though the rock pools were open to the ocean at high tides. This study indicates that the abundance of juvenile E. daemelii is low, especially north of Port Stephens where adults are most abundant. Use of the small baited video cameras proved to be a successful sampling method to confirm that juvenile E. daemelii utilise rock pool and shallow reef intertidal habitats in the early stages of their life cycle.