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

SummaryA 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 (G€ unther, 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 AE 1.1 cm SE) were found in intertidal habitats along approx. 420 km of coastline. The smallest juvenile was L T 3 cm and the largest fish was stereo measured at L T 26.5 cm. E. daemelii were found to tolerate a large range of water quality parameters, particularly temperature (mean 21.7°C AE 0.7 SE, min = 16.8°C and max = 31.2°C) and dissolved oxygen (mean 11.2 mg L À1 AE 1.3 SE, min = 5.7 mg L À1 and max = 19.2 mg L À1). 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.

Detecting Native Freshwater Fishes Using Novel Non-invasive Methods

“…In this study, we used only one camera per pool; however, depending on the research needs and environmental factors, different approaches can be used. For example, the use of two stereo-cameras mounted at a fixed distance, calibrated with a scale bar, can accurately measure the size of fishes for population-structure analysis (Harvey et al, 2002;Harasti et al, 2014), or multiple cameras can be used at a site to increase detection of rare fishes (Castañeda et al, 2020). An additional resource necessary for eDNA at the base camp is a dedicated sterile space for eDNA filtration, which may not be readily available in many remote areas.…”

Genetically determined population structure of hogfish (Labridae: Lachnolaimus maximus) in the southeastern United States

“…Alternatively, another explanation may be avoidance of the plankton nets by larger larvae, especially during daylight hours. Hence, other sampling techniques (e.g., the use of light traps, trawl nets, or video stations; Harasti et al, 2014) and survey designs specific to collection of larger fish (e.g., between 8.4 and 13.1 mm BL) should be used to sample fish and determine more precisely the size at settlement.…”

How to build a low-cost underwater camera housing for aquatic research

“…There are many uses for camera systems in underwater environments and their flexibility is only limited by the creativity of the researcher. To list a few applications, underwater cameras can be used to study fish behaviour (Hammar et al 2013;Binder et al 2014;Domenici et al 2014), monitor interactions with fishing gear (Jury et al 2001;Bacheler et al 2013;Robbins et al 2013), evaluate bycatch reduction devices (Favaro et al 2013;Cairns et al 2014;Lomeli and Wakefield, 2014), assess abundance and community structure (Clarke et al 2012;Harasti et al 2014), or map habitat and bathymetry (Schmidt and Rzhanov 2012). However, many studies involving action cameras are still limited by the duration and quality of video they are able to record.…”