Taking a deeper look: Quantifying the differences in fish assemblages between shallow and mesophotic temperate rocky reefs

RESEARCH ARTICLE Taking a deeper look: Quantifying the differences in fish assemblages between shallow and mesophotic temperate rocky reefs Joel Williams ID1☯*, Alan Jordan1☯, David Harasti1☯, Peter Davies2‡, Tim Ingleton2‡ a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 1 Fisheries Research, NSW Department of Primary Industries, Nelson Bay, New South Wales, Australia, 2 New South Wales Office of Environment and Heritage, New South Wales, Sydney, Australia ☯ These authors contributed equally to this work. ‡ These authors also contributed equally to this work. * Abstract OPEN ACCESS Citation: Williams J, Jordan A, Harasti D, Davies P, Ingleton T (2019) Taking a deeper look: Quantifying the differences in fish assemblages between shallow and mesophotic temperate rocky reefs. PLoS ONE 14(3): e0206778. https://doi.org/ 10.1371/journal.pone.0206778 Editor: Heather M. Patterson, Department of Agriculture and Water Resources, AUSTRALIA Received: October 18, 2018 Accepted: February 26, 2019 Published: March 15, 2019 Copyright: © 2019 Williams et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: The data underlying the results presented in the study are available from GlobalArchive metadata records; 201611_HunterCMR30mins_stereoBRUVs, 201608_PSGLMP_StereoBRUVs (https://globalarchive. org/geodata/data/campaign/get/170 and https:// globalarchive.org/geodata/data/campaign/get/199). Funding: This work was undertaken for the Marine Biodiversity Hub, a collaborative partnership supported through funding from the National Environmental Science Program (and previously The spatial distribution of a species assemblage is often determined by habitat and climate. In the marine environment, depth can become an important factor as declining light and water temperature leads to changes in the biological habitat structure. To date, much of the focus of ecological fish research has been based on reefs in less than 40 m with little research on the ecological role of mesophotic reefs. We deployed baited remote underwater stereo video systems (stereo-BRUVS) on temperate reefs in two depth categories: shallow (20–40 m) and mesophotic (80–120 m), off Port Stephens, Australia. Sites were selected using data collected by swath acoustic sounder to ensure stereo-BRUVS were deployed on reef. The sounder also provided rugosity, slope and relief data for each stereo-BRUVS deployment. Multivariate analysis indicates that there are significant differences in the fish assemblages between shallow and mesophotic reefs, primarily driven by Ophthalmolepis lineolatus and Notolabrus gymnogenis only occurring on shallow reefs and schooling species of fish that were unique to each depth category: Atypichthys strigatus on shallow reefs and Centroberyx affinis on mesophotic reefs. While shallow reefs had a greater species richness and abundance of fish when compared to mesophotic reefs, mesophotic reefs hosted the same species richness of fishery-targeted species. Chrysophrys auratus and Nemodactylus douglassii are two highly targeted species in this region. While C. auratus was numerically more abundant on shallow reefs, mesophotic reefs provide habitat for larger fish. In comparison, N. douglassii were evenly distributed across all sites sampled. Generalized linear models revealed that depth and habitat type provided the most parsimonious model for predicting the distribution of C. auratus, while habitat type alone best predicted the distribution of N. douglassii. These results demonstrate the importance of mesophotic reefs to fishery-targeted species and therefore have implications for informing the management of these fishery resources on shelf rocky reefs. PLOS ONE | https://doi.org/10.1371/journal.pone.0206778 March 15, 2019 1 / 20 Fishes on mesophotic and shallow temperate reefs through the National Environmental ResearchProgram). NESP Marine Biodiversity Hub partners include the Institute for Marine and Antarctic Studies, University of Tasmania; CSIRO, Geoscience Australia, Australian Institute of Marine Science, Museum Victoria, Charles Darwin University, University of Western Australia, NSW Office of Environment and Heritage, NSW Department of Primary Industries and the Integrated Marine Observing System. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests: The authors have declared that no competing interests exist. Introduction The spatial distribution of a species assemblage is strongly determined by habitat and physical conditions [1,2], and in the marine environment depth is an important factor [3–5]. On the inner continental shelf the decreased light conditions with increasing water depth results in a change from macroalgal to sessile invertebrate dominated habitat composition [6,7]. In temperate waters this change occurs at depths of around 20–30 m, although variations occur reflecting localised conditions [8–10]. To date, much of the research on rocky reefs on the inner shelf has been focussed on reefs in depths less than 20 m reflecting the widespread use of scuba to conduct such surveys. There are few standardised tools to quantitatively survey fish at greater depths. This is despite the significant range of pressures on deeper rocky reefs across the continental shelf, such as commercial and recreational fishing that target reef-associated species [11–13]. In recent decades there has been anecdotal evidence that recreational fishers have an increased technical capacity such as side-scan or multibeam sonar and electric reels and are therefore, able to target deeper reefs. Previously these reefs may have provided refuge for older, mature individuals [14,15]. Thus, with increasing recreational fishing activity at these depths it is important that we gain a better understand on the abundance and diversity of fishes at depths >30m. Mesophotic reefs are those characterised by the presence of light-dependent corals and associated communities often between the depths of 30–40 and 150 m in tropical and subtropical regions of the world [7,16–19]. Furthermore, there is now a broad understanding that this zone can be divided into the upper and lower mesophotic zone with a transition zone at ~60 m depending on water clarity and temperature [19]. The recent worldwide expansion of multibeam acoustic surveys of continental shelf waters has revealed that they form extensive areas of habitat in many regions [9,20,21]. Mesophotic reefs are often continuous with shallow reefs, resulting in potentially strong connectivity across a large depth gradient, a feature common in the Great Barrier Reef, Australia, north eastern Brazil and the Hawaiian Archipelago [6,7,22,23]. They can also form d (...truncated)