AUTHOR=Speed Conrad W. , Meekan Mark G. , Birt Matthew J. , Parsons Miles J. G. , McLean Dianne , Taylor Brett M. , Thomas Luke , McCauley Robert , Semmens Jayson M. , Newman Stephen J. 

TITLE=Trophic Structure and Diet of Predatory Teleost Fishes in a Tropical Demersal Shelf Ecosystem

JOURNAL=Frontiers in Marine Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.871611

DOI=10.3389/fmars.2022.871611

ISSN=2296-7745

ABSTRACT=<p>Predatory fishes are a major component of many tropical fisheries, although little is known about their diet and trophic structure, which can hinder effective management. We used stable isotopes δ<sup>15</sup>N and δ<sup>13</sup>C in conjunction with dietary prey items of five fishes (<italic>Lutjanus sebae</italic>, <italic>Lethrinus punctulatus</italic>, <italic>Epinephelus areolatus</italic>, <italic>Epinephelus multinotatus</italic>, and <italic>Plectropomus maculatus</italic>) to describe the diet and trophic structure across this assemblage. A total of 153 isotope and 87 stomach content samples were collected at two locations that were ≈30 km apart, over two sampling trips, separated by three months. There was clear separation of species’ mean δ<sup>15</sup>N and δ<sup>13</sup>C values in isotopic space; the highest mean δ<sup>15</sup>N was exhibited by <italic>E. multinotatus</italic> (13.50 ± 0.11 SE) and the lowest was <italic>L. punctulatus</italic> (11.05 ± 0.13). These two species had the lowest overlap of isotopic niche space, whereas the highest overlap occurred between <italic>L. sebae</italic> and <italic>P. maculatus</italic>. δ<sup>15</sup>N increased with fish body size for all species. However, body size was not significantly related to δ<sup>13</sup>C values for any species. There was a notable shift in both δ<sup>15</sup>N and δ<sup>13</sup>C between sampling trips, with δ<sup>13</sup>C being more depleted in the second trip. There was also a difference in δ<sup>13</sup>C between locations for all species, suggesting localised foraging. A multiple tissue comparison for <italic>L. sebae</italic> indicated positive relationships for both δ<sup>15</sup>N and δ<sup>13</sup>C between dorsal fin and muscle tissue. Mean δ<sup>15</sup>N values were the same for both fin (12.1 ± 0.10 SE) and muscle tissue (12.1 ± 0.09 SE), although δ<sup>13</sup>C was more enriched in fin (-15.6 ± 0.14 SE) compared to muscle tissue (-17.3 ± 0.11 SE). The most common dietary items across species were teleosts and crustaceans, which was consistent with isotope data indicating a reliance on a demersal food web (δ<sup>13</sup>C values ranging from -18 to -15‰). The results from our study indicate a dynamic spatio-temporal trophic structure and diet for commercially important demersal species and highlight the benefits of a multi-facetted sampling approach.</p>