Effects of climate-related ichthyofaunal shifts and an invasive mesopredator on Gulf of Mexico reef fishes

Dr Anthony R. Marshak1, Dr Kenneth L. Heck, Jr.2

1ECS Federal LLC In Support Of NOAA Fisheries, Washington, United States, 2Dauphin Island Sea Lab, Dauphin Island, United States

Large and apparently unprecedented increases in the abundance of juvenile gray snapper (Lutjanus griseus), lane snapper (L. synagris), groupers and other tropically-associated fishes within northern Gulf of Mexico (nGOM) seagrass meadows have been recently documented.  Although occurring infrequently within the nGOM, their increased abundance has been suggested to reflect regional warming trends, and has resulted in higher numbers within offshore adult habitats.  Additionally, recent invasion by the Indo-Pacific red lionfish (Pterois volitans) into nGOM offshore habitats has been documented.  Increases in tropically-associated confamilials, and invasive lionfish, could result in pronounced competitive interactions with nGOM reef fishes, such as juvenile red snapper (L. campechanus), and cause shifts in the species composition of offshore fish assemblages.  As larger, abundant lane snapper and red lionfish have been observed in complex reef habitats, they may potentially cause localized displacements of other reef fishes.  We experimentally investigated the intensity of these interactions between increasingly abundant tropical snapper species, red lionfish, and indigenous members of the nGOM reef fish community in large outdoor mesocosms.  Compared to tropical counterparts, increased partial roving behavior, aggression, and predatory activity by red snapper were observed, suggesting their greater ability to exploitatively compete against lower latitude snappers.  However, differential competitive advantages between nGOM fishes and lionfish were observed, with red snapper less active in the presence of lionfish, and lionfish also consuming more prey than tropically-associated snappers. Our findings contribute to the assessment of the impacts of compounded warming-related species shifts and marine invasions upon the nGOM reef-associated fish community.


Tony Marshak has a background in marine fisheries ecology, having conducted field and experimental investigations into the ecological effects of fishing and climate change on tropical and subtropical fisheries species and their communities. He currently works as a Research Associate in support of NOAA Fisheries Office of Science and Technology, where he co-leads its habitat science program and conducts research on marine ecosystems. His recent research is focused on examining multidisciplinary approaches for implementing ecosystem-based fisheries management, and in understanding the effects of human stressors and climate change on species and their habitats.  Originally from Texas, Tony received his B.S. from Texas A&M University, his M.S. from the University of Puerto Rico, and his Ph.D. from the University of South Alabama.

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