A Comparison of Fish Community Structure at Mesophotic Artificial Reefs and Natural Banks in the Western Gulf of Mexico

Abstract

Oil and gas platforms along the northwestern Gulf of Mexico (GOM) shelf have served as artificial reefs since oil and gas exploration intensified in the 1950s. As these structures are decommissioned, they must be removed; however, some are converted to permanent artificial reefs. Despite the potential effects these artificial habitats may have on marine fisheries, investigations that assess the fish communities inhabiting these structures relative to natural habitats are rare. During fall 2012, we used remotely operated vehicle surveys to compare fish communities between artificial reefs (i.e., reefed platforms; n = 5) and adjacent natural banks (n = 5) in the western GOM. Our surveys successfully documented 79 species representing 28 families. Multivariate analyses suggested that fish communities at artificial reefs were distinct from those at natural banks. Post hoc analyses indicated that the differences were driven by high abundances of transient, midwater pelagics and other gregarious species at artificial reefs. Many fisheries species, like the Red Snapper Lutjanus campechanus, were found in both habitat types, with density at artificial reefs estimated to be nearly eight times greater than at natural banks. Despite lower densities at natural banks, the disproportionately large areas of these habitats resulted in relatively high total abundance estimates-approximately 5% of the 2012 GOM Red Snapper annual catch limit (3.67 million kg [8.08 million lb])-a finding that has significant implications for Red Snapper and artificial reef management in the GOM. Our study suggests that although fish community structure may differ between these two habitats, artificial reefs serve as important habitat for species like Red Snapper by potentially diverting fishing pressure from natural habitats; however, future studies that address speciesspecific life history traits will be needed to better understand the function and performance of artificial reefs in supporting fisheries productivity.

A Comparison of Size Structure, Age, and Growth of Red Snapper from Artificial and Natural Habitats in the Western Gulf of Mexico

“…Because Red Snapper can form dense aggregations (Stanley and Wilson 1997), gear saturation may have been a potential issue affecting estimates of relative abundance, as the SEAMAP vertical lines used in this study consisted of only 10 hooks per backbone. Although vertical lines were not close to being fully saturated (i.e., one fish per hook), relative abundance in our study was similar among artificial reefs, standing platforms, and natural banks surveyed-a finding that is inconsistent with previous studies demonstrating higher relative abundance of Red Snapper at artificial habitats than at natural habitats (Patterson et al 2014;Karnauskas et al 2017;Streich et al 2017). For example, remotely operated vehicle transects conducted at artificial reefs and natural banks in the same region estimated that Red Snapper density was nearly eight times greater at artificial reefs (Streich et al 2017).…”

“…Although vertical lines were not close to being fully saturated (i.e., one fish per hook), relative abundance in our study was similar among artificial reefs, standing platforms, and natural banks surveyed-a finding that is inconsistent with previous studies demonstrating higher relative abundance of Red Snapper at artificial habitats than at natural habitats (Patterson et al 2014;Karnauskas et al 2017;Streich et al 2017). For example, remotely operated vehicle transects conducted at artificial reefs and natural banks in the same region estimated that Red Snapper density was nearly eight times greater at artificial reefs (Streich et al 2017). These previous studies relied on video-based surveys, which are generally less affected by gear saturation and may provide less-biased indices of abundance given adequate environmental conditions (e.g., visibility; Harvey et al 2012;Ajemian et al 2015b).…”

Habitat‐Specific Reproductive Potential of Red Snapper: A Comparison of Artificial and Natural Reefs in the Western Gulf of Mexico

“…; Streich et al. ). However, large portions of the Gulf are dominated by mud bottom, with relatively few areas of natural hard‐bottom bank, which may be a limiting factor for Red Snapper populations (Shipp and Bortone ).…”

“…; Streich et al. ). There is evidence that in some locales, Red Snapper associate with artificial structures over long periods of time (Szedlmayer and Schroepfer ), whereas in other areas, Red Snapper exhibit low site fidelity to artificial structure (Peabody and Wilson ).…”

Habitat Selection Important for Red Snapper Feeding Ecology in the Northwestern Gulf of Mexico

“…In the western Gulf off the Texas coast, Red Snapper diets were found to be similar among natural reefs and standing and toppled oil platforms (Downey 2016). The natural reefs sampled by Simonsen et al (2015), Tarnecki and Patterson (2015), Davis et al (2015), and Downey (2016) are of lower habitat complexity than the natural reefs on the western part of the Louisiana shelf edge (Rezak et al 1985;Gardner and Beaudoin 2005;Streich et al 2017;T. A. Langland, personal observation), so additional information on Red Snapper diets from more complex reefs is needed to further assess differences in feeding ecology.…”