An Analysis of Artificial Reef Fish Community Structure along the Northwestern Gulf of Mexico Shelf: Potential Impacts of “Rigs-to-Reefs” Programs

Abstract

Artificial structures are the dominant complex marine habitat type along the northwestern Gulf of Mexico (GOM) shelf. These habitats can consist of a variety of materials, but in this region are primarily comprised of active and reefed oil and gas platforms. Despite being established for several decades, the fish communities inhabiting these structures remain poorly investigated. Between 2012 and 2013 we assessed fish communities at 15 sites using remotely operated vehicles (ROVs). Fish assemblages were quantified from standing platforms and an array of artificial reef types (Liberty Ships and partially removed or toppled platforms) distributed over the Texas continental shelf. The depth gradient covered by the surveys (30–84 m) and variability in structure density and relief also permitted analyses of the effects of these characteristics on fish richness, diversity, and assemblage composition. ROVs captured a variety of species inhabiting these reefs from large transient piscivores to small herbivorous reef fishes. While structure type and relief were shown to influence species richness and community structure, major trends in species composition were largely explained by the bottom depth where these structures occurred. We observed a shift in fish communities and relatively high diversity at approximately 60 m bottom depth, confirming trends observed in previous studies of standing platforms. This depth was also correlated with some of the largest Red Snapper captured on supplementary vertical longline surveys. Our work indicates that managers of artificial reefing programs (e.g., Rigs-to-Reefs) in the GOM should carefully consider the ambient environmental conditions when designing reef sites. For the Texas continental shelf, reefing materials at a 50–60 m bottom depth can serve a dual purpose of enhancing diving experiences and providing the best potential habitat for relatively large Red Snapper.

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

“…The observation of invasive Red Lionfish at both natural and artificial habitats is notable given their negative impacts on native fish recruitment (Albins and Hixon 2008). Furthermore, subsequent ROV-based surveys of artificial reefs in our region indicate that Red Lionfish have become more common (Ajemian et al 2015b); therefore, we recommend continued monitoring of these habitats to determine the Red Lionfish's potential impacts on fish community structure. …”

“…Dennis and Bright (1988) presented the first quantitative study of fish communities at natural banks off the coast of Texas by using data from submersible transects. Using remotely operated vehicle (ROV) surveys, Ajemian et al (2015b) recently performed the first comprehensive assessment of fish community structure among artificial reefs (standing platforms, RTR artificial reefs, and liberty ship reefs) in the region. In their assessment, bottom depth alone best explained the observed patterns in fish community structure, and Ajemian et al (2015b) speculated that variation in artificial reef fish communities was driven by the ambient communities present among the various depth strata.…”

“…When this depth was reached, the ROV performed another rove around the outer surface of the down-current side of the reef. This method was recently demonstrated to be effective in documenting the reef fish community over the large vertical expanse of RTR structures (Ajemian et al 2015a(Ajemian et al , 2015b. Because artificial reef sites contained multiple RTR structures, we attempted to survey at least two structures when currents and other conditions allowed.…”

“…The MinCount, also commonly referred to as MaxN, is a conservative metric that minimizes the probability of double-counting. It represents the maximum number of individuals on the screen at any one time during the survey, and its use as an index of relative abundance is widespread throughout the literature (Ellis and DeMartini 1995;Cappo et al 2004;Wells and Cowan 2007;Campbell et al 2015;Ajemian et al 2015aAjemian et al , 2015b. Community analyses.-We began our comparison of fish communities on artificial reefs and natural banks by assessing species frequency of occurrence and by identifying and enumerating species that were unique to either habitat.…”

Fungal diversity of marine biofilms on artificial reefs in the north-central Gulf of Mexico

“…Artificial reefs in coastal areas can increase fishing yields, amplify oyster habitats, contribute to shoreline stabilization, mitigate organic pollution, and enhance water quality (Pickering et al 1999, Davis et al 2002, Miller 2002. Artificial shoreline structures including reefs, seawalls, embankments, jetties, and piers have become widespread landscape elements in developed coastal regions around the world; however, their resulting ecological impacts remain under-studied (for examples of very recent discourse on the subject, see Ajemian et al 2015, Mazzei and Biber 2015, Scott et al 2015; also refer to Chapman and Bulleri 2003 for earlier work).…”