Abstract
AbstractArtificial reefs are commonly created with the goal of enhancing fish populations. However, many studies evaluating their effects on these populations have been hindered by a lack of preconstruction data from existing natural habitats and temporal comparisons with control areas. Here, we present findings from a before–after control–impact study designed to assess the effects of a new artificial reef on fish populations in the western Gulf of Mexico. Vertical line and fish traps were used to sample the reef site and a paired control site with soft bottom substrates for 1 year before and 2 years after reef construction. Prior to reef construction in October 2013, and over bare substrates in general, infrequent catches of sea catfishes and small coastal sharks were observed. With the exception of rare occurrences of juvenile Gray Triggerfish Balistes capriscus and Red Snapper Lutjanus campechanus, which were observed only during the summer recruitment season, the control site exhibited a lack of reef species. In contrast, we documented dramatic increases in the frequency of occurrence and abundance of multiple reef species at the reef site following the addition of structured habitat. Distinct cohorts of Red Snapper could be followed through time suggesting site fidelity, and few fish greater than age 2 years were captured indicating limited migration of older fish from other areas. Given that the reef supported high densities of juvenile Red Snapper that were in good condition, growing quickly, and protected from potential shrimp trawl mortality, export of juveniles (i.e., production) to the adult population was evident and likely greater on a per‐unit‐area basis than for the control site. Our study highlights the potential benefits of artificial reefs to species like Red Snapper; however, future studies should investigate the relative roles of emigration and fishing mortality to better understand the effects of these structures on reef fish population dynamics.
Highlights
Red Snapper that were in good condition, growing quickly, and protected from potential shrimp trawl mortality, export of juveniles to the adult population was evident and likely greater on a per-unit-area basis than for the control site
Several important reef fish species in the Gulf of Mexico (GOM) including Red Snapper Lutjanus campechanus and Gray Triggerfish Balistes capriscus commonly reside at artificial reefs where they are captured in directed fisheries, and both stocks are currently considered to be overfished (Gallaway et al 2009; Simmons and Szedlmayer 2011; SEDAR 2013, 2015)
94% of these fish were captured at the Corpus Christi Nearshore Reef (CCNR) site; large increases in CPUE of Red Snapper and Gray Triggerfish were observed with both sampling gears after the construction of CCNR (Table 1)
Summary
Red Snapper that were in good condition, growing quickly, and protected from potential shrimp trawl mortality, export of juveniles (i.e., production) to the adult population was evident and likely greater on a per-unit-area basis than for the control site. In the northern Gulf of Mexico (GOM), large and active artificial reef programs have resulted in the deployment of thousands of artificial reefs (Minton and Heath 1998; Kaiser and Pulsipher 2005; Gallaway et al 2009) These artificial structures may benefit reef fish populations as they provide additional hard-bottom “reef” habitat on a shelf dominated by mud and sand substrates (Parker et al 1983; Dufrene 2005). A myriad of factors influence artificial reef function; continued effort to identify artificial reefs that best support the enhancement of exploited reef fish populations and understanding which species and life stages that may benefit is necessary for the effective assessment of these habitats and their future deployments as a management tool. Given the overfished status of multiple fisheries in the GOM and the expectation of future artificial reef deployments, habitat monitoring studies of this nature are warranted, as such approaches can identify artificial reefs that may disproportionately contribute to the recovery and maintenance of these stocks
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