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

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 species-specific life history traits will be needed to better understand the function and performance of artificial reefs in supporting fisheries productivity

Age, growth, and mortality of King Mackerel in the western Gulf of Mexico

Objective Temporal and spatial variation in growth can have significant implications for the assessment and management of exploited populations. Therefore, the age and growth of King Mackerel Scomberomorus cavalla were estimated for the western Gulf of Mexico, where there are large gaps in the available data. Methods A total of 727 sagittal otoliths from 411 females, 248 males, and 68 individuals of unknown sex were collected from headboats, private recreational anglers, tournaments, and fishery-independent sampling and aged. Result Ages ranged from 0 to 17 years with lengths ranging from 13 to 147 cm fork length. The distribution of lengths and ages differed marginally for fishing sector (i.e., tournament vs. headboat vs. private). The fish that were collected from tournaments were larger than those collected from headboats and private anglers. The distribution of lengths and ages did vary by sex, with females obtaining larger sizes than males. However, there was no difference in mean age by sex. Using the multimodel approach, the Richards model improved the fit for both the youngest and oldest fish in the sample relative to the other growth models that were evaluated. Sex-specific differences in the Richards model were detected, with females growing larger than males but more slowly. Although peak catch was observed at age 5, King Mackerel were not fully recruited to the recreational fishery until age 6. The Chapman-Robson Peak Plus estimate of Z was 0.37. Conclusion These data provide a contemporary snapshot of size structure, age, growth, and mortality for King Mackerel from an undersampled region of the Gulf of Mexico and highlight several key considerations for upcoming stock assessments

Utility of citizen science data: A case study in land-based shark fishing.

Involving citizen scientists in research has become increasingly popular in natural resource management and allows for an increased research effort at low cost, distribution of scientific information to relevant audiences, and meaningful public engagement. Scientists engaging fishing tournament participants as citizen scientists represent ideal scenarios for testing citizen science initiatives. For example, the Texas Shark Rodeo has begun shifting to conservation-oriented catch-and-release practices, which provides a unique opportunity to collect data on a large scale for extended periods of time, particularly through tagging large numbers of sharks for very little cost compared to a directed scientific study. However, critics are somewhat skeptical of citizen science due to the potential for lack of rigor in data collection and validation. A major management concern for shark fisheries is the ability of anglers to identify species. We tested some of the assumptions and value of citizen-collected data by cross-verifying species identification. Specifically, the purpose of this study was to evaluate the accuracy of shark species identifications made by anglers fishing in the Texas Shark Rodeo using photographs that were submitted as a requirement for tournament participation. Using a confusion matrix, we determined that anglers correctly identified 97.2% of all shark catches submitted during the Texas Shark Rodeo from 2014-2018; however, smaller sharks and certain species, including blacknose and spinner sharks, were more difficult to identify than others. Most commonly confused with blacktip sharks, spinner sharks were most commonly identified incorrectly (76.1% true positive rate [TPR]) followed by blacknose (86.8% TPR), finetooth (88.0% TPR), and Atlantic sharpnose sharks (93.8% TPR). This study demonstrated that citizen scientists have the ability to identify sharks with relatively low error. This is important for science and management, as these long-term datasets with relatively wide geographic scope could potentially be incorporated into future assessments of sharks in the Gulf of Mexico

New Insights Into the Seasonal Movement Patterns of Shortfin Mako Sharks in the Gulf of Mexico

Highly mobile apex predators such as the shortfin mako shark (mako shark; Isurus oxyrinchus) serve an important role in the marine ecosystem, and despite their declining populations and vulnerability to overexploitation, this species is frequently harvested in high abundance in both commercial and recreational fisheries. In 2017, the North Atlantic stock was deemed overfished and to be undergoing overfishing and was recently listed in CITES Appendix II. Effective management of this species can benefit from detailed information on their movements and habitat use, which is lacking, especially in the Gulf of Mexico, a potential mating and parturition ground. In this study, we used satellite telemetry to track the movements of mako sharks in the western Gulf of Mexico between 2016 and 2020. In contrast to previous studies that have primarily tagged juvenile mako sharks (>80% juveniles), ∼80% of sharks tagged in this study (7 of 9) were presumed to be mature based on published size-at-maturity data. Sharks were tracked for durations ranging from 10 to 887 days (mean = 359 days; median = 239 days) with three mature individuals tracked for >2 years. Mako sharks tagged in this study used more of the northwestern Gulf of Mexico than reported in previous movement studies on juveniles, suggesting potential evidence of size segregation. While one mature female remained in the Gulf of Mexico over a >2-year period, predominantly on the continental shelf, two mature males demonstrated seasonal migrations ∼2,500 km from the tagging location off the Texas coast to the Caribbean Sea and northeastern United States Atlantic coast, respectively. During these migrations, mako sharks traversed at least 12 jurisdictional boundaries, which also exposed individuals to varying levels of fishing pressure and harvest regulations. Movement ecology of this species, especially for mature individuals in the western North Atlantic, has been largely unknown until recently. These data included here supplement existing information on mako shark movement ecology and potential stock structure that could help improve management of the species

A Comparison of Private Recreational Fishing Harvest and Effort for Gulf of Mexico Red Snapper during Derby and Extended Federal Seasons and Implications for Future Management

Fisheries managers often use regulations such as bag, size, and season limits to manage recreational anglers and prevent overharvest, and this has been the case for the Gulf of Mexico Red Snapper Lutjanus campechanus fishery, which has been highly regulated for over 20 years. During this period, the federal season for private recreational anglers has decreased from year-round in 1996 to only 3 d in 2017. However, in 2017 the private recreational season was reopened for an additional 39 d. This scenario allowed us to examine a very short, derby-style initial season with an unexpected extended season and make comparisons with longer-term data sets from the Texas Parks and Wildlife Department's angler-intercept program, where we hypothesized that harvest and effort may not be directly related to season length. Our data indicated that there were higher harvest and effort rates during the initial season than during the extended season, and these differences were a function of extended season length (i.e., future access) and weather. The harvest and effort rates of the extended season were not proportional to the initial season, suggesting that recreational anglers compensated for reductions in season length by compressing their effort into the shortened season. While our results suggest that an extended season results in a reduction of daily harvest and effort rates, it is important to have programs in place to closely monitor the total harvest in a timely manner to prevent overharvest

Influence of Hurricane Activity on Acoustic Array Efficiency: A Case Study of Red Snapper within an Artificial Reef Complex

Meteorological disturbances, such as hurricanes, can cause wide distributional changes to fish populations, but studies documenting fish movement in response to these disturbances are rare and serendipitous. We opportunistically examined how a hurricane influenced behavior of Red Snapper Lutjanus campechanus at an artificial reef complex in the western Gulf of Mexico. Red Snapper had a variety of responses, with some fish emigrating and some remaining on site during Hurricane Harvey—a category 4 storm. Hurricane-induced destruction or alteration of habitat may alter space use behavior of fish. However, caution should be used when interpreting behavior without the inclusion of array performance, which may change due to environmental conditions. Importantly, when acoustic array efficiency was not accounted for in space use analyses, mean kernel utilization distribution (m3) was marginally different among the periods before, during, and after Hurricane Harvey. However, when mean daily array efficiency was included as a covariate, space use among the three periods was not significantly different. Hurricanes can affect the movement and residency of marine species and can be an important driver in the displacement of populations and degradation of habitats, but array efficiency should be incorporated to prevent misinterpreting the behaviors of tagged fish

Trophic ecology of red snapper Lutjanus campechanus on natural and artificial reefs: interactions between annual variability, habitat, and ontogeny

In the Gulf of Mexico (GOM), oil and gas platforms have created an expansive network of artificial reefs. Generally, policies mandate removal of these structures post-production; however, many enter ‘Rigs-to-Reefs’ (RTR) programs that convert the rig materials into artificial reefs (‘reefing’). Despite the growth of RTR programs worldwide, the functionality of the resulting habitats remains uncertain, particularly due to the lack of comparative studies with natural systems. To address this data gap as it relates to trophic ecology, we compared annual, ontogenetic, and habitat-specific diet and stable isotope signatures (δ13C and δ15N) of adult red snapper Lutja - nus campe chanus (n = 1585) from relic coralgal natural reefs to those of fish from standing and reefed platforms located in similar depth strata of the northwestern GOM. Stomach content analyses revealed significant effects of year, habitat, and total length on prey composition. Subsequent analyses of stable isotope values by size class identified a non-linear relationship with ontogeny. δ13C and δ15N values at reefed platforms and natural reefs decreased in the medium size class (401− 600 mm total length), whereas fish from standing platforms exhibited more consistent feeding patterns across ontogeny. Annual variability was also observed in δ13C and δ15N values, with 2013 and 2014 significantly different from 2015. These findings suggest that the trophic impacts of habitat type on reef fishes are more complex than previously considered in the GOM and that reefed platforms provide foraging opportunities more similar to natural reefs than standing platforms

Effects of a New Artificial Reef Complex on Red Snapper and the Associated Fish Community: an Evaluation Using a Before–After Control–Impact Approach

Artificial 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

Social media shines light on the “hidden” impact of nighttime guided-gigging charters on Texas’ Southern Flounder fishery: A stab in the dark

Southern Flounder (Paralichthys lethostigma) populations are declining in the Gulf of Mexico basin. This is particularly true in Texas, where this unique and culturally important fishery has been in decline since the 1980s despite increasingly stringent regulatory measures. Current angler-intercept creel surveys used to estimate recreational flounder harvest levels are conducted during daylight hours and do not account for the high levels of nighttime flounder gigging (spearing) activity, a popular and efficient harvest method for this fishery. There are legitimate scientific and logistical concerns that have prevented the use of wide-spread nighttime creel surveys to monitor the flounder gigging fishery in the past, however this has made accurate catch and effort estimates difficult to obtain. Given the concern about this economically important fishery’s status, we adopted a unique approach utilizing social media to provide unprecedented information into this fishery’s impact during periods that are not traditionally monitored. Specifically, we reconstructed seasonal flounder harvest and effort metrics stemming from the nighttime recreational guided flounder gigging sector over 2.6 years using guided flounder gigging charter photo archives publicly available through Facebook. These metrics show large average client party sizes, large trip harvests, and near-perfect bag limit efficiencies. Temporal trends indicated peak recreational guided flounder gigging effort and harvest occurs during the summer months, a time not traditionally associated with flounder gigging. The addition of nighttime guided-gigging recreational harvest estimates from this study to traditional daytime harvest estimates and commercial harvest estimates resulted in total annual harvest estimates nearly two times greater than current estimates. Overall, this study demonstrates the high pressure guided-gigging charters are placing on Texas’ flounder fishery and illustrates the critical need for additional information on the nighttime recreational flounder fishery for both guided and private gigging anglers. Moreover, our results also demonstrate the usefulness of mining social media platforms to capture catch and effort data that are otherwise unavailable

Spatial distribution and movement of Atlantic tarpon (Megalops atlanticus) in the northern Gulf of Mexico.

Atlantic tarpon (Megalops atlanticus) are capable of long-distance migrations (hundreds of kilometers) but also exhibit resident behaviors in estuarine and coastal habitats. The aim of this study was to characterize the spatial distribution of juvenile tarpon and identify migration pathways of adult tarpon in the northern Gulf of Mexico. Spatial distribution of juvenile tarpon was investigated using gillnet data collected by Texas Parks and Wildlife Department (TPWD) over the past four decades. Generalized additive models (GAMs) indicated that salinity and water temperature played a significant role in tarpon presence, with tarpon occurrences peaking in the fall and increasing over the past four decades in this region. Adult tarpon caught off Texas (n = 40) and Louisiana (n = 4) were tagged with acoustic transmitters to characterize spatial and temporal trends in their movements and migrations. Of the 44 acoustic transmitters deployed, 18 of the individuals were detected (n = 16 west of the Mississippi River Delta and n = 2 east of the Mississippi River Delta). Tarpon tagged west of the Mississippi River Delta off Texas migrated south in the fall and winter into areas of south Texas and potentially into Mexico, while individuals tagged east of the delta migrated into Florida during the same time period, suggesting the presence of two unique migratory contingents or subpopulations in this region. An improved understanding of the habitat requirements and migratory patterns of tarpon inhabiting the Gulf of Mexico is critically needed by resource managers to assess the vulnerability of each contingent to fishing pressure, and this information will guide multi-state and multi-national conservation efforts to rebuild and sustain tarpon populations