Red Snapper Lutjanus Campechanus Research Articles

Benthic modification and biotic associations at natural and artificial habitats excavated by Epinephelus morio and Lutjanus campechanus

Pockmarks are abundant seafloor features worldwide and, in West Florida Shelf waters <110 m deep, are thought to be sites of sediment excavation primarily by red grouper Epinephelus morio, although red snapper Lutjanus campechanus also excavate sediment. During 2014-2017, side-scan sonar (445 kHz) was used to locate and deploy stereo-baited remote underwater video arrays within view of 202 such excavations in waters 17-110 m deep on the West Florida Shelf off the Florida Panhandle and Peninsula. Three excavation habitat classes included 73 isolated excavations on open sand, 74 associated with low-relief hard bottom, and 55 associated with artificial reefs. Physical characteristics of excavations varied between regions, among habitats, and with depth; mean diameter (±1 SE) was 9.9 ± 0.3 m (range: 3-24.6 m). Excavations not around artificial reefs contained 6.9 ± 0.5 m2 (0-27.7 m2) of exposed rock, and epibenthic growth covered 33 ± 2% of the interiors. Members of 99 fish genera were identified. Fish abundance was greatest at isolated excavations which showed similar evenness to excavated artificial reefs; diversity was higher at excavated low-relief hard bottom. L. campechanus was much more common in Panhandle waters, especially at excavated artificial reefs which had subsided 0.8 ± 0.1 vertical meters below the seafloor (i.e. 48 ± 4% of the structure). These biotic and abiotic characteristics of excavations highlight the importance of E. morio’s ecosystem-engineering services and provide new insight into the contributions of L. campechanus in creating or maintaining excavations at natural and anthropogenic habitats.

Red snapper excavate sediments around artificial reefs: observations of ecosystem-engineering behavior by a widely distributed lutjanid

Hard substrate and vertical relief are limited habitat resources for reef-associated species in many regions. On the West Florida Shelf (WFS) of the Gulf of Mexico, red grouper Epinephelus morio act as ecosystem engineers by excavating sediments to expose limestone bedrock. Excavations can exceed 25 m in diameter and 2 m in depth and are among the most abundant WFS seafloor features at depths between 40 and 110 m. As part of a survey of hard-bottom habitats and associated reef fish assemblages, 1203 excavations were identified in WFS waters along the Florida Panhandle between 2014 and 2019. These excavations often contained subsided artificial reef material within their interior and infrequently included E. morio among observed fishes. We video-identified red snapper Lutjanus campechanus excavating sediments around 2 subsided artificial reefs in 2015 and 2017 for a total of approximately 56 min of excavation activity. A total of 24 excavation events were documented around a tire pile in 2015, and 5 were documented around a pyramid-shaped reef module in 2017. These observations help to explain the subsidence of artificial reefs and apparent excavation around their bases despite the scarcity of previously known excavating species. This suggests that L. campechanus might be ecosystem engineers on the WFS.

Calibration of fish counts in video surveys: a case study from the Southeast Reef Fish Survey

Changes to sampling gears or vessels can influence the catchability or detectability of fish, leading to biased trends in abundance. Despite the widespread use of underwater video cameras to index fish abundance and the rapid advances in video technology, few studies have focused on calibrating data from different cameras used in underwater video surveys. We describe a side-by-side calibration study (N = 143 paired videos) undertaken in 2014 to account for a camera change in the Southeast Reef Fish Survey, a regional-scale, multi-species reef fish survey along the southeast United States Atlantic coast. Slope estimates from linear regression for the 16 species included in the analyses ranged from 0.21 to 0.98, with an overall mean of 0.57, suggesting that original cameras (Canon Vixia HF-S200) observed an average of 43% fewer fish than newer cameras (GoPro Hero 3+). Some reef fish species had limited calibration sample sizes, such that borrowing calibration information from related or unrelated species was justified in some cases. We also applied calibrations to 11-year video time series of relative abundance of scamp Mycteroperca phenax and red snapper Lutjanus campechanus (N = 13,072 videos), showing that calibrations were critical to separating changes in camera sightability from true changes in abundance. We recommend calibrating data from video cameras anytime changes occur, and pairing video cameras to the extent possible to control for the spatial and temporal variability inherent in fish populations and environmental conditions. Following these guidelines, researchers will be able to maintain the integrity of valuable long-term video datasets despite intentional or unavoidable changes to video cameras over time.

Validating matches of electronically reported fishing trips to investigate matching error

AbstractObjectiveRecently, researchers have developed methods for combining probability samples and non‐probability samples. In recreational fisheries management, data from probability samples are typically counts of catch from a random sample of trips intercepted by a sampler, while non‐probability samples consist of catch data that are collected in self‐reports made to a fishery management agency. These reports are typically transmitted electronically and are known as an electronic logbook (ELB). Even when such reporting is mandated, compliance is not universal. Since the inclusion probability for any particular angler is unknown, the ELB sample is a non‐probability sample. We used data from a 2017 Gulf of Mexico (GoM) pilot study in which charter captains volunteered to electronically report their catch. At the dock, they could also be intercepted by a sampler, at which time their catch was observed. Estimates of total catch can be generated if trips from the two data sets can be accurately matched. Several states in the GoM implement similar ELB reporting augmented with a probability sample. However, there is an apparent discrepancy between National Oceanic and Atmospheric Administration (NOAA) estimates of the total and the ELB estimates for the same geographies. We seek to investigate the extent to which matching errors contribute to the discrepancies.MethodsWe employed probabilistic record linkage to match reports with intercepts and developed a validation tool to examine the matches. Using our validation tool, we examined several methods of estimating the total catch of Red Snapper Lutjanus campechanus in the GoM to investigate the potential cause of the discrepancy.ResultWe found the existing differences between the NOAA estimates and estimates resulting from combining ELB reports in this application were likely not due to matching error but instead were apparently derived from other sources of non‐sampling error.ConclusionThis has implications for new and existing ELB implementations, which are gaining popularity. The tool and results we provide can allow other implementations to better match reports with intercepts and offers a way to examine the extent to which matching errors affect the bias of estimates. Our work also shows that agencies should focus on non‐sampling errors besides matching error to reduce bias. Our tool may also be extended to examine such non‐sampling errors, such as the assumption that reporting and interception are independent.

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

AbstractMeteorological 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.

Development of Survey Methods to Effectively Sample Juvenile Red Snapper along the Atlantic Coast of Florida

AbstractUnderstanding of the early life history of Red Snapper Lutjanus campechanus throughout the U.S. Atlantic Ocean (hereafter, “Atlantic”) is limited, in part, due to the paucity of juveniles (<150 mm TL) collected in long‐term fishery‐independent surveys in the region. This is in sharp contrast to the Gulf of Mexico (hereafter, “Gulf”), where juvenile Red Snapper have been consistently collected in surveys. This apparent regional disparity is poorly understood. Red Snapper nursery habitats may differ between the Atlantic and the Gulf, previous Atlantic surveys may not have included important nursery habitat, or sampling gear used in the Atlantic may not be effective at collecting juveniles. A 2‐year fishery‐independent study was conducted along the Atlantic coast of Florida to test whether juvenile Red Snapper could be effectively sampled with two types of gear not commonly used there: a semi‐balloon trawl like those used in long‐term groundfish surveys in the Gulf and small‐mesh Z‐traps. In total, 194 Red Snapper were collected in the trawl samples and 202 Red Snapper were collected in the Z‐trap samples—mostly juveniles (age 0 and age 1) captured in nearshore waters (<30 m deep). Like the Gulf, shallow coastal waters in the Atlantic likely function as nursery habitat for Red Snapper. Primarily small age‐0 Red Snapper were collected during trawl sampling, which targeted unconsolidated nonreef habitats, whereas larger age‐0 and age‐1 and older Red Snapper were collected during trap sampling, which targeted hard‐bottom reef habitats. Although this study represents the most successful sampling of juvenile Red Snapper in the Atlantic to date, further research is required to delineate the northern and southern extents of Red Snapper nursery grounds. Nevertheless, our results provide a framework for developing a fishery‐independent survey that targets juvenile Red Snapper in the Atlantic to provide valuable data for quantifying recruitment and monitoring the status and recovery of this economically important species.

Potential Implications of Excluding Live‐Bottom Habitat from a Bottom‐Trawl Survey in the Eastern Gulf of Mexico

AbstractData provided by the Southeast Area Monitoring and Assessment Program (SEAMAP) shrimp/groundfish trawl survey have long been used in assessing diverse managed taxa, including several reef fishes; however, there are rising concerns over the impacts of trawling on live‐bottom habitats. Using data collected from summer SEAMAP trawl surveys (2009–2016; N = 1,103), we examined how avoiding areas of live‐bottom habitat might affect the survey's ability to assess interannual changes in abundance of managed reef fish taxa. Trawl samples at 48% of sampling sites contained <50 kg of sponge, and 12% of sampling sites contained at least 50 kg of sponge, while 40% of sites had zero sponge bycatch. Mean number of taxa, taxonomic richness, and taxonomic diversity were significantly higher as sponge bycatch increased, while the total number of individuals remained the same. To examine interannual variability of managed reef fish taxa, annual indices of relative abundance were calculated on different subsets of data (all data, data excluding sites with sponge bycatch ≥50 kg, and data excluding all sites with sponge bycatch). For Red Snapper Lutjanus campechanus and pink shrimp Farfantepenaeus duorarum, indices and general trends were largely unaffected by excluding sites with sponge, but for most selected taxa (e.g., Gray Triggerfish Balistes capriscus and Red Grouper Epinephelus morio), overall trends were affected by excluding sites that contained sponge bycatch, and in some cases the frequency of occurrence did not meet the requirement to calculate an index of abundance (i.e., <5%) when sponge sites were excluded (e.g., Hogfish Lachnolaimus maximus). Efforts to mitigate survey interactions with live‐bottom habitats will likely alter the utility of survey data and the ability to assess managed species, so careful consideration is needed to evaluate any trade‐offs between the benefits of the trawl survey for fishery assessments and the benefits of protecting the habitat.

Evaluation of red snapper Lutjanus campechanus trophic dynamics with simultaneous stomach content and stable isotope analysis

The importance of multiple prey taxa to red snapper Lutjanus campechanus diet was investigated using simultaneous stomach content analysis (SCA) and stable isotope analysis (SIA) over a 2 yr period in the north-central Gulf of Mexico (GOM) across 3 depth strata and 3 artificial structure types. Stable nitrogen isotope values were also used to estimate the trophic positions (TPs) of red snapper and prey items. SCA results showed that a variety of taxonomic prey groups were consumed, but the most frequent prey were stomatopods, portunid crabs and several families of fish. Some isotopic differences were found between red snapper size and age classes and across habitat types and depth strata for each sampling year; however, no consistent differences were found across the entire study period. Stable isotope mixing model results showed that diet varied annually, with sciaenid fishes being the greatest contributor in 2016 and portunid crabs in 2017, with the remaining proportions split across other taxa. Red snapper TP ranged from 3.4 to 4.8, while that of most prey groups was highly variable. The consistency in red snapper isotope values and the isotopic inconsistency of prey groups suggests that individual red snapper feed evenly across a taxonomically and isotopically diverse prey field. These results help develop a better understanding of reef ecology and food web structure in the northern GOM. Future investigations of red snapper diet that characterize reef habitats in terms of the available prey field and environmental conditions would improve our understanding of its trophic role in reef food webs.

Designing Cost‐Effective Artificial Reefs: Fine‐Scale Movement and Habitat Use of Red Snapper around a Nearshore Artificial Reef Complex

AbstractArtificial reefs are commonly used to provide structured habitat in areas with limited natural habitat to enhance the environment. Creating artificial reefs is expensive, and materials are often limited; thus, discussions are needed regarding the best material and design to maximize reefing efficiency while best meeting the goal of reefing programs. We tracked Red Snapper Lutjanus campechanus, an economically important and reef‐dependent species, by using a Vemco Positioning System to determine fine‐scale movements and habitat use around a nearshore reef comprised of three types of reefing structure: concrete reef pyramids, concrete culverts, and a sunken ship. Habitat use (core volume and home range, or the probability of a fish being absent 50% or 5% of the time, respectively) was significantly different by month, with the largest movements during summer months. Mean depth values also differed by study month (February–August), with Red Snapper residing deepest in the water column during August and shallowest during April. In the summer months, differences among structure types were observed in core volume use but not home range, suggesting that Red Snapper used similar‐sized areas on all three structure types. A high reported recapture rate (77%; 10 of 13 fish) indicated that these easily accessible nearshore reefs undergo heavy fishing pressure. Half of the recaptures were reported as recaptured on a structure other than their tagging structure; however, tagged fish spent the greatest percentage of time on their tagging structure. Red Snapper habitat use was influenced more by the presence of structure than by the type of reefing structure. Using the results from this study combined with a cost comparison of reef types, we argue that use of the least expensive reefing material that covers the largest area may be the best policy in designing future artificial reefs.

Absolute Abundance Estimates for Red Snapper, Greater Amberjack, and Other Federally Managed Fish on Offshore Petroleum Platforms in the Gulf of Mexico

AbstractOffshore petroleum platforms provide habitat utilized by an array of reef fish that are valuable to both commercial and recreational fishers. However, thousands of offshore platforms have been decommissioned in the Gulf of Mexico over the past decade, with many of the removals being accomplished using explosive severance methods. Here, we estimate the impact of platform removal in the Gulf of Mexico on five stocks of federally managed reef fish based on the percentage of each stock that is resident on platforms. We conclude that the gulfwide impact of removal will be relatively minor (1% to 8% of the estimated stock abundance) for four species, Red Snapper Lutjanus campechanus, Gray Triggerfish Balistes capriscus, Vermilion Snapper Rhomboplites aurorubens, and Cobia Rachycentron canadum. In contrast, losses for the Greater Amberjack Seriola dumerili stock would potentially represent 45% of the known stock. An alternative explanation is that the actual abundance of Greater Amberjack is much larger than the most recent stock size estimate; in either case, we suggest this issue needs further examination. Removal impacts could also be significant for reef‐fish fisheries (especially the Red Snapper fishery) in areas where platforms are presently abundant but other high‐relief natural or artificial reefs are not present. Removal of the platforms from these areas will greatly impact the local fisheries.

Discard Mortality of Red Snapper Released with Descender Devices in the U.S. South Atlantic

AbstractFishery regulations mandate the release of many caught fish, elevating the importance of having accurate estimates of discard mortality. Red Snapper Lutjanus campechanus are overfished and undergoing overfishing in the southeast U.S. Atlantic, in part due to the high number of releases that die from discard mortality. We used acoustic telemetry to track the fine‐scale movements of hook‐and‐line‐caught Red Snapper released with descender devices at a hard‐bottom site off North Carolina, USA. Movement characteristics of known‐fate (live and dead) Red Snapper were used to infer fates of other individuals, from which we generated a proportional mortality estimate of 0.08 (95% CI = 0.00–0.17) for successfully descended Red Snapper with no hook trauma. This best‐case mortality estimate was then used in a simulation to estimate overall Red Snapper discard mortality for the recreational fishery in the southeast U.S. Atlantic based on hooking location and a depth of approximately 37 m. For this fishery, we estimated the median proportional rate of discard mortality to be 0.13 (2.5% and 97.5% percentiles = 0.10, 0.17) if all released individuals were descended. This estimate is lower than the discard mortality values (˜0.2–0.3 for the recreational fishery) used in the current Red Snapper stock assessment, but it is likely not reflective of the current reality given that descender use is not 100% in this region; this estimate is also depth specific. Increased use of descender devices will reduce discard mortality for Red Snapper, enhancing efforts to rebuild this stock.

Reproductive characteristics of Red Snapper Lutjanus campechanus on artificial reefs in different jurisdictions

Reproductive activity of Red Snapper Lutjanus campechanus (Poey, 1860) at artificial reefs (ARs) are only recently being investigated. Yet, the management of the fishery differs on a regional basis with state and federal jurisdictions, and reproductive differences among regions have not been investigated. To compare the reproductive activity of L. campechanus among state (inshore) and federal (offshore) jurisdictions, individuals were collected in the northwestern Gulf of Mexico from four ARs on a quarterly basis for 2 yrs. Inshore sites exhibited fishing pressure year round whereas offshore sites only had fishing season open during a few months of summer. Collected individuals were measured for weight and length, then aged, sexed, and reproductive phase identified using the following metrics: resting, spawning capable, actively spawning, and regressing. Individuals in all reproductive phases were collected at three of the four sites. Spawning season was observed from April to September, with June identified as the induction of the peak spawning period. Hydrated oocytes were observed, which indicated imminent spawning within 12 h. Although 79% of female L. campechanus at all sites combined were mature based on reproductive phase, most fish were small, young, and inshore sites only made up 12% of the mature females. Several individuals were mature at offshore sites compared to only a few at inshore sites, yet fishing pressure was higher at inshore sites. We suggest that L. campechanus were spawning capable and actively spawning when those individuals were several years of age, but younger, barely mature individuals comprised the majority. Thus, L. campechanus include ARs in their life cycle and directly spawn on state and federal ARs when given enough time to achieve reproductive maturity. However, fisheries management should consider enforcing higher restrictions depending on the jurisdiction to allow individuals to mature and spawn before capture in both state and federal jurisdictions.

The Role of Maturity in Artificial Habitat Selection by Female Red Snapper

AbstractThe Red Snapper Lutjanus campechanus is a reef‐associated species found throughout the Gulf of Mexico that relies on artificial structures for habitat. In this study, we used Bayesian models to determine habitat selection by different sizes and ages of female Red Snapper and to identify whether there was a difference in habitat selection between immature and mature fish. Red Snapper (n = 693) were sampled using vertical longlines from March or April through November of 2016–2018 off the coast of Mississippi at different artificial structure types (platforms, artificial reefs, and rigs‐to‐reef structures [hereafter, “rigs‐to‐reefs”]) and depths (shallow, <20 m; mid‐depth, 20–49 m; and deep, 50–100 m). To adjust for the traditional occurrence of mature fish being larger and older than immature fish, only fish within the intersection of the FL (n = 616) and age (n = 622) ranges of immature and mature classes were used in these analyses. Fork length and age of immature and mature fish increased with increasing depth, but immature fish had a larger increase in FL per unit depth than mature fish. Immature fish on artificial reefs were found to be older than immature fish at platforms, while there was no age difference between the two structures for mature fish. There was no difference in FL or age between rigs‐to‐reefs and platforms or artificial reefs for immature fish, but FL and age of mature fish were greater at rigs‐to‐reefs than at platforms and artificial reefs. However, maturity did not play a role in how age increased with depth or with differences in FL between artificial reefs and platforms for mature fish. These differences in habitat use based on maturity should be considered along with FL and age to inform management regulations for Red Snapper.

Understanding and Enhancing Angler Satisfaction with Fisheries Management: Insights from the “Great Red Snapper Count”

AbstractManagement of Gulf of Mexico Red Snapper Lutjanus campechanus has been a topic of much scientific debate and intensive public scrutiny. In response to political, public, and management desires for more robust data on Red Snapper populations, a gulfwide initiative commonly referred to as the “Great Red Snapper Count” (GRSC) was funded to estimate the absolute abundance of Red Snapper in the U.S. Gulf of Mexico. Here, we describe the results of an online survey designed to (1) characterize the social dimensions of Red Snapper anglers, (2) measure satisfaction with current Red Snapper populations and regulations, (3) assess overall patterns of awareness of the GRSC, and (4) evaluate the potential benefits of GRSC stakeholder engagement videos. A key finding of our survey was that awareness of the GRSC was associated with up to three times higher satisfaction with fisheries management. Through an in‐survey experiment, we found that anglers that were presented a video on specific GRSC project components reported slightly higher management satisfaction than those presented an overview video or no video. Collectively, our results indicate that angler awareness, when underpinned by effective engagement and outreach activities, can enhance angler satisfaction.

Stable Isotopic Niche Variability and Overlap across Four Fish Guilds in the North‐Central Gulf of Mexico

AbstractThe quantification of niche diversity and niche overlap is useful for understanding the impacts of fisheries regulation and management. In this work, we evaluate isotopic niche size and overlap at the guild and species levels. Specifically, we analyzed guild‐ and species‐specific isotopic niche space and niche space overlap using the SIBER and nicheROVER packages, and we evaluated length‐specific and geographic contrasts in isotopes for fishes in the north‐central Gulf of Mexico. Stable carbon and nitrogen isotope values (δ13C and δ15N) of fish species were compared among four ecotype‐based fish guilds: estuarine, coastal migratory pelagic (CMP), reef, and large offshore pelagic (LOP). Significant differences in the mean stable isotope values were found among fish guilds. Estuarine guild species exhibited the highest δ13C variability, and Red Drum Sciaenops ocellatus were the most isotopically diverse. Variability of δ13C for CMP fish was comparable to that of some estuarine species, whereas reef and LOP fish were less variable. Fishes within the LOP guild had the largest δ15N range. Reef guild fishes had the smallest isotopic niche space and LOP guild species consistently had the largest, although no species in any guild occupied as large of an isotopic niche space as Red Drum. Distinct and well‐separated isotopic niches were also observed between most estuarine species and CMP species; however, high niche overlap was observed for species within the reef and LOP guilds. We found a positive relationship of δ15N and fish TL for Red Drum, Blackfin Tuna Thunnus atlanticus, and Yellowfin Tuna T. albacares, and we found that δ15N values for Red Drum and Red Snapper Lutjanus campechanus showed distinct isotope differences between geographic areas. This study provides data not only on how species within and without ecotypes interact but also on the variability of their interactions, all of which can inform ecosystem‐based fisheries management models.

Importance of Depth and Artificial Structure as Predictors of Female Red Snapper Reproductive Parameters

AbstractThe Red Snapper Lutjanus campechanus is a structure‐associated species occurring across a wide depth range in the northern Gulf of Mexico. We used the random forest machine learning algorithm to understand which habitat and individual fish characteristics could predict reproductive parameters of female Red Snapper. We evaluated fish captured from 2016 to 2018 on three artificial structure types with various structure heights at depths of 100 m or less. Overall, we found that depth and month were important predictors for most reproductive parameters, but the type of structure (artificial reefs, oil platforms, and rigs‐to‐reefs structures) was not important. Maturity was correctly classified in 88.9% of the cases when using the random forest ensemble model, with important predictors including FL, depth, structure height, and month of collection. Spawning seasonality (measured as gonadosomatic index [GSI]) was correctly classified in 59.5% of the cases when using histology reproductive phase, FL, month, and depth variables. Reproductively active or inactive females were correctly classified in 89.3% of the cases using GSI, month, FL, and depth, while females in the developing versus spawning capable phases were correctly classified in 82.2% of the cases using GSI, FL, month, and depth. Histological indicators that show potential spawning within a 36‐h period were correctly classified 61.5% of the time, with the best predictors being depth, FL, GSI, and month. Stepwise regression indicated that month was the only factor that significantly predicted contrasts in relative batch fecundity, with significantly greater values in August compared to all other months. Our findings suggest that female Red Snapper reproductive effort is not consistently or well predicted by artificial structure type or height but that a combination of fish FL, month, and depth can predict reproductive characteristics of female Red Snapper.

Assessing the Relative Selectivity of Multiple Sampling Gears for Managed Reef Fishes in the Eastern Gulf of Mexico

AbstractFishery‐independent data are important for the effective management of reef fishes in the eastern Gulf of Mexico. Proper characterization of selectivity, or the effectiveness of each type of sampling gear in capturing a species or a size‐class, is essential to ensure that assessment models treat various sources of data appropriately. In this study, we analyzed fishery‐independent data that was collected using stereo‐baited remote underwater video (S‐BRUV) arrays, chevron traps (TRAP), and two types of hooked gear (repetitive timed‐drop [RTD] and vertical longline [VLL]) to assess gear‐related differences of species composition and size selectivity of managed reef fishes in the eastern Gulf of Mexico. Significant differences were detected in the assemblage structures of reef fishes in relation to region, gear type, and depth. Overall, eight managed species were identified as contributing to the top 70% of the assemblage structure for each gear type. Stereo‐baited remote underwater video had the highest abundances for most of the species and the highest number of species captured, while VLL had the lowest. Two economically and ecologically important species (Red GrouperEpinephelus morioand Red SnapperLutjanus campechanus) were common to all four gear types, and the size selectivity of these two species generally overlapped. However, significant differences among gear types were detected. Unimodal selection curves for hooked gears indicated that size of Red Snapper and Red Grouper increased as hook size increased. These data provide insight on species and size selectivity of multiple gears, which will contribute to future survey design and aid in the management of reef‐fish populations.

Movement patterns of red snapper Lutjanus campechanus based on acoustic telemetry around oil and gas platforms in the northern Gulf of Mexico

Offshore oil and gas platforms in the northern Gulf of Mexico are known aggregation sites for red snapper Lutjanus campechanus. To examine habitat use and potential mortality from explosive platform removals, fine-scale movements of red snapper were estimated based on acoustic telemetry from March 2017 to July 2018. Study sites in the northern Gulf of Mexico, USA, included one platform off coastal Alabama (30.09°N, 87.88°W) and 2 platforms off Louisiana (28.81°N, 91.97°W; 28.92°N, 93.15°W). Red snapper (n = 59) showed a high affinity for platforms, with most (94%) positions being recorded within 95 m of the platforms. Home range areas were correlated with water temperature and inversely correlated with dissolved oxygen concentrations. During summer and fall, red snapper used larger areas and many fish (54%) emigrated from their platforms but most (83%) returned in ≤3 d. Site fidelity for red snapper was 31% yr-1 and residency time was 7 mo, but the probability-of-presence at platforms was 70% after 1 yr, indicating the importance of platforms for this species. Overall fishing mortality was high for platforms (F = 0.86, 95% CL = 0.47-1.40), but since the stock is managed on a quota basis this high mortality should have little effect on total stock abundance. Thus, platforms can still provide an important habitat for red snapper, and consideration of area use patterns, fishing mortality and environmental factors can reduce red snapper mortality when scheduling explosive platform removals. As such, the present study indicates that an optimum time for explosive removal would be in late summer after the red snapper fishing season is completed.

A high proportion of red snapper sold in North Carolina is mislabeled.

Seafood mislabeling occurs when a market label is inaccurate, primarily in terms of species identity, but also regarding weight, geographic origin, or other characteristics. This widespread problem allows cheaper or illegally-caught species to be marketed as species desirable to consumers. Previous studies have identified red snapper (Lutjanus campechanus) as one of the most frequently mislabeled seafood species in the United States. To quantify how common mislabeling of red snapper is across North Carolina, the Seafood Forensics class at the University of North Carolina at Chapel Hill used DNA barcoding to analyze samples sold as “red snapper” from restaurants, seafood markets, and grocery stores purchased in ten counties. Of 43 samples successfully sequenced and identified, 90.7% were mislabeled. Only one grocery store chain (of four chains tested) accurately labeled red snapper. The mislabeling rate for restaurants and seafood markets was 100%. Vermilion snapper (Rhomboplites aurorubens) and tilapia (Oreochromis aureus and O. niloticus) were the species most frequently substituted for red snapper (13 of 39 mislabeled samples for both taxa, or 26 of 39 mislabeled total). This study builds on previous mislabeling research by collecting samples of a specific species in a confined geographic region, allowing local vendors and policy makers to better understand the scope of red snapper mislabeling in North Carolina. This methodology is also a model for other academic institutions to engage undergraduate researchers in mislabeling data collection, sample processing, and analysis.

Catchability of reef fish species in traps is strongly affected by water temperature and substrate

It is commonly assumed in surveys that the likelihood of capturing or observing individuals of a given species is constant. Yet evidence is building that catchability, or the likelihood of catching an individual present at a site, can vary. We used 5465 paired trap-video samples collected along the southeast US Atlantic coast in 2015-2018 to estimate trap catchabilities of 6 reef fish species (gray triggerfish Balistes capriscus, red porgy Pagrus pagrus, vermilion snapper Rhomboplites aurorubens, black sea bass Centropristis striata, red snapper Lutjanus campechanus, white grunt Haemulon plumierii) as the ratio of trap catch to standardized site abundance from corresponding videos. Species-specific trap catchabilities were then related to 2 primary predictor variables: water temperature and percent of the visible bottom consisting of rocky substrate. Water temperature strongly influenced trap catchabilities for all species after standardizing for all other variables. The 4 warm-water species displayed strong positive relationships between catchability and temperature; of these species, the smallest absolute increase in catchability occurred for vermilion snapper (0.0 at ~14°C to 0.05 at ~28°C) and the largest occurred for white grunt (0.0 at ~14°C to 0.49 at ~28°C). The 2 cooler-water species displayed either a dome-shaped (red porgy) or negative relationship (black sea bass) between catchability and temperature. Furthermore, trap catchabilities for all species declined substantially (42-80%) as the percent hard bottom of the site increased. Only when catchability is properly accounted for can results be considered unbiased and subsequent management advice be considered accurate.