Red Grouper Epinephelus Morio 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.

Potential Impact of Climate Change on Fish Reproductive Phenology: A Case Study in Gonochoric and Hermaphrodite Commercially Important Species from the Southern Gulf of Mexico

In tropical regions, temperature is the fundamental environmental factor controlling the reproduction-related physiological activities of fish. Tropical fish are particularly sensitive to climate change since they develop in a relatively stable thermal environment. A review was done to assess the potential effect of temperature rise on reproduction and population structure in the commercially important hermaphrodite grouper and wrasse species, and in gonochoric snapper species in the southern Gulf of Mexico. Temperature increase can disturb the aromatase synthesis and/or activity, which can affect the reproductive cycle and sexual differentiation in all studied species and the sexual inversion process in sequential hermaphrodites. Moreover, a mistiming or discontinuity in spawning seasonality could occur, with an alteration in the sex ratio in favor of males and a consequent reduction in populations’ fecundity. Furthermore, if the level of fishing exploitation enhances species’ sensitivity to environmental changes, then the stock of red grouper Epinephelus morio would be more affected by temperature increases than other species because it is the only fish population in the Campeche Bank currently assessed as overexploited.

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.

Modeling Discards in Stock Assessments: Red Grouper Epinephelus morio in the U.S. Gulf of Mexico

To be as accurate as possible, stock assessments should account for discard mortality in fisheries if it occurs. Three common approaches to modeling discards in assessments are to lump dead discards with landings, treat dead discards as their own fleet, or link them conversely with landings through use of a retention function. The first approach (lumping) implicitly assumes that the selectivity of landings applies also to discards. In many cases, that assumption is false, for example, if discards comprise smaller fish than do landings. The latter two approaches avoid the assumption by modeling discards explicitly with their own selectivity pattern. Here, we examine these approaches to modeling discards. Using a simulation study, we demonstrate that the two approaches to modeling discards explicitly can provide identical results under both static and time-varying conditions. Then, using a stock assessment case study of red grouper Epinephelus morio in the U.S. Gulf of Mexico, we demonstrate that in practice the approaches to modeling discards can provide different outcomes, with implications for the resultant management advice. We conclude by comparing and contrasting the different approaches, calling for more research to elucidate which approach is most suitable under various sources of error typically encountered in discard data.

Mercury accumulation in reef fishes: a comparison among red grouper, scamp, and gag of the Atlantic southeastern US and evaluation of "grouper" consumption guidelines.

In fish consumption advisories pertaining to Hg, grouper species in the family Serranidae are often lumped together and labeled generically as Grouper. However, grouper species vary considerably in growth rate, maximum age, and maximum size. This study examined the variability of Hg concentrations and bioaccumulation rates (increase of Hg concentrations in relation to age) for populations of three long-lived, slow-growing, protogynous hermaphrodite grouper species, gag Mycteroperca microlepis, scamp M. phenax, and red grouper Epinephelus morio, which are commercially and recreationally important in the offshore waters of the US southeastern region. A total of 268 samples from the three grouper species were processed for Hg analysis from 2013-2015. Concentrations of Hg ranged from 0.03 to 0.87ppm wet weight, with a mean of 0.30ppm. Gag accumulated Hg at a faster rate (as measured by the increase of Hg with fish age) than the other two species. Size, age, and δ15N were significant predictors for Hg in the two Mycteroperca species, while size and age were significant predictors for Hg in red grouper. Two of the three species had mean Hg concentrations within the one meal per week "Good Choices" consumption category (red grouper and scamp), and one species (gag) had a mean Hg level within the two meals per week "Good Choices" consumption category as advised by the US EPA and US FDA. These results support the separation of grouper species in advisories.

Biomass dynamic model for multiple data series: An improved approach for the management of the red grouper (Epinephelus morio) fishery of the Campeche Bank, Mexico

This study analyzed the current status of the population and stock assessment of the red grouper Epinephelus morio from the Campeche Bank, Yucatán, based on the Schaefer biomass dynamic model and considering the three fleets that operate in the study area. Thus, five indices of relative abundance were used, expressed as catch per unit effort (CPUE). The carrying capacity (K) of the red grouper population was 293,851 t, with an intrinsic growth rate (r) of 0.232. The study indicated that the greatest contribution to the adjustment of the model was due to the CPUE of the industrial Mexican fleet. The catchability values showed differences between the fractions of red grouper caught using trips and hooks. Estimates of maximum sustainable yield (MSY= 17,031 t) and biomass at MSY (BMSY= 146,929 t) indicated that the current catch and the biomass are below their reference points, denoting a marine resource that has been overharvested. Historical analysis of the biomass and harvest ratio for the red grouper estimated from the Kobe diagram showed that the red grouper fishery has transitioned from overfished-overharvested from 1984 to 2014 to overfished-underharvested in 2015. Because the E. morio stock is particularly low in abundance, catches must be drastically reduced to allow the stock to recover more quickly. Only low quotas (3,200–4,000 t) or an annual harvest rate of 6% will reach the BMSY in the long term, recognizing that, for both management strategies, the MSY will not be reached for at least 15 years.

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.

High predatory efficiency and abundance drive expected ecological impacts of a marine invasive fish

The ecological impacts of invasive species are highly variable and mediated by many factors, including both habitat and population abundance. LionfishPterois volitansare an invasive marine species which have high reported detrimental effects on prey populations, but whose effects relative to native predators are currently unknown for the recently colonized eastern Gulf of Mexico. We used functional response (FR) methodology to assess the ecological impact of lionfish relative to 2 functionally similar native species (red grouperEpinephelus morioand graysby grouperCephalopholis cruentata) foraging in a heterogeneous environment. We then combined theper capitaimpact of each species with their field abundance to obtain a Relative Impact Potential (RIP). RIP assesses the broader ecological impact of invasive relative to native predators, the magnitude of which predicts community-level negative effects of invasive species. Lionfish FR and overall consumption rate was intermediate to that of red grouper (higher) and graysby grouper (lower). However, lionfish had the highest capture efficiency of all species, which was invariant of habitat. Much higher field abundance of lionfish resulted in high RIPs relative to both grouper species, demonstrating that the ecological impact of lionfish in this region will be driven mainly by high abundance and high predator efficiency rather thanper capitaeffect. Our comparative study is the first empirical assessment of lionfishper capitaimpact and RIP in this region and is one of few such studies to quantify the FR of a marine predator.

Factors Affecting Catchability in Longline Fishing of Red Grouper in the Southeastern Gulf of Mexico

AbstractCatchability (q) is a key parameter in stock assessment that can vary in response to biological (e.g., abundance), spatial (e.g., fishing zones), and fishing technique and tactic (e.g., fishing gear design) factors. Few studies have been done on the influence of these sources of variation on q estimates. Catchability was calculated for Red Grouper Epinephelus morio caught with bottom longlines in two coastal zones fished by the small‐scale fleet in Yucatan, Mexico. Experimental data collected from these catches were used to assess the effect on q‐values of fishing zone and depth stratum, hook and bait size, and fish length. Three longlines were each equipped with one of three sizes (13/0, 14/0, or 15/0) of Mustad circle hooks. Bait was Atlantic Thread Herring Opisthonema oglinum in one of two sizes: 4 or 8 cm long. Sampling occurred in two zones (west and east coast) and in three depth strata (10–15 m, 15–20 m, and >20 m). Generalized linear models were used to identify any effect of the analyzed variables on q. Fishing depth and bait size alone had no apparent effect on q, but a combined effect of hook (14/0) size and bait (8 cm) size on q was observed. Fishing zone, hook size, and fish total length were significant sources of variation. The observed catchability patterns suggest possible high fishing mortality in juvenile Red Grouper related to fishing zone, hook and bait size, and fish length, highlighting the need to consider these variables to improve stock assessments of the Campeche Bank Red Grouper fishery.

Temporal Persistence of Red Grouper Holes and Analysis of Associated Fish Assemblages from Towed Camera Data in the Steamboat Lumps Marine Protected Area

AbstractThe Red Grouper Epinephelus morio is an ecologically and economically important Gulf of Mexico reef fish species. The well‐documented excavation behavior of this species generates several‐meter‐wide holes that serve as habitat in otherwise structureless areas. These mesohabitats are notably dense within the Steamboat Lumps (SL) Marine Protected Area (MPA) in the eastern Gulf of Mexico. Previous work in the SL‐MPA used high‐resolution multibeam bathymetry to analyze changes in hole density and structure (width, height, and slope) between 2006 and 2009. The present study utilizes additional multibeam data collected in 2017 to further these analyses. Overall, the density of holes within the SL‐MPA continued to increase, but no definite trend in structural changes could be identified. Additionally, a towed camera was used to directly observe 95 holes, of which 63 had detectable reef fishes. Within the occupied holes, approximately 46% had a Red Grouper or other grouper species (Epinephelidae) present. The most frequently observed species within the occupied holes were invasive lionfish Pterois spp., which were present in 84% of the holes. The increasing density of Red Grouper holes in the SL‐MPA indicates that the closure of the area may be resulting in a more robust local population of this species. However, quick colonization of the holes by lionfish has occurred, and additional studies are necessary to determine the impact of this on grouper and other native reef fish populations found within this type of uniquely created habitat.

Handle with Care: Establishing Catch Limits for Fish Stocks Experiencing Episodic Natural Mortality Events

Harmful blooms of the dinoflagellate Karenia brevis, known as “red tides,” are responsible for major episodic fish kills in the Gulf of Mexico. In response to management concerns, we conducted a management strategy evaluation to examine whether decision‐making reactivity to event occurrence or precautionary catch limit reductions could aid in achieving fishery objectives. Simulated stock dynamics were representative of Gulf of Mexico Red Grouper Epinephelus morio, and assessment of simulated data involved estimation of time‐varying natural mortality. We found that both unresponsive yet precautionary catch limits and reactive decision making could improve achievement of fishery objectives, although practical impediments to reactive strategies abound. Where catch limit reductions were introduced to buffer against scientific uncertainty, a trade‐off was evident that required recognizing constraints in stock assessment reliability (given the complexities of estimating time‐varying natural mortality) and balancing these constraints against desirability for high catch rates. Our study provides a narrative on the ways in which management guidance can be structured to address uncertainty about future occurrences of episodic natural mortality events.

Does the Lunar Cycle Affect Reef Fish Catch Rates?

AbstractThe lunar cycle was examined as a potential source of variation in CPUE for the most common commercial reef fish species captured in the Gulf of Mexico. Using fishery observer data for species captured with bottom longline and vertical line gear types, the analyses modeled CPUE with two different approaches: (1) a generalized additive model with cyclic splines to explain nonlinear variations with the 29.5‐d lunar cycle; and (2) a generalized linear model using periodic regression with the sine and cosine functions to describe cyclic variations in CPUE. A lunar effect on catch rates was detected for Red Grouper Epinephelus morio and Tilefish Lopholatilus chamaeleonticeps; however, no lunar effect was detected for Yellowedge Grouper Hyporthodus flavolimbatus, Red Snapper Lutjanus campechanus, or Vermilion Snapper Rhomboplites aurorubens based on either method. The lunar effect in the bottom longline fishery differed between species, with increased CPUE consistently predicted to occur near the new moon for Red Grouper and to take place proximal to the full moon for Tilefish. Red Grouper captured with vertical line gear had two CPUE increases predicted around the waxing and waning lunar phases. Inconsistencies in lunar effect between gear types for Red Grouper were present, possibly due to different mechanisms affecting CPUE. Results suggest that lunar cycles influence catch rates for some of the reef fish species examined and should be considered as potential environmental covariates for standardizing nominal CPUE.Received October 14, 2016; accepted February 2, 2017 Published online April 11, 2017

Sink or swim? Factors affecting immediate discard mortality for the gulf of Mexico commercial reef fish fishery

Fishery observer data collected from June 2006 through December 2015 in the Gulf of Mexico commercial reef fish fishery were examined to determine if any covariates available affected immediate discard mortality for six species: red grouper Epinephelus morio, red snapper Lutjanus campechanus, vermilion snapper Rhomboplites aurorubens, gag grouper Mycteroperca microlepis, scamp grouper Mycteroperca phenax, and speckled hind Epinephelus drummondhayi. Using logistic regression models, this study predicted immediate discard mortality was positively correlated with increased depths, seasons associated with warmer water temperatures, and external evidence of barotrauma. Additionally, bottom longline gear increased the predicted probability of immediate mortality compared to vertical line gear for all species except vermilion snapper. Air bladder venting significantly decreased the predicted probability of immediate mortality for all species except speckled hind. Future research incorporating tag-recapture data into the current observer program for the commercial reef fish fishery is vital to assess if condition assessment at release can be relied on as an accurate proxy for long-term survival. This research provides information that managers could potentially use to make more informed decisions when implementing measures such as changes to existing size limits, venting requirements, and seasonal, area, or gear restrictions intended to reduce unwanted discard mortality.

Mapping the Soundscape Off the Southeastern USA by Using Passive Acoustic Glider Technology

AbstractThe purpose of this study was to explore the soundscape of shelf‐edge Atlantic waters of the southeastern USA (SEUS) during winter by using passive acoustic and autonomous glider technologies, with a focus on the distribution of groupers. An autonomous glider was deployed off the SEUS coast near Cape Canaveral, Florida, on March 3, 2014, and transited to Cape Fear, North Carolina, where it was retrieved on April 1, 2014. Using satellite and hydrodynamic model data for guidance, the glider piloted in and out of the Gulf Stream, taking advantage of the high currents to reach the targeted sampling area. Ambient noise was recorded by an integrated passive acoustic recorder during the 29‐d mission, in which the glider traveled 895 km and reached waters 267 m deep. A variety of sounds was identified in the acoustic recordings, including sounds generated by Red Grouper Epinephelus morio and toadfishes Opsanus sp.; two sounds previously documented in the Gulf of Mexico that were suspected to be produced by fish; whistles and echolocation from marine mammals; and extensive vessel noise. Numerous sounds from previously undocumented sources were also recorded. The Red Grouper was the only serranid that was consistently identified from the sound data, with detections occurring within and outside of South Atlantic Fishery Management Council marine protected areas. This research demonstrates the potential utility of a glider‐based passive acoustic approach as a component of a program to map fish, marine mammal, and vessel distributions over large scales.

Redescription of Philometra margolisi Moravec, Vidal-Martínez et Aguirre-Macedo, 1995 (Nematoda: Philometridae), a gonad-infecting parasite of the red grouper Epinephelus morio (Serranidae) in the Gulf of Mexico.

The insufficiently known nematode species Philometra margolisi Moravec, Vidal-Martínez et Aguirre-Macedo, 1995 (Philometridae) is redescribed based on light and scanning electron microscopical (SEM) examinations of specimens collected from the gonad of the type host, the red grouper Epinephelus morio (Valenciennes) (Serranidae, Perciformes), in the northern Gulf of Mexico off Florida, USA. Also, new prevalence data for females of P. margolisi were derived from 188 fish, and a subset of these (n = 38) were used to determine prevalence and intensity of male nematodes. The male of this species was studied with SEM for the first time, which revealed some new, taxonomically important morphological features. The male posterior end had a V-shaped caudal mound, four pairs of minute adanal papillae, a pair of large papillae located posterior to the cloacal aperture and a pair of very small phasmids. The distal end of the gubernaculum is unique among all gonad-infecting species of Philometra parasitizing serranids in that its ventral surface is flat, smooth, without the usual two longitudinal grooves; the dorsal lamellate structures on the gubernaculum are also different in this species. In contrast to data in the original species description, the body length of gravid females of P. margolisi was 132-280 mm. Overall prevalence for male nematodes (76.3%) was much higher than for females (15.4%), and female nematode prevalence was higher in samples collected during host spawing season than out of season (27.1% and 3.3%, respectively).

Native grouper indirectly ameliorates the negative effects of invasive lionfish

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 558:267-279 (2016) - DOI: https://doi.org/10.3354/meps11808 Native grouper indirectly ameliorates the negative effects of invasive lionfish Robert D. Ellis1,3,*, Meaghan E. Faletti2 1Florida State University, Department of Biological Science, Tallahassee, Florida 32306, USA 2Florida Fish and Wildlife Conservation Commission, Division of Marine Fisheries Management, 2950 Executive Center Circle East, Tallahassee, Florida 32301, USA 3Present address: Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research Institute, 100 8th Ave. SE, St. Petersburg, Florida 33701, USA *Corresponding author: robert.ellis@myfwc.com ABSTRACT: Non-trophic interactions between Indo-Pacific lionfish Pterois volitans and P. miles and Atlantic and Caribbean reef fishes are not yet well understood. To determine the effects of potential competitive and behavioral interactions between native predators and invasive lionfish, we experimentally altered the presence of lionfish and red grouper Epinephelus morio in karst solution holes in Florida Bay, USA, and then tracked subsequent changes in the juvenile reef fish and motile macroinvertebrate communities for 6 wk. Relative to solution holes where we excluded both predators, mean juvenile reef fish abundance declined 83.7% in solution holes with a lionfish but increased by 154% in solution holes with a red grouper. There was no difference in juvenile reef fish abundance in solution holes with both lionfish and red grouper compared to holes where we excluded both predators. The composition of lionfish stomach contents shifted from mostly teleost fishes when lionfish were present in solution holes alone, to mostly crustaceans when in the presence of a red grouper. Concurrently, the abundance of 2 species of cleaner shrimp (Ancylomenes pedersoni and Periclimenes yucatanicus) decreased by 14.7% when lionfish were present but increased by 56.2% at holes where lionfish were excluded. We suggest that these results are due to altered lionfish predatory behavior in the presence of red grouper and highlight the importance of maintaining intact native predator communities for ameliorating the negative effects of the lionfish invasion. KEY WORDS: Lionfish · Red grouper · Interspecific interactions · Community ecology · Reef fish · Invasive species · Ecological impacts Full text in pdf format Supplementary material PreviousCite this article as: Ellis RD, Faletti ME (2016) Native grouper indirectly ameliorates the negative effects of invasive lionfish. Mar Ecol Prog Ser 558:267-279. https://doi.org/10.3354/meps11808 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 558. Online publication date: October 25, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Cross‐Shelf Habitat Occupancy Probabilities for Juvenile Groupers in the Florida Keys Coral Reef Ecosystem

AbstractIn the Florida Keys coral reef ecosystem, delineation of reef fish distributions in relationship to habitat patterns is important for improving the design characteristics of fishery‐independent surveys. Efficient survey design depends on analysis of fish distribution patterns to inform and improve the precision of future surveys. We used a diver visual survey to quantify occupancy patterns of preexploitation‐size Black GrouperMycteroperca bonaciand Red GrouperEpinephelus morio. The survey was based on a stratified random sampling design with strata reflecting cross‐shelf coral reef habitat types. A multiple spatial scale modeling approach confirmed a cross‐shelf occurrence gradient for Red Grouper, with higher nearer‐to‐shore occupancy probability and lower offshore occupancy probability. Black Grouper occurrence followed a latitudinal gradient, with higher occurrence probabilities in the lower Florida Keys than in the upper Keys. Local habitat characteristics measured within reef strata suggested that occupancy relationships for both species varied according to vertical relief. Our analysis also included multilevel slope coefficients (random effects), which revealed unforeseen variance structure in Black Grouper occurrence probability among cross‐shelf reef strata. Our study improves on previous qualitative observations of juvenile grouper distributions in the Florida Keys and highlights the use of multilevel models in revealing variance structures of fish distributions not revealed by fixed‐effects models. Our analysis contributes to a discussion about foraging characteristics in producing the observed distributional patterns, and we suggest that examining the links between the distributions of forage fishes and larger predators (i.e., groupers) would be a useful step in improving survey stratification schemes.Received February 23, 2015; accepted July 2, 2015

Influence of Circle Hook Size on Catch Rate and Size of Red Grouper in Shallow Waters of the Southern Gulf of Mexico

AbstractHigh rates of undersized catch and discard mortality are common in fisheries for Red Grouper Epinephelus morio in the Gulf of Mexico and Atlantic Ocean. Reducing undersized catch rate in these fisheries requires more effective regulation of the minimum size limit (MSL). One potential method is to regulate hook selectivity for target species. Three circle hook sizes (11/0, 12/0, and 13/0) were tested to assess the effect of hook size on Red Grouper catch rate and size in the shallow waters of the Yucatan Peninsula coast, which is the primary fishing zone for the region's small‐scale grouper (family Epinephelidae) fishery. Red Grouper was always the numerically dominant species in catches (76–81%) for all hook sizes. Hook size did not affect mean catch rate. Significantly longer fish were caught in the 13/0 hook size treatment than in the 11/0 and 12/0 treatments, which did not differ. Nonetheless, when considering the MSL regulation applicable in Mexico's Red Grouper fishery (36.3 cm TL), high percentages of undersized Red Grouper were still caught, regardless of hook size. The hook sizes required in the Yucatan small‐scale fishery (10/0–12/0) provide little if any improvement in Red Grouper MSL regulation. Real improvement would require the effective release of undersized fish as well as a reduction in the number of undersized specimens caught and in potential cryptic sources of fish release mortality (e.g., barometric trauma). Furthermore, the current applicable Red Grouper MSL only really attempts to control growth overfishing and ignores recruitment overfishing.Received December 22, 2014; accepted September 3, 2015

Effects of preservation methods of muscle tissue from upper-trophic level reef fishes on stable isotope values (δ (13)C and δ (15)N).

Research that uses stable isotope analysis often involves a delay between sample collection in the field and laboratory processing, therefore requiring preservation to prevent or reduce tissue degradation and associated isotopic compositions. Although there is a growing literature describing the effects of various preservation techniques, the results are often contextual, unpredictable and vary among taxa, suggesting the need to treat each species individually. We conducted a controlled experiment to test the effects of four preservation methods of muscle tissue from four species of upper trophic-level reef fish collected from the eastern Gulf of Mexico (Red Grouper Epinephelus morio, Gag Mycteroperca microlepis, Scamp Mycteroperca phenax, and Red Snapper Lutjanus campechanus). We used a paired design to measure the effects on isotopic values for carbon and nitrogen after storage using ice, 95% ethanol, and sodium chloride (table salt), against that in a liquid nitrogen control. Mean offsets for both δ13C and δ15N values from controls were lowest for samples preserved on ice, intermediate for those preserved with salt, and highest with ethanol. Within species, both salt and ethanol significantly enriched the δ15N values in nearly all comparisons. Ethanol also had strong effects on the δ13C values in all three groupers. Conversely, for samples preserved on ice, we did not detect a significant offset in either isotopic ratio for any of the focal species. Previous studies have addressed preservation-induced offsets in isotope values using a mass balance correction that accounts for changes in the isotope value to that in the C/N ratio. We tested the application of standard mass balance corrections for isotope values that were significantly affected by the preservation methods and found generally poor agreement between corrected and control values. The poor performance by the correction may have been due to preferential loss of lighter isotopes and corresponding low levels of mass loss with a substantial change in the isotope value of the sample. Regardless of mechanism, it was evident that accounting for offsets caused by different preservation methods was not possible using the standard correction. Caution is warranted when interpreting the results from specimens stored in either ethanol or salt, especially when using those from multiple preservation techniques. We suggest the use of ice as the preferred preservation technique for muscle tissue when conducting stable isotope analysis as it is widely available, inexpensive, easy to transport and did not impart a significant offset in measured isotopic values. Our results provide additional evidence that preservation effects on stable isotope analysis can be highly contextual, thus requiring their effects to be measured and understood for each species and isotopic ratio of interest before addressing research questions.