Red Snapper Lutjanus Campechanus Research Articles

Diel spawning periodicity of red snapper Lutjanus campechanus in the northern Gulf of Mexico

Ovaries of red snapper Lutjanus campechanus were examined histologically to determine rates of oocyte maturation, diel spawning periodicity and whether lunar cycle influenced spawning rhythm. Hydration of red snapper oocytes began during the mid‐morning hours; c. 5 h was necessary for oocytes to become fully hydrated and ovulation occurred no more than 5 h after oocytes attained full hydration. Appearance of fresh postovulatory follicles after 1330 hours and the absence of hydrated oocytes after 1830 hours signified that red snapper spawning occurred during this 5 h period. In addition, evidence of a peak in spawning was seen near 1600 hours. Postovulatory follicles degenerated within a 24 h time period. A lunar spawning cycle was not evident.

Characterization of an Experimental Indoor Larval Production System for Red Snapper

AbstractOver the past several years, we have developed an experimental‐scale rearing system for larval red snapper Lutjanus campechanus that combines extensive outdoor production of live‐feed zooplankton with intensive larval fish rearing. The salient features of the system are (1) use of size‐graded copepods as live feed; (2) culture in clear water; (3) three‐phase water management consisting of an initial static water phase followed by a volume‐doubling phase in which water is gradually added and, finally, a recirculation‐biofiltration phase; (4) a lowered salinity of 25 g/L water; and (5) an indoor location at constant temperature under artificial light. A total of 19,835 juvenile red snapper were produced from 12 larval rearing tanks in three separate batches with an overall survival of 16.5%. Survival varied from 1% to 31% in individual larval rearing tanks. Water quality variables (oxygen, temperature, salinity, total and un‐ionized ammonia, nitrite, nitrate, pH, and alkalinity) were not significantly correlated with larval fish survival. A mean number of 5.36 copepods/mL was added daily to larval tanks during the culture period, with a range of 0.57–23.48 copepods/mL. There was no correlation between mean feed rates and survival in individual tanks. The mean residual copepods per milliliter averaged 2.24, with a range of from 0 to 15.86. There was a significant negative correlation between residual copepod density and survival.

Physiological Effects of Swim Bladder Overexpansion and Catastrophic Decompression on Red Snapper

AbstractThe commercial and recreational harvests of red snapper Lutjanus campechanus in the Gulf of Mexico have declined over the past five decades, prompting strict regulations. Release mortality associated with catastrophic decompression (CD) is a possible cause for the continuing decline, although to date no physiological data exist to support this assumption. Using a flow‐through high‐pressure chamber, subadult red snapper were acclimated to 101.2, 405.3, 608.0, and 1,215.9 kPa, simulating depths typical of their distribution (as deep as 200 m), and then decompressed at a rate of 10.1 kPa/s. Lateral and dorsal X‐ray imaging in combination with necropsy showed that swim bladders expanded in a predictable manner. Ventral expansion into the caudal body cavity space occurred at lower pressures, whereas expansion into the cranial portion of the body cavity occurred at the highest pressure. Expansion patterns resulted in over 70 different overexpansion injuries, the most severe being to vital organs. Our results suggest a specific suite of clearly identifiable injuries associated with CD that increase in number and severity as retrieval depth increases. A more thorough understanding of catastrophic decompression syndrome will provide insight into the declining fishery and aid in developing effective physiology‐based management strategies.

Long-Term Residence of Red Snapper on Artificial Reefs in the Northeastern Gulf of Mexico

Red snapper Lutjanus campechanus (N = 54) were tagged and tracked on 12 artificial reefs in the northeastern Gulf of Mexico. Fish were surgically implanted with ultrasonic transmitters and monitored with Vemco remote receivers and Sonotronics surface receivers from August 2000 to 2004. Four fish were manually tracked from the surface overnight, and their positions were recorded every hour for either 9 or 16 h. The total length of fish tagged was 589 ± 14 mm (mean ± SE). The number of detections by the remote receivers was 290,340 ± 44,696. By the end of this study, 5 fish were still being tracked, 8 fish had been lost immediately after tagging, 15 fish had been caught by fishers, and 26 fish had been lost after extended tracking. Red snapper were resident on artificial reefs for 218 ± 28 d, and residence time ranged from 1 to 595 d. We estimated that most (67%) of the tagged red snapper showed long-term residence (117–595 d), 13% were resident for 8–91 d, and 20% left the tagging site soon after release (<4 d). Fish were resident on the same artificial reef over all seasons (winter, spring, summer, and fall), and no seasonal changes in proximity to the reef were detected. Red snapper left the receiver range (1.6 km) for short time periods; for example, fish 25 left the reef 285 times for 1–4 h over a 335-d period. However, all fish spent most of their time (98%) within the receiver range. We detected diel changes in proximity to the reefs (N = 8), but patterns varied. In this study, red snapper showed high site fidelity over long time periods, which suggested that artificial reefs provided suitable habitat for red snapper in the northeastern Gulf of Mexico.

Increasing Production of Copepod Nauplii in a Brown-Water Zooplankton Culture with Supplemental Feeding and Increased Harvest Levels

Abstract Two experiments were performed to investigate increasing the number of copepod nauplii obtained from a brown-water zooplankton culture for feeding to larval red snapper Lutjanus campechanus. Brown-water zooplankton cultures rely on the regular exchange of (brown) estuarine water to nourish and harvest the copepods. The majority of copepods in both experiments were Acartia tonsa. The goal of the first experiment was to determine whether adding rice bran to a brown-water zooplankton culture would increase copepod density. Brown-water zooplankton cultures supplemented with rice bran had significantly higher naupliar densities than either brown-water zooplankton cultures without rice bran or zooplankton cultures supplemented with rice bran but without brown-water exchanges. Both the rice-bran-supplemented brown-water zooplankton culture and the rice bran zooplankton culture had higher copepodid densities than the brown-water zooplankton culture, but they were not different from each other. The goal o...

Cryopreservation of sperm of red snapper ( Lutjanus campechanus)

Interest in the culture of snappers (family Lutjanidae) has developed throughout the world because of declines in wild stocks combined with a consistent high demand and market value. Some snappers, such as the red snapper Lutjanus campechanus have proven to be difficult to spawn and culture in captivity. As part of a larger study to improve propagation techniques for red snapper, procedures were developed for the collection, handling, and commercial-scale cryopreservation of sperm. Utilization of cryopreserved sperm in spawning of red snapper allows efforts to be focused on maintaining female broodstock, monitoring ovarian development, and increasing efficiency during the strip-spawning process. Red snapper were collected during the 2000 and 2001 spawning seasons (May to August) off coastal Louisiana by hook and line. Testes were surgically removed and sliced to release sperm. Sperm were collected in 50-ml centrifuge tubes and diluted 1:3 (v:v) with calcium-free Hanks' balanced salt solution. Dimethyl acetamide, dimethyl sulfoxide, methanol, and glycerol were evaluated as cryoprotectants. Dimethyl sulfoxide produced the smallest reduction in motility of sperm cells in acute toxicity trials and produced the highest motilities after thawing (71±16%) in initial cryopreservation trials. During the 2-year study, sperm samples from 20 red snapper were frozen using commercial-scale cryopreservation methods developed for dairy bulls. Although sperm motility after thawing was typically greater than 80%, comparison with fresh samples revealed a significant difference in motility ( P=0.048). Refrigerated and cryopreserved sperm samples with motilities above 80% were used in fertilization trials. Fertilization rates were variable among females (11–85%), although results with refrigerated (non-frozen) and cryopreserved sperm were highly correlated ( r=0.85). These results demonstrate that refrigerated and cryopreserved sperm were each effective for the artificial fertilization of red snapper eggs.

Effect of Hypoxia on the Distribution of Fishes Associated with a Petroleum Platform off Coastal Louisiana

AbstractA combination of hydroacoustics and visual survey techniques were used to estimate the abundance, size distribution, and species composition of fishes at a petroleum platform in the northern Gulf of Mexico. The effect of dissolved oxygen (DO) concentration on the density and distribution of fishes at this de facto artificial reef was examined. The techniques used permitted surveys of the entire water column, providing a more accurate reflection of the effect of a highly variable phenomenon (i.e., hypoxia) that may not be measured with traditional fisheries sampling equipment. Hypoxic conditions were observed during two of the five trips to the petroleum platform, South Timbalier 54. When hypoxia was present, fish density was dramatically higher in the strata immediately above the hypoxia. It was difficult to determine the exact impact of hypoxia on target strength (a measure of fish size), as the larger mean target strengths observed in the spring and summer may be due to seasonal factors and not to hypoxia alone. With the exception of the fall 1995 survey (which had significantly higher density and abundance estimates than other surveys), the estimated number of fishes did not vary among any of the sample periods. Even when 32% (15–22 m) of the water column was hypoxic (summer 1996), abundance estimates were slightly higher than in other survey periods without hypoxia (except fall 1995). While hypoxia reduced the availability of the water column to fishes, they concentrated where favorable DO levels were found. This included demersal species such as red snapper Lutjanus campechanus, which were found higher in the water column than expected.

Development, growth, and yolk utilization of hatchery-reared red snapper Lutjanus campechanus larvae

The development of yolk-sac larvae of red snapper Lutjanus campechanus from endogenous utilization of nutrient sources to the development of feeding ability is described, with the aim of better understanding the high mortalities observed at first-feeding. Larvae from several spawns were reared at a salinity of 31 and a temperature of 28°C. Yolk utilization rate, changes in body parameters and the development of morphological characters were observed. Maximum stan- dard length (LS) and body depth were observed concurrently with yolk-sac exhaustion at 56 h post- fertilization (hpf). A decrease in LS, body width and body depth was observed following yolk-sac exhaustion. Orbit pigmentation, followed by jaw articulation, were observed at 65 hpf. Substantial cranial and body cavity development occurred in the absence of visible yolk material. Complete absence of visible yolk-sac material and less than 2% of the oil globule volume at hatching were observed at the time of development of feeding ability. This indicates an absence of a transitional feeding period and the critical nature of first-feeding in this species within controlled environments.

Genetic Variation and Relatedness of Juvenile Red Snapper Sampled from Shrimp Trawls in the Northern Gulf of Mexico

AbstractWe studied genetic variation and genetic relatedness among young‐of‐the‐year (age‐0) Gulf of Mexico red snapper Lutjanus campechanus sampled as bycatch in two separate shrimp trawl tows offshore of Galveston, Texas, and in a reference (control) group composed of multiple samples from within the same geographic area. Allelic and haplotypic variation was assayed at 11 microsatellite loci and mitochondrial DNA, respectively. Samples taken as bycatch from shrimp trawls did not differ from the reference group in allele richness, gene diversity, or allele frequency, indicating that most of the genetic variability within the cohort studied was attributable to fish sampled during single, localized tows of the shrimp trawler. Estimates of the variance of pairwise relatedness in the reference sample and in one of the bycatch samples were zero, whereas in the other bycatch sample the variance estimate was 0.001 (P = 0.1). A positive variance suggests that this sample contained individuals that were more closely related genetically than would be expected by chance alone. Because the relatedness estimators are sensitive to sample size, the number of loci, and allele distributions, further studies employing larger sample sizes and additional loci are warranted.

Diel Feeding Patterns of Red Snapper on Artificial Reefs in the North‐Central Gulf of Mexico

AbstractDiets of red snapper Lutjanus campechanus were compared among four diel feeding periods (dawn, day, dusk, and night) and among three standard length size‐classes: small (200–299 mm), medium (300–399 mm), and large (400–499 mm). Fish were collected from August through October 2000 in the north‐central Gulf of Mexico. A total of 432 stomachs were examined, of which 164 (37%) contained prey. Size‐class influenced diets; diets of small red snapper were dominated by fish, those of medium red snapper by fish and tunicates, and those of large red snapper by crabs and fish. Red snapper fed on prey from several different habitats. Small red snapper fed mostly on reef and sand prey types; medium red snapper fed on similar portions of reef, sand, and mixed prey types; and large red snapper fed on mixed prey types. Adjusting for fish size, mean gut fullness was significantly lower for the dusk than for the day period. Fish were the most important prey for all periods. The second most important prey group changed with period: stomatopods for dawn, tunicates for day, and crabs for dusk and night periods. Prey habitat type also varied over periods. Sand prey type dominated dawn and dusk periods, whereas reef prey type dominated day and night periods. We used multidimensional scaling analysis to compare the relative influence of diel period to size‐class on red snapper diets. This analysis suggested that fish size‐class had a greater influence on red snapper diet than did period. However, with size effects removed, red snapper still showed significant diet shifts with periods.

Use of bomb radiocarbon to validate otolith section ages of red snapper Lutjanus campechanus from the northern Gulf of Mexico

The red snapper Lutjanus campechanus is an important recreational and commercial fish species in the northern Gulf of Mexico. Management approaches have varied in part because of uncertainty of their longevity. Snapper ages have been based on presumed otolith annuli; however, this methodology has not been validated for all age classes. A recent technique to validate otolith age utilizes the increase in oceanic 14C resulting from atmospheric testing of nuclear bombs during the 1950s and 1960s. Analyses of annuli from living corals and fish otoliths from 1900 to the present have documented that elevated 14C input has occurred throughout the world's oceans. We validated otolith section age estimates through accelerator mass spectrometry analysis of bomb‐produced 14C in red snapper (otoliths) hatched before, during, and after the nuclear testing periods. Delta 14C data from the otoliths of red snapper with presumed birth dates between 1960 and 1973 clearly reflect the sharp increase in oceanic radiocarbon attributable to previous nuclear testing. Similarities between the otolith and nearby coral △14C chronologies suggest that annulus‐based age estimates of red snapper are valid on average to within 1–3 yr. In addition, this study provides the first carbonate bomb radiocarbon time series from the northern Gulf of Mexico.

Movement of Tagged Red Snapper in the Northern Gulf of Mexico

Abstract A tagging study of adult red snapper Lutjanus campechanus was conducted in an area of artificial reefs in the northcentral Gulf of Mexico during March 1995 through August 1999. A total of 2,932 red snapper angled at nine artificial reef tagging sites were measured and tagged with internal anchor tags. Tagged fish were either released over their site of capture or transported to another tagging site for release. Of the 561 recaptures made of 519 fish (42 multiple recaptures), 235 recaptures were made at tagging sites on subsequent tagging trips and 326 recoveries were reported by recreational and commercial fishers. Mean distance moved was 29.6 km; the farthest distance moved was 352 km. Mean time at liberty was 404 d; the longest time at liberty was 1,501 d. During the study, two strong hurricanes passed near the study area. The occurrence of hurricanes significantly affected the probability of red snapper movement, as did time at liberty, total length of fish tagged, and transportation of fish t...

Experimental Evaluation of Potential Effects of Habitat Size and Presence of Conspecifics on Habitat Association by Young-of-the-Year Red Snapper

The potential effects of habitat size and the presence of larger conspecifics on habitat association by young-of-the-year (YOY) red snapper Lutjanus campechanus was evaluated in 2.2 m3 laboratory tanks. Our results indicate that YOY red snapper have a strong affinity for structure, which ranged in these experiments from open-sand bottom to concrete-block, artificial reef-like habitats. Mean distance of YOY red snapper from the blocks decreased significantly and the time spent near the structures increased significantly as the size of the habitat increased. However, when larger subadult snapper were present, both distances to the reefs and time that YOY spent near them was significantly reduced, as the larger conspecifics actively defended the structure from occupation by YOY. If similar interactions occur in situ, small snapper that attempt to move onto reefs from the shrimping grounds that serve as nursery areas for juveniles may be subject to predation pressures by piscivorous fishes inhabiting the reefs. Finally, in experiments that used both larger conspecifics and alternate prey similar in size to the YOY red snapper, results indicated that larger snapper preferentially consumed the alternate prey and did not cannibalize the YOY red snapper. Nevertheless, YOY still were not permitted to occupy the artificial reef habitats in any experiments when larger conspecifics were present in the tanks. If results of these experiments are exportable to the field, they may partially explain the observation that YOY red snapper in natural populations are more often found in shallower water on shrimping grounds, whereas larger juveniles begin to recruit to the offshore reefs once they have obtained a size refuge. If additional studies conclude that YOY red snapper are attracted to larger or more complex habitats but avoid these structures because of pressure from larger juveniles and/or adults, the strategy of continued placement of artificial reefs large enough to attract adult snapper and other piscivores in and near the inshore shrimping grounds should be reassessed.

A Bioeconomic Assessment of Gulf of Mexico Red Snapper Management Policies

Abstract The stocks of red snapper Lutjanus campechanus in the Gulf of Mexico have experienced a serious decline owing to (1) the overharvesting of adults by the commercial and recreational fisheries and (2) the incidental harvesting and discarding of juveniles by the shrimp fishery. In an effort to rebuild these stocks, since 1984 a series of policies has been implemented by the National Marine Fisheries Service and the Gulf of Mexico Fishery Management Council. To date, however, the results of these policies have not been completely addressed. This study comprehensively assesses their biological and economic consequences using integrated biological and economic models of the red snapper and shrimp fisheries. The analysis indicates that a combined-policy approach (implementing a joint policy for the red snapper and shrimp fisheries) is preferable to an individual-policy approach.

DNA Microsatellite Loci and Genetic Structure of Red Snapper in the Gulf of Mexico

Abstract Five polymorphic microsatellite loci were developed from genomic DNA of red snapper Lutjanus campechanus and used to evaluate genetic variation among 194 red snapper sampled from three locations in the northern Gulf of Mexico and one location off the northern Yucatan Peninsula in Mexico. From 5 to 13 alleles were observed per locus, and expected heterozygosities ranged from 0.143 to 0.779. No significant departures from expectations of Hardy–Weinberg equilibrium were found at any locus either within samples or when samples were pooled across localities. Locus-by-locus tests of allele-frequency homogeneity over the four localities were nonsignificant. Weir and Cockerham's θ at each locus ranged from −0.003 to 0.012, and Statkin's R ST at each locus ranged from −0.014 to 0.008. None of the estimates of θ and R ST differed significantly from zero, and magnitudes of θ and R ST did not appear to vary with geographic distance between localities. These results are consistent with the hypothesis that red...

Delineation of Essential Habitat for Juvenile Red Snapper in the Northwestern Gulf of Mexico

Seasonal habitat suitability index models were developed for juvenile red snapper Lutjanus campechanus in the western Gulf of Mexico. Habitat factors considered in the analysis included water temperature, salinity, and dissolved oxygen at the bottom; depth and density of offshore petroleum platforms; and low-relief bottom structures. High-value habitat for juvenile red snapper is characterized by depths between 18 and 64 m, water temperatures of 24–26°C, salinities around 35%, and dissolved oxygen levels of at least 5 mg/L. Density of low-relief structures was not a significant habitat element, and an inverse association was found between juvenile red snapper abundance and the density of offshore platforms. Results of the model analysis suggest that the step-like expansion of the hypoxic area (dissolved oxygen ≤ 2 mg/L) offshore of the mouth of the Mississippi River and west to the Louisiana–Texas border, which first occurred in 1993, has reduced habitat carrying capacity for juvenile red snapper in this region by up to 25%, averaging 19%. This environmental change may limit the level to which overfished Gulf red snapper stocks can be rebuilt to historical levels.

Reduction of Juvenile Red Snapper Bycatch in the U.S. Gulf of Mexico Shrimp Trawl Fishery

Bycatch reduction devices (BRDs) have been mandated for use in the U.S. Gulf of Mexico shrimp fishery to reduce shrimp trawl mortality of juvenile red snapper Lutjanus campechanus. Conditional survival of juvenile red snapper from shrimp trawl bycatch has been estimated to be on the order of 12%. The BRDs have been estimated to reduce shrimp trawl bycatch mortality by more than the 50% reduction that has been estimated as necessary to rebuild the stock by the target date of 2019. Results from analyses in this study that used observer data collected during 1992–1996 do not support this contention. A low fraction of the annual bycatch occurs during times of the year when BRDs effectively exclude juvenile red snapper at the sizes encountered. Maximum potential exclusion of juvenile red snapper with the use of BRDs is only about 25–27%, not 59% as has been previously estimated. If rebuilding requires a 50% reduction in age-0 and age-1 red snapper bycatch mortality to achieve the stock recovery targets, this study's results clearly demonstrate that the BRD by itself will not produce the mortality reductions necessary to meet this objective.

Comparison of growth rate and formation of otolith increments in age-0 red snapper

For wild red snapper Lutjanus campechanus, mean otolith increment deposition rate after marking with oxytetracycline dihydrate (OTC) was daily (0.97 increments day−1) when growth rates were fast (0.63 mm fork length, LF day−1), but were not daily (0.82 increments day−1) when somatic growth was slow (0.2 mm LF day−1). For reared larvae (n=8), increment deposition rates were daily (0.99–1.03 increments day−1), and growth rates ranged from 0.6 to 0.9 mm LF day−1. Growth rate affected increment deposition rate as a threshold function, i.e. when growth rate was <0.3 mm LF day−1, deposition was less than daily, but above this level increment deposition did not exceed a daily rate. As growth rates increased increment widths increased. Examination of a sub-sample (n=8) of the otoliths from the slowest growing wild fish by scanning electron microscopy did not increase increment counts. Because L. campechanus are late spring-early summer spawners, young fish can expect maximum growth due to warm summer temperatures. Thus, daily ageing methods should be well suited to this species.

Population Structure of Red Snapper from the Gulf of Mexico as Inferred from Analysis of Mitochondrial DNA

Abstract Variation in mitochondrial DNA (mtDNA) was examined among 707 red snapper Lutjanus campechanus representing 16 samples taken during 3 years from localities in the northern and western Gulf of Mexico. Ninety-two composite mtDNA haplotypes were revealed by 13 restriction enzymes (representing 93 inferred restriction sites). Significant heterogeneity (P = 0.042) in mtDNA haplotype frequencies was detected among the 16 samples; however, homogeneity tests of mtDNA haplotype frequencies between or among samples taken in different years at the same locality and among samples at different localities within the same year, were not significant. No phylogeographic structure of haplotypes was evident, nor were rare haplotypes clustered geographically. Spatial autocorrelations did not differ significantly from those expected when no correlation exists. These findings are consistent with the hypothesis that a single breeding population of red snapper inhabits the northern Gulf of Mexico. Intrapopulational mtDN...

Variability of Fishing Mortality by Age: Consequences for Maximum Sustainable Yield

Abstract The influence of variation in age-specific vulnerability to fishing on maximum sustainable yield (MSY) in numbers and weight was evaluated with simulation techniques that incorporated biological characteristics of red snapper Lutjanus campechanus and an arbitrary stock–recruitment relation. I evaluated MSY for 10 arbitrary selectivity ogives that systematically varied from greater vulnerability to fishing mortality among the oldest ages to greater vulnerability among the youngest ages. The values of MSY in numbers and weight varied by factors of 2.6 and 4.5, respectively, for the range of selectivity schedules examined. Because selectivity schedules often are not constant through time, values estimated from catch data should be viewed with caution when they are applied in current management settings. Further, setting MSY as a management objective will often be insufficient for developing management advice unless the desired longterm age composition of the catch or some other qualifying factor is ...