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White spot syndrome virus (WSSV) is a virulent disease that disrupts shrimp farm operations throughout the world. While the United States has had only limited outbreaks of WSSV within the past several decades, it is important to ensure that this disease does not infect wild penaeid shrimp populations. In Texas, there is a potential for WSSV to spread to wild penaeid populations in the Gulf of Mexico via infected imported nonnative bait shrimp, imported broodstock, or wild crustacean hosts. Due to these potential threats, the Texas Parks and Wildlife Coastal Fisheries Division monitored WSSV in wild brown shrimp Farfantepenaeus aztecus and white shrimp Litopenaeus setiferus from seven major bay systems along the Texas coast during 2019. While no positive samples were detected from the collected shrimp, a power analysis illustrated a potential for low-level WSSV prevalence within Texas shrimp populations that would not be detectable by this monitoring survey. Overall, WSSV does not appear to be a major threat in the Texas region of the Gulf of Mexico, but continual observation and monitoring of wild penaeid shrimp is necessary to protect this resource from future WSSV outbreaks.

A series of experiments were conducted to examine the effects of salinity (1‐48g/L) on the biological performance, as evaluated by growth and survival, of the Pacific white shrimp, Litopenaeus vannamei, and the Atlantic white shrimp, Litopenaeus setiferus, reared at temperatures of 20, 24 or 28C. Poor growth and survival of L. vannamei was observed after 21‐28d of culture at low salinity (2 and 4g/L) at 20C. Raising salinity to 8 and up to 32g/L significantly increased survival at this temperature, indicating that avoiding low temperatures is critical for survival of this species when reared at low salinity. A major improvement in the growth rate of L. vannamei was observed at 24C, but it still was sub-optimal compared to growth observed at 28C. Irrespective of salinity, high survival rates were observed at both 24 and 28C, but variable growth rates were recorded. Contrary to L. vannamei, the Atlantic white shrimp, L. setiferus, which was reared for 28d at 24C only, had better growth performance at 8g/L compared to 2, 16 and 32g/L. Under equal experimental conditions, L. setiferus had considerably lower weight gain and survival than L. vannamei.

The value of wetlands is reflected in the relative abundance and production of nekton, but these population variables have been difficult to estimate because of sampling problems, landscape complexity, tidal dynamics, and limited information on growth and mortality. We combined a landscape analysis of land-water patterns in regularly flooded wetlands of lower Galveston Bay, Texas, with data on small-scale (1-50-m) distribution patterns of nekton over the marsh surface to estimate population abundances of juvenile brown shrimp Farfantepenaeus aztecus, white shrimp Litopenaeus setiferus, and blue crab Callinectes sapidus. Using information on size frequencies, size-weight relationships, and growth rates, we estimated the wet biomass and production of these species from salt marshes and open-water habitats. In 17,673 ha of marsh complex (vegetation with a 150-m water buffer) in lower Galveston Bay, we estimated the standing crops (number/ha) at 19,382 for brown shrimp, 17,406 for white shrimp, and 1...

An increasing boating population has led to extensive propeller scarring in many shallow seagrass meadows, and research has focused on relating scarring to nekton abundance; however, little information exists on the impacts on habitat functionality. In this study we moved beyond simple measures of faunal density as an indicator of habitat quality by comparing the growth rates of common estuarine nekton in different levels of propeller scarring in Redfish Bay, Texas. Growth rates of selected fauna were examined by using field enclosures and otolith microstructure analysis. Otolith microstructure analysis on pinfish Lagodon rhomboides indicated no difference in growth rates at various scarring intensities. We conducted field growth enclosure experiments on a common decapod crustacean, the white shrimp Litopenaeus setiferus. White shrimp showed significantly lower growth in highly scarred areas than in reference sites. These results suggest that regions of low-level propeller scarring (less than 15%...

We examined conditions under which white shrimp (Litopenaeus setiferus) post-larvae enter an estuarine channel receiving high freshwater discharge and one receiving negligible discharge in the Ossabaw Sound system of Georgia, USA, during 1997 and 1998. We used surface nets to collect plankton over several 14-day periods, during which consecutive tows were made at night against the flooding current at stations in the inlet channels. During these sampling periods, additional intensive periods of around-the-clock surface and near-bottom (using a bottom sled) plankton tows were made. Data on oceanographic conditions were obtained from moored instrument arrays and shipboard sampling. We identified three key factors that influenced the densities of post-larval white shrimp in time and space within the Ossabaw inlet system. The first factor was a critical minimum temperature of coastal waters of 27–28°C. Once the threshold temperature was reached, lunar tidal stage became a key factor when the full duration of the flood tide coincided with darkness during peak ingress. This peak also coincided with an increase in water level within the system by more than 0.2 m, which induced an additional influx of water that reinforces the flood current over the ingress period. Our results suggest that the direction of subtidal currents (into or out of the system) becomes a significant factor in post-larval ingress when influx of water coincides with the time of favorable temperature conditions and nighttime flood tides.

Observations of ciliates using the Chatton–Lwoff wet silver method, Wilbert's protargol impregnation method, and silver carbonated method revealed the infraciliature and nuclear apparatus of species collected from the blue crab (Callinectes sapidus) and brown shrimp (Farfantepenaeus aztecus) from Mississippi, white shrimp (Litopenaeus setiferus) from South Carolina, northern shrimp (Pandalus borealis) from Maine, and water associated with each. Specimens were measured and photographed under an Evolution MP 5.0 RTV digital camera system. More than 26 ciliate species, belonging to 21 families in 11 orders, were observed. Among them, five species occurred on or in the blue crab, four on the brown shrimp, two on the white shrimp, and three on the northern shrimp. Of those, only three infested more than one host species. We have seen additional symbiotic species on other specimens of the same hosts but not on those reported here. A total of 16 free-living ciliate species occurred in the systems associated with the decapods. Among them, scuticociliates were the most important ones that could infect the decapods. One of these, Uronema marinum, also occurred in the hemolymph of the blue crab and impaired its health. The research was supported by the USDA, CSREES Grant No. 2002-38808-01381 and the Blue Crab Advanced Research Consortium (BCARC), NOAA, NA17FU2841.

Of principal concern to those who regulate shrimp harvesting gear are the quantity and composition of nontargeted species (bycatch) harvested by any allowable gear type. The use of skimmer trawls in the Florida shrimp fishery is a contested issue, in part because little bycatch characterization data exist for this gear. We characterized skimmer trawl bycatch and evaluated the efficiency of the Florida Fisheye (FFE) bycatch reduction device in a skimmer trawl typically used by commercial fishermen in Apalachicola Bay, Florida, an area with an active fishery for white shrimp Litopenaeus setiferus (also known as Penaeus setiferus). In general, the finfish bycatch in a 4.9-m-long × 3-m-wide skimmer trawl net equipped with an FFE was significantly lower than that in an identical net towed simultaneously but without the FFE; the two nets, however, did not differ in the quantity of shrimp retained. The magnitude of the reduction in bycatch in the FFE-equipped net varied between seasons (spring and fall)...

Georgia's food shrimp fishery is currently managed on the premise that a relationship exists between the abundance of spring-spawning white shrimp Litopenaeus setiferus and the abundance of fall recruits. Spawners are caught primarily during May and June, and fall recruits are caught from August through January. The efficacy of this management approach is unknown because the relationship between the two segments of the shrimp fishery has never been evaluated. We applied Beverton–Holt and Ricker spawner–recruit curves to fishery-independent and fishery-dependent indices to determine whether spawner abundance could be used to reliably predict the abundance of fall recruits. The commercial landings (lb) from May and June combined were used as the fishery-dependent spawner index, and monthly catch-per-unit-effort (CPUE) values observed during April, May, and June were used as fishery-independent spawner indices. Potential spawner– recruit models were evaluated for each set of indices and the resultin...

Analysing the population genetic structures of sympatric species provides opportunities to compare patterns of population genetic structure and phylogeography in order to gain insight into the factors that influence the development of the observed patterns. In this study, we compared the population genetic structures and phylogeographies of brown shrimp (Farfantepenaeus aztecus) and white shrimp (Litopenaeus setiferus), two sympatric penaeid shrimp species that inhabit the waters of the eastern USA, using sequence analysis of the mitochondrial DNA control region. Brown shrimp showed no significant phylogenetic structure or population subdivision, and closely related haplotypes were geographically dispersed. Mismatch analysis indicated that brown shrimp experienced a late-Pleistocene era sudden population expansion. In contrast, white shrimp had a complex haplotype phylogeny consisting of two distinct lineages and two less well-defined sublineages, and the haplotypes and lineages were geographically structured. Mismatch analysis for white shrimp also showed evidence of sudden population expansion, albeit for each lineage separately and more recently than in the brown shrimp. These disparate patterns may have developed as a result of species-specific differences in physiological tolerances and habitat preferences that caused greater fluctuations in white shrimp population sizes and reductions in long-term effective population size relative to that of the brown shrimp, and thereby increased the susceptibility of the white shrimp populations to stochastic genetic change.

The white shrimp (Litopenaeus setiferus) is a commercially and recreationally valuable species, yet little is known of its population structure or genetic diversity. White shrimp are distributed along the Atlantic coast of the United States and from the west coast of Florida to the Bay of Campeche, Mexico. In this study, shrimp were collected from North Carolina, South Carolina (four separate collections were taken from 1995 to 1999), Georgia, the Atlantic and Gulf coasts of Florida, Louisiana, Texas and Mexico. DNA was isolated from these individuals, and genetic variation was assessed at six microsatellite loci. These loci were, for the most part, highly polymorphic with an average expected heterozygosity of 0.68. Deviations from Hardy-Weinberg proportions were observed over all samples, but experimental results suggested the presence of null alleles, which confounded a biological interpretation of this result. Pairwise tests of the similarity of allele frequency distributions and distance measure analyses showed broad-scale genetic homogeneity superimposed over occasional indications of random geographical and temporal differentiation. FST and RST estimates over all loci and samples were 0.002 or less and indicated little population structure. Weak but significant genetic differentiation was evident only between pooled western Atlantic and pooled Gulf of Mexico samples. Within the Gulf of Mexico or within the western Atlantic, the large-scale genetic homogeneity observed may be a consequence of genetic mixing resulting from pelagic larvae and adult migrations, while the random local genetic differentiation may be a result of genetic sampling or experimental sampling error. The weak differentiation between shrimp from the Gulf of Mexico and the western Atlantic can be explained by a relatively recent separation of these two populations and/or small amounts of ongoing gene flow.

A histopathological survey of wild and cultured shrimp from the Gulf of Mexico was carried out to determine the prevalence and severity of infectious diseases and parasites, affecting four species of penaeid shrimp (Litopenaeus setiferus, Farfantepenaeus aztecus, F. duorarum, and L. vannamei). Around 60 shrimp were obtained from each of 10 sampling stations during different months in 1999 and 2000. One station was a shrimp culture farm from Tamaulipas State, and nine were wild stations from Tamaulipas (five), Veracruz (one), and Campeche (three) States. Thirty shrimp from each station were used for histological analysis. The remaining shrimp were frozen and kept at −20 C to carry out PCR techniques to determine the presence of white spot syndrome virus (WSSV). Some in situ hybridization analyses were applied to ascertain cases of WSS viral disease. Fresh analysis was carried out in shrimp from only one station for parasite identification. The histopathological survey performed on 688 shrimp showed no evidence of viral diseases. Two shrimp from one station were histologically diagnosed as having presumptive WSSV. Tissues from the same shrimp were processed for in situ hybridization and another 20 samples from the same station were processed to run PCR techniques. In each case, the results were negative. The same PCR procedure was applied to the rest of the frozen samples and none of them showed the presence of the WSSV. No important bacterial infections were observed in any of the wild or cultured shrimp analyzed. Fresh analysis demonstrated the presence of the cestode Prochristianella hispida and the gregarines Cephalolobus penaeus and Nematopsis penaeus. Histological analysis showed that the abundance of P. hispida varied from 7 to 90%, and G1 to G4 grades of severity were observed, with G1 being the most common. Gregarines were commonly observed in the histological slides, with a prevalence varying from 3 to 56% and G1 severity in most cases. Haplosporidan infection was observed in one sample of F. duorarum, which is the first report of this parasite in this host. Two invasive epibionts, the filamentous bacteria Leucothrix sp. and the ciliate Ascophrys sp., were found in four sampled stations. The study showed that in ten stations sampled from 1999 to 2000 in the Gulf of Mexico, shrimp populations had no serious infectious diseases.

This present study was designed to investigate the effects of stocking density and water exchange on the growth rate, survival and performance index of L. setiferus postlarvae under controlled laboratory conditions. The experiment was done with postlarvae (PL10 to PL40) at densities of 50, 150, 250 and 350 shrimp/m2 and various different water exchanges rate per day (0, 6, 12 and 18%). The maximum growth rate was obtained for shrimp with 12% water exchange per day at all densities. A reduction of the maximum growth rate was observed in relation to density with the highest values in shrimp stocked in a density of 50 and 150 shrimp/m2 (mean value of 0.53 mg/d) and the lowest in shrimp stocked in a density of 350 shrimp/m2 (0.24 mg/d). The multiple regression equation obtained to relate performance index (growth rate* survival : PI), shrimp density (X1) and water exchange (X2) was: PI = 0.31 + (0.001) X1+ 0.039 X2+ 2.28 × 10−6 X12+ (−0.0017) X22+ (0.000026)X1X2,R2= 0.78; P > 0.03. According to this equation the optimum shrimp density-water exchange comhination was between 5 to 12% of water exchange at stocking density of between 50 and 150 shrimp/m2. Salinity, ammonia-N and nitrite-N increased according to the time spent in tanks without water exchange. With no (0%) water exchange, water quality parameters measured were outside the optimum for L. setiferus postlarvae. The use of optimum density and water exchange in a nursery system for L. setiferus with optimum variables established is proposed.