Brown Shrimp Farfantepenaeus Aztecus Research Articles

Hydrodynamic regulation of salt marsh contributions to aquatic food webs

Vegetated salt marsh habitats are widely considered critical for supporting many species of nekton, yet direct evidence of the processes controlling marsh habitat use for most species remains elusive. We related salt marsh flooding patterns and nekton trophic dynamics among 14 sites spanning 2500 km across the northern Gulf of Mexico (GoM) and southern Atlantic coasts of the USA. Functional access for nekton to marsh vegetation (edge flooded to ≥5 cm depth) ranged from 90% access in the western GoM and Pamlico Sound. Food web mixing models based on stable isotope analysis show that the impor- tance of Spartina trophic support for common nekton may be regulated by the duration of marsh surface flooding. In particular, the potential contribution of Spartina production was positively related to indices of marsh surface flooding for brown shrimp Farfantepenaeus aztecus, white shrimp Litopenaeus setiferus, small (≤60 mm carapace width) blue crabs Callinectes sapidus, grass shrimp Palaemonetes pugio, and killifish Fundulus heteroclitus/grandis. The value of Spartina salt marsh production to several common species of nekton appears to depend, at least in part, on direct access to the vegetated marsh surface, which is regulated by hydrodynamics. Hence, the substantial geographic and temporal variability in marsh flooding regulates the func- tional roles and value of these tidal wetlands for aquatic organisms.

Aggregation on the edge: effects of hypoxia avoidance on the spatial distribution of brown shrimp and demersal fishes in the Northern Gulf of Mexico

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 445:75-95 (2012) - DOI: https://doi.org/10.3354/meps09437 Aggregation on the edge: effects of hypoxia avoidance on the spatial distribution of brown shrimp and demersal fishes in the Northern Gulf of Mexico J. Kevin Craig* Florida State University Coastal and Marine Laboratory, 3618 Highway 98, St. Teresa, Florida 32358-2702, USA Present address: Southeast Fisheries Science Center, NOAA National Marine Fisheries Service, 101 Pivers Island Road, Beaufort, North Carolina 28516-9722, USA *Email: kevin.craig@noaa.gov ABSTRACT: The northwestern Gulf of Mexico shelf experiences the largest seasonal hypoxic (dissolved oxygen, DO ≤ 2.0 mg l−1) zone in the western hemisphere. This study uses bottom trawl and hydrographic surveys over 3 yr to quantify low DO avoidance thresholds, patterns of aggregation in nearby oxygenated refuge habitats, and spatial overlap of brown shrimp Farfantepenaeus aztecus and several finfishes on the nearshore Louisiana shelf. On average, DO avoidance thresholds were low (1 to 3 mg l−1) and near incipient lethal levels for similar species, suggesting organisms avoid the lowest, lethal DO levels on the shelf. Avoidance thresholds varied both within and among years, indicating that behavioral responses to low DO are context-dependent and vary in relation to the severity of hypoxia and possibly other factors. Despite the absence of physical barriers to movement, evading organisms aggregated at short distances (1 to 3 km) just beyond the margins of the hypoxic zone, indicating that sublethal and indirect effects of hypoxia are probably most intense within a relatively narrow region along the hypoxic edge. DO avoidance thresholds and patterns of aggregation were similar between brown shrimp, the primary target of the commercial shrimp trawl fishery, and several juvenile and small adult finfishes that comprise most of the bycatch. In addition, spatial overlap between brown shrimp and finfishes was highest in the years when hypoxia was most severe, and this effect was stronger for benthic fishes than for pelagic fishes. These results suggest the potential for enhanced harvest and bycatch interactions along the margins of the hypoxic zone as an indirect effect of hypoxia-induced shifts in spatial ­patterns. Such spatially mediated indirect effects are an important means by which hypoxia ­influences mobile species in the Gulf. KEY WORDS: Eutrophication · Spatial statistics · Avoidance behavior · Bycatch · Catchability · Fishery interactions · Dead zone · Farfantepenaeus aztecus · Mississippi River plume Full text in pdf format PreviousNextCite this article as: Craig JK (2012) Aggregation on the edge: effects of hypoxia avoidance on the spatial distribution of brown shrimp and demersal fishes in the Northern Gulf of Mexico. Mar Ecol Prog Ser 445:75-95. https://doi.org/10.3354/meps09437 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 445. Online publication date: January 20, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Predicting the effects of freshwater diversions on juvenile brown shrimp growth and production: a Bayesian-based approach

Freshwater diversions from the Mississippi River may help restore coastal wetlands in Louisiana, but their implementation will alter temperature and salinity regimes, potentially affecting juvenile shrimp growth and production. We developed a bioenergetics model for brown shrimp Farfantepenaeus aztecus to investigate water temperature and salinity effects on brown shrimp growth. The model used a Bayesian framework that provided estimates of parameter and model uncertainty. Temperature affected shrimp metabolism, whereas salinity modified food availability. Mortality was modeled using a size-dependent function. We examined the effects of diversion timing (February, March, April and May), length (2× 14, as well as 30 and 60 d), temper- ature change (+1, 0, −1, −5 and -10°C), initial salinity (5, 15, 25), salinity during the diversion (2, 5, 10, 15, 20 and 25) and prey biomass response time (7, 14 and 28 d) on juvenile brown shrimp production. Diversions during February and March had little effect on shrimp, but 30 and 60 d diversions starting in April and May often had large, negative effects on production. April and May diversions that dropped water temperature by 5°C or more could decrease juvenile brown shrimp production by 40 to 60% compared with the baseline, no diversion scenarios. Whether changes in salinity had a positive or negative effect on brown shrimp production depended on the initial salinity of the scenario. Longer diversions and slower prey response times extended the duration brown shrimp were exposed to either the positive or negative effects of diversions, and this magnified the overall (positive or negative) effect on shrimp production. Limiting diversions to February and March when brown shrimp populations are not abundant would minimize nega- tive effects on shrimp production, though managers will be constrained by the needs of other spe- cies such as oysters, as well as ecosystem considerations.

Seasonal variability in food consumption, body composition and allometric relationships in the brown shrimp Farfantepenaeus aztecus (Ives, 1891) (Decapoda, Penaeidae) from Tamiahua Lagoon, Veracruz

The effect of salinity and temperature regimes, typical of most contrasting periods of the annual cycle (warm and cold) at Tamiahua lagoon, Veracruz, Mexico, on food consumption, body composition and allometric relationships of juveniles of the brown shrimp Farfantepenaeus aztecus (Ives, 1891) were examined. The following morphometric and tissue composition parameters were measured: total length (TL), cephalothorax length (CL), wet weight (WW), dry weight (DW), % body water content, organic matter (OM), total minerals (TM) and energy content (EC). The digestive tract of shrimps collected from both warm and cold periods was analysed determining its composition, quantity, and caloric content of the ingested food. Allometric relationships were calculated among: DW-WW, WW-TL and CL-TL. OM and TM content were correlated with the shrimp’s body weight. During the cold and warm seasons, salinity fluctuated between 24 and 36 psu and 12-36 psu, and average temperatures between 25 and 30°C, respectively. WW-TL and CL-TL relationships were statistically different among shrimps from both seasons. Body water content varied significantly, altering the DW-WW relationship, being higher in the warm season. No significant seasonal variation was detected in the shrimp’s OM, TM and EC. A shift in shrimp feeding habits was distinguished in the two seasons examined. Carnivorous habits prevail in winter whilst herbivory is more frequently observed during the warm season. However, the food energy remained relatively stable in both seasons, indicating that shrimp consume available resources in the lagoon in order to compensate for the absence of other food components and thus to maintain a constant energy flow independent of the season.

Variation in penaeid shrimp growth rates along an estuarine salinity gradient: Implications for managing river diversions

Freshwater inflows from river diversions may affect nekton populations by altering the salinity and temperature of estuarine waters. To investigate the influence of these environmental variables on the growth and survival rates of brown shrimp Farfantepenaeus aztecus and white shrimp Litopenaeus setiferus, we conducted field experiments in May and September 2007 to expose experimental animals to the range of different combinations of salinity and water temperature that commonly occur in an estuarine environment. Growth rates for shrimp held in mesocosms for approximately 7 days were compared among four locations and three treatments; locations were identified by the dominant marsh vegetation and distance from the Gulf of Mexico (low to high salinity: Intermediate, Brackish, Saline UE = Saline Up Estuary, Saline DE = Saline Down Estuary). At each location, the treatments were replicated four times and included shallow water with additional food, shallow water without food added, and deeper water (an attempt to expose animals to lower temperatures). Our experiments were designed to test the null hypothesis that shrimp growth and survival rates did not differ by location or treatment. Both brown shrimp and white shrimp grew more slowly at the Intermediate than higher salinity locations. Potential prey (benthic infauna) biomass was relatively low at both the Intermediate and Brackish locations in May, and both shrimp species consistently grew faster in mesocosms where food was added. We conclude that reduced growth in low salinity environments is likely due to the combined effects of increased metabolic costs and less food in these areas. River diversions that reduce estuarine salinities over a large portion of available habitat during peak recruitment periods may reduce overall growth rates and shrimp productivity in the affected areas.

Salinity, Temperature, and Seasonality Effects on the Metabolic Rate of the Brown Shrimp Farfantepenaeus aztecus (Ives, 1891) (Decapoda, Penaeidae) from the Coastal Gulf of Mexico

Abstract The routine metabolic rate (QO2 in mg O2 g−1 DW h−1) was measured in juveniles of the brown shrimp, Farfantepenaeus aztecus (Ives, 1891) at salinity and temperature ranges prevailing during the cold and warm seasons at the coastal lagoon of Tamiahua, Veracruz, Mexico. A semi-closed respirometer was employed, with eight 4-L experimental chambers, each containing two shrimp of similar size and sex. The shrimp were fasting and in the intermoult stage, and acclimated to the chambers for 12 h prior to determining oxygen consumption. Oxygen measurements were taken every two hours with a partial replacement of water and aeration of one hour between readings. In a 24 h cycle, 6 to 8 measurements were made. Relations between QO2 and DW, for the different salinity and temperature conditions tested, were calculated and adjusted to the equation: QO2 = αDWβ. Two-way ANOVA was applied to analyse the effect of salinity, temperature, time of day, and body weight on F. aztecus QO2. Salinity had no significant (p > 0.05) effect upon the shrimp's routine metabolic rate at intervals of 26 to 34 psu and 22 to 36 psu, typical of the cold and warm seasons, respectively. However, seasonal temperature variation did significantly affect the shrimp's QO2, thus suggesting the existence of a different "pattern of acclimatization" in the energy requirements of the individuals from both seasons. The results indicate that the population of F. aztecus from this area of the Gulf of Mexico may represent a "cline", the physiological response of the components of which differs from that of other brown shrimp populations distributed over a wide geographical range in the western tropical Atlantic.

Effects of Marsh Terracing on Nekton Abundance at Two Locations in Galveston Bay, Texas

We evaluated two marsh terracing restoration projects (GI=Galveston Island State Park, PM=Pierce Marsh) to compare nekton density and biomass between locations and among habitat types (open water pre-construction, open water post-construction, terrace marsh, terrace pond). Most (72%) animals collected were decapod crustaceans. Few differences in nekton abundance were observed over time (pre-construction versus post-construction open water). Comparisons of pre-construction to post-construction open water showed that the locations differed environmentally (e.g., turbidity) and in populations of nekton species. Density and biomass of gulf menhaden Brevoortia patronus and spot Leiostomus xanthurus in spring and density of white shrimp Litopenaeus setiferus in fall were higher at PM than GI, whereas densities and biomass of blue crab Callinectes sapidus, density of pink shrimp Farfantepenaeus duorarum, and biomass of brown shrimp Farfantepenaeus aztecus in the fall were higher at GI than PM. Despite location differences, constructing terraces appeared to benefit fishery species at both locations. Densities of brown shrimp, blue crab, white shrimp (fall), and pink shrimp (fall) and the biomass of brown shrimp, blue crab, and white shrimp (fall) were higher in terrace marsh than open water. Marsh terracing appears to be an effective tool for enhancing fishery habitat in degraded coastal systems.

Did the Texas Closure Increase Brown Shrimp Catches off Texas?

AbstractThe annual catch of brown shrimp Farfantepenaeus aztecus off Texas is forecasted by the National Marine Fisheries Service using a model that relates spring (April–June) juvenile abundance in Galveston Bay to subsequent offshore catch (July to the following June). The model is not well documented, nor has it been used rigorously to examine the success of management actions in enhancing the fishery. State and federal agencies use an areal closure of Gulf of Mexico waters deeper than 4 fathoms from late May to early July to increase shrimp abundance, catch, and value by delaying the harvest of emigrating juvenile shrimp. This study reports a preclosure (1960–1980) regression that explained over 70% of the variation in offshore Texas catches as a function of the juvenile abundance index from Galveston Bay. Positive effects of the closure—in terms of increasing the catch for a given level of juvenile abundance in 1981–2007—were not found in this study. However, the utility of the relationship between the juvenile abundance index and catch as a forecasting tool continued through 2007, but with less precision than in the preclosure regression.

Quantifying the Economic Effects of Hypoxia on a Fishery for Brown Shrimp Farfantepenaeus aztecus

AbstractAlthough hypoxia is a threat to coastal ecosystems, policy makers have limited information about its economic impacts on fisheries. Studies using spatially and temporally aggregated data generally fail to detect statistically significant effects of hypoxia on fisheries. Limited recent work using disaggregated fishing data (microdata) has revealed modest effects of hypoxia on the catches of recreationally harvested species. These studies did not account for important spatial and temporal aspects of the system, however. For example, the effects of hypoxia on catch may not materialize instantaneously but involve a lagged process reflecting cumulative past exposure. This paper develops a differenced bioeconomic model to account for the lagged effects of hypoxia on the North Carolina fishery for brown shrimp Farfantepenaeus aztecus. The model integrates high‐resolution oxygen monitoring data with fishery‐dependent microdata from North Carolina's trip ticket program to investigate the detailed spatial and temporal relationships of hypoxia to commercial fishery harvests. The main finding is that hypoxia may have resulted in a 12.9% annual decrease in the brown shrimp harvest during the period 1999–2005. The paper also develops two alternative models—a nondifferenced model and a polynomial distributed lag model—whose results are consistent with those of the main model.

Relating large-scale climate variability to local species abundance: ENSO forcing and shrimp in Breton Sound, Louisiana, USA

Climate creates environmental constraints (filters) that affect the abundance and distri- bution of species. In estuaries, these constraints often result from variability in water flow properties and environmental conditions (i.e. water flow, salinity, water temperature) and can have significant effects on the abundance and distribution of commercially important nekton species. We investigated links between large-scale climate variability and juvenile brown shrimp Farfantepenaeus aztecus abundance in Breton Sound estuary, Louisiana (USA). Our goals were to (1) determine if a tele- connection exists between local juvenile brown shrimp abundance and the El Nino Southern Oscilla- tion (ENSO) and (2) relate that linkage to environmental constraints that may affect juvenile brown shrimp recruitment to, and survival in, the estuary. Our results identified a teleconnection between winter ENSO conditions and juvenile brown shrimp abundance in Breton Sound estuary the follow- ing spring. The physical connection results from the impact of ENSO on winter weather conditions in Breton Sound (air pressure, temperature, and precipitation). Juvenile brown shrimp abundance effects lagged ENSO by 3 mo: lower than average abundances of juvenile brown shrimp were caught in springs following winter El Nino events, and higher than average abundances of brown shrimp were caught in springs following La Nina winters. Salinity was the dominant ENSO-forced environ- mental filter for juvenile brown shrimp. Spring salinity was cumulatively forced by winter river dis- charge, winter wind forcing, and spring precipitation. Thus, predicting brown shrimp abundance requires incorporating climate variability into models.

Using nekton growth as a metric for assessing habitat restoration by marsh terracing

We conducted field growth experiments to evaluate marsh-terracing restoration in Galveston Bay, Texas (USA). Growth rates were compared for selected species held in mesocosms for ~7 d within 4 habitat type treatments: terrace marsh edge (TerM), terrace pond (TerP), reference marsh edge (RefM), and reference pond (RefP). Environmental variables were measured during each experiment, and values measured inside the experimental mesocosms generally tracked outside values. Mean daily growth rates were 0.7 to 1.9 mm (30 to 143 mg) for brown shrimp Farfantepenaeus aztecus, 0.4 to 1.2 mm (8 to 67 mg) for white shrimp Litopenaeus setiferus, 0.3 to 0.6 mm (15 to 194 mg) for blue crab Callinectes sapidus, and 0.1 to 0.4 mm (0.3 to 3 mg) for daggerblade grass shrimp Palaemonetes pugio. No difference was detected in growth rates among treatments for blue crab and daggerblade grass shrimp. White shrimp growth rates in August 2002 were higher in TerP than RefP, and in October 2002, were higher in RefP than TerM. Brown shrimp grew more rapidly in RefM than TerM in early May 2003, but mean growth rates were similar in both habitat types later in May 2003, and significantly lower than growth rates in RefP and TerP. Even though growth rates were not consistently higher in terrace habitat types, production rates may be higher in terrace fields than over shallow non-vegetated bottom (the habitat type replaced by marsh terracing); much higher densities of fishery species in terrace habitats more than compensate for occasionally lower growth rates there. However, our production rates should be used cautiously, because we did not include mortality rates in these estimates. We recommend using a combination of different metrics, including mortality rate, to assess secondary productivity of marsh terracing or other restoration projects.

Using Conventional Analysis in Parallel with Geographical Information Systems Techniques to Examine the Distribution of Brown Shrimp in the Mississippi Sound

AbstractA geographical information systems technique for visualizing spatial data was used in conjunction with standard analytical procedures to examine the size‐specific distribution of brown shrimp Farfantepenaeus aztecus in nearshore nursery areas and open waters of the Mississippi Sound. Brown shrimp abundance was assessed during 2000, 2001, and 2002 by means of an otter trawl along 10 transects consisting of three stations each. The number of brown shrimp, together with the dissolved oxygen, temperature, and salinity values, were collected at each sampling station. A decreasing trend in salinity was observed from east to west. The highest salinities were measured in 2000. No temporal patterns in dissolved oxygen or temperature were apparent. Brown shrimp showed the highest abundances in western Mississippi Sound, an area adjoining the extensive marshes of St. Tammany and St. Bernard parishes in Louisiana. The average size of the brown shrimp in the western sound was smaller than that of the brown shrimp in other areas, indicating continued recruitment in the former area.

Relative influence of habitat fragmentation and inundation on brown shrimp Farfantepenaeus aztecus production in northern Gulf of Mexico salt marshes

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 359:185-202 (2008) - DOI: https://doi.org/10.3354/meps07380 Relative influence of habitat fragmentation and inundation on brown shrimp Farfantepenaeus aztecus production in northern Gulf of Mexico salt marshes B. M. Roth1, K. A. Rose1, L. P. Rozas2, T. J. Minello3 1Department of Oceanography and Coastal Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, USA 2NOAA Fisheries, SEFC/Estuarine Habitats and Coastal Fisheries Center, Lafayette, Louisiana 70506, USA 3NOAA Fisheries, Galveston Laboratory, Galveston, Texas 77551, USA *Email: broth2@lsu.edu ABSTRACT: We used a spatially explicit individual-based model to investigate the relative influences of inundation and habitat fragmentation on brown shrimp Farfantepenaeus aztecus production in northern Gulf of Mexico (NGOM) salt marshes. The model simulates the mortality, growth, and movement of a population of brown shrimp from their arrival in Spartina salt marsh as post-larvae in spring to their emigration as sub-adults in summer and fall. We quantified production in terms of sub-adult export, growth production (a measure of total shrimp growth), and trophic transfer (total shrimp mortality). We utilized a factorial design to simulate shrimp on all combinations of 4 maps that represented an idealized progression of habitat fragmentation and 4 inundation regimes from each of 2 locations in the NGOM (Louisiana and Texas). We also quantified the configuration of the marsh landscape to determine if specific metrics could be utilized as a proxy for shrimp production within a single inundation regime. Our results indicate that inundation is more important than habitat fragmentation for determining sub-adult export, growth production, and trophic transfer, but that marsh configuration has a strong influence on shrimp production within a single inundation regime. Inundation affected all 3 measures of shrimp production, primarily due to decreased mortality incurred when shrimp have access to vegetation through marsh flooding. We conclude that simple metrics of marsh configuration are capable of adequate predictions of shrimp production in static landscapes, but future research must consider the dynamic relationship between inundation and marsh fragmentation to fully assess how these forces affect shrimp production. KEY WORDS: Farfantepenaeus aztecus · Fragmentation · Inundation · Production · Spartina · Salt marsh · Gulf of Mexico · Estuaries · Individual-based model Full text in pdf format PreviousNextCite this article as: Roth BM, Rose KA, Rozas LP, Minello TJ (2008) Relative influence of habitat fragmentation and inundation on brown shrimp Farfantepenaeus aztecus production in northern Gulf of Mexico salt marshes. Mar Ecol Prog Ser 359:185-202. https://doi.org/10.3354/meps07380 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 359. Online publication date: May 05, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Population and Production Estimates for Decapod Crustaceans in Wetlands of Galveston Bay, Texas

Abstract 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...

Nekton populations, long-term wetland loss, and the effect of recent habitat restoration in Galveston Bay, Texas, USA

We used data from 1984 samples taken approximately monthly over 11 yr (1982 to 1992) with a 2.6 m 2 drop sampler to quantify and compare nekton densities in Spartina alterniflora marsh edge and over adjacent shallow nonvegetated bottom (SNB) in Carancahua Cove, Galveston Bay estuary, Texas, USA. We also used a Geographic Information System (GIS), aerial photography, and population models to track changes in wetland area and trends in fishery populations over time. Decapod crustaceans were less speciose than fishes (35 vs. 60 species) in our samples, but this taxo- nomic group accounted for most (91%) of the animals we collected. Annual variability in animal abundance was high. Most species peaked in abundance during spring or fall, and were absent or occurred at low densities during winter. Mean densities of all abundant decapod crustaceans and several abundant fishes in our study were significantly greater in marsh vegetation than over SNB. Based on our GIS analysis, we estimated that 61% of the wetlands in the study area were converted to open water between 1982 and 1995; marsh edge (marsh within 1 m of the shoreline) was reduced by 70% during the same period. Our fishery models showed that brown shrimp Farfantepenaeus aztecus, white shrimp Litopenaeus setiferus, and blue crab Callinectes sapidus populations also declined substantially during this period as the area of wetlands and marsh edge was reduced. A marsh-terracing project in 1999 replaced some open water with marsh, and our models show that populations of these fishery species rebounded in response to this recent restoration effort.

Nekton of new seagrass habitats colonizing a subsided salt marsh in Galveston Bay, Texas

Subsidence and erosion of intertidal salt marsh at Galveston Island State Park, Texas, created new areas of subtidal habitat that were colonized by seagrasses begining in 1999. We quantified and compared habitat characteristics and nekton densities in monospecific beds of stargrassHalophila engelmanni and shoalgrassHalodule wrightii as well as adjacent nonvegetated substrates. We collected 10 replicates per habitat type during April, July, October, and December 2001. Most habitat characteristics varied with season. Water temperature, salinity, and dissolved oxygen were similar among habitat types. Turbidity and depth were greatest inH. engelmanni beds and least inH. wrightii beds.H. engelmanni exhibited shorter leaves and higher shoot density and biomass core−1 thanH. wrightii. Densities of almost all dominant species of nekton (fishes and decapods) were seasonally variable, all were higher in seagrass habitats than in nonvegetated habitats, and most were higher in one seagrass species than the other. Naked gobyGobiosoma bosc, code gobyGobiosoma robustum, bigclaw snapping shrimpAlpheus heterochaelis, and blue crabCallinectes sapidus, were most abundant inH. engelmanni. Brown shrimpFarfantepenaeus aztecus, brackish grass shrimpPalaemonetes intermedius, and daggerblade grass shrimpPalaemonetes pugio were most abundant inH. wrightii. PinfishLagodon rhomboides and pink shrimFarfantepenaeus duorarum were equally abundant in either seagrass. Most dominant nekton varied in size by month, but only two (L. rhomboides andC. sapidus) exhibited habitat-related differences in size. Nekton densities in these new seagrass habitats equaled or exceeded densities associated with historical and current intertidal smooth cordgrassSpartina alterniflora marsh. Continued seagrass expansion and persistence should ensure ecosystem productivity in spite of habitat change.

Cloning and characterisation of mitochondrial manganese superoxide dismutase (mtMnSOD) from the giant freshwater prawn Macrobrachium rosenbergii

A cDNA encoding a mitochondrial manganese superoxide dismutase (mtMnSOD) was cloned from the hepatopancreas of giant freshwater prawn Macrobrachium rosenbergii using reverse transcription polymerase chain reaction (RT-PCR) by degenerate primers. Both 3′- and 5′-regions were isolated by rapid amplification of cDNA end (RACE) PCR method. Analysis of nucleotide sequence revealed that the mtMnSOD full-length cDNA consists of 1202 bp containing an open reading frame of 654 bp, which encodes a protein consisting of 218 amino acids including a signal peptide of 16 amino acid residues. The calculated molecular mass of the mature proteins (202 amino acids) is 24 kDa with an estimated p I of 7.12. Two putative N-glycosylation sites, NXT and NXS were observed in the mtMnSOD. Manganese superoxide dismutase signatures from 180 to 187 (DVWEHAYY), and four conserved amino acids responsible for binding manganese were observed (H48, H96, D180 and H184). Sequence comparison showed that the mtMnSOD deduced amino acid sequence of Macrobrachium rosenbergii has similarity of 88%, 78%, 56%, 54% and 46% to that of blue crab Callinectes sapidus, crucifix crab Charybdis feriatus, brown shrimp Farfantepenaeus aztecus, European lobster Palinurus vulgaris, and grass shrimp Palaemontes pugio, respectively, and has similarity of 45%, 44%, 43%, 26% and 25% to cytMnSOD (cytosolic MnSOD) deduced amino acid sequence of blue crab C. sapidus, prawn M. rosenbergii, tiger shrimp Penaeus monodon, grass shrimp P. pugio and brown shrimp F. aztecus, respectively. Quantitative real-time RT-PCR analysis showed that levels of mtMn-SOD transcripts in hepatopancreas and haemocytes were not significantly different between the M. rosenbergii injected with Lactococcus garvieae, and that injected with saline after 3 h to 24 h.

ESTIMACIÓN DE LA ABUNDANCIA DE CAMARÓN CAFÉ (<i>Farfantepenaeus aztecus</i>) EN LAS COSTAS DE TAMAULIPAS, 2002

Se presentan los resultados de la evaluación de la abundancia de camarón café (Farfantepeneaus aztecus ) en las costas de Tamaulipas durante el verano de 2002. Se realizaron cuatro cruceros de pesca exploratoria en las costas de Tamaulipas en agosto en donde se analizaron los valores de biomasa por área barrida. Estos valores fueron comparados con los obtenidos en cruceros de pesca exploratoria previos. La información fue complementada con datos de la estructura por tallas observadas durante mayo en Laguna Madre y tallas capturadas durante julio en altamar. Los resultados muestran que los rendimientos de la captura y la bio masa existentes son menores a los meses anteriores. Asi mismo, la estructura de tallas en el sistema lagunar, en la costa y la zona lejana a la costa (20 m a 42 m de profundidad) muestran un retraso en el reclutamiento y una desaceleración en el crecimiento, posiblemente como resultado de la anormalidad en la temperatura y la precipitación. Los valores bajos de la bio masa y las tallas observadas provocaron que los rendimientos en las capturas comerciales de altamar fueran menores a lo esperado. Abundance as sessment of brown shrimp (Farfantepenaeus aztecus) in Tamaulipas coasts, 2002 Results from brown shrimp (Farfantepenaeus aztecus ) abundance evaluation of the coasts of Tamaulipas during summer of 2002 are presented. Four exploratory fishing cruises were carried out in the coasts Tamaulipas during August, where bio mass values were analyzed by swept area. These values were compared with data of previous exploratory fishing cruises. The information was complemented with data of size structure, observed during May in Laguna Madre and information from a survey carried out in June 2001. The results shown that the yield of capture and bio mass existing are smaller than the previous months. Likewise, the structure of sizes in the inshore system, from the coast and the distant zone to the coast (20 m to 42 m depth) shown a de lay in the recruit ment and abundance on decrease, possibly explained as a result of a temperature and rain fall abnormality. The low values observed of bio mass and sizes, caused that yields in the commercial captures of open sea were smaller than the expected ones.

A Three‐Year Survey of Penaeid Shrimp and Callinectid Crabs from Texas Coastal Waters for Signs of Disease Caused by White Spot Syndrome Virus or Taura Syndrome Virus

AbstractThe Gulf of Mexico has the largest shrimp industry in the United States, including both natural fisheries and aquaculture resources. Aquaculture production comes primarily from Texas shrimp farms. With intensification of the farmed shrimp industry and international commerce in aquatic species, the incidence of infectious disease outbreaks has become a growing problem. In 1995, the Texas farmed shrimp industry suffered heavy losses during an outbreak of Taura syndrome virus. Rapid disease transmission, in conjunction with high pond mortalities during the grow‐out season, revealed the need for a structured preventive health plan with stringent biosecurity measures. In addition, native indigenous shrimp and crab species have never been systematically evaluated for infectious disease agents. Concern for these native species prompted the Texas Parks and Wildlife Department to initiate a survey to evaluate the general health status of select indigenous marine invertebrate species along the Texas coast. From October 1997 through September 2000, 5,399 commercially important wild penaeid shrimp (2,009 white shrimp Litopenaeus setiferus, 2,868 brown shrimp Farfantepenaeus aztecus, and 522 pink shrimp F. duorarum) and 935 crabs (630 blue crabs Callinectes sapidus and 305 lesser blue crabs C. similis) were collected from randomly selected locations in nine Texas coastal bay systems and evaluated for known viral pathogens with the use of histopathology and in situ hybridization. In this study, only the virus Baculovirus penaei was detected in three brown shrimp. Taura syndrome virus and white spot syndrome virus were not detected within the testing limitations of this study.

Effect of salinity and temperature on thermal tolerance of brown shrimp Farfantepenaeus aztecus (Ives) (Crustacea, Penaeidae)

The critical thermal maxima (CTMax) of Farfantepenaeus aztecus was not affected significantly by salinity ( P > 0.05 ). A direct relationship was obtained between the critical temperature and the acclimation temperature which increased at intervals of 3–5 °C. The end point of CTMax in F. aztecus was loss of righting response (LRR). The acclimation response ratio (ARR) for the juveniles of the brown shrimp ranged between 0.20 and 0.80, which agreed with others obtained for crustaceans from tropical and subtropical climates. The brown shrimp should not be exposed to conditions that cause total disorientation; if this is avoided, it will permit an increase in growth and reduce mortalities in culture populations.