Young Shrimp Research Articles

Molecular Approaches Detect Early Signals of Programmed Cell Death in Hippolyte inermis Leach.

The protandric shrimp Hippolyte inermis is the only known marine invertebrate whose sex determination is strongly influenced by the composition of its food. In H. inermis, a sex reversal is triggered by the ingestion of diatoms of the genus Cocconeis associated with leaves of the seagrass Posidonia oceanica. These diatoms contain compounds that promote programmed cell death (PCD) in H. inermis and also in human cancer cells. Transcriptomic analyses suggested that ferroptosis is the primary trigger of the shrimp's sex reversal, leading to the rapid destruction of the androgen gland (AG) followed by a chain of apoptotic events transforming the testes into ovaries. Here, we propose a molecular approach to detect the effects of compounds stimulating the PCD. An RNA extraction method, suitable for young shrimp post-larvae (five days after metamorphosis; PL5 stage), was established. In addition, six genes involved in apoptosis, four involved in ferroptosis, and seven involved in the AG switch were mined from the transcriptome, and their expression levels were followed using real-time qPCR in PL5 fed on Cocconeis spp., compared to PL5 fed on a basic control feed. Our molecular approach, which detected early signals of sex reversal, represents a powerful instrument for investigating physiological progression and patterns of PCD in marine invertebrates. It exemplifies the physiological changes that may start a few days after the settlement of post-larvae and determine the life destiny of an individual.

Comparison of stress tolerance of hybrid and selfed offspring of two populations of Litopenaeus vannamei

In recent years, as the marine environment has been deteriorated, the aquaculture water environment has also been negatively affected to varying degrees. Negative environmental factors make extremely damaging to organisms, resulting in stress-induced diseases and high mortality rates of cultured shrimp. Therefore, stress resistance breeding of Litopenaeus vannamei and evaluating the stress tolerance of the breeding population are urgently needed now. Litopenaeus vannamei collected from Thailand (T) and the United States (M) were used as parents, while four progeny populations of TT, MM, TM, and MT were constructed by diallel cross, with a total of 20 families. The tolerance of young shrimp to high ammonia-N, high pH, and low salt was compared through a 96-h acute toxicity test; the heterosis of each mating combination was analyzed; and the tolerance of parents and offspring was evaluated. Here we show that under 96 h of high ammonia-N, high pH, and low salt stress, the mortality rates of each family were 19.52%–92.22%, 23.33%–92.22%, and 19.33%–80.00%, respectively. There were significant differences in the tolerance of different families to ammonia-N, pH, and salinity stress (P < 0.05). The population with a female parent from the United States had stronger tolerance to ammonia-N, pH, and low salt stress than the population with a female parent from Thailand. The population with a male parent from Thailand had weaker tolerance to pH and low salt stress than the population with a male parent from the United States, but it was superior to the population with a male parent from the United States under ammonia-N stress. The heterosis rates of the hybrid population TM in acute high ammonia-N, high pH and low salinity were 81.67%, 44.58% and −10.13%, respectively; However, the heterosis rates of the MT population were 14.89%, 38.89%, and −8.96%, respectively. The overall resistance of the four populations showed MM > MT > TT > TM. The population TM had obvious heterosis in high ammonia-N and high pH tolerance traits, and the family MM7 had a strong low salt tolerance, so it can be considered a candidate family for subsequent breeding work. Moreover, variability in stress resistance and heterosis of stress resistance of different populations obtained by family selection was discussed in this paper. The experimental results provide a basis for screening new strains of vannamei shrimp with strong stress resistance through family breeding.

Activity of Garlic (Allium Sativum L.) Extract Against Vibrio Parahaemolyticus Bacteria

Vibriosis is the primary bacterial illness shrimp farmers face due to mass death in young shrimp, called Early Mortality Syndrome (EMS). The etiology of this disease is Vibrio parahaemolyticus bacterium. Garlic (Allium sativum L.) is one of the natural compounds that can suppress the growth of Vibrio parahaemolyticus bacteria. This study aims to assess the effect of garlic extract on the growth of Vibrio parahemolyticus bacteria in 96 percent ethanol solvent at garlic extract concentrations of 20%, 40%, 60%, and 80%. The Kirby-Bauer disc diffusion method is utilized, which estimates the diameter of the inhibitory zone surrounding the disc. Making garlic extract by maceration using 96% ethanol solvent and evaporated with a rotary vacuum evaporator. The results showed that a ethanol 96% extract of garlic with concentrations of 20%, 40%, 60%, and 80% had antibacterial activity on V. parahaemolyticus bacteria with an average inhibition zone diameter of 4.9 mm, 8.4 mm, 9.4 mm, 11.9 mm, respectively. This study concluded that garlic extracts have antibacterial activity against Vibrio parahaemolyticus.

Construction of an easily detectable transgenic Synechococcus elongatus PCC 7942 against White Spot Syndrome Virus using vp28 and mOrange Gene and its metabolism in shrimp.

White spot syndrome is an epidemic disease caused by the highly contagious and lethal white spot syndrome virus (WSSV), resulting in huge economic losses to the global aquaculture industry. VP28 is the main structural protein in the capsule of WSSV and is important in the early stage of infection. Under an excitation wavelength of 548 nm, the mOrange fluorescent protein releases a 562 nm emission wavelength, which is different from the autofluorescence of cyanobacteria. Therefore, using this characteristic combined with the receptor system of Synechococcus elongatus PCC 7942, we constructed transgenic S. elongatus to express the recombinant protein VP28-mOrange. In addition, PCR and western blotting were used to confirm the stable expression of the target gene in cyanobacteria. Using mOrange tracer features, we explored the recombinant protein VP28-mOrange in the metabolic cycle of young Litopenaeus Vannamei after feeding. After the young shrimp had stopped consuming transgenic cyanobacteria, the 24 to 33 h fluorescence signal in the intestine was very weak, and almost disappeared after 36 h. We explored the protective effect of transgenic vp28-mOrange S. elongatus within 48 h of being ingested by L. vannamei and set WSSV challenges at 2, 12, 24, and 48 h post-immunization. However, the survival rate of L. vannamei decreased as the time of the WSSV challenge increased. The survival rate on the seventh day was 81%, 52%, 45.5%, and 33.3% for shrimps challenged for 2, 12, 24, and 48 h, respectively. Enzyme activity can also support this conjecture, the enzyme activity indexes of the experimental groups were significantly reduced compared to positive and wild-type controls. Therefore, this immune agent functioned as a preventive agent. Compared with the traditional method, this method was easy to detect and can visualize the digestion of transgenic cyanobacteria in the Litopenaeus vannamei intestine.

Diet, ontogenetic changes and rhythm of feeding activities in Macrobrachium macrobrachion (Herklots, 1851) (Decapoda, Palaemonidae) in the waterbodies and rivers of Benin, West Africa

Abstract Knowledge of the diet of Macrobrachium macrobrachion (Herklots, 1851) in its natural environment is a key factor facilitating its successful breeding. We have analysed the stomach content of 452 specimens collected from the Ouémé River Delta (ORD) (338 stomachs) and from the Mono River/Grand-Popo Lagoon complex (MGLC) (114 stomachs), from February to October 2016. The analysis enables to calculate the coefficient of vacuity for the ORD (3.50%) and for the MGLC (3.50%). The results show that M. macrobrachion has a detritivore-omnivore type of diet, feeding mainly on phytoplankton (diatoms and cyanophytes) and detritus. However, the diet of the young shrimps, composed mostly of insect larvae, differs from that of adult. In the adult M. macrobrachion, the pace of feeding activities is greatest in the morning (6.00 to 9.00 am), low in middle of the day (10.00 am to 13.00 pm), and there is a slight trophic activity between 17.00 and 22.00 pm. Outside of the above periods, i.e., from 14.00 to 16.00 pm and 23.00 pm to 5.00 am, the species is at rest. Juveniles feed at dawn. In the nighttime and at dusk, groups of shrimps of varying sizes do feed. The findings of this study suggest that live prey is the best feed for the larvae of M. macrobrachion in captivity and should be distributed preferably early in the morning.

Profitability and Sustainable Use of Traps for Amazon Shrimp (Macrobrachium amazonicum) From the Amazon River

The objective of this study was to evaluate the profitability, productivity and selectivity of traps used for the capture of freshwater prawn using different spacings between the laths. This study was developed in the estuary of the Amazon River near Santana island, Amapá, Brazil. Collections were conducted using traps called “matapi”, which are cylindrical shrimp traps made with wooden slats or laths, with funnel-shaped entrances at both sides, and the spacings between the laths ranged between 1 to 10 mm in 1 mm increments. Each trap was covered with a net called a “sobrematapi”, or trap cover. The length of carapace in centimeters and the weight in grams were measured for all specimens. The shrimp were categorized into small, medium, and large size classes. Selectivity curves were used to determine selectivity for the different lath spacings. Traps with lath spacing below 7mm should be considered as being predatory because they allow for the capture of small individuals, with more than 50% of these being captured using spacings from 1 to 5mm. Despite the fact that spacings between 8 and 10mm captured lower quantities of shrimp, this enabled the capture of larger specimens with a similar total biomass yield, and this spacing is considered to be the most ecologically and economically viable. In order to minimize the capture of young shrimp without drastically affecting economic yield, it is suggested that shrimp trap lath spacings be above 6mm.

ECONOMIC FEASIBILITY FOR THE PRODUCTION OF LIVE BAITS OF LAMBARI (<i>Deuterodon iguape</i>) IN RECIRCULATION SYSTEM

Sport fishing is a growing segment in the fishing sector in Brazil. It is, however, an activity that depends upon young shrimp and fish offer to supply live bait demand, its extraction might result on overfishing and compromise natural stock. The intensive cultivation in water recirculation system is a worldwide trend for aquaculture, which, in addition to increasing productivity, minimizes the impact of effluent emission on the environment, reinforcing sustainability. This study analyzed the economic viability of establishing farms for the cultivation of lambari (Deutorodon iguape) in water recirculation system to meet the market demand of sport fishing for live baits. Twelve fiberglass tanks with a volume of 1500 L and a unit area of 1.32 m2 (production units - PU) were installed in a total area of 130m2. There were also six fiberglass tanks of 2,000 L capacity each, filled with water and 600 kg of clamshells acting as biological filter. Three production cycles were performed, each lasting 60 days. In each cycle 10,800 D. iguape fingerlings were added, acquired from local fish farming, at a 600 fish m-3 density, totalizing 900 fish per PU, with medium size and weight of 10 ± 1.2 mm e 1.1 ± 0.29 g. We used the following indicators: modified internal rate of return (MIRR), net present value (NPV), annualized net present value (ANPV) and payback period (PP). The best scenario, with 90% survival rate and unitary selling prices of US$ 0.30, showed MIRR 33.19%, NPV (10%) US$ 42,174.03, ANPV (10%) US$ 6,863.63 and PP 0.9 years, demonstrating be interesting the production of live baits in the conditions proposed in this study.

THE EFFECTS OF RAINFALL ON Penaeus monodon Fabricius POPULATIONS IN THE SEGARA ANAKAN LAGOON, CENTRAL JAVA, INDONESIA

Segara Anakan Lagoon (SAL) is widely known as a traditional fishing ground for many aquatic organisms and is located in Central Java, in an area with high rainfall rates. The objectives of this study were to determine the effects of rainfall on the distribution of Penaeus monodon Fabricius in SAL and/or mangrove waters and to explain the cause of yearly fluctuations in this area’s fish catch during a 13-year period from 1998 to 2011. The effects of rainfall on the local distribution and abundance of shrimp in SAL, Cilacap, Central Java, Indonesia, were examined using the Anco method for three periods, namely: first period (i.e., commercial catch production, 1998–2011), second period (December 2010–November 2011) and third period (December 2011–April 2012) as part of a shrimp fishery and eco-biology study in this region. The marked increase in rainfall from 557 mm during the East Monsoon (June–August) to 1,225 mm in the second transition season (September–November) and West Monsoon (December–February) in the Segara Anakan region enhanced the seasonal movement of shrimp into the Zone IV fishing ground and produced an initial increase in the abundance of adults (CL>25 mm) in the region from 312 to 2,630 individuals. This initial increase in adult abundance enhanced the shrimp’s reproductive potential, while heavy rainfall indirectly assisted the recruitment of young shrimp into the estuary, their growth, and survival, to increase shrimp abundance in the following year. Lower rainfalls from July to September) adversely affected shrimp population and usually resulted in smaller populations (312 individuals). Statistical analysis of the relationship between shrimp catch and annual rainfall showed a high level of significance at 1%.

Critical better management practices and critical bio-security measures for prevention of entry and spread of white spot virus and pathogenic Vibrio in grow-out farms of cultured Penaeus monodon in Sri Lanka

Since the first record of white spot disease (WSD) in 1996, PCR tested, white spot virus (WSV) free post larvae of Penaeus monodon (Fabricius 1798) are stocked in grow-out farms as the major bio-security measure. However, significantly high mortality in young shrimp and total rejection of harvest have been recorded in North Western Province, Sri Lanka due to WSD and/or vibriosis. Present study was planned to identify critical better management practices (CBMPs) and critical bio-security measures (CBSMs) that should be strictly adopted to prevent the entry and spread of WSV and pathogenic Vibrio in grow-out farms of P. monodon. A questionnaire survey, carried out at randomly selected 100 grow-out farms located in the North Western Province, revealed that there was a relationship between the occurrence of WSD and /or vibriosis and levels of practicing better management practices (BMPs) and/or bio-security measures (BSMs). Proper pre-stocking pond preparation, adoption of zero water exchange, monitoring and controlling water quality parameters including pathogenic Vibrio in culture water and use of a suitable bioaugmenter and a probiotic were identified as the CBMPs while proper disinfection of culture water, stocking of WSV and MBV free post larvae and prevention of WSV contamination through other routes over the rearing period were the identified CBSMs. Entry and spread of WSV and pathogenic Vibrio in P. monodon grow-out farms in the North Western Province, Sri Lanka could be prevented by strict adoption of CBMPs and CBSMs identified during the present study.

The Origin of Large-Bodied Shrimp that Dominate Modern Global Aquaculture.

Several shrimp species from the clade Penaeidae are farmed industrially for human consumption, and this farming has turned shrimp into the largest seafood commodity in the world. The species that are in demand for farming are an anomaly within their clade because they grow to much larger sizes than other members of Penaeidae. Here we trace the evolutionary history of the anomalous farmed shrimp using combined data phylogenetic analysis of living and fossil species. We show that exquisitely preserved fossils of †Antrimpos speciosus from the Late Jurassic Solnhofen limestone belong to the same clade as the species that dominate modern farming, dating the origin of this clade to at least 145 mya. This finding contradicts a much younger Late Cretaceous age (ca. 95 mya) previously estimated for this clade using molecular clocks. The species in the farmed shrimp clade defy a widespread tendency, by reaching relatively large body sizes despite their warm water lifestyles. Small body sizes have been shown to be physiologically favored in warm aquatic environments because satisfying oxygen demands is difficult for large organisms breathing in warm water. Our analysis shows that large-bodied, farmed shrimp have more gills than their smaller-bodied shallow-water relatives, suggesting that extra gills may have been key to the clade’s ability to meet oxygen demands at a large size. Our combined data phylogenetic tree also suggests that, during penaeid evolution, the adoption of mangrove forests as habitats for young shrimp occurred multiple times independently.

Substitución de alimento por gallinaza en la producción comercial de camarones peinados en Honduras

The objective of this research was to determine the effects of substituting chicken manure for the common feed stuffs used In the first four to eight weeks of the growing period of shrimp. Economical evaluations of shrimp production was also considered. Twelve man made ponds (2.2-3.0 ha) located at Granjas Marinas, San Bernardo, S.A, San Bernardo, Choluteca, Honduras were assigned to four treatments at random and seeded with young shrimp (average weight 0.8 g) at a rate of 5/m2 on September 7, 1998. The treatments tested were: 1) (STANDARD) the normal treatment used at Granjas Marinas San Bernardo which consisted in the application of chicken manure during the first eight weeks plus added feed, 2) (FEED) feed only, 3) (4 WEEKS) chicken manure only during the first four weeks followed by feeding, 4) (8 WEEKS) chicken manure only during the first eight weeks followed by feeding. After ninety nine days ofshrimp cultivation, there was Do Increase In production using low rates of chicken manure (60 kg total solids/ha/week) during the first eight week of feeding. It was also found not to be economical to feeding for low rates of fertilization with chicken manure, especially after the first two or three weeks of cultivation. The average weight of shrimp for treatments FEED 14,4, and STANDARD 14.1, was significantly greater than that observed for 4 WEEKS 12.2, and 8 WEEKS 17-1. The average shrimp production was 7-41% greater In STANDARD and FEED treatments (%)* and 518 kg/ha respectively) compared to 4 WEEKS (476 kg/ha) and 8 WEEKS (368 kg/ha). However, there were no significant differences between treatments due to the high amount of variability caused by survival rates (P<0.01). The total costs for FEED and STANDARD were significantly greater compared to 4 and 9 WEKS. This was due to a greater feed utilization in the previous treatments. Estimated gains In FEED (L. 30851ha) and STANDARD (L. 3026/ha) were 27-58% greater than 4 and 8 WEEKS (L. 2389/ha, and 1947/ha respectively). This was due to the Increased production obtained with greater prices received for the larger shrimp obtained in FEED and STANDARD treatments. There was potential to significantly increase the estimated gains by substituting feed for fertilization with chicken manure at a higher rate of application (250 kg/ha/week) during the first four to eight weeks of cultivation.

Simulating environmental effects on brown shrimp production in the northern Gulf of Mexico

Brown shrimp (Farfantepenaeus aztecus) support a commercially important fishery in the northern Gulf of Mexico, and juveniles use coastal estuaries as nurseries. Production of young shrimp from any given bay system, and hence commercial harvest of sub-adults and adults from the Gulf, is highly variable from year to year. We describe development of a spatially-explicit, individual-based model representing the cumulative effects of temperature, salinity, and access to emergent marsh vegetation on the growth and survival of young brown shrimp, and we use the model to simulate shrimp production from Galveston Bay, Texas, U.S.A. under environmental conditions representative of those observed from 1983 to 2012. Simulated mean annual (January through August) production ranged from 27.5kgha−1 to 43.5kgha−1 with an overall mean of 34.3kgha−1 (±0.70kgha−1 SE). Sensitivity analyses included changing values of key model parameters by ±10% relative to baseline. Increasing growth rates 10% caused a 16% increase in production, whereas a 10% decrease resulted in an 18% decrease in production. A 10% increase in mortality probabilities resulted in a production decrease of 15% while a 10% decrease resulted in an 18% increase in production. We also changed values of environmental input data by ±10%. Mean production estimates increased 11% in response to increasing tide heights (and thus, marsh habitat access) and decreased 19% with a decrease in tide height (and marsh access). The thirty year mean production was affected negatively by both the 10% increase and decrease in air temperature (−2% and −14%, respectively). Simulations in which bay water salinities were entirely low (0–10PSU), intermediate (10–20PSU), or high (>20PSU) resulted in mean baseline production rates being reduced by 55, 7, and 0%, respectively. Uncertainty in model estimates of shrimp production were related to the magnitude and the timing of postlarval shrimp recruitment to the bay system. Simulations indicated that mean production decreased when recruitment occurred earlier in the year under all environmental conditions. Mean production varied with environmental conditions, however, when recruitment was delayed. The model reproduced biomass and size distribution patterns observed in field data. Although annual variability of modeled shrimp production did not correlate well (R2=0.005) with fisheries independent trawl data from Galveston Bay, there was a significant correlation with similar trawl data collected in the northern Gulf of Mexico (R2=0.40; p=0.0005). Identifying and representing spatially variable factors such as predator distribution and abundance among bays, therefore, may be the key to understanding bay-specific contributions to the adult stock.

การบริหารเงินทุนธุรกิจกุ้งในภาวะเศรษฐกิจถดถอย (Fund Management of Shrimp Business under the Economic Recession)

Thai Abstract: ในการศกษาวจยเกยวกบการบรหารเงนทนธรกจกง ในภาวะเศรษฐกจถดถอยเนอ งจากการลงทนเลยงกงขาวแวนนาไมในประเทศไทยประสบปญหาการขาดทนเนองจากเกดโรคระบาดในกงขาวแวนนาไม ทเรมระบาดอยางหนกในป พ.ศ.2555 โดยเฉพาะอยางยงปญหาโรคกงตายดวน หรอทรจกในชอของโรค EMS การเพาะเลยงกงขาวแวนนาไม ไมมขอบเขตทแนนอน ขนอยกบสภาพแวดลอมและปญหาตางๆ ทเกดขนในแตละฟารม อยางไรกตามหลกเกณฑพนทางฐานวชาการไดนาองคความรมาประยกตในการจดการเพาะเลยงกงขาวแวนาไม เพอใหเกดประสทธภาพสงสด ดวยแนวคดเกยวกบการบรหารและการจดการ แนวทางการเพม ผลผลต ราคากงจะเปลยนแปลงตามอปสงคและอปทานของตลาดโลกและตลาดภายในประเทศถาสนคามปรมาณมาก จรรยาบรรณในการดาเนนธรกจ การปรบระดบการผลตและการใชปจจยการผลตททา ใหตนทนเพม เทากบรายไดเพม ดวยการวดผลงานเชงดลยภาพใหกบผประกอบการเลยงกง ขาวแวนนาไมในพนทภาคใตเปนอยางด English Abstract: This is a part of the research about the financial management of shrimp farming businesses during economic recession. White shrimp (Litopenaeus Vanamei) farming businesses in Thailand have been in trouble since a massive epidemic in 2012, especially for the Early Mortality Syndrome (EMS) which effects are fatal to young shrimp. White shrimp farming’s operation generally depends on each farm’s environment and its various problems. However, if entrepreneurs can apply all knowledge and theory of the white shrimp farming, it could make this business achieve maximum efficiency in farming management. With the management concept to increase productivity, the shrimp price will change depending on supply and demand in both the global and domestic markets. If there are many products in the market, the ethic of the business operation is to change the levels of production and turn to use production factors that make the increasing production cost equal to the increasing income. By supporting this, there should be a good Balance Scorecard performance to help entrepreneurs of white shrimp farming businesses in the South of Thailand.

Shrimp (Pandalus borealis) growth and timing of the spring phytoplankton bloom on the Newfoundland–Labrador Shelf

AbstractWe examined latitudinal and temporal changes in the availability of food for young shrimp (Pandalus borealis) on the Newfoundland–Labrador Shelf, using a suite of quantitative characteristics of the spring phytoplankton bloom determined from satellite ocean colour data, including bloom initiation time, maximum chlorophyll concentration, timing of the maximum, and bloom duration. We found significant correlations between bloom intensity, timing, and the size of young shrimp. The results are discussed in relation to the observation that, since the early 1990s, carapace lengths of shrimp have been decreasing in many Northwest Atlantic stocks.

An advanced irradiation facilities and its usage

A carrier type gamma irradiator is an advanced device currently installed in Qingdao Irradiation Center (QIC) and has been put into operation for nine years in Qingdao, China. It utilizes Co-60 as the radiation source; the initial Co-60 loading is 1.48×1016 Bq (0.4 million Curies). Rubber, natural and synthetic polymers, heat-shrinkable films and tubes, disposable medical supplies, some foods and drugs have been irradiated for test in the past. Especially a great success achieved on the radiation of compound food for young shrimp. The practice demonstrates that the bacteria in the compound food can be destroyed by the irradiation at optimum dosage between 5 000‐6 000 Gy.

Nekton use ofVallisneria americana Michx. (Wild celery) beds and adjacent habitats in Coastal Louisiana

We compared nekton use ofVallisneria americana Michx. (submerged aquatic vegetation, SAV) with marsh shoreline vegetation and subtidal nonvegetated bottom (SNB) using a 1-m2 drop sampler in the oligohaline area of Barataria Bay, Louisiana. Mean densities of most abundant species were significantly different among six habitat types. Harris mud crabRhithropanopeus harrisii, Ohio shrimpMacrobrachium ohione, blue crabCallinectes sapidus, daggerblade, grass shrimpPalaemonetes pugio, white shrimpLitopenaeus setiferus (fall), rainwater, killifishLucania parva, naked gobyGobiosoma bosc, code gobyGobiosoma robustum (fall), speckled worm eelMyrophis punctatus (fall), and gulf pipefishSyngnathus scovelli (spring), were much more abundant, and species richness also was greater, inVallisneria than over SNB.Vallisneria supported densities of most species that were similar to those in marsh vegetation, although naked goby and gulf pipefish were more abundant inVallisneria, and speckled worm eel and saltmarsh topminnowFundulus jenkinsi were more abundant in marsh. Within theVallisneria bed, densities of Harris mud crab, rainwater killifish, and speckled worm eel were higher at sites near the marsh (SAV Inside Edge) than at sites more distant from the marsh (SAV Outside Edge), and Ohio shrimp (fall) densities were higher in the interior of the bed than along the edges. The mean size of blue crab was larger in marsh thanVallisneria and large inVallisneria than SNB. White shrimp did not differ in size among habitat types.Vallisneria beds may provide an important nursery habitat for young blue crab and white shrimp that use oligohaline estuarine areas. These SAV beds can provide an alternative structural habitat to emergent vegetation during periods of low water, becauseVallisneria occurs in the subtidal and generally persists throughout the year on the Gulf coast. Species whose young thrive in low-salinity waters and also depend on structure would benefit most fromVallisneria habitat in estuaries.

Aspectos reprodutivos de Potimirim glabra (Kingsley) (Crustacea, Decapoda, Atyidae) no Rio Sahy, Mangaratiba, Rio de Janeiro, Brasil

The reproductive aspects of the freshwater shrimp Potimirim glabra (Kingsley, 1878) were studied from September 1997 to February 1999. Monthly, samples were collected with sieves, on the river edge, under the edging vegetation or in small pools. At the laboratory, shrimps were sexed and measured in their total lenght, from the tip of the rostrum to the end of telson with precision callipers. The ovigerous shrimps were separated and counted for fecundity determination. The eggs diameter was measured with calibrated stereomicroscope. A total of 3281 shrimps were collected, among which, 47% male, 46% female (13.4% ovigerous females) and 7% young shrimps. The Sex ratio was 1:1. Ovigerous females were present during all seasons, but the reproductive peak occurred in spring. The ovigerous female showed total lenght from 9.5 to 26.0 mm and carapace lenght from 1.6 to 7.3 mm. The mean fecundity was 545 eggs per female, with a minimun of 223 eggs and a maximum of 860 eggs. The first sexual maturation probably occur at 9.5 mm total lenght. The mean diameter of the eggs size was 0.32 mm (minor) and 0.53 mm (major).

Some factors affecting size distribution and density of grass shrimp (Palaemonetes pugio) populations in two New Jersey estuaries

Mature Palaemonetes pugio, from a polluted estuary, Piles Creek (PC) are larger than those in a more pristine estuary in Tuckerton (TK). Possible causes for the differences in size-structure could be differences in environmental factors at the two creeks, differential competition at the two sites, inherent factors causing a greater growth rate in the PC population, differences in reproductive timing, or differential predation at the two sites. Lab microcosm studies were used to examine the possibility of inherent population differences or environmental conditions (including differences in salinity) causing faster growth in PC. There was no evidence that PC shrimp grew faster than TK shrimp, nor that PC conditions fostered greater growth compared to TK. Salinity adjustments in PC and TK tanks also had no effect on growth. Therefore, it appears that genetic and environmental factors did not play a significant role in greater shrimp growth in PC. In the field, data on relative abundances of Fundulus heteroclitus and P. pugio, and size-frequency distributions of P. pugio were collected from the two estuaries. Gravid females and recruits of young shrimp physically appeared at approximately the same time within both systems, eliminating earlier reproduction as a cause of the size discrepancy. There were three times as many shrimp in PC than in TK (eliminating the possibility of increased population density and competition at TK as a cause) and three times as many F. heteroclitus present in TK than in PC. Since it has already been established that the Fundulus at PC are smaller than at TK and that they are poor predators, differences in Fundulus predation would appear to be an important factor in determining the number and size-frequency of the grass shrimp.

Population Dynamics, Reproduction and Growth of Upogebia Pusilla (Decapoda, Thalassinidea) in the Evros Delta (North Aegean Sea)

[Monthly samples of Upogebia pusilla were collected from February 1983 to February 1984 in an area of the Evros Delta located close to the sea, where salinity and temperature of the water ranged from 4 to 25% and 4.3° to 24.5°C, respectively. Population density and wet weight biomass varied greatly, being higher in summer. Young shrimps appeared in August and had a maximum life span of approximately three years. Ovigerous females were found from April to August. The frequency of females among the collected individuals was 0.393. The smallest ovigerous female had a total length (TL) of 39 mm, while the maximum TL for females was 82 mm and for males 106 mm. Growth in age classes I and II was greater in the period from July to August. Mean growth of carapace length (CL) was described by the Von Bertalanffy function. A positive correlation existed between total length and CL or wet weight (W)., Monthly samples of Upogebia pusilla were collected from February 1983 to February 1984 in an area of the Evros Delta located close to the sea, where salinity and temperature of the water ranged from 4 to 25% and 4.3° to 24.5°C, respectively. Population density and wet weight biomass varied greatly, being higher in summer. Young shrimps appeared in August and had a maximum life span of approximately three years. Ovigerous females were found from April to August. The frequency of females among the collected individuals was 0.393. The smallest ovigerous female had a total length (TL) of 39 mm, while the maximum TL for females was 82 mm and for males 106 mm. Growth in age classes I and II was greater in the period from July to August. Mean growth of carapace length (CL) was described by the Von Bertalanffy function. A positive correlation existed between total length and CL or wet weight (W).]

Swimming Behaviour During the Larval Development of the Shrimp Metapenaeus Ensis (De Haan, 1844) (Decapoda, Penaeidae)

The swimming behaviour of the larvae and postlarvae of Metapenaeus ensis was studied using a videotape analysis technique. Nauplii alternate between periods of rapid swimming and rest. Protozoeae swim continuously in a smooth and rather slow gliding motion. The swimming behaviour of mysis I and II consists of smooth gliding movement broken periodically by jumps and spiral rolls. Mysis III tends to swim for a short period and then sinks passively through the water column. Sinking behaviour persists as the young shrimp begins to spend more time near the bottom and becomes a bottom dweller after 4 or 5 days of postlarval development. The ability to swim in a backward direction was first observed in mysis III. Ventral flexion of the abdomen is used to provide backward darts in postlarvae. Larvae and postlarvae of M. ensis have the ability to modify their swimming behaviour in response to changes in food conditions. Swimming speed of mysis III and postlarvae was lower in animals fed with algae than in animals fed with both algae and Artemia nauplii. Most developmental stages exhibited faster swimming when starved.