Adult Shrimp Research Articles

Lethal levels of hypoxia for gulf coast estuarine animals

There is increasing concern about eutrophication and subsequent hypoxia problems in estuaries. The US Environmental Protection Agency has developed Water Quality Criteria (WQC) for dissolved oxygen (DO) in saltwater for Cape Cod, MA to Cape Hatteras, NC but inadequate data exists for development of such criteria for other coastal geographic areas. We performed acute tests with two species of crustaceans and seven species of estuarine fishes native to the Gulf of Mexico to complement the data base for northeastern species. Flow-through tests were conducted for either 24- or 48-h at test temperatures from 24 to 28°C and at salinities from 20 to 31.5‰. Estimated 24-h LC50 values obtained for crustaceans ranged from 1.36 mg/l for adult pink shrimp to 1.56 mg/l for 10-day-old mysids. Similarly, estimated LC50 values for fish ranged from 1.34 mg/l in one of the three tests with pinfish to 2.22 mg/l in one of the two tests with scaled sardines. The majority of mortality attributable to low DO concentrations in our experiments usually occurred within the first 4 h of exposure. LC50 values for the species tested are below the WQC recommended protective limit of 2.3 mg/l for juvenile and adult animals.

Isolation and characterization of two actins of the Pacific white shrimp, Litopenaeus vannamei

Two actin genes named actinT1 and actinT2 were isolated and sequenced from the Pacific white shrimp, Litopenaeus vannamei, by screening from a shrimp eyestalk cDNA library. L. vannamei actinT1 cDNA has a 1,128-bp open reading frame encoding for 376 amino acids while L. vannamei actinT2 cDNA has a 1,131-bp open reading frame coding for 377 amino acids. Alignment of the actinT1 and actinT2 cDNA sequences showed that these two actin genes share a sequence identity of 86% at amino acid residues. When compared with actins of several other invertebrate and vertebrate species, the nucleotide sequence of actinT1 is highly homologous (97–100%) with beta-actins, while actinT2 shares 86–95% identity with alpha-actins on the nucleotide level. Phylogenetic analysis and BLAST searches indicated that the ActinT1 protein is identical to crustacean beta-actins, while the ActinT2 protein is highly homologous to crustacean alpha-actins. Constitutive expression of the actinT1 and actinT2 genes were detected by RT-PCR in all adult shrimp organs, including brain, eye-stalk, gill, heart, hemolymph, hepatopancreas, muscle, swimming legs, and stomach, as well as in the shrimp zygote, nauplius, and mysis life stages. These data will facilitate attempts to clone and identify more shrimp genes and constitutive shrimp promoters.

The Ontogeny of Isosmotic Intracellular Regulation in the Diadromous, Freshwater Palaemonid Shrimps, Macrobrachium Amazonicum and M. Olfersi (Decapoda)

Abstract To elucidate the osmoregulatory mechanisms underpinning the invasion of fresh water by the palaemonid Crustacea, we investigate the contribution of free amino acids (FAA) to intracellular isosmotic regulation in selected ontogenetic stages of two diadromous, neotropical shrimps, Macrobrachium amazonicum and M. olfersi, exposed to fresh water or to saline media. We also evaluate anisosmotic/ionic extracellular regulatory capability in adult M. amazonicum alone; all data for adult M. olfersi are from McNamara et al. (2004). Adult shrimps show similar osmotic and ionic regulatory capabilities, including elevated hemolymph osmolality in fresh water, moderate isosmotic points, hyper-regulatory capability up to 20‰, and good tolerance of saline media. However, the two species rely on brackish water to different degrees to complete their life cycles: while M. olfersi zoeae 1 and 2 survive well in fresh water, those of M. amazonicum die within two hours. Total FAA titers increase significantly over the o...

Effects of coal combustion residues on survival, antioxidant potential, and genotoxicity resulting from full-lifecycle exposure of grass shrimp (Palaemonetes pugio Holthius)

Coal combustion residues (CCRs), largely derived from coal-fired electrical generation, are rich in numerous trace elements that have the potential to induce sublethal effects including oxidative stress, alterations in antioxidant status and DNA single strand breaks (SSB). CCRs are frequently discharged into natural and man-made aquatic systems. As the effects of CCRs have received relatively little attention in estuarine systems, the estuarine grass shrimp, Palaemonetes pugio, was chosen for this study. Grass shrimp were exposed in the laboratory to CCR-enriched sediments and food over a full life cycle. Survival to metamorphosis was significantly reduced in CCR-exposed larvae (17+/-4 versus 70+/-13% in the controls) but not in the juveniles or adults. The COMET assay, a general but sensitive assay for genotoxicity, was used to quantify DNA SSB in the adults. Total antioxidant potential was examined to assess the overall antioxidant scavenging capacity of CCR-exposed and non-exposed adult grass shrimp. Grass shrimp exposed to CCR significantly accumulated selenium and cadmium compared to unexposed shrimp, although an inverse relationship was seen for mercury accumulation. Chronic CCR exposure caused DNA SSB in hepatopancreas cells, as evidenced by the significantly increased percent tail DNA, tail moment, and tail length as compared to reference shrimp. However, no significant difference was observed in total antioxidant potential. Our findings suggest that genotoxicity may be an important mode of toxicity of CCR, and that DNA SSB may serve as a useful biomarker of exposure and effect of this very common, complex waste stream.

Acute Toxicity and Acetylcholinesterase Inhibition in Grass Shrimp (Palaemonetes pugio) and Oysters (Crassostrea virginica) Exposed to the Organophosphate Dichlorvos: Laboratory and Field Studies

The use of various organophosphates to control mosquito populations is a common practice across the globe. We review the literature (LC50s) on dichlorvos, the primary breakdown product of Dibrom, and use laboratory and field experiments to determine the lethal and sublethal (bioassays) effects of dichlorvos on two widely distributed and ecologically important estuarine invertebrate species, the marsh grass shrimp, Palaemonetes pugio and the Eastern oyster, Crassostrea virginica. Laboratory results based on LC50s and sublethal acetylcholinesterase (AChE) inhibition activity bioassays indicate that adult grass shrimp are more sensitive (approximately 500 x ) to dichlorvos than juvenile oysters. Although potentially an important factor for intertidal or shallow-dwelling estuarine organisms, the toxicity of dichlorvos was not enhanced in the presence of simulated sunlight for adult P. pugio. The most notable decreases in AChE activity were for grass shrimp and oysters exposed to dichlorvos concentrations above those considered ecologically relevant. In field experiments, both species were deployed in cages in unsprayed (n = 2) and sprayed (n = 3) sites and water samples collected pre- and post-spraying. Quantifiable dichlorvos levels were measured at the two narrowest creek treatment sites following mosquito spraying, suggesting that overspray can occur and there was evidence of a sublethal AChE response at these same sites. However, experiments at the widest creek revealed no measurable dichlorvos or sublethal responses. Results from this research suggest that adult grass shrimp are more sensitive to dichlorvos than juvenile oysters. Spraying near small tidal creeks may have measurable impacts on resident species, while larger (wider) creeks appear to be capable of buffering organisms from transient fluxes of mosquito control agents that may enter the system.

Molecular cloning and characterization of the crustacean hyperglycemic hormone cDNA from Litopenaeus schmitti

The crustacean hyperglycemic hormone (CHH) plays an important role in the regulation of hemolymph glucose levels, but it is also involved in other functions such as growth, molting and reproduction. In the present study we describe the first CHH family gene isolated from the Atlantic Ocean shrimp Litopenaeus schmitti. Sequence analysis of the amplified cDNA fragment revealed a high nucleotide sequence identity with other CHHs. Northern blot analysis showed that the isolated CHH mRNA from L. schmitti is present in the eyestalk but not in muscle or stomach. We also investigated the ability of dsRNA to inhibit the CHH function in shrimps in vivo. Injection of CHH dsRNA into the abdominal hemolymph sinuses resulted in undetectable CHH mRNA levels within 24 h and a corresponding decrease in hemolymph glucose levels, suggesting that functional gene silencing had occurred. These findings are the first evidence that dsRNA technique is operative in adult shrimps in vivo.

Feeding ecology of the grooved tiger shrimp Penaeus semisulcatus De Haan (Decapoda: Penaeidae) in inshore waters of Qatar, Arabian Gulf

The feeding ecology of the green tiger shrimp Penaeus semisulcatus was studied in inshore fishing grounds off Doha, Qatar, using a combination of stable isotope (δ13C and δ15N) analysis and gut contents examination. Samples of post-larvae, juvenile and adult shrimp and other organisms were collected from intertidal and subtidal zones during the spawning season (January–June). Shrimp collected from shallow water seagrass beds were mostly post-larvae and juveniles and were significantly smaller than the older juveniles and adults caught in deeper macroalgal beds. Gut content examination indicated that post-larvae and juvenile shrimp in seagrass beds fed mainly on benthos such as Foraminifera, polychaetes, benthic diatoms and small benthic crustaceans (amphipods, isopods and ostracoda), whereas larger shrimp in the macroalgal beds fed mainly on bivalve molluscs and to a lesser extent polychaetes. In shrimp from both seagrass and algal beds, unidentifiable detritus was also present in the gut (18, 32%). δ13C values for shrimp muscle tissue ranged from −9.5 ± 0.26 to −12.7 ± 0.05‰, and δ15N values increased with increasing shrimp size, ranging from 4.1 ± 0.03 to 7.7 ± 0.11‰. Both δ15N values and δ13C values for shrimp tissue were consistent with the dietary sources indicated by gut contents and the δ13C and δ15N values for primary producers and prey species. The combination of gut content and stable isotope data demonstrates that seagrass beds are important habitats for post-larvae and juvenile P. semisulcatus, while the transition to deeper water habitats in older shrimp involves a change in diet and source of carbon and nitrogen that is reflected in shrimp tissue stable isotope ratios. The results of the study confirm the linkage between sensitive shallow water habitats and the key life stages of an important commercially-exploited species and indicate the need for suitable assessment of the potential indirect impacts of coastal developments involving dredging and land reclamation.

Cathepsin B and Glutathione Peroxidase Show Differing Transcriptional Responses in the Grass Shrimp, Palaemonetes pugio Following Exposure to Three Xenobiotics

The common molecular biology techniques, suppressive-subtractive hybridization (SSH) and semi-quantitative real-time PCR (SQRT-PCR), were used to identify differentially expressed genes in the grass shrimp, Palaemonetes pugio following exposure to three different xenobiotics. Lab-acclimated adult male grass shrimp were exposed to empirically derived 96-hr male-specific LC50 concentrations of fipronil (FP, a phenylpyrazole GABA disrupting pesticide), endosulfan (ES, a cyclodiene GABA disrupting pesticide), or cadmium (Cd), as well as a control (CC). An SSH gene expression library was constructed from surviving shrimp from the fipronil and control exposures. Clones obtained by SSH were identified by searching against the NCBI website. A total of 42 genes were identified that were up-regulated by FP exposure, and 47 that were down-regulated. A subset of the affected genes was tested with SQRT-PCR to verify responsiveness to fipronil, as well as to endosulfan and cadmium. Two genes showed strong and significant responses to the exposures: glutathione peroxidase was significantly up-regulated by all three exposures, while Cathepsin B was strongly responsive to the two pesticides, but not to cadmium.

Isotopic reconstruction of marine food webs using cephalopod beaks: new insight from captively raised Sepia officinalis

Cephalopod beaks are a valuable source of material for stable isotope analysis to reconstruct the feeding ecology of cephalopods and their predators. We conducted a controlled captive-rearing experiment on the cuttlefish Sepia officinalis L., 1758 to 10 months of age. During the first and second months of life, animals were fed mysids ( Mysidopsis sp.) and shrimp ( Palaemonetes pugio Holthuis, 1949), but after 2 months, they were fed a homogeneous diet of shrimp ( Farfantepenaeus aztecus (Ives, 1891) and Litopenaeus setiferus (L., 1767)) until sampling. Soft tissues such as buccal mass, arm, and mantle were enriched in 15N over the shrimp diet by about 3.3‰, with little change in 13C, a result in keeping with previous findings for other marine predators. However, beaks showed little isotopic enrichment over the diets at the time of beak formation, with the beak rostral tips representing the neonatal diet and the remaining beak material representing the adult (shrimp) diet. Additionally, for four wild cephalopod species ( Todaropsis eblanae (Ball, 1841), Illex coindetii (Verany, 1839), Loligo vulgaris (Lamarck, 1798), and S. officinalis) obtained commercially in France, we measured δ13C and δ15N values in lower beaks and soft tissues. Similar to the results of our captive study, soft tissues were consistently enriched in 15N over beaks by an average of 4.8‰ (range 3.9‰–6.1‰) but were slightly depleted in 13C by 0.8‰ (0.7‰–1.2‰). The isotopic measurement of cephalopod beaks can thus be used to directly trace the isotopic composition of cephalopod diets and will be a powerful tool in the reconstruction of higher-trophic-level predators of cephalopods, since beaks are often the only material remaining for analysis from field samples.

The Shrimp Caridina nilotica in Lake Victoria (East Africa), Before and After the Nile Perch Increase

The shrimp Caridina nilotica is a major prey of the introduced Nile perch in Lake Victoria. In spite of heavy predation, the density of shrimps increased after the Nile perch boom and the concomitant disappearance of the haplochromine cichlids. In the same period, the mean size of gravid shrimps and the size at first maturity declined. This seems to indicate an increased predation pressure on adult shrimps. Before the Nile perch upsurge, specialised shrimp eaters and piscivores, among the haplochromine cichlids, only took adult shrimps, whereas we assume that most haplochromines used to include juvenile shrimps into their diet. Another important predator on adult shrimps was Bagrus docmak. The combined density of predators on adult shrimps in the pre-Nile perch era was estimated at 10 kg ha−1 and the potential predators on juveniles were estimated at 170 kg ha−1. After the Nile perch upsurge, only Nile perch up to 10 cm TL and Rastrineobola argentea fed on juvenile shrimps (ca. 36 kg ha−1) and Nile perch from 10 to 50 cm TL (ca. 13 kg ha−1) fed on adults. These rough estimates of the biomass of predators on shrimps before and after the Nile perch upsurge indicate a reduced predation pressure on juvenile shrimps. The disappearance of the haplochromines may have released competition with small Nile perch for juvenile shrimps, thus enhancing the recruitment of Nile perch.

Effects of the insecticide permethrin on three life stages of the grass shrimp, Palaemonetes pugio

Toxicity of the pyrethroid insecticide permethrin was assessed using three life stages of the estuarine grass shrimp, Palaemonetes pugio. Adult and larval shrimp were tested with and without sediment. An aqueous embryo test was also conducted. Cellular stress biomarkers, glutathione, and lipid peroxidation, were assessed. Larval shrimp were the most sensitive life stage with a 96-h lethal concentration (LC 50) value of 0.05 μg/L, compared to 0.25 μg/L for adults, and 6.4 μg/L for embryos. The presence of sediment significantly decreased toxicity of permethrin to both adult and larval shrimp. Permethrin exposure increased time to hatch in embryos and decreased swimming behavior of larvae. Lipid peroxidation levels were significantly decreased in the adult shrimp, but increased in larval shrimp exposed to permethrin. Low levels of permethrin may negatively affect grass shrimp health and survival. Permethrin use in the coastal zone should be carefully managed to avoid adverse impacts on nontarget estuarine organisms.

Estrutura populacional dos camarões simpátricos Potimirim glabra e Potimirim potimirim (Crustacea, Decapoda, Atyidae) no rio Sahy, Rio de Janeiro, Brasil

Este trabalho teve por objetivo obter conhecimento sobre a estrutura populacional de dois camarões de água doce simpátricos, Potimirim glabra (Kingsley, 1878) e Potimirim potimirim (Müller, 1881) no rio Sahy, Mangaratiba, Rio de Janeiro, Brasil. Os indivíduos foram coletados mensalmente durante o período de setembro de 1997 a fevereiro de 1999 utilizando-se peneiras, que foram passadas sob a vegetação marginal, superfície de rochas e pequenas poças d'água, num esforço de 15 minutos por coletor. Os animais foram separados quanto ao sexo e mensurados em relação ao comprimento total e do cefalotórax. Um total de 4.889 indivíduos foram coletados no rio Sahy: 3.281 P. glabra e 1.608 P. potimirim. A razão sexual observada foi de 1:1 para P. glabra e 1:2,3 para P. potimirim. Em ambas populações, cinco estágios de maturidade sexual foram determinados, sendo as populações constituídas principalmente por camarões adultos. O recrutamento de juvenis apresentou diferenças em ambas as espécies. O recrutamento de P. glabra ocorreu durante todo o período de estudo, exceto na primavera, enquanto que P. potimirim foi registrado somente no outono. A distribuição sazonal de fêmeas ovígeras de P. glabra é similar ao de P. potimirim, com reprodução na primavera e no verão.

Immunostimulation of white shrimp ( Litopenaeus vannamei) following dietary administration of Ergosan

Ergosan an algal product containing 1% alginic acid, developed for use in aquaculture and reported to have immunomodulatory activity, was administered orally to intermoult adult white shrimp ( Litopenaeus vannamei) for 15 days. Examination of haemolymph proteins using SDS–PAGE did not reveal any obvious differences between control and Ergosan treated shrimp. Similarly, total haemocyte counts were found to be roughly equivalent for both the control and experimental samples. However, differential analysis of haemocyte populations revealed marked changes in terms of the relative levels of hyaline, semi-granular, and particularly granular haemocytes between the two groups. Moreover, enhancement of the in vitro antimicrobial activity of haemolymph towards two shrimp pathogenic Vibrio isolates was recorded for shrimp fed with Ergosan. Finally, shrimp fed with Ergosan showed a significant increase in relative growth when compared with control groups.

Composition and nutritional efficacy of adult fairy shrimp Streptocephalus dichotomus as live feed

Success in aquaculture is based on various criteria, in which selection of a suitable feed and its potential use is important. The suitability and potential use of the adult fairy shrimp, Streptocephalus dichotomus, as a live feed was investigated. S. dichotomus contains 55% protein, 9% carbohydrate, 19% lipids, 10% ash and an energy value of 20 kJ/g, which is equivalent to Artemia sps. The amino acid composition of adult S. dichotomus was determined; the levels of essential amino acids in proteins were 7.7% lysine, 2.8% methionine, 1.6% histidine, 7.4% arginine, 4.6% isoleucine, 8.2% leucine, 4.9% valine, 4.3% glycine, and 5% threonine which are higher than those of the Artemia. Analysis of the carotenoids showed the presence of astaxanthin, canthaxanthin and β-carotene. Effective utilization of adult fairy shrimp was studied using the ornamental fish, Carassius auratus, which showed equivalent growth performance similar to Artemia. The biochemical analyses of whole tissue of the fish fed with live feeds showed their efficient utilization. Fatty acid and amino acid compositions of carcasses of fish fed live diets showed their efficient consumption. Energy budget analysis of fish fed on the fairy shrimp, S. dichotomus, revealed that about 99.6% of the consumed feed was assimilated with a conversion ratio of 1.59, similar to Artemia (99.4% assimilated with a conversion ratio of 1.44). The presence of carotenoids, high energy content and optimal nutritional value offers the advantages of fairy shrimp as live feed in freshwater aquaculture.

Activation of lipid catabolism by the water-soluble fraction of petroleum in the crustacean Macrobrachium borellii

Little is known about the effect of the water-soluble fraction of crude oil (WSF) on lipid metabolism in invertebrates. The effect of the WSF on the triacylglycerol (TAG) mobilization, fatty acid activation and degradation was evaluated in the decapod Macrobrachium borellii, exposing adult and eggs at different stages of development for 7 days to a sublethal concentration of WSF. Using radioactive tracers, mitochondrial palmitoyl-CoA synthetase (ACS), triacylglycerol lipase (TAG-lipase) and fatty acid β-oxidation system activities were assayed. Before studying the effect of WSF, the kinetic parameters of ACS were determined in purified mitochondria. Its optimal temperature and pH were 32 °C and 8.0, respectively, the apparent K m 2.48 μmol l −1, and its V max of 1.93 nmol min −1 mg protein −1. These kinetic parameters differed significantly from this shrimp's microsomal isoform. After 7 days exposure to a sublethal concentration of WSF (0.6 mg/l), changes were observed in the enzymatic activity of all enzymes or enzymatic system assayed in adult midgut gland as well as in stage 5 eggs, a period of active organogenesis. An increase in the mobilization of energy stores was detected as early as stage 4, where TAG-lipase activity increased by 27% in exposed eggs. The increase was even more marked in exposed eggs at stage 5 where a three-fold rise (154%) was determined. Exposed adult shrimp also showed an augmented lipase activity by 38%. Fatty acid β-oxidation increased by 51.0 and 35.5% in midgut gland and eggs at stage 5, respectively, but no changes were observed at less-developed stages. Mitochondrial fatty acid activation by ACS also increased in adults and stage 5 eggs by 7.4 and 52.0%, respectively. A similar response of the lipid catabolic pathways to WSF contamination in both adult and eggs, suggests that the exposure to this pollutant causes an increase in the energy needs of this shrimp. When validated by field studies, these catabolic enzymes could be employed as early pollution biomarkers.

Superoxide radical production in response to environmental hypoxia in cultured shrimp

Markers of oxidative stress in response to hypoxia and reoxygenation were assessed in Pacific white shrimp (Litopenaeus vannamei). Adult shrimp were either exposed to hypoxia (1 mg O2/L) for 6, 12, or 24 h followed by 1-h reoxygenation, or exposed to hypoxia for 24 h followed by 1- to 6-h reoxygenation. In all cases, shrimp maintained at constant normoxia were used as controls. Spectrophotometric techniques were applied to analyze lactate concentration, superoxide radical (O2˙−) production, lipid peroxidation (TBARS), and antioxidant capacity status in muscle, hepatopancreas, and gill samples. Results indicate differences among tissues, even under control conditions. O2˙− production and TBARS levels were higher in hepatopancreas than in gill or muscle. No effect of exposure to hypoxia was found. However, reoxygenation following exposure to hypoxia was found to affect the oxidative metabolism of muscle and hepatopancreas from cultured shrimp. Lactate concentration and O2˙− production increased while antioxidant capacity decreased in hepatopancreas and muscle in the first hours of reoxygenation. This could translate into tissue damage, which may significantly jeopardize the commercial aquaculture product.

Toxicity of the Mosquito Control Pesticide Scourge® to Adult and Larval Grass Shrimp (Palaemonetes pugio)

This study investigated the toxicity of various concentrations of technical resmethrin and Scourge® on adult and larval Palaemonetes pugio, a common grass shrimp species. Two types of tests were conducted for each of the resmethrin formulations using adult and larval grass shrimp life stages, a 96-h static renewal aqueous test without sediment, and a 24-h static nonrenewal aqueous test with sediment. For resmethrin, the 96-h aqueous LC50 value for adult shrimp was 0.53 μg/L (95% confidence interval (CI): 0.46–0.60 μg/L), and for larval shrimp was 0.35 μg/L (95% CI: 0.28–0.42 μg/L). In the presence of sediment, technical resmethrin produced a 24-h LC50 value for adult shrimp of 5.44 μg/L (95% CI: 4.52–6.55 μg/L), and for larval shrimp of 2.15 μg/L (95% CI: 1.35–3.43 μg/L). For Scourge®, the 96-h aqueous LC50 for adult shrimp was 2.08 μg/L (95% CI: 1.70–2.54 μg/L), and for larval shrimp was 0.36 μg/L (95% CI: 0.24–0.55 μg/L). The 24-h sediment test yielded an LC50 value of 16.12 μg/L (95% CI: 14.79–17.57 μg/L) for adult shrimp, and 14.16 μg/L (95% CI: 12.21–16.43 μg/L) for larvae. Adjusted LC50 values to reflect the 18% resmethrin concentration in Scourge® are 0.37 μg/L (adult), 0.07 μg/L (larvae) for the 96-h aqueous test, and 2.90 μg/L (adult), 2.6 μg/L (larvae) for the 24-h sediment test. Larval grass shrimp were more sensitive to technical resmethrin and Scourge® than the adult life stage. The results also demonstrate that synergized resmethrin is more toxic to P. pugio than the nonsynergized form, and that the presence of sediment decreases the toxicity of both resmethrin and Scourge®

Sea surface temperature and the brown shrimp ( Farfantepenaeus aztecus) population on the Alabama, Mississippi, Louisiana and Texas continental shelves

Analysis of the Southeast Area Monitoring and Assessment Program – Gulf of Mexico (SEAMAP-GM) summer and fall trawl survey data covering the Alabama, Mississippi, Louisiana and Texas continental shelves for the period 1987–2000 shows that the annual number n and weight w of the brown shrimp per trawl is positively correlated with annual sea surface temperature (SST) averaged over the continental shelves. Correlations of the monthly anomalous SST by calendar month with the annual shrimp data are highest in April and May. Past work has suggested a possible reason for this: juvenile brown shrimp, which mainly develop from postlarvae in coastal estuaries in April and May, grow faster in warmer water and are therefore more likely to escape predators. Since the juvenile shrimp population is a good predictor of the adult shelf shrimp population, and since the estuarine and shelf SST are closely linked, it is reasonable that April and May shelf SST should be positively correlated with the number and weight of brown shrimp per trawl. Shrimp are more numerous in the summer and the correlation of April and May SST anomaly is much higher for the number and weight per trawl in the summer than in the fall. Hindcasts are made using the simple linear statistical prediction model n = α + β · SSTA , where SSTA is the anomalous April–May departure of SST from the annual cycle. The cross-verified correlation between model and observed n is r = 0.77. A similar model for w gave r = 0.79. A prediction model for summer shrimp alone had cross-verified correlations r = 0.79 for n and 0.86 for w. Based on the 2004 April–May SST anomaly, annual and summer models predict that n and w should be close to average in 2004.

Recovery of a tropical stream after a harvest‐related chlorine poisoning event

Summary1. Harvest‐related poisoning events are common in tropical streams, yet research on stream recovery has largely been limited to temperate streams and generally does not include any measures of ecosystem function, such as leaf breakdown.2. We assessed recovery of a second‐order, high‐gradient stream draining the Luquillo Experimental Forest, Puerto Rico, 3 months after a chlorine‐bleach poisoning event. The illegal poisoning of freshwater shrimps for harvest caused massive mortality of shrimps and dramatic changes in those ecosystem properties influenced by shrimps. We determined recovery potential using an established recovery index and assessed actual recovery by examining whether the poisoned reach returned to conditions resembling an undisturbed upstream reference reach.3. Recovery potential was excellent (score = 729 of a possible 729) and can be attributed to nearby sources of organisms for colonisation, the mobility of dominant organisms, unimpaired habitat, rapid flushing and processing of chlorine, and location within a national forest.4. Actual recovery was substantial. Comparison of the reference reach with the formerly poisoned reach indicated: (1) complete recovery of xiphocaridid and palaemonid shrimp population abundances, shrimp size distributions, leaf breakdown rates, and abundances of oligochaetes and mayflies on leaves, and (2) only small differences in atyid shrimp abundance and community and ecosystem properties influenced by atyid shrimps (standing stocks of epilithic fine inorganic and organic matter, chlorophyll a, and abundances of chironomids and copepods on leaves).5. There was no detectable pattern between any measured variables and distance downstream from the poisoning. However, shrimp size‐distributions indicated that the observed recovery may represent a source‐sink dynamic, in which the poisoned reach acts as a sink which depletes adult shrimp populations from surrounding undisturbed habitats. Thus, the rapid recovery observed in this study is consistent with results from other field studies of pulse chlorine disturbances, harvest‐related fish poisonings, and recovery of freshwater biotic interactions, but it is unlikely to be sustainable if multiple poisonings deplete adult populations to the extent that juvenile recruitment does not offset adult shrimp mortality.

Reproductive biology of the female Japanese mantis shrimp Oratosquilla oratoria (Stomatopoda) in relation to changes in the seasonal pattern of larval occurrence in Tokyo Bay, Japan

: The reproductive traits and the monthly larval abundance of the mantis shrimp Oratosquilla oratoria were investigated in Tokyo Bay, Japan, in 2002. The goal of the study was to elucidate the cause of changes in the monthly pattern of larval abundance from the 1980s to the 1990s as these changes relate to variation in the stock size of the adult shrimp. Oogenesis was divided into 10 stages by histological observation. The developmental stage of oocytes in an individual's ovary was synchronous, suggesting that almost all the oocytes in an ovary are spawned at the same time. The size at first maturity was estimated to be 7 ≤ body length (BL) < 8 cm. Fecundity was expressed as a function of BL, ranging from 19 300 eggs for 8 cm BL to 92 100 eggs for 14 cm BL. Small female shrimps (<10 cm BL) spawned around August. Most large female shrimps (≥10 cm BL) spawned around May, and some large female shrimps also spawned until September. Although most large female shrimps spawned in spring, the larval abundance was low before July and high from August onwards. The results suggest that a substantial decrease in the stock size of large individuals causes the low larval abundance before July.