Distribution Of Shrimp Research Articles

Population structure, fecundity and ecological aspects of freshwater shrimp species (Decapoda, Palaemonidae) of an urban forest fragment in central Amazonia, Brazil

Information about population structure, ecological aspects and reproductive biology of Amazonian freshwater shrimps is scarce in the scientific literature and concentrated in studies conducted in rivers. In this study we present data about species composition, population structure, abundance, fecundity and effects of abiotic factors on the distribution of freshwater shrimps in small streams at an urban forest fragment in Manaus, Central Amazonia. We collected the shrimps using minnow-traps in 12 first- and second-order streams in dry and rainy seasons. We found four species: Macrobrachium ferreirai Kensley & Walker, 1982, Macrobrachium inpa Kensley & Walker, 1982, Macrobrachium nattereri (Heller, 1862) and Pseudopalaemon amazonensis Ramos-Porto, 1979. First order streams had a higher number of species. Adults and juveniles of all species and ovigerous females were found in the majority of the sampling events. Males were more abundant and larger than females in all species of Macrobrachium. All species had a few, large eggs. The abundance of M. nattereri was affected by stream size and temperature. The population structure of the studied species was different from those in other studies on shrimp populations in Central Amazonia and other regions of Brazil, indicating effects of sampling methods and the structure and size of water bodies on the population structure in different regions. The presence of ovigerous females in all sampling periods indicates continuous reproduction.

Experimental Infection and Detection of Necrotizing Hepatopancreatitis Bacterium in the American LobsterHomarus americanus

Necrotizing hepatopancreatitis bacterium (NHPB) is an obligated intracellular bacteria causing severe hepatopancreatic damages and mass mortalities in penaeid shrimp. The worldwide distribution of penaeid shrimp as alien species threatens the life cycle of other crustacean species. The aim of the experiment was to evaluate the possibility of experimentally infecting the American lobster (Homarus americanus) with NHPB extracted from shrimp hepatopancreas. Homogenates from infected shrimp were fed by force to lobsters. Other group of lobsters was fed with homogenates of NHPB-free hepatopancreas. After the 15th day from initial inoculation, the presence of NHPB was detected by polymerase chain reaction in feces and hepatopancreas from lobsters inoculated with infected homogenates. Necrotized spots were observed in the surface of lobster hepatopancreas. In contrast, lobsters fed on NHPB-free homogenates resulted negative for NHPB. Evidence suggests the plasticity of NHPB which can infect crustacean from different species and inhabiting diverse latitudes. Considering the results, the American lobster could be a good candidate to maintain available NHPB in vivo.

Occurrence and distribution of freshwater shrimp in the Isazu and Yura Rivers, Kyoto, western Japan

Occurrence and distribution of freshwater shrimp in the Isazu and Yura Rivers, Kyoto, western Japan

Towards a more complete understanding of the life cycle of brown shrimp (Crangon crangon): modelling passive larvae and juvenile transport in combination with physically forced vertical juvenile migration

In this study we developed and utilized a complex model approach to investigate the impact of stage-specific transport processes on the development and spatial distribution of brown shrimp (Crangon crangon) post-larvae and juveniles in the German Bight. First, we focused on drift processes during the pelagic larval stage by coupling an individual-based model for egg and larval development ‘off-line’ to a 3D hydrodynamic model utilizing the Lagrangian method. Secondly, we investigated tidal-induced transport processes after juvenile settlement. To determine the tidal cycle, the model coupling was accomplished ‘on-line’ by resolving the individual-based model and hydrodynamic model with the same time step. The vertical migration of juveniles, a prerequisite for the selective tidal stream transport (STST), was modelled as a sub-grid scale physical process (balance of forces: gravitation, buoyancy, Stoke’s friction and dynamic uplift) and considered complex particle dynamics. We applied the model to test temperature and salinity cues as possible tidal indicators utilized by juvenile brown shrimp. Our results indicated that transport processes could significantly change the timing and spatial distribution of post-larval abundance. We also showed that the small-scale hydrodynamic forcing acting on the bodies of juvenile brown shrimps was sufficient to account for the vertical migration required to use STST. For both investigated tidal cues STST performing juvenile brown shrimp were transported on-shore. A faster and more continuous STST was calculated for the salinity cue, resulting in larger abundances of brown shrimp in estuarine areas.

These Squatters Are Not Innocent: The Evidence of Parasitism in Sponge-Inhabiting Shrimps

Marine sponges are frequently inhabited by a wide range of associated invertebrates, including caridean shrimps. Symbiotic shrimps are often considered to be commensals; however, in most cases, the relationship with sponge hosts remains unclear. Here we demonstrate that sponge-inhabiting shrimps are often parasites adapted to consumption of sponge tissues. First, we provide detailed examination of morphology and stomach contents of Typton carneus (Decapoda: Palaemonidae: Pontoniinae), a West Atlantic tropical shrimp living in fire sponges of the genus Tedania. Remarkable shear-like claws of T. carneus show evidence of intensive shearing, likely the result of crushing siliceous sponge spicules. Examination of stomach contents revealed that the host sponge tissue is a major source of food for T. carneus. A parasitic mode of life is also reflected in adaptations of mouth appendages, in the reproduction strategy, and in apparent sequestration of host pigments by shrimp. Consistent results were obtained also for congeneric species T. distinctus (Western Atlantic) and T. spongicola (Mediterranean). The distribution of shrimps among sponge hosts (mostly solitary individuals or heterosexual pairs) suggests that Typton shrimps actively prevent colonisation of their sponge by additional conspecifics, thus protecting their resource and reducing the damage to the hosts. We also demonstrate feeding on host tissues by sponge-associated shrimps of the genera Onycocaris, Periclimenaeus, and Thaumastocaris (Pontoniinae) and Synalpheus (Alpheidae). The parasitic mode of life appears to be widely distributed among sponge-inhabiting shrimps. However, it is possible that under some circumstances, the shrimps provide a service to the host sponge by preventing a penetration by potentially more damaging associated animals. The overall nature of interspecific shrimp-sponge relationships thus warrants further investigation.

Temporal and spatial distribution of fish and shrimp assemblage in the Bakkhali river estuary of Bangladesh in relation to some water quality parameters

Fish and shrimp species, together with water quality data, were collected from two different stations located inside the Bakkhali river estuary of Bangladesh during winter, premonsoon and monsoon periods. Significant temporal differences were observed for water temperature, salinity and dissolved oxygen. The average catch of fish and shrimps per net between stations varied between 1.89±0.36kg at station 1 and 7.54±4.39kg at station 2, while the average catch in winter, premonsoon and monsoon periods found to be 2.79±1.08kg/net, 6.31±1.03kg/net and 5.06±2.89kg/net, respectively, with a significant difference in catch per net between stations although no significant difference in catch per net was observed between seasons. A total of 18,467 individuals of fish (35 species) and shrimp (10 species) were found in the present study. Three species of shrimps were observed to be dominant (>10.0%) and these were Metapenaeus lysianassa (17.07%), Ambassis dussumieri (14.54%) and Macrobrachium villosimanus (12.13%). Clear differences in faunal abundances were observed between seasons and stations with higher mean abundances during winter (1747.83±421.99 individual/5kg) and at Station 1 (1444±866.74 individuals/5kg). Similarly, the diversity indices, both Shannon–Wiener and Margalef, showed significant differences between stations and seasons (except Shannon for stations). Analyses of similarity (ANOSIM) results confirm both spatial and temporal differences in species community structure with a highly diverse assemblage. Canonical Correspondence Analysis results indicated that salinity and transparency were the main variables influencing fish and shrimp distribution in the Bakkhali river estuary.

Variation in the distribution of ocean shrimp (Pandalus jordani) recruits: links with coastal upwelling and climate change

In this analysis, an atypical northward shift in the distribution of age-1 ocean shrimp (Pandalus jordani) recruits off Oregon in 2000 and 2002–2004 was linked to anomolously strong coastal upwelling winds off southern Oregon (42°N latitude) in April–July of the year of larval release (t−1). This is the first clear evidence that strong upwelling winds can depress local recruitment of ocean shrimp. Regression analysis confirmed a long-term negative correlation between loge of ocean shrimp recruitment and April sea level height (SLH) at Crescent City, California, in the year of larval release, for both northern and southern Oregon waters. The regional pattern of ocean shrimp catches and seasonal upwelling winds showed that, although the timing of the spring transition as reflected in April SLH drives ocean shrimp recruitment success off Oregon generally, the strength and consistency of spring upwelling limits the distribution of large concentrations of ocean shrimp at the southern end of the northern California/Oregon/Washington area. A northward shift in 1999 and 2001–03 in the northern edge of this ‘zone of maximum upwelling’ is the likely cause of the weak southern Oregon recruitment and resulting atypical distribution of ocean shrimp observed off Oregon in 2000 and 2002–04, with a return to a more typical catch distribution as spring upwelling moderated in subsequent years. It is noted that a northward shift in the conditions that produce strong and steady spring upwelling winds is consistent with many predictions of global climate models under conditions of global warming.

Spatiotemporal variations of the ichthyofaunal structure accompanying the seabob shrimp, Xiphopenaeus kroyeri (Crustacea: Penaeidae), fishery in important fishery areas of the Santa Catarina shore, Brazil

The present study analyzed qualitatively and quantitatively the temporal and spatial changes in the fish assemblages present in seabob shrimp distribution sites in two important fishing areas of the Santa Catarina coast. Monthly bottom trawls, conducted between March 2007 and February 2008 in Balneario Barra do Sul and Penha, yielded a total of 38,608 specimens belonging to 54 species, of which 35 occurred in both regions. The Sciaenidae was the most represented family in both number of species and abundance of individuals. The dominant species were Stellifer rastrifer (Jordan, 1889), S. brasiliensis (Schultz, 1945), Paralonchurus brasiliensis (Steindachner, 1875), Isopisthus parvipinnis (Cuvier, 1830), Trichiurus lepturus (Linnaeus, 1758), and Pellona harroweri (Fowler, 1917). The ichthyofaunal structure showed a spatiotemporal dependence with significant differences in March 2007 and January and February 2008 between Balneario Barra do Sul and Penha. The main differences were attributed to dominant species, which were responsible for significantly altering the abundance of the assemblages. The species richness was similar in both sites, whereas the diversity and equitability indices showed monthly fluctuation patterns that differed between Balneario Barra do Sul and Penha. The Shannon index differed in August, September and November 2007 and January and February 2008, with an H' ranging from 0.74 to 1.98 influenced by dominant species, whereas significant variations were observed for the Pielou index in November 2007 and February 2008. The Berger-Parker index demonstrated a clear dominance pattern where the monthly numeric contribution of a single species ranged from approximately 30 to 80%. Although the results showed differences between fishing grounds 25% of the time, we conclude that fish assemblies captured as accompanying fauna in artisanal seabob shrimp fisheries showed statistically similar characteristics for most of the year, although Balneario Barra do Sul and Penha are 35 km away from each other.

Spatial and temporal patterns of species composition and distribution of shrimp community in the Gonghu Bay, Lake Taihu

分别于2005年4月、7月、10月利用蹦网对贡湖湾虾类种类组成和时空分布进行调查.共采集到虾类9605尾, 属于2科3属5种, 分别是秀丽白虾(Exopalaemon modestus)、日本沼虾(Macrobrachium nipponense)、锯齿新米虾中华亚种(Neocaridina denticulata sinensis)、细足米虾(Caridina nilotica gracilipes)、细螯沼虾(Macrobrachium superbum).其中, 秀丽白虾的数量占总数量的63.79%、细足米虾占13.93%, 锯齿新米虾中华亚种占12.69%, 日本沼虾占9.46%, 细螯沼虾占0.11%.虾类密度分布随生境类型和季节不同而有差异, 不同生境中虾类密度分布由大到小顺序是:微齿眼子菜区、混合植被区、马来眼子菜区、沿岸少草区及裸地区, 生物量分布的大小顺序是:微齿眼子菜区、马来眼子菜区、混合植被区、沿岸少草区及裸地区.季节分布中, 虾类密度和生物量分布最大的均为夏季(7月), 其次为春季(4月)和秋季(10月)。;The species composition, spatial and temporal distribution of shrimps in the Gonghu Bay (Lake Taihu) were investiga-ted by sampling with pop-net in April, July and October of 2005.The total of 9605 individuals belonging to 5 species, 3 genera and 2 families were collected.The relative percentage of Exopalaemon modestus, Caridina nilotica gracilipes, Neocaridina denticulata sinensis, Macrobrachium nipponense to the tota1 is 63.79%, 13.93%, 12.69% and 9.46%, respectively.Based on the type and coverage of aquatic vegetation, the lake was categorized into 5 habitat types:Potamogeton maackianus habitat, mixed sub-merged macrophyte habitat, Potamogeton malaianus habitat, littoral zone with a little macrophyte habitat, and naked habitat.The density sequence of all shrimps from high to low is Potamogeton maackianus habitat, mixed submerged macrophyte habitat, Potamogeton malaianus habitat, littoral zone with a little macrophyte habitat and naked habitat.The biomass of shrimps decreased substantially in Potamogeton maackianus habitat, Potamogeton malaianus habitat, combined submerged macrophyte habitat, littoral zone with a little macrophyte habitat, and naked habitat.Each of the dominant species preferred the Potamogeton maackianus habi-tat.In terms of seasonal variation, both the largest density and biomass of the dominant shrimps were in summer (July), followed by spring (April) and autumn (October).

Effects of coupled natural and anthropogenic factors on the community structure of diadromous fish and shrimp species in tropical island streams

Summary 1. Overlapping river and road networks provide a framework for studying the complex interactions between natural and human systems, with river-road intersections as focal areas of study. Roads can alter the morphology of stream channels, pose barriers to freshwater fauna, provide easy access to streams for humans and non-native species and accelerate the expansion of urban development. 2. We determined what variables control the structure of diadromous fish and shrimp communities and assessed whether particular road crossings altered community structure in north-eastern Puerto Rico. We identified 24 sites that represented a range of river and road sizes across two catchments that drain El Yunque National Forest in Puerto Rico. 3. The location of natural barriers and the size of stream pools were the most important variables for predicting six of fifteen fish and shrimp distributions. Predatory fishes were predicted to be limited to areas in the river network below large, steep waterfalls, whereas adult shrimp Atya lanipes (Atyidae) were predicted to be present above these waterfalls. The fish Awaous banana was predicted to be present in pools >11.6 m wide, whereas the shrimp Xiphocaris elongata was predicted to be present in pools <10.4 m wide. The distributions of nine species were predicted poorly, but three of these species were common and three were rare. 4. Although urban and agricultural land covers were among the top three predictors of five species distributions, they were probably good predictors because they were correlated with the natural gradient. Further study is necessary to disentangle natural and anthropogenic gradients. 5. Road crossings, 10 of which were culverts, were not dispersal barriers for fishes or shrimps. On average, species were present both upstream and downstream from road crossings at 68% of sites where they occurred. Absences upstream or downstream from road crossings occurred at 16% of sites each and likely resulted from a failure to detect species. 6. Several existing features of these catchments and taxa may aid in fish and shrimp conservation. The headwaters are protected by management practices of El Yunque National Forest, connectivity within the river network has been maintained, and the diadromous life history of these organisms makes them resilient to pulsed disturbances.

Effects of artificial substrates on the growth, survival and spatial distribution of Litopenaeus vannamei in the intensive culture condition

In order to investigate the effects of artificial substrates (vertical surface of polypropylene fabrics) on cultured shrimp, we reared 28-day old Litopenaeus vannamei post-larvae (PL28) intensively for 90 days at a density of 510 shrimp/m 2 in each of 8 tanks. Two tanks containing no artificial substrate were a control group, and 1, 3 and 5 artificial substrates were present in other 6 tanks. The volume of each tank was 100 L. In the tanks with artificial substrates, the percentage of shrimp distribution on the bottom was less significant (P<0.05) than that in the control tanks. The percentage of shrimps attached to the artificial substrates increased and fewer shrimp occupied the tank bottom as more artificial substrates were added to the tanks. Moreover the trends were more significant as rearing days increased. These results showed that artificial substrates could disperse the shrimp from the tank bottom onto the artificial substrates and thus alleviate the negative effect of high stocking density on shrimp growth in the tanks. Both the average weight and survival in the tanks with artificial substrates were significantly higher (P<0.05) than those in the control tanks. Furthermore, weight and survival increased when more artificial substrates were added. Because the shrimps in all tanks were supplied with suitable water quality and adequate nutritional food, we suggest that the differences of growth and survival were affected mainly by living space added with the addition of artificial substrates.

Distribution and Abundance of Planktonic Shrimps in the Southern Sea of Korea during 1987-1991

Distribution and abundance of planktonic shrimps were studied in the southern sea of Korea from 1987 to 1991. Nine species of five genera belonging to three families were identified. Of these, Leptochela sydniensis and Lucifer intermedius were predominant species and Lucifer penicilifer and Lucifer typus were common species. Remaining five species, Acetes chinensis, Leptochela gracilis, Lucifer chacei, Process wheeleri and Sergestes similis occurred sporadically and rarely. The distribution pattern of planktonic shrimps varied with species and sampling periods. L. intermedius occurred abundantly along inshore waters. L. penicilifer and L. typus appeared in both inshore and offshore waters, but more abundantly in offshore waters under influence of the Tsushima Current. In conclusion, the distribution patterns of planktonic shrimps may be related with hydrographic characteristics and seasonality in the southern sea of Korea.

Relationship between environment and the occurrence of the deep-water rose shrimp Aristeus antennatus (Risso, 1816) in the Blanes submarine canyon (NW Mediterranean)

We performed a multidisciplinary study characterizing the relationships between hydrodynamic conditions (currents and water masses) and the presence and abundance of the deep-water rose shrimp Aristeus antennatus in a submarine canyon (Blanes canyon in the NW Mediterranean Sea). This species is heavily commercially exploited and is the main target species of a bottom trawl fishery. Seasonal fluctuations in landings are attributed to spatio-temporal movements by this species associated with submarine canyons in the study area. Despite the economic importance of this species and the decreases in catches in the area in recent years, few studies have provided significant insight into the environmental conditions driving shrimp distribution. We therefore measured daily A. antennatus catches over the course of an entire year and analyzed this time series in terms of daily average temperature, salinity, mean kinetic energy (MKE), and eddy kinetic energy (EKE) values using generalized additive models and decision trees. A. antennatus was captured between 600 and 900 m in the Blanes canyon, depths that include Levantine Intermediate Water (LIW) and the underlying Western Mediterranean Deep Water (WMDW). The greatest catches were associated with relatively salty waters (38.5–38.6), low MKE values (6 and 9 cm 2 s −2) and moderate EKE values (10 and 20 cm 2 s −2). Deep-water rose shrimp occurrence appears to be driven in a non-linear manner by environmental conditions including local temperature. A. antennatus appears to prefer relatively salty (LIW) waters and low currents (MKE) with moderate variability (EKE).

Patterns of periphyton chlorophyll and dry mass in a neotropical stream: a cheap and rapid analysis using a hand-held fluorometer

Periphyton distribution is affected by various physical, chemical and biological factors at different scales. In the present study, a cheap and rapid method of measurement was used to obtain the many samples necessary for spatial analysis of periphyton along an altitudinal gradient in a low-order stream in south-east Brazilian Atlantic rain-forest. Fluorescence and turbidity were measured using a hand-held fluorometer and calibrated to the chlorophyll and dry mass of periphyton. Periphyton on the horizontal and vertical surfaces of different boulders was examined and shading and water current were measured as covariables. The three upstream sites with higher abundances of potentially grazing and bioturbing shrimps and mayflies had significantly less periphyton dry mass than the three downstream sites. Chlorophyll was positively related to water current, but not to shading. Variabilities in the dry mass and chlorophyll among boulders within sites were not associated with the distribution of shrimps and mayflies. The in vivo measurement was cheap, rapid, sensitive and reasonably precise compared with standard methods. The necessary sacrifice of detail of pigments (different chlorophylls and pheophytin) and dry mass (organic and inorganic constituents) and probably precision was compensated for by the insights gained from the ability to obtain a large number of samples in a hierarchical design.

Secondary production, longevity and resource consumption rates of freshwater shrimps in two tropical streams with contrasting geomorphology and food web structure

Summary1. Freshwater shrimps often dominate the biomass of tropical island streams and are known to have strong effects on stream ecosystem structure and function, but little effort has been dedicated toward quantifying basic energetic and life history attributes such as growth, production and longevity. Such information is critical for understanding both the role of shrimps in ecosystem dynamics and the gravity of threats to shrimp populations posed by human activities such as shrimp harvesting, dam construction and water withdrawal.2. We quantified growth rates and secondary production of dominant freshwater shrimps for 3 years in two Puerto Rican headwater streams that differ in food web structure because of the presence or absence of predatory fishes that are excluded from reaches above waterfalls. Using growth data, we constructed a minimum longevity model to explore the likely minimum life spans of the two dominant taxa (Atya spp. and Xiphocaris elongata). Finally, we used a bioenergetics model to quantify annual consumption rates of major basal resources by the two taxa.3. Daily growth rates ranged from −0.001 to 0.011 day−1, were inversely related to body size, and were higher for small individuals of X. elongata than Atya spp. Mean annual shrimp biomass and secondary production were an order of magnitude higher in the stream that lacked predatory fishes (biomass: 4.34 g AFDM m−2; production: 0.89 g AFDM m−2 year−1) than in the stream with predatory fishes (biomass: 0.12 g AFDM m−2; production: 0.02 g AFDM m−2 year−1). Production : biomass ratios ranged from 0.01 to 0.38.4. Our longevity model predicted a minimum life span of 8 years for Atya spp. and 5 years for X. elongata in the stream lacking predatory fishes. In contrast, due to a larger average size of X. elongata in the stream with predatory fishes, our model predicted a minimum life span of 11 years. Actual life spans of these taxa are likely to be much longer based on long‐term observations of marked individuals.5. Estimated consumption rates from the bioenergetics model indicated that Atya spp. and X. elongata are important processors of organic matter resources in streams where they occur at high densities. Atya spp. and X. elongata appeared capable of consuming a large proportion of algal and insect production and the proportion of direct leaf litter inputs consumed was also appreciable (c. 40–60%). However, the consumption of suspended fine particulate organic matter (SFPOM) by Atya spp. is probably only a minor proportion of total SFPOM flux in these streams.6. Our study suggests that geomorphic features such as waterfalls may play an important role in controlling the distribution and production of freshwater shrimps through their effects on predatory fish movement. Spatial differences in shrimp densities result in landscape‐scale variation in the significance to ecosystem processes of these long‐lived organisms, particularly as processors of major organic matter resources.

Geochronology of the Archean of Australia

The Archean eon is a chronometrically defined subdivision of the Precambrian that extends from 3800 to 2500 Ma. In the Australian continent, Archean rocks (i.e. those with sedimentary deposition or igneous crystallisation ages confidently interpreted to be older than 2500 Ma) occur in the Pilbara and Yilgarn Cratons of Western Australia, the Mulgathing and Sleaford Complexes in the Gawler Craton of South Australia and as minor inliers in the Pine Creek Orogen of the Northern Territory. Metamorphosed lithological components with igneous or sedimentary precursors inferred to be of Archean age also occur in the Browns Range Dome and Billabong Complexes of the Tanami Inlier, Northern Territory, and possibly also in the Broken Hill Inlier. This contribution outlines aspects of the historical development of geochronological methods applied to the Archean of Australia, the respective strengths and weaknesses of these methods and how our understanding of the continent's Archean geology and tectonics was related to this development. The geological formation of the Yilgarn and Pilbara Cratons is investigated using a new statistical approach based on the distribution of SHRIMP U–Pb zircon and monazite dates obtained from rock samples that may have complex mineral age populations. Spatial and temporal characteristics of the magmatic episodes identified in the Yilgarn and Pilbara granite–greenstone terranes are atypical of rift/collision processes attributable to tectonic-plate interactions, but are consistent with their interpretation as a response to major mantle convection events. The strengths of this geochronology-based approach are demonstrated by its application to the Narryer Gneiss Complex of the northwestern part of the Yilgarn Craton. It is shown that this approach offers unique insights into geological events that may be under-represented at the outcrop scale due to later crustal re-working.

Spatial and temporal variations in abundance and biomass of penaeid shrimps in the subtropical Conceição Lagoon, southern Brazil

This one-year study investigated spatial and temporal variations in the abundance and biomass of the pink shrimp species, Farfantepenaeus paulensis and Farfantepenaeus brasiliensis, in the Conceição Lagoon, southern Brazil (September 2003–August 2004). The influence of salinity, water temperature, and rainfall on shrimp distribution was evaluated. Shrimps were caught monthly at three areas within the Conceição Lagoon (Canto, CA; Centro, CE; and Costa, CO). A total of 744 shrimps were sampled, with F. brasiliensis being the dominant species. The two penaeid species were present throughout the year and significant differences were observed between seasons, with F. paulensis being more abundant during the summer and F. brasiliensis in the autumn, suggesting differential migration timing to the sea, differences in recruitment time and an ontogenetic temporal partitioning. Farfantepenaeus paulensis exhibited a homogeneous spatial distribution, whereas F. brasiliensis was more abundant in CE and CO, suggesting that habitats in this coastal lagoon are heterogeneous. Among the abiotic factors, temperature and salinity seemed to be important variables in defining seasonal and spatial patterns, respectively, of the abundance of F. brasiliensis.

SPECIES AND DISTRIBUTION OF PENAEOID SHRIMPS IN THAILAND

Species and distribution of Penaeoid shrimps in Thailand were studied in specimens of shrimp collected from fish markets and fishing ports of 23 provinces along the Gulf of Thailand and the Andaman Sea coast. Identification of species was based on the morphological characters of rostrum, carapace, branchiae, antennule, antenna, third maxilliped, pereiopods, pleopods, abdomen, telson, petasma, thelycum, and the colored pattern of the whole body based on keys and diagnoses available from the current literature. A total of 50 species from 13 genera and 3 families of Penaeoidea were identified in coastal provinces of the Gulf of Thailand and the Andaman Sea. Additional research is needed to more clearly define the distribution of shrimp species in the Gulf of Thailand and the Andaman Sea coasts.

Distribution and bioturbation effects of the tropical alpheid shrimp Alpheus macellarius in sediments impacted by milkfish farming

The impact of milkfish fish pens on the distribution of the alpheid shrimp Alpheus macellarius was studied in the Bolinao area, Philippines. In addition, the impact of the alpheid shrimp on sediment biogeochemistry, including organic matter mineralization, nutrient and sulfur cycling was compared in sediments affected and unaffected by fish farming. The fish farming activity had negative impact on the distribution of shrimps by reducing the abundance up to 60% in the vicinity of the net pens, and to almost absence inside the net pens. At a farm site abandoned seven month prior to sampling the abundance of shrimps was still low and sediment pools of reduced sulfur high, indicating a slow benthic recovery. The shrimp had large physical impact on the sediments, and the mineralization rates were stimulated by the presence of the shrimp in pristine sediments, whereas the fish farm impacted sites showed high mineralization rates both in sediments with and without the presence of the shrimp suggesting that the organic matter enrichment stimulated the mineralization in these low-organic sediments, whereas the shrimp had less impact. Sulfate reduction rates and in particular pools of sulfides increased in the farm impacted sediments, and sulfate reduction was an important process for organic matter mineralization (>67%) in all sediments. Although the shrimp had minor effect on the organic matter mineralization and nutrient fluxes in the farm impacted sediments, they appeared to increase the oxidation of sulfides by increasing the zone of oxidized surface sediment and thereby improving the sediment conditions for recolonization after fish farming has ceased.

Distribution and abundance of penaeid shrimps in a hypersaline lagoon in northwestern Mexico, emphasizing the brown shrimp Farfantepenaeus californiensis life cycle

Life histories of penaeid shrimp have been classified according to the preferred habitats of postlarval, juvenile, and adult stages, ranging from exclusively estuarine to exclusively offshore waters. Brown shrimp Farfantepenaeus californiensis migrate to an offshore habitat at the juvenile stage or even a smaller body size. This paper presents results of monthly samplings from 24 stations over 1 year in the Agiabampo Lagoon complex, a hypersaline lagoon in northwestern Mexico. Five species of penaeid shrimp were identified, with brown shrimp the most abundant during the year of sampling. Results suggest that residency of brown shrimp inside this lagoon is longer than reported in previous studies. An interaction between length and environmental variables (near-surface temperature, salinity, and rainfall) appear to be cues concerning migration.