Small Prawns Research Articles

Fish Biodiversity and Suggested Conservation Measures of Transboundary River Someshwari in Netrokona, Bangladesh

Considering the importance of fish biodiversity for sustainable management of river fisheries, this study aims to explore and evaluate the fish biodiversity of Someshwari River along with conservation measures from November 2020 to October 2021. Data collection was carried out in Jaria, Susang Durgapur, Shivganj Bazar and Bijoypur of Netrokona district. Questionnaire interview, Focus Group Discussion (FGD), Direct observations, Key Informant Interview (KII) was used to collect data. During the study period, 23 species under 12 families were determined. Among them 6 finfish species are endangered, 4 are critically endangered, 5 are vulnerable, 7 are data deficient, and 2 are not threatened, respectively which includes highest catch catfishes at about 26.62%. However, the lowest amount catch constituted the Miror carp of about 5.29%. After the catfish, the second highest catch was 15.9% of small prawn. Another dominant group major carps contained 11.26%, and barbs remained at 11% of the catch and the loaches constituted 1.3% of the total catch. In addition, other groups like Mola carplet 7%, gourami 2.20%, Spiny eels 9.86% etc. were found in the Someshwari river. There were about 81% fish for food and 17% ornamental fish. Fourteen distinct types of fishing equipment were used namely: nets, traps, hooks, and lines, and wounding equipment. Finally, indiscriminate use of harmful gear, extraction of sand and rock, inadequate supervision of Governments and Non Governemental orgazizations, pollution from the adjacent areas, high interest rate of bank loan were understood as common constraints in the study area. Therefore, recommendations were made to improve river fisheries management through habitat restoration, increasing public awareness, prohibition on exploiting brood fish and active participation for sustainable catch.

Nutritional comparison of experimentally and commercially sun-dried lean fish and small prawns of Bangladesh

Nutritional comparison of experimentally and commercially sun-dried lean fish and small prawns of Bangladesh

Effects of a Popular Aquatic Pest Control Agent among Carp Aqua-culturists on Aquatic Microfauna Dynamics

Cypermethrin is gaining popularity among fish farmers community to control aquatic insect pests and ectoparasites. Effect of cypermethrin application at farmer select dose (@0.003 ppm) on aquaculture pests (Notonecta & small prawn) commonly found in tropical ponds along with fish fry was assessed. Effect of cypermethrin application on the composition and survivability dynamics of aquatic microfauna namely rotifer, copepod and cladocera for 8 days was studied in tropical pond conditions. Cypermethrin cause significantly higher mortality to notonecta and prawn compared to fish fry within 24 h of exposure (P<0.05).

Connectivity between a spatial management network and a multi-jurisdictional ocean trawl fishery

Spatial management is often applied in penaeid trawl fisheries to avoid non-optimal size classes of target species, by providing areas of refuge from trawl fishing effort. Efficient application of spatial management relies on having a detailed knowledge of animal movements, particularly for species with complex life histories. Using Eastern King Prawn (Penaeus (Melicertus) plebejus; EKP) as a case study, we examine how spatial and temporal factors can influence connectivity between a spatial management network designed to protect small prawns from capture by trawlers, and a multi-jurisdictional (Queensland [Qld] and New South Wales [NSW]) fishery. Over 7500 prawns were tagged across multiple years in three northern NSW spatial management areas, and 786 tagged prawns were recaptured across both jurisdictions. The majority of prawns tended to be recaptured from deeper waters adjacent to, or directly north of, the spatial management areas, but tagging location and release timing influenced recapture patterns. Cohorts tagged early in the growth season showed lower recapture rates, but were larger on average at recapture, and had migrated further. Prawns reached the fishery in the adjacent jurisdiction (Qld) within 54 days-post tagging, but for most cohorts the majority of recaptures were in NSW zones. Overall, there was good connectivity between all spatial management areas and the NSW fishery, and tagged prawns also reached the Qld spawning areas. This represents an optimal scenario for NSW fishers (who forgo capture of prawns within these spatial management areas): the prawns protected in the closure areas primarily contribute to harvest of larger sized prawns within NSW waters; and a portion of the protected prawns survive to reach the southern Queensland spawning grounds, which is the primary source of recruits for northern NSW nurseries. These findings are broadly relevant to defining the role and impact of established and proposed spatial management networks within penaeid fisheries.

Social interaction in males of the Amazon river prawn Macrobrachium amazonicum (Heller, 1862) (Decapoda, Palaemonidae)

Abstract The large size variation of Macrobrachium amazonicum reflects a complex population structure that consists of four morphotypes, called TC (Translucent Claw), CC (Cinnamon Claw), GC1 (Green Claw 1), and GC2 (Green Claw 2). The effect of the largest morphotype (GC2) claws on development and behaviour of the smallest male morphotype (TC) was analysed through manipulations of the large prawn’s second pair of claws. TC males were paired for 75 days in aquaria with (a) an intact GC2, (b) a GC2 with immobilized dactyls, and (c) a GC2 without chelipeds. Isolated TC males served as a control. The maintenance activities of TC males and social interactions with the GC2 morphotype were monitored. Survival and growth of TC males was lower in relation to the control when they were paired with intact GC2 males. Aggressive interactions were carried out almost exclusively by GC2 and strongly affected the behaviour of the small prawns. The absence of chelipeds and immobilization of dactyls in GC2 prawns reduced the negative effect on the development of TC males and agonistic behaviour. The social interactions between GC2 and TC prawns reflect a stable dominance hierarchy. The large claw of the GC2 morphotype plays a major role in the social interaction.

Multitrophic diversity sustains ecological complexity by dampening top-down control of a shallow marine benthic food web.

Biodiversity is typically considered as a one-dimensional metric (e.g., species richness), yet the consequences of species loss may be different depending on where extinctions occur in the food web. Here, I used a manipulative field experiment in a temperate subtidal marine system to explore the implications of diversity loss at multiple trophic levels for ecosystem functioning and food web structure. The four manipulated predators included the small painted goby and common prawn, which are also fed on by the larger black goby and shore crab. Antagonistic interactions between the manipulated predators (e.g., intraguild predation, intimidation, interference competition) limited their negative effects on the rest of the food web. Top-down control was so suppressed at the highest level of multitrophic diversity that the resulting food webs were as complex and productive as those containing no manipulated predators. Negative interactions between the predators weakened as multitrophic diversity decreased, however, resulting in stronger consumption of lower trophic levels and a simpler food web with lower rates of two key ecosystem processes: primary production and decomposition. These results show how indirect interactions between predators on multiple trophic levels help to promote the complexity and functioning of natural systems.

Trophic Ecology and Ecological Function for Oriental River Prawn (Macrobrachium nipponense) in the South-to-North Canal System

The South-to-North Canal System (SNCS) is the largest water diversion project in the world, and it transports water from water-sufficient southern and central to water-deficient northeastern China. The oriental river prawn is the most adaptable prawn species in this ecosystem and a dominant member of the benthic community. In this study, in order to obtain more information regarding the ecological functions of the prawn in the benthic food webs of the SNCS ecosystem, the trophic ecology of the prawn from the canal and the upstream reservoir was compared in the two ecosymtems. The prawn stable isotopic compositions of different prawn sizes (large, medium and small), niche spaces and the trophic positions were compared between the two ecosymtems. Results showed that in the main canal, particulate organic matter (POM) composed more than 40% of the food consumed by all three size prawns. Compared to small prawn, the diet of medium and large prawns were proportionally higher in POM and zooplankton. In the upstream reservoir, large prawn fed primarily on benthic microalgae, which composed 72.8% of the prawn diet. The pelagic food webs provided 93.5% food source for the canal prawn, while the benthic food webs afforded 72.4% food source for the reservoir prawn. Thereafter, the ecological functions of the prawn in the two ecosystems were also different due to their varied food diet. Careful considerations were suggested when using biomanipulation in the SNCS ecosystem.

Morphology and molecular phylogeny of Macrobrachium suphanense sp. nov. (Decapoda: Palaemonidae) from Thailand.

A small freshwater prawn in Thailand has been found to be a new species and is named Macrobrachium suphanense (Decapoda: Palaemonidae). Fully grown male M. suphanense appeared very different from the most closely related male of M. sintangense: size smaller, second pereiopod smaller and less robust, rostrum form different and, in females, fewer eggs. Less closely related, fully grown M. dolatum has sharper distal cutting edge on fixed finger and M. hungi has longer rostrum than M. suphanense. DNA analyses put M. suphanense, M. sintangense and M. nipponense in the same clade with M. nipponense sister to the other two. Two more clades consist of M. dienbienphuense and M. niphanae on the one hand and M. lanchesteri and M. rosenbergii on the other. The relationship among the three clades is not clearly resolved.

Biochemical Quality Assessment of Fish Powder

The study carried out with a view to determining proximate and mineral composition of fish powder of five freshwater fish samples (Hypophthalmicthys molitrix, Labeo rohita, Cirrnina mrigala and Puntius sophore and small prawns). The samples collected from five local fish markets of Rajshahi city corporation were subjected to washing, gutting drying and grinding in order to make powder and homogenized sample which were preserved into plastic container for chemical analyses. All the activities were conducted in the laboratory of department of Fisheries, University of Rajshahi, Bangladesh. Major nutrient compositions of powder products such as protein, lipid, moisture, ash, carbohydrate, phosphorus, iron and calcium were estimated. Chemical compositions were found to vary among the species. The protein, lipid, moisture and ash content of five samples ranged from 54.31 (P. sophore) to 68.90% (small prawns), 13.33 (P. sophore) to 19.33% (L.rohita), 11.55 (L. rohita) to 13.95% (H. molitrix) and 0.16 (small prawns) to 0.44% (C. mrigala), respectively. The highest value of carbohydrate was 19.23% (P. sophore) and the lowest was 1.75% (C. mrigala). The calcium, iron and phosphorus content of the selected species varied from 2.49 (L. rohita) to 2.55g/kg (small prawns), 0.043 (H. molitrix and P. sophore) to 0.184g/kg (C. mrigala) and 0.94 (L. rohita) to 1.91g/kg (P.sophore), respectively.

A Quick View on Biology of Near Threatened Peacock Eel (<i>Macrognathus aculeatus</i>) in Khulna Region of Bangladesh

The Peacock eel, Macrognathus aculeatus is a near threatened highly valuable small indigenous species in Bangladesh. It is not only toothsome nutritive table fish but also notable aquarium species but still rely on natural stock. Keeping in mind the paucity of information on the biology which is crucial to develop artificial propagation and culture technique of this species, the present research was performed as an attempt to contribute to the information on the taxonomy and other biological aspects of M. aculeatus. Total 50 samples were collected from Khulna region during April to May 2014 to assay. The taxonomical study revealed that the total length, standard length, head length, eye diameter, pre and post orbital length; length of dorsal, anal and caudal fin; length of upper and lower jaw; body depth and width, distance between dorsal fin to caudal fin ranged from 17.00-21.00, 15.00-19.00, 0.80-3.00, 0.20-0.40, 0.50-2.10, 0.30-1.70, 3.10-6.70, 3.50-6.30, 0.50-1.50, 0.30-1.00, 0.70-1.80, 0.90-2.30, 0.60-1.20, 0.70-2.40 cm respectively, additionally meristic character’s formula appeared like D. 19 - 39, A. 11 - 18, C. 29 – 52, L. 11-15 and number of eye spots on dorsal fin, 3-10. Turning to the biological inquiry which showed that the fish weight (g), gonad weight (g), liver weight (g), gut weight (g), gonadosomatic, alimentosomatic and hepatosomatic index and condition factor ranged from 15.10-28.60, 2.32-3.18, 0.029-0.044, 0.64-1.08, 9.69-14.79, 2.58-4.15, 0.11-0.19 and 0.30-0.40 respectably. The mean values of hepatosomatic and alimentosomatic indices persuaded greater liver activity and feeding intensity in M. aculeatus. Moreover, stomach content depicted that the diet of peacock eel composed of small fish species, small prawn, prawn larvae, earthworm, water strider, insects pupae, Metaphire posthuma, Caenorhabditis, sand and mud for instance, which in brief expressed that M. aculeatus is omnivorous in its feeding habits. Indeed, this preliminary research outcome would be utile for the species identification, seed production, developing culture technologies as well as biodiversity conservation of this near threatened fish species.

Size-selective predation by all-male prawns: implications for sustainable biocontrol of snail invasions

All-male populations of the freshwater prawn Macrobrachium rosenbergii were recently produced by a novel temporal RNA interference (RNAi)-based biotechnology for aquaculture purposes. This biotechnology opens the way to the wide use of all-male prawn populations as sustainable biocontrol agents against invading populations of freshwater snails, for which there is currently no environmentally friendly solution. Among the most damaging of the invasive freshwater snail species are the apple snails (Pomacea spp.), which inflict major damage on natural ecosystems and rice fields. The proposed use of all-male prawn populations as environmentally friendly biocontrol agents against invasive freshwater snails has several advantages: efficient predation by the prawns over a wide range of freshwater snails, the ready availability of the prawns, and the monosex non-reproductive nature of the biocontrol agents. Since the aquatic predators are strongly size selective, we quantified the predation rate as a function of body size of both predator and prey (M. rosenbergii and P. caniculata). Medium-sized and large prawns (~10–30 g) efficiently preyed small and medium-sized snails (up to 15 mm), while small prawns (up to 4 g) immediately and completely eradicated snail hatchlings. Medium-sized prawns (~22 g) exterminated a significant fraction of snail biomass within 24 h (up to 58% of their body mass) after being introduced into a tank of snails. A typical ‘climbing-to-the surface’ anti-predator behavior of the snails was recorded. The potential of all-male prawns as efficient biocontrol agents over hatchling and adult apple snails as part of an integrated pest management program is discussed. Our experiments set the stage for evaluating the ecological and economic implications of this generic solution for a wide variety of habitats.

Machine Vision Support System for Monitoring Water Quality in a Small Scale Tiger Prawn Aquaculture

A fuzzy-based machine vision system was designed to support an industrial sensor based small scale tiger prawn aquaculture system. This system is based on the behavioral movements of tiger prawns as they are subjected to different stress levels such as unsafe values of dissolved oxygen, temperature, salinity and ph. Each parameter is carefully adjusted to trigger a change in the normal behavior or movement of tiger prawns. The change in the behavior of the tiger prawn, as seen by the machine vision system, may serve as a level detection or an alarm system that will aid the sensor based system in terms of monitoring the water quality of the aquaculture environment. This machine vision system may be used to trigger the actuators needed to correct the dangerous water quality parameter back to its safe level. This research is done in real time using two basic web cameras to support industry grade sensors in maintaining the safe water quality level for this small scale habitat.

Desperate Prawns: Drivers of Behavioural Innovation Vary across Social Contexts in Rock Pool Crustaceans.

Innovative behaviour may allow animals to cope with changes in their environment. Innovative propensities are known to vary widely both between and within species, and a growing body of research has begun to examine the factors that drive individuals to innovate. Evidence suggests that individuals are commonly driven to innovate by necessity; for instance by hunger or because they are physically unable to outcompete others for access to resources. However, it is not known whether the factors that drive individuals to innovate are stable across contexts. We examined contextual variation in the drivers of innovation in rock pool prawns (Palaemon spp), invertebrates that face widely fluctuating environments and may, through the actions of tides and waves, find themselves isolated or in groups. Using two novel foraging tasks, we examined the effects of body size and hunger in prawns tested in solitary and group contexts. When tested alone, small prawns were significantly more likely to succeed in a spatial task, and faster to reach the food in a manipulation task, while hunger state had no effect. In contrast, size had no effect when prawns were tested in groups, but food-deprived individuals were disproportionately likely to innovate in both tasks. We suggest that contextual variation in the drivers of innovation is likely to be common in animals living in variable environments, and may best be understood by considering variation in the perception of relative risks and rewards under different conditions.

Investigation into Carnivorous Feeding Nature of Piranha (<i>Pygocentrus nattereri</i>) under Laboratory Condition in Bangladesh

An experiment was carried out to know the carnivorous feeding nature of piranha (Pygocentrus nattereri) under laboratory condition for a period of 36 days. One-month old nine fish were stocked in nine separate glass aquaria having three feeding treatments each with three replications. Fish were fed with nursery feed (Sabinco feed) in treatment 1 (T1); 50% live + 50% dead small prawns (Macrobrachium rosenbergii) and small fishes (Esomus danricus and Amblypharyngodon mola) in treatment 2 (T2); and 100% live small prawn and fishes in treatment 3 (T3) twice a day at the rate of 10% body weight. The average weight gain was significantly (P<0.05) higher in T2 (21.02 ± 0.72) than in T1 (-1.824 ± 0.35) and T3 (15.36 ± 4.96). The SGR (% day-1) recorded was significantly (P<0.05) higher in T2 (12.04 ± 0.01) than T3 (11.77 ± 0.09). No unused feed was found in T2 and T3 but some unused feed was found in T1. The stomach length, gut length and the RLG values of piranha were significantly (P<0.05) higher than that of taki, Channa punctatus but not of boal, Wallago attu. The presence of razor sharp teeth in both jaws and 30-32 pyloric caeca with 1.84 RLG value are attributed to the piranha as carnivore.DOI: http://dx.doi.org/10.3329/pa.v21i1-2.16764 Progress. Agric. 21(1 & 2): 151 - 158, 2010

A trap with a twist: evaluating a bycatch reduction device to prevent rockfish capture in crustacean traps

Abstract Favaro, B., Duff, S. D., and Côté, I. M. 2013. A trap with a twist: evaluating a bycatch reduction device to prevent rockfish capture in crustacean traps. – ICES Journal of Marine Science, 70:114–122. Bycatch, or the incidental capture of non-target species, occurs in fisheries around the world, with often detrimental ecological consequences. Bycatch reduction devices (BRDs) that increase catch specificity have been used successfully in some fisheries, and the development of such devices remains an important component of the global effort to reduce bycatch rates. We tested novel devices designed to exclude juvenile rockfish (Sebastes spp.) from traps used to catch spot prawns (Pandalus platyceros), a commercially important species in British Columbia, Canada. The devices included reductions in trap opening sizes and novel bent-tunnel openings. Reducing trap opening size did not affect bycatch rates of rockfish or other non-target fish species. In contrast, bent-tunnel BRDs eliminated rockfish bycatch, and two of the bent-tunnel variants also excluded other fish species. However, prawn catch rates were reduced in all modified gear, and large prawns were often excluded more than small prawns. Videos recorded in situ revealed that prawn attempts to enter traps took longer and were more likely to fail in BRD-equipped than in unmodified traps. We conclude that bent-tunnel BRDs have the potential to be useful, but improvements are needed to increase prawn catch to levels similar to that of unmodified traps.

Isolation and characterization of microsatellite DNA loci from Sillago sihama

The silver sillago, Sillago sihama Forsskal is naturally distributed in Indo–West Pacific: Red Sea and Knysna, South Africa to Japan and south to Australia (Wantiez 1993), and is common along beaches, sandbars, mangrove creeks and estuaries. Adults bury themselves in the sand when disturbed (McKay 1992), and feed mainly on polychaete worms, small prawns (Penaeus), shrimps and amphipods (Allen et al. 2002). This fish is found in all Chinese waters including East China Sea, Yellow Sea, Bohai Sea, South China Sea, and the Northern Bay. In China, it is a common marine food fish species, and the supply of this fish relies on capture from the wild. So far, studies of this species have focussed on ecology (Lee et al. 1981; Lu et al. 2008), morphology of early development (Wan 1996), discrimination of the genus Sillago with sagittal otolith shape (Pan and Gao 2010), and phylogenetic relationships of the genus Sillago (Xue et al. 2010; Gao et al. 2011). In the present study, we developed 66 microsatellite loci isolated from a dinucleotide-enriched genomic library of S. sihama using the fast isolation by AFLP of sequences containing repeats (FIASCO) protocol of Zane et al. (2002). These markers should provide a tool for assessing genetic diversity and population structure of wild stocks.

Oxygen Consumption of the Prawn Macrobrachium americanum over the Temperature Range of its Native Environment and in Relation to its Weight

AbstractCauque prawns Macrobrachium americanum of four different weights were tested at different temperatures to determine the differences in their oxygen consumption. The prawns were studied in a closed respirometer system in individual assays of 30 min each. Temperature (18–30°C) had a noticeable effect on oxygen consumption for all weights of prawns; weight had a less significant effect. In all cases, the mass‐specific oxygen consumption rate of small prawns was higher than that of large prawns for all of the temperatures studied.

Effect of eyestalk ablation on the metabolic activities of two penaeid prawns: Metapenaeous monoceros and M. dobsoni (De Man)

Metabolic activities in two penaeid prawns Metapenaeus monoceros and M. dobsoni in two size ranges of 35–40 mm and 65–70 mm for the former, and 35–40 mm and 48–53 mm for the latter, were observed for 16 days to study the effect of unilateral (UEA) and bilateral eyestalk ablation (BEA). In both species, BEA prawns of the two size groups consumed more oxygen than the UEA prawns, leading to higher metabolic activity. Small size groups revealed more metabolic activity than the large size ones, In both species, trend for the oxygen consumption (OC) was a steadily decreasing function of time in the small size group, but a steady state condition was observed in the large size group. The small size prawns showed higher amount of ammonia excretion (AE) than the large ones. BEA prawns of both size groups excreted more ammonia than the UEA with higher ammonia quotient (AQ) values, leading to higher metabolic activity, suggesting that measures should be taken for keeping the level of ammonia in the culture to the minimum for the safety of the culture. Changes in AQ are highly age‐sensitive, this being explained by higher order polynomials, unlike that observed in the OC and AE trend, with respect to time. These changes induced in the metabolic activities are discussed.

Behavioural responses of zooplankton to the presence of predatory jellyfish

The major objective of this study was to investigate the behavioural responses of several zooplankton species to the presence of the scyphozoan jellyfish, Catostylus mosaicus. Specific aims included: identifying taxa that were not captured by C. mosaicus; investigating whether some of these taxa were able to detect and avoid water that had been exposed to C. mosaicus; and determining if positive phototaxis of crab megalopae was suppressed in the presence of C. mosaicus. Zooplankton not caught by C. mosaicus were identified by comparing the zooplankton present in the water column to those on the oral arms of the jellyfish. C. mosaicus mainly caught mollusc veligers and copepods, but did not catch crab megalopae, small prawns or post-flexion fish larvae. The hypothesis that these taxa were able to avoid swimming in water exposed to C. mosaicus was tested using water-choice experiments in a flume tank. A significant proportion (18–25%) of larval barramundi ( Lates calcarifer) avoided swimming in the plume of water that had been exposed to C. mosaicus but mud crab ( Scylla serrata) megalopae and juvenile prawns showed no response. The effect of C. mosaicus on the positive phototaxis of S. serrata megalopae was tested using 1 m tall glass towers. Megalopae were exposed to one of four treatments: filtered seawater (a control), an oral arm of C. mosaicus, an oral arm that had been sealed in plastic, and mucus from C. mosaicus. Megalopae migrated higher into the water column in the control than in treatments containing cues from the jellyfish. These findings suggest that blooms of jellyfish may induce behavioural changes in some zooplankton.

Fish assemblage of a traditional fishery and the seasonal variations in diet of its most abundant species Wallago attu (Siluriformes: Siluridae) from a tropical floodplain

The fish assemblage of a traditional Kata fishery and the stomach contents of Wallago attu were studied over a period of one year from a large floodplain system in Bangladesh. A total of 19 species of fish and 2 species of shrimp were recorded. W. attu (9.7–17.8%), Mystus vittatus (6.0–11.3%), M. aor (5.0–12.1%), Amblypharyngodon mola (4.4–9.3%) and Mastacembelus armatus (3.5–10.5%) dominated the catch. W.␣attu occupied the top position in abundance throughout the year, followed by M. vittatus and M. aor. Bagridae, Siluridae and Cyprinidae were three major families that contributed respectively 21.0, 17.4 and 16.1% of the total catch. Considerable seasonality was observed in the abundance of different fishes. A total of 14 different prey items were recorded, belonging to three major groups (fish, prawn and plant matters). The fish fed on at least eight species of small fishes (A. mola, M. vittatus, M. cavasius, Puntius stigma, P. ticto, Puntius sp., Glossogobius guris, and Heteropneustes fossilis) and some other unidentified small fishes. Other major prey items were small prawn, fish and prawn remains, and macroalgae. A. mola was the most important food item, contributing 23.7% of the total amount of diet by weight and 19.9% by frequency of occurrence. A. mola was followed by unidentified small prawn (13.7%), M. vittatus (13.1%), and unidentified small fishes (8.8%) by weight and by unidentified small fishes (15.9%), fish remains (12.5%), and M.␣vittatus (12.3%) by occurrence. Of the major diet categories, fish contributed 74.3% of the total diet by weight and 80.9% by occurrence, prawn contributed 18.5% by weight and 11.0% by occurrence and plants contributed 7.2% by weight and 8.1% by occurrence. A. mola and small shrimps were positively selected by W. attu. We concluded that W. attu is a piscivorous predator with potential impacts on prey fish communities; we also hypothesized that a specialized food-web based on the Kata fishery exists in and around the Katas which is of particular ecological significance.