Shrimp Stocks Research Articles

THE INFLUENCE OF STOCKING DENSITIES ON WHITE SHRIMP (Litopenaeus vannamei) REARED USING INTENSIVE SYSTEM: PRODUCTION PERFORMANCE AND WATER QUALITY

ABSTRACT The increasing trend of vaname shrimp cultivation production encourages farmers to increase their cultivation production. The success of vaname shrimp cultivation can be seen from the ability to measure the capacity of shrimp biomass in maintenance activities and stocking density patterns based on the maximum capacity of the pond in each plot. The purpose of this study was to analyze vaname shrimp cultivation activities for a period of 2 years (2023-2024) in intensive system ponds based on different stocking density patterns at 140 shrimp/m2 and 190 shrimp/m2. This study was carried out for 6 cultivation cycles, each cycle was carried out for 100 days. The results of statistical tests showed that the shrimp stocking density pattern had a significant effect (p <0.05) on biomass, productivity, survival and feed conversion ratio. The average survival rate of 140 shrimp/m2 stocking density was 85.33%, biomass was 3,327.75 kg, FCR was 1.44 and productivity was 30.8 tons/ha. The average survival rate with a stocking density of 190 shrimp/m2 was 73.66%, biomass 1,981.87 kg, FCR 1.59 and productivity 12.38 tons/ha. This shows that biomass, SR, and productivity decreased while FCR tended to increase in cultivation with a stocking density of 190 shrimp/m2. The results of water quality showed an increase in the Total Organic Matter value of 110-250 mg/l at a stocking of 190 shrimp/m2. This shows that there is an increase in organic matter in the maintenance pond which affects the survival of shrimp in the pond so that it affects the biomass and productivity of whiteleg shrimp. A stocking density of 140 shrimp/m2 can be recommended for application in intensive whiteleg shrimp cultivation. Keywords: intensive system, stocking density, water quality, whiteleg shrimp

Enhancing Sustainability and Conservation of White Shrimp Penaeus schmitti in Northeast Brazil: Insights Into Life History, Reference Points, and Management Strategies for Beach Seining

ABSTRACTArtisanal fishing significantly not only contributes to socioeconomic development of numerous countries but also exerts pressure on natural populations. The white shrimp (Penaeus schmitti) is a key species in Brazilian artisanal fisheries, yet it is currently classified as data‐deficient. Conducting comprehensive studies on its population dynamics is essential to establish reference points that guarantee sustainable fishing. Therefore, we estimated population parameters to assess status of the white shrimp stock captured by beach seining in Northeast Brazil. Monthly samples of white shrimp were collected using a beach trawl. Based on population parameters, the white shrimp population in the study area, the sex ratio was 1 male to 1.29 females, with females larger and heavier than males. Weight–length relationships revealed positive allometric growth for males, females, and grouped sexes, with no significant difference between sexes. Asymptotic length, t_achor, and growth performance index also did not differ between sexes; however, the growth coefficient was higher for females. Beach trawling in northeastern Brazil predominantly targeted adult white shrimp, with carapace length at first capture (Lc50) averaging 2.12 cm for females and 2.19 cm for males. Mortality and exploitation rates were below maximum sustainable levels, so the stock was classified as underexploited. Overall, beach‐seine fishing was less harmful to this stock (F = 1.42) than motorized fishing and can be considered a sustainable fishing activity for the white shrimp population.

Fishers' perception and activity shifts in a dolphin bycatch mitigation context

Fishing exclusion zones aim to reduce cetacean bycatch, but often neglect social and ecological side effects, exacerbating social injustices and reshaping fishing practices. We present a case study of an endangered population of Lahille's bottlenose dolphins (Tursiops truncatus gephyreus) in a Brazilian coastal lagoon, known for its unique cooperation with net-casting fishers. However, the local small-scale fisheries (SSF) also employ other fishing gears that contribute to dolphin bycatch, prompting the enforcement of a fishing ban in the area. We investigated fishers' socioeconomic conditions, evidence of social disparities, perceptions on dolphin bycatch, and projected changes on fisheries activities to understand the repercussions of the ban. We categorized 128 surveyed fishers into five groups based on socioeconomic factors and their reliance on dolphin-cooperative and gillnet fisheries. Our findings revealed significant disparities in social capital among fishers and their different attitudes towards dolphin bycatch, highlighting unforeseen consequences. To investigate how fishers would likely shift fishing practices, we considered two management scenarios: 1) should dolphin-fishing cease due to unsuccessful bycatch mitigation, fishing efforts would shift towards shrimp trawling, seine nets, and gillnet effort; 2) if gillnet-fishing is successfully banned as a bycatch mitigation measure, a shift to shrimp trawling and cast net effort. Both scenarios would intensify pressure on shrimp stocks, which are already heavily exploited in this socioecological system. Our research underscores the importance of contemplating alternatives to achieve sustainable outcomes when designing bycatch mitigation measure. Furthermore, our results point to the importance of a participatory governance approach, grounded in the socioeconomic context, to safeguard the livelihoods of small-scale fishers and foster broader conservation efforts beyond species-specific concerns.

Robust deep learning based shrimp counting in an industrial farm setting

Shrimp production is one of the fastest growing sectors in the aquaculture industry. Despite extensive research in recent years, stocking densities in shrimp systems still depend on manual sampling which is neither time nor cost efficient and additionally challenges shrimp welfare. This paper compares the performance of automatic shrimp counting solutions for commercial Recirculating Aquaculture System (RAS) based farming systems, using eight Deep Learning based methods. The entire dataset includes 1379 images of shrimps in RAS farming tanks, taken at a distance using an iPhone 11 mini. These were manually annotated, with bounding boxes for every clearly visible shrimp. The dataset was partitioned into training (60 %, 828 samples), validation (20 %, 276 samples) and test (20 %, 275 samples) splits for purposes of training and evaluating the models. The present work demonstrates that state-of-the-art object detection models outperform manual counting and achieve high performance across the entire production range and at various circumstances known to be challenging for object detection (dim light, overlapping and small animals, various acquisition devices and image resolutions and camera distance to object). Highest counting performance was obtained with models based on YOLOv5m6 and Faster R–CNN (as opposed to neural network autoencoder architecture to estimate a density map). The best model generalizes well on an independent test set and even shows promising performance when tested with different taxa. The model performs best at densities below 200 shrimps per image with an overall error of 5.97 %. It is assumed that this performance can be improved by increasing the dataset size, especially with images at high shrimp stocking density, and it is strongly believed that a performance below the 5 % error threshold is close to being achieved, which will allow for deployment of the model in an industrial setting.

Empirical dynamic modeling for sustainable benchmarks of short-lived species

Abstract The abundance dynamics of short-lived marine species often exhibit large-amplitude fluctuations, potentially driven by unknown but important species interactions and environmental effects. These complex dynamics pose challenges in forecasting and establishing robust reference points. Here, we introduce an empirical dynamic modeling (EDM) framework using time-delay embeddings to recover unspecified species interactions and environmental effects, and use walk-forward simulations with varying harvest rates to estimate maximum sustainable yield (MSY). Firstly, we apply our framework to simulated data under various dynamics scenarios and demonstrate the statistical robustness of EDM-based MSY. Secondly, we apply our framework to abundance and catch time series (>30 years) of federally managed brown shrimp stocks in the US Gulf of Mexico. We identify nonlinear signals and achieve high prediction accuracy in the empirical dynamics of brown shrimp. Lastly, based on the EDM of brown shrimp dynamics, we obtain MSY for timely and effective management. Our results highlight the utility of EDM in deriving reference points for short-lived species, particularly in situations where stock abundance and catch dynamics are influenced by unobserved species interactions and environmental effects in a complex ecosystem.

Analisis Peramalan Persediaan Bahan Baku dan Penentuan Stok Penyangga (Buffer Stock) Udang Vaname (Littopenaeus Vannamei)

This study examines the analysis of raw material inventory forecasting and buffer stock of vaname shrimp at one of the fishery companies in Makassar Industrial Estate (PT Bogatama Marinusa Makassar). The analysis method used to determine the supply of raw materials needed by the company is the ARIMA Box-Jenkins method. This method is used to forecast raw material inventory on time series data. Determination of buffer stock is done using standard deviation and policy factors. Vaname shrimp (Littopenaeus vannamei) raw material data was obtained from 2020 to 2022 (156 weeks). The results showed that the highest amount of raw material inventory occurred in October week 147 in 2022, amounting to 152,792 tons, while the lowest amount of raw material inventory occurred in May week 122 in 2022, amounting to 13,102 tons. The best vaname shrimp raw material inventory model is the ARIMA (1,1,1) model which has a Sum Square Error (SSE) value of 1.70250, Mean Square Error (MSE) value of 0.0112007. This model is used to forecast raw material inventory for the next 48 weeks. The forecasting results show that there will be a decrease in week 1 to week 6 and a relative increase in raw materials in week 7 to week 48 with a MAPE value of 4.54%. The amount of buffer stock that must be owned by the company is 37.311 tons.

Learning from the history of red shrimp fisheries in the Mediterranean to improve sustainability of deep-water bottom trawling

Abstract As deep-water red shrimp (DWRS) trawl fisheries gain importance in the Mediterranean, their impact on fragile deep-sea ecosystems requires careful management. We reviewed the historical development of DWRS fisheries in the Mediterranean to propose a harvest strategy that would enhance fishery sustainability, while preserving habitat and community integrity. We considered two representative typologies of DWRS fisheries: a domestic fleet operating within the Italian territorial waters of the Ligurian Sea, and a distant fleet operating mostly in international waters of the central-eastern Mediterranean and sharing shrimp stocks with non-European countries. Our proposed management approach is based on three main harvesting measures: (i) preventing the uncontrolled growth in number of trawlers, (ii) adopting a catch control regime, and (iii) identifying a network of deep-water areas designated alternately for fishing and conservation purposes. As with fisheries in other regions, new fishing grounds should be explored using “encounter protocols” to avoid areas hosting species indicators of Vulnerable Marine Ecosystems. Additionally, empirical indicators such as catch rate thresholds derived from fishers’ experience, could be used to move from one fishing ground to another to avoid local depletion of DWRS abundance and a decrease in fishery profitability.

AVALIAÇÃO DA PESCA DE CAMARÕES NO NORDESTE DO BRASIL 2000-2016

The aim of this article was to reevaluate the total catch data and provide indicators for fisheries management that will help to ensure the sustainability of the marine shrimp resource in Sergipe. Marine shrimp fisheries are generally important for Brazil, but particularly for the state of Sergipe. This article makes use of the historical catch data from 2000 to 2016 for analyzing the state of marine shrimp fisheries in Sergipe. The assessments were carried out using the CMSY++ model, a method that uses the Bayesian/state-space approach, to estimate fish stocks for which available data are limited. The results of the analysis with the Bayesian of Shaefer model (BSM) for the grouped shrimp stock were: MSY 1.42, 95% CL = 1.24 – 1.66; Fmsy 0.394, 95% CL = 0.272 – 0.536; Bmsy3.59, 95% CL = 2.54 - 5.53; Biomass (last year) 4.6, 2.5th perc=3.11, 97.5 perc=7.09 B/Bmsy (last year) 1.28, 2.5th perc=1.05, 97.5 perc=1.48; Fishing mortality (last year) 0.235, 2.5th perc=0.138, 97.5 perc=0.387; Exploitation F/Fmsy 0.599, 2.5th perc=0.416, 97.5 perc=0.878. The results for the Xiphopenaeus kroyeri stock were: MSY 1.13, 95% CL = 0.984 - 1.31; Fmsy 0.417, 95% CL = 0.283 – 0.552; Bmsy 2.71, 95% CL = 1.98 – 4.21; Biomass (in the last year) 3.5, 2.5th perc=2.39, 97.5 perc=5.37; B/Bmsy (last year) 1.29, 2.5th perc=1.06, 97.5 perc=1.5; Fishing mortality (last year) 0.247, 2.5th perc=0.147, 97.5 perc=0.401; Exploitation F/Fmsy OPEN ACCESS ActaPesca Araújo et al. (2024), ActaPesca News 12(1):23-47 DOI 10.46732/actafish.2024.12.1.23-47 Acta of Fisheries and Aquatic Resources 24 0.594, 2.5th perc=0.409, 97.5 perc=0.882. All the biological reference points obtained with BSM showed that the grouped shrimp stock and, particularly, the Atlantic seabob shrimp stock (X. kroyeri), do not indicate overfishing, suggesting that both stocks were exploited during the analysed period (2000-2016) at a level compatible with maximum sustainable yield.

Smart Shrimp Farming Using Internet of Things (IoT) and Fuzzy Logic

In the case of ponds with Litopenaeus Vannamei shrimp, water quality parameters play a significant role in shrimp growth. Leveraging technology enhances water quality to optimize growth and survivability in the shrimp farming industry. The research aimed to empower local farmers with smart shrimp farming technologies, including Information Technology (IT), such as the Internet of Things (IoT), and Fuzzy Logic. The research also involved a comparison between Litopenaeus Vannamei shrimp in two different aquariums: one serving as a control group and the other implementing IoT and Fuzzy Logic for a period of 30 days. The initial Litopenaeus Vannamei shrimp stocking was 135 shrimps for control aquariums and 132 for experimental aquariums. Then, the research used Arduino ESP 8266, Raspberry Pi 3, and SciKit-Fuzzy library to record and process the data. Through the application of IoT and Fuzzy Logic, the research successfully increases survivability by 6%, specific growth rate by 28%, and length by 8% in 30 days compared to conventional methods. The results highlight the potential use of technology in Litopenaeus Vannamei shrimp farming. The proposed system’s hardware and software architecture can be easily scaled to accommodate the needs of Litopenaeus Vannamei shrimp farmers with multiple ponds, offering flexibility and adaptability.

Distribution pattern and habitat use of the protandrous shrimp Pandalus latirostris in relation to environmental characteristics in Akkeshi waters on the pacific coast of eastern Hokkaido, Japan

A sampling of the protandric shrimp, Pandalus latirostris, was conducted at fixed sites from July 2015 to March 2020 in Akkeshi Bay and the connecting Lake Akkeshi on the Pacific coast of eastern Hokkaido. Based on the occurrence pattern of P. latirostris, most individuals begin mating as males at Age-1, followed by a sex change to females, spawn eggs as females at Age-2, and hatch their eggs in the spring of Age-3. Pre-hatching ovigerous females were mainly found in eelgrass beds near and in Lake Akkeshi, where the water temperature was relatively high. The females probably migrate there to hatch their eggs, making sure of the high survival and growth of the hatched larvae. Juveniles and small males were also abundant in near and in Lake Akkeshi, indicating that many larvae remained in the eelgrass beds where they hatched. These eelgrass beds play an important role in the maintenance of the shrimp population as a major egg-hatching site and nursery habitat in Akkeshi waters. With ontogenetic development, the occurrence rate of P. latirostris gradually increased on the offshore side of Akkeshi Bay, with its body size being larger. As P. latirostris grow, they will probably disperse to the offshore side of Akkeshi Bay. However, the density of P. latirostris in the eelgrass bed in the bay near the lake was extremely high, with its strong preference at all ontogenetic stages. This eelgrass bed would help maintain the shrimp population as a “key habitat” for the shrimp. The site-specific environmental characteristics of vegetation beds influence the distribution and abundance of individuals within a population of P. latirostris through their growth and the associated change in habitat preference. In this study, the importance of maintaining the diverse habitats of P. latirostris will be discussed as part of the shrimp stock management measures.

Assessment of Three Major Shrimp Stocks in Bangladesh Marine Waters Using Both Length-Based and Catch-Based Approaches

Penaeus monodon (tiger shrimp), Metapenaeus monoceros (brown shrimp), and Fenneropenaeus indicus (white shrimp) are the most economically important shrimp species in the waters of the Bay of Bengal, Bangladesh. This is the first analytical study to assess three major shrimp stocks using both length-based and catch-based methods, such as length-based Bayesian biomass estimation (LBB), length-based indicator (LBI), and a catch-based method entitled JABBA (Just Another Bayesian Biomass Assessment), to explore and process the data; estimate the growth parameters, with length at first capture; present relative biomasses; and approximate the reference points. The parameters of the von Bertalanffy Growth Function (VBGF) analysis for the tiger, brown, and white shrimps were L∞ = 113.0 mm, 85.4 mm, and 76.4 mm, respectively, for carapace length. Our results showed that the relative biomass level (B/BMSY) of the tiger shrimp was 0.43, suggesting an overfished status, and brown and white shrimps were 0.84 and 0.96, indicating that they were fully exploited but not overfished. This study, therefore, advised an optimum carapace length limit to catch from 57.0–70.0 mm for tiger shrimp, 44.0–53.0 mm for brown shrimp, and 40.0–48.0 mm for white shrimp. The estimated maximum sustainable yield (MSY) reference points were as follows: optimal biomass BMSY = 3116 mt, 15,885 mt, and 2649 mt for tiger, brown, and white shrimp, respectively, and optimal harvest rate uMSY = 12%, 33%, and 8% for tiger, brown, and white shrimp, respectively. The average annual catch values for the last ten years were 265 mt, 2396 mt, and 115 mt below the estimated MSY values of 389 mt, 4899 mt, and 209 mt for tiger, brown, and white shrimp, respectively. But, brown shrimp had the estimated highest carrying capacity (31,770 mt) and intrinsic growth rate (0.66) than the tiger and white shrimp, which was replicated distinctly in the graphical representation of the Kobe plot and the surplus production plot. Hence, the brown shrimp stock is estimated to be in a better state than the tiger and white shrimp stocks.

Spatially explicit stock assessment uncovers sequential depletion of northern shrimp stock components in the North Sea

Abstract Space is a critical component of fisheries management. Despite this, very few of the world's fish and shellfish stocks are currently assessed using methods that are spatially structured. In the Northeast Atlantic, northern shrimp in the North Sea and Skagerrak, is currently assessed using a spatially structured assessment model. This metapopulation model includes two spatial units (the Norwegian Deep and the Skagerrak), however, in the recent past, the fishery on northern shrimp in the North Sea also occurred in a third neighbouring fishing area, the Fladen Ground. Here, we have reconstructed the dynamics of northern shrimp in the Fladen Ground using historic landings, a standardized commercial index of abundance and fragmented survey data and integrated this third spatial unit into the assessment model of the stock. In doing so, we find evidence of sequential spatial depletion, whereby high rates of fishing mortality have successively eroded stock components in a west to east pattern of overexploitation and produced cryptic collapses. This finding is the first documented case of sequential spatial depletion in the Northeast Atlantic, a phenomenon that could be common and largely overlooked by stock assessment methods that are inherently non-spatial.

Distribution and Abundance of Shrimp Larvae in The East Beach of Aceh, East Aceh Regency, Indonesia

Shrimp fisheries are one of the targets for local governments in designing and developing a marine protected area, especially in East Aceh Regency. In general, one of the efforts to preserve shrimp production requires information on larval distribution. The larval phase in the shrimp life cycle is essential for continuing stock production in nature. This study aims to analyse the distribution of shrimp larvae which become potential resources. This study was conducted at ten stations in the coastal area in April and September 2015. The data collected used a “bongo net” with a mesh size of 500 mm with a mouth opening of 60 cm and a length of 3 metres which was pulled flat at a speed of ± 2 knots for 10 minutes. Faund, the highest shrimp larvae abundance, was the family Palaemonidae. At the same time, the lowest was the family Sergestidae. In addition, found two families (Squillidae and Penaidae) were besides these, other shrimp species were grouped in the unidentified category. To conduct further research, such as analysis of habitat utilisation and degradation status that can affect shrimp stocks, risk assessment and evaluation, and support factors, as input in determining the conservation area of shrimp resources.

The effects of stocking density and artifical substrate on production of pacific white shrimp Litopenaeus vannamei and water quality dynamics in greenhouse-based biofloc systems

Inland shrimp aquaculture has increased in popularity in recent years as a means of providing fresh seafood to consumers away from the coasts. With adequate marketing,fresh shrimp fetch relatively high prices and can give farmers a means of diversifying, production. In temperate regions such as Kentucky, low-cost high tunnel greenhouses may be used to extend the growing season of warm-weather crops, including tropical animals such as penaeid shrimp. To optimize investments, inland producers are constantly exploring methods to increase overall production. A 100 day-long study examined the effects of stocking density and artificial substrates on water quality, stable isotope dynamics, and production of Litopenaeus vannamei using biofloc-based aquaculture systems in greenhouses. Four treatments were compared: High Density Substrate (HD/S), High Density No-Substrate (HD/NS), Low, Density Substrate (LD/S), and Low Density No-Substrate (LD/NS). Four high tunnel greenhouses each contained four 10.9 m3 tanks. The experiment was blocked by location such that one replicate from each treatment was randomly assigned within each greenhouse to account for potential environmental variation. Each tank was outfitted with a settling chamber for solids filtration, and 13.1 m2 of polypropylene, construction safety fencing was used as substrate in the substrate-containing tanks. Shrimp were stocked into the experimental systems at 2.71 g mean weight; high density treatments were stocked with 300 shrimp/m3, while low density treatments were stocked with 200 shrimp/m3. Water temperatures were significantly lower over the course of the entire study within substrate treatments. pH throughout the study was significantly lower within substrate treatments and high density treatments. Stable isotope data indicated that very little of the carbon and nitrogen in shrimp tissues was likely sourced from biofloc and periphyton material. Low density treatments had significantly lower FCRs than high density treatments. However, the addition of substrate in the HD/S treatment resulted in significantly more efficient shrimp FCR than was observed in the HD/NS treatment. The HD/S treatment also had significantly higher, shrimp biomass than all other treatments. High density treatments had significantly higher FCR and lower survival than low density treatments. This study demonstrates that artificial substrates can reduce some of the negative effects of high shrimp stocking density, with significant improvements in FCR and biomass production. Although it is important to note the implications for water quality, adding substrate to facilitate high density shrimp culture in high tunnel greenhouses can facilitate higher stocking density without compromising the size of the animals

Steam Precooking to Delay Spoilage of Shrimp Stock Awaiting for Processing in Cottage Industry

Steaming as precooking methods were explored to reduce spoilage of raw shrimp awaiting for smoking process in cottage industry. Raw shrimp steamed for 20 min are stocked at ambient temperature (29-30°C) to assess spoilage kinetic. Microbiological and physico-chemical parameters are recorded. Data showed that steam precooking eliminated spoilage bacteria (Enterobacteriaceae, Pseudomonas spp.) and delays production of basic volatile compounds, extending raw shrimp storage up to 12 hours at ambient temperature, while raw non steamed shrimp were stored up to 6 hours in the same conditions. This study identified an attainable method to be used by stakeholders to delay spoilage of shrimp stocks awaiting smoking.

Production of Pacific white shrimp under different stocking density in a zero-water exchange biofloc system: Effects on water quality, zootechnical performance, and body composition

This experiment was conducted to compare water quality, growth performance, body composition, and insulin growth factor gene expression of Pacific white shrimp, Litopenaeus vannamei, reared under different stocking densities (100, 200, 300, and 400 shrimp m−3) in a biofloc system with zero-water exchange for nine weeks. The results demonstrated that all the water quality variables remained within the acceptable range that are presumed to be safe levels for Pacific white shrimp farming. The weight gain ratio and specific growth rate of shrimp reduced by increasing the stocking density to the lowest values of 2800.00 ± 105.32 % and 5.34 ± 0.11 % d−1, respectively, in shrimp reared under the highest stocking density (400 shrimp m−3). The highest feed conversion ratio was also obtained under the highest stocking density of shrimp (P < 0.05). A significant decreasing trend of the insulin growth factor-1 gene expression was observed by increasing the shrimp stocking density (P < 0.05). The final yield of shrimp in the present study significantly increased by increasing the shrimp stocking density and reached the maximum value of 3.05 ± 0.21 kg m−3 at the highest stocking density. There was no significant difference in the carcass composition of the shrimp among the experimental treatments (P < 0.05), except for lipid content which was significantly higher in shrimp reared under the lowest stocking density (100 shrimp m−3) (P < 0.05). Findings of the current study confirmed a clear effect of stocking density on growth performance of the Pacific white shrimp with the recommended density of 400 shrimps m−3 to achieve the maximum yield, while the stocking density of 100 shrimps m−3 is feasible to reach the highest weight gain and probability of Pacific white shrimp cultured in a biofloc system with zero-water exchange for the present experimental condition, genetics used and nutrition supplementation.

Results of trawl surveys in Khanka lake in 2018 and 2020

Since 2022, the possibility of trawl fishing on Khanka Lake has been opened. In 2018 and 2020, accounting work was carried out using a beam trawl. Studies have shown that the highest biomass in trawl catches was far eastern freshwater shrimp (Palaemon modestus), noodle fish, sharpbelly, bagrid catfish and humpback. According to the trawl survey, the stocks of shrimp and small fish species amounted to 3,5–4,6 thousand tons. Taking into account the underestimation of these biological resources during the performance of work, the resource base can be at the level of 14,0–15,0 thousand tons.

Shrimps distribution and their relationship to the environmental variables in Arafura Sea

Arafura Sea is well-known as the important area for commercial shrimp fisheries in Indonesia. The density of shrimps was highly influenced by their fishing pressure and environmental condition. The objective of this research was to study the distribution of shrimps based on its stock density and their relationship with the environmental variables. Trawling swept area method was used in 16 sampling sites of Arafura Sea during the transition monsoon in 2016. Some environmental variables in bottom layers as shrimp habitat were measured, including chlorophyll-a, dissolved oxygen, depth, salinity, temperature and pH. The results showed that the largest density of shrimps was found in the southern coast of Aru where it has the largest concentration of chlorophyll-a and dissolved oxygen. Among all the environmental variables, Chlorophyll-a was the main variable affected the density of shrimps. Three most dominant species were Penaeus semisulcatus, Metapenaeus endeavouri and Metapenaeus ensis. There was indication of the decreasing shrimp stock in Arafura Sea. The ecosystem-based fisheries management should be developed to rebuild the stock density and to enhance the environmental quality of Arafura Sea.

A bayesian network to inform the management of key species in Kosterhavet National Park under contrasting storylines of environmental change

Global climate change and related land use changes are expected to impose unprecedented pressures on coastal biodiversity and ecosystem processes. To sustainably manage coastal ecosystems, it is crucial to predict the consequences of human activities for coastal ecosystems and identify areas for directed abatement measures. Empirical data together with expert knowledge and evidence from the literature were integrated into a Bayesian Belief Network (BBN) for a marine protected area, the Kosterhavet National Park off the Swedish west coast. The variability and interactions of anthropogenic pressures and two key ecosystem components, eelgrass meadows and northern shrimp stock, were tested under four storylines of environmental change. The results show that of the influential drivers of environmental change, only three variables (bottom trawling, leisure boating and aquaculture) are manageable within the national park itself. Scenario analysis suggested that notable gains of both ecosystem components were most likely under a storyline of sustainable development, assuming a radiative forcing of 4.5 W/m2 by 2100 in concert with a preventive cooperation among neighboring countries and a tighter restriction of commercial and recreational uses in the park area. The findings suggest that the sustainable management of eelgrass meadows and northern shrimp stock in Kosterhavet National Park requires both local measures at the scale of the park's water bodies and, to a greater part, also regional measures, e.g., to reduce nutrient influx from adjacent water bodies. In conclusion, this approach can help practitioners to make more informed management decisions and foresee the effects of routes of socio-economic development.

Assessing the Population Structure of the Southern Brown Shrimp Farfantepenaeus subtilis (Pérez-Farfante 1967) Using Different Sampling Methods

We analyzed the population structure of Farfantepenaeus subtilis off Sergipe, northeastern Brazil, comparing different sampling methods. Samples were obtained between March 2015 and May 2016 from the commercial shrimp fleet based in the fishing ports of Aracaju (only shrimps categorized by size: small, medium, and large) and Pirambu (shrimps + bycatch), both operating in the same area. Each specimen was measured and weighed: total length – TL (mm), carapace length – CL (mm), and live weight – LW (g). The sex and maturity stage were identified. A total of 4,657 specimens was sampled, with 91.5% originating from Aracaju and 8.5% from Pirambu. Females were larger and heavier than males in both fleets (Aracaju and Pirambu). Inflexion points were observed in the relationships between TL and CL for both sexes (both fleets). The weight-length relationships indicated a negative allometry for both sexes (both fleets). The size at first maturity (CLm) for females was 19.75 mm and 18.94 mm for Aracaju and Pirambu, respectively, and 15.26 mm for males (only for the Aracaju fleet). The reproduction was continuous, with a peak observed in September–October. Except for growth, mortality, distribution, and abundance, both sampling methods allowed for estimating parameters for the population structure and dynamics of F. subtilis. Larger sample sizes would allow for the estimation of growth and mortality parameters when bycatch is included such as the case of the Pirambu fleet. Thus, fishery-dependent data may be used to partially monitor shrimp stocks in Sergipe and other localities where limiting resources are available.