Commercial Shrimp Farms Research Articles

Commercial Shrimp Ponds Versus Seminatural Mudflats as Wading Bird Foraging Habitat in Northwest Ecuador

The conservation of wading birds is increasingly dependent upon determining the ability of human-modified habitats to serve as surrogates for natural habitats. The suitability of commercial shrimp farms and seminatural estuarine mudflats in Northwest Ecuador as foraging habitat for wading birds was assessed by observing the foraging efficiency, diet and behavior of Great (Ardea alba) and Snowy (Egretta thula) Egrets, censusing wading birds, and measuring prey availability (i.e. prey density, standing crop, water depth and diversity). Mean annual wading bird density was greatest in shrimp ponds, but was greater on mudflats during the breeding season when energy demands are most critical. Foraging efficiency (capture/strike) was greater on average in shrimp ponds than on mudflats, and both Great and Snowy Egrets captured significantly larger prey items (in both length and mass) there than on mudflats. However, intake rates (g/minute) were significantly greater on seminatural mudflats than in shrimp ponds during the breeding season. Prey standing crop, mass of individual prey items and water depths were all significantly greater in shrimp ponds than on mudflats, while the opposite was true for prey density and diversity. Shrimp ponds provide important foraging habitat for Great and Snowy Egrets, particularly during harvest events and during the non-breeding season, while four other wading bird species (Tricolored Heron (Egretta tricolor), Little Blue Heron (Egretta caerulea), Yellow-crowned Night Heron (Nyctanassa violacea) and Striated Heron (Butorides striatus)) were precluded from foraging in most ponds due in part to deeper water (>30 cm), pond bathymetry, larger prey items and differing foraging behaviors. While important to Great and Snowy Egrets, shrimp ponds do not appear to provide suitable foraging habitat for all other diurnal wading bird species within the local community, and do not likely serve as complete ecological substitutes for natural foraging habitat throughout coastal Ecuador.

Modeling partial harvesting in intensive shrimp culture: A network-flow approach

Despite the promising laboratory results and theoretical arguments on the potential of partial harvesting in enhancing the productivity and profitability of intensive shrimp growout facilities, the implementation of partial harvesting in practical operation is rather difficult due to its complex nature. In this paper, we developed a practical model of partial harvesting using the network-flow approach so that it can be readily implemented and solved in MS EXCEL. We demonstrated the use of this spreadsheet model with data from a commercial shrimp farm in Hawaii. The results indicate that the model is capable of identifying the efficient harvest policy as well as assessing the viability of partial harvesting under a variety of managerial conditions and objectives.

National Initiatives, Local Effects: Trade Liberalization, Shrimp Aquaculture, and Coastal Communities in Orissa, India

Commercial shrimp farming in India expanded rapidly after trade liberalization initiatives were introduced in the early 1990s. This article examines the social, economic and environmental impacts that have been generated in communities along Orissa's Coast in east India. The results suggest that macro-level policies such as trade liberalization are useful at the national level, but at the local level they can generate imbalanced growth. Although the shrimp farming industry has generated substantial foreign exchange, at the local level it has widened the gap between rich and poor. To protect the livelihoods of the rural communities and the environment, India needs to formulate effective coastal resource management policies and establish adequate institutions at the local level. This will help ensure a stable source of income from shrimp farming for small-scale farmers and minimize adverse impacts on the local environment.

Performance of an intensive nursery system for the Pacific white shrimp, Litopenaeus vannamei, under limited discharge condition

The considerable impact of disease outbreaks on commercial shrimp farming during the last two decades has significantly affected the operational management of shrimp farms worldwide. Crop losses forced shrimp producers to look for more sustainable culture practices and facility designs to minimize the risk associated with exposure to viral pathogens. Shrimp culture under limited discharge can increase biosecurity and minimize losses to disease outbreaks while reducing negative environmental impact. A 71-day nursery study was conducted in greenhouse-enclosed raceways to evaluate the effect of two water exchange regimes and the use of foam fractionators on selected water quality indicators, growth, survival, and health of Litopenaeus vannamei postlarvae (PL). Four 40m3 raceways were stocked with 4–5-day-old PL at a density of 4050PLm−3. All raceways were equipped with high pressure rapid sand filter, a pump, a center longitudinal partition over a 5.1cm PVC pipe with nozzles, eighteen 5.1cm airlift pumps, six 1m long air diffusers and a 5.1cm Venturi injector. Two out of the four raceways were each equipped with a home-made foam fractionator (FF). Average water usage in the two raceways operated with FF was 3.35%d−1 compared to the 9.37%d−1 used in the other two. Shrimp in the raceways operated with FF and the lower water exchange had greater mean final weight (1.91 and 2.0g vs. 1.73 and 1.43g), survival (100 and 92.4% vs. 55.9 and 81.8%), yield (7.64 and 6.89kgm−3 vs. 3.92 and 4.74kgm−3) and FCR (0.97 and 1.06 vs. 1.36 and 1.64) values than those operated without FF and with higher water exchange rate. Disease diagnostic results showed no signs of viral pathogen infection. Histological observations of samples collected at the study termination suggest that the shrimp raised in the higher water exchange raceways had greater external fouling and higher intestinal bacterial load than those maintained at lower water exchange. Nitrite–nitrogen was significantly lower in the reduced water exchange than the higher exchange raceways, whereas reactive phosphorus, turbidity, and algal density were significantly higher. No other differences in water quality were found between treatments. This study demonstrated the feasibility of producing healthy juveniles of the Pacific white shrimp under limited discharge conditions in tanks operated with foam fractionators with good growth, survival, yield and FCR results.

Use of system dynamics modelling in design of an environmental restoration banking institution

This paper describes a system dynamics model developed to inform design of a proposed environmental restoration banking system. The purpose of the proposed system is to facilitate restoration of extensive areas of mangrove forests that have been cleared or damaged in large part by expansion of the commercial shrimp farming industry. A case study is developed for mangrove restoration in Thailand; however, the model is seen as applicable to a number of countries which have experienced severe mangrove loss. The scheme is based on environmental mitigation banking principles, in which users of an environmental resource are required to purchase from a mitigation bank credits representing restorations undertaken to compensate for environmental damage, thereby achieving “no net loss” of the environmental asset. The scheme proposed in this paper differs from usual mitigation banking practise in that the objective is to restore large degraded areas over and above present rates of consumption. Model simulations show that the restoration banking system may be effective in restoring coastal mangroves and in rehabilitating the coastal shrimp farming industry that is dependent on environmental services provided by the mangrove stock.

Nitrogen dynamics in the settlement ponds of a small-scale recirculating shrimp farm (Penaeus monodon) in rural Thailand

Rural shrimp farmers in Thailand are being encouraged to adopt practices that will reduce the quantity and improve the quality of their effluent. A simple and cheap option for small-scale shrimp farmers is to use settlement ponds to store and remediate discharge water before being re-used. We undertook a detailed study of the settlement ponds in a small-scale commercial black tiger shrimp farm typical of rural Thailand. We found that over a 9-week period, following the harvest of one of the two farm production ponds, total nitrogen (TN) concentrations in the water column were reduced by 30%, with the greatest removal (56%) occurring during the fifth week. There was a 10% increase in dissolved organic nitrogen (DON) concentrations during the trial. Sediments were a source of total ammonia nitrogen (TAN), and the re-mineralisation rate was the highest in the first two settlement ponds. Coconut fronds added to two of the four settlement ponds to increase the surface area available for microbial activity were found to provide a site for microbial re-mineralisation of TAN, the photosynthetic uptake of TAN and oxidised nitrogen (NOx) and nitrification. The water column was a net assimilator of TAN through autotrophic uptake. This study has shown that settlement ponds are capable of reducing water column N concentrations; however, sediment must be managed to reduce re-mineralisation during successive cropping cycles. In addition, coconut fronds were shown to improve N removal, although they should be periodically removed to maintain efficiency.

Development of monoclonal antibodies against VP28 of WSSV and its application to detect WSSV using immunocomb

White spot disease (WSD) is an important viral disease of penaeid shrimp caused by white spot syndrome virus (WSSV). WSSV isolated from WSD outbreaks in commercial shrimp ( Penaeus monodon) farms in India were propagated in the laboratory in healthy shrimp. The virus was purified from the infected tissues by sucrose gradient centrifugation. The VP28 was electroeluted from SDS-PAGE gels and was used to immunize Balb/c mice to produce hybridomas secreting monoclonal antibodies (MAb) against WSSV. A total of five hybridoma clones secreting MAbs to VP28 were produced. The MAbs were of the isotypes IgG1, IgG2b and IgM. The MAbs reacted with VP28 of WSSV and not with any other viral or shrimp protein in western blot. The MAbs were used to develop dot immunoblot assay using an immunocomb to detect WSSV from field samples. The test developed had an analytical sensitivity of 625 pg and a diagnostic sensitivity of 100% compared to single step polymerase chain reaction (PCR). The test can be used as an alternate for first step PCR to detect WSSV from field samples.

Utilization of a Fish Pump for Harvesting Shrimp from Tanks and Ponds

Commercial shrimp farms located throughout the world utilize several techniques to harvest shrimp from ponds and raceways. Commonly, farmers drain their systems and collect shrimp in nets, mesh bags or baskets as water passes through the drain. Other methods for partial harvest include cast netting or trapping the shrimp as water exits the pond gates during receding tides. Recently, modified mechanical pumps have proven to be very effective at harvesting shrimp from ponds and raceways. This document is FA123, one of a series of the Fisheries and Aquatic Sciences Department, UF/IFAS Extension. Original publication date February 2006. FA123/FA123: The Utilization of a Fish Pump for Harvesting Shrimp from Tanks and Ponds (ufl.edu)

A necrotizing hepatopancreatitis (NHP) outbreak in a shrimp farm in Campeche, Mexico: A first case report

Shrimp culture is the most profitable type of aquaculture in Mexico and it is highly developed in the northern states of the Pacific coast. A reduced number of commercial shrimp farms have been established along the coast of the Yucatan Peninsula and have initiated operations with Litopenaeus vannamei. The Federal Government is concerned about the use of exotic species for aquaculture and has prompted research on domestication of Gulf of Mexico native penaeids. This paper reports the first outbreak of necrotizing hepatopancreatitis (NHP) in a farm culturing L. vannamei in Campeche State, Southern Mexico. The implications of this finding with respect to native shrimp species and aquaculture development for the region are discussed.

Utilização da artêmia nacional como dieta para pós-larvas do Litopenaeus vannamei (Boone, 1931) na fase berçário

Experiments were carried out in a commercial marine shrimp farm to evaluate growth and survival rate of the Litopenaeus vannamei post-larvae during nursery phase using different diets. The nursery tanks (60 m3) will be provided with post-larvae of 19 days (PL19) with a density of 16 PL/liter. The post-larvae were submitted to a Commercial Feeding Method (MAC) and an Artemia Feeding Method (MAA). Considering the correlations between weight and length, and between weight and culture duration, a better efficiency (p

Influência de duas dietas na qualidade da água dos tanquesberçário, utilizados no cultivo do camarão marinho <em>Litopenaeus vannamei</em>

Experiments were carried out in a commercial marine shrimp farm in order to evaluate the use of two diets in Litopenaeus vannamei post-larvae, during nursery phase, on physiochemical wastewater quality. Two feeding methods were adopted: Commercial Feeding Method (MAC) and Artemia Feeding Method (MAA).0 The nursery tanks (60 m 3 ) were provided with 19 days post-larvae (PL 19 ) with a stocking density of 16PL/liter. After 10 days of culture, the concentrations of nitrogen (ammonia, nitrite and nitrate) and phosphorus compounds (total phosphorus and orthophosphate) in the nursery tank were smaller for MAC, rather than MAA treatment (p < 0.05). Consequently, MAA treatment induced low levels of daily compounds increment, thus contributing to a significant reduction of the nutrients that caused water eutrophication.

Optimal production schedule in commercial shrimp culture

Using an extended version of the optimal scheduling model developed by [Yu, R., Leung, P.S., 2005. Optimal harvesting strategies for a multi-cycle and multi-pond shrimp operation: a practical network model. Math. Comput. Simulation. 68, 339-354.], this study attempts to demonstrate the impact on the optimal production schedule and its resulting economic performance of shrimp farming from variability in survival rate, growth rate, price seasonality and labor force constraints. The influence of these factors is described quantitatively within the context of a commercial shrimp farm operating in Hawaii. The managerial objective being expressed is to project a scheduling scenario that maximizes the net revenue from a 40 pond farm during a two year planning horizon, subject to a set of biological and economic conditions. These inherently practical results indicate that these factors can be managed to substantially improve the profitability of such a shrimp farm. It is apparent that continued development and application of this capability can have profound implications to the profitability of many multi-pond, multi-cycle farming operations.

Unique lesions and viral-like particles found in growth retarded black tiger shrimp Penaeus monodon from East Africa

The problem of growth retardation in cultured black tiger shrimp, Penaeus monodon was observed at one commercial shrimp farm in East Africa in mid 2004. The mean body weight of the shrimp at the sixth month in affected ponds was only 19 ± 4 g, which was 30% less than the expected size of normal shrimp grown within the same period at this farm. A preliminary examination for pathogenic bacteria, parasites and viruses revealed mild bacterial infections in a few specimens but all were negative for 7 known pathogenic shrimp viruses, either by assays using polymerase chain reaction (PCR) technology or by histological examination. A subsequent examination of a second lot of samples prepared for transmission electron microscopy (TEM) revealed the presence of previously undescribed lesions in the lymphoid organ and gills. In semithin sections stained with toluidine blue, these were apparent as large cytoplasmic inclusions that were not visible in normal tissue sections stained with hematoxylin and eosin. By TEM, the cytoplasmic inclusions contained large numbers of non-enveloped, icosahedral virions of approximately 25 nm diameter. Given the unique nature of the lesions and the negative results with molecular tests for known shrimp viruses, it is possible that the particles seen constitute a new viral pathogen of shrimp. The retarded growth problem in East Africa resembles a similar problem called monodon slow growth syndrome (MSGS) that has been problematic with P. monodon in Thailand since 2001. Whether the slow growth in Africa and Thailand are due to the same or related pathogens or some other factor(s) remains to be explored.

Effects of feeding frequency on feed leaching loss and grow-out patterns of the white shrimp Litopenaeus vannamei fed under a diurnal feeding regime in pond enclosures

Feed management plays a major role in the economical and environmental status of shrimp farms. It involves basic aspects such as when, where and how much to feed. Studies were conducted under pond conditions in order to determine the effects of feeding frequency on the grow-out patterns of Litopenaeus vannamei. Feed loss of crude protein (CP), lipid and dry matter (DM) over different water exposure periods were also investigated. In a commercial shrimp farm, 25 open-bottom enclosures (5 treatments and 5 replicates) of 50 m 2 each were installed in a 7.43-ha grow-out pond and stocked at 80 shrimp/m 2 (2.7 ± 1.52 g body weight). Shrimp were fed a commercial pelleted feed, delivered exclusively in feeding trays 2 (at 0700 and 1700 hours), 3 (at 0700, 1100 and 1500 hours), 4 (at 0700, 1000, 1300 and 1500 hours), 5 (at 0700, 0900, 1200, 1500 and 1700 hours) and 6 times/day (at 0700, 0900, 1100, 1300, 1500 and 1700 hours). Feed was made available over continuous 24-h periods and remains were collected at next feeding. After 8 h of water immersion, feed CP and lipid level dropped from 39.58% to 34.07% and from 9.25% to 7.88%, respectively. Leaching of feed CP and lipid was not statistically different over the study period. Long feed water exposure generated significant losses in DM. Leaching of DM reached 4.65 ± 0.34% after the first hour of water immersion, peaking at 8 h (10.20 ± 0.48%). Shrimp were harvested at day 84 of grow-out, when average body weight ranged from 9.7 ± 1.75 to 10.9 ± 1.90 g. No shrimp performance benefit could be detected by adopting higher diurnal feeding frequencies. Although shrimp fed five times/day showed superior grow-out performance indices, at harvest no statistical differences were detected in shrimp survival (64.1 ± 11.7%), shrimp yield (0.46 ± 0.08 kg/m 2) and feed conversion ratio (2.85 ± 1.42) between feeding treatments. Also, no consistent growth pattern could be detected in relation to feeding treatments over the rearing cycle. The present study demonstrated that when feed rations are only adjusted at a weekly basis, using as the only criteria shrimp estimated biomass, delivering feed more than twice per day is not advantageous in the grow-out of L. vannamei.

Viral resistance in shrimp that express an antisense Taura syndrome virus coat protein gene

Taura syndrome virus (TSV) is a major cause of mortality and morbidity in shrimp, and has a profound economic impact on commercial U.S. shrimp farming. This paper describes the stable expression of an antisense Taura syndrome virus-coat protein (TSV-CP) gene construct in shrimp zygotes, via transfection using jetPEI reagent, over a period of at least 236 days. The transgenic shrimp showed no statistically significant difference from normal control shrimp in terms of weight gain or their appearance, morphology, swimming and eating activities. When challenged with live TSV, the transgenic shrimp exhibited increased resistance to the TSV infection (83% survival rate) as compared to control animals (44% survival rate). This work demonstrates that transgenic shrimp, which stably express an antisense transcript from the TSV-CP gene, are partially resistant to TSV infection. These data may have an important implication for commercial shrimp farming.

Predicting shrimp growth: Artificial neural network versus nonlinear regression models

This study evaluated the potential of artificial neural networks (ANN) as an alternative to the traditional statistical regression techniques for the purpose of predicting shrimp growth in a commercial setting. Empirical data collected from a commercial shrimp farm in Hawaii was used for this evaluation. Eight regression functional forms (i.e., linear, polynomial, log reciprocal, von Bertalanffy, Gompertz, logistic and exponential) were employed as counterparts to ANN. The specific models were first estimated from a dataset consisting of 459 records and then applied to a dataset consisting of 249 records to validate their predictive performance. Performance was assessed by four measures (i.e., root mean square error (RMSE), R 2, the percentage of wrong turning points and the percentage of predicted values that are within the 5% tolerance of the corresponding actual values). The results indicated that ANN outperformed regression models for the complex set of conditions typical of a commercial production environment. ANN generated a slightly better descriptive shrimp growth curve than the best ones generated from nonlinear models and made the most accurate prediction. Hence, we conclude that ANN represents a valuable tool for predicting shrimp growth for the variable set of growth conditions typifying commercial shrimp farms.

Sustainable aquaculture and producer performance: measurement of environmentally adjusted productivity and efficiency of a sample of shrimp farms in Mexico

The competition among shrimp producing countries, the rapid advances in technology and the increase in market demand suggest that the shrimp industry at a global level and in Mexico in particular needs to take appropriate measures to maintain its viability and be able to compete successfully. This can be achieved by making better use of the available scarce resources and appropriate technology without further deteriorating the environment. Decision makers, i.e. policy-makers and farmers, are challenged with the responsibility of planning and conducting aquaculture development in a sustainable way whereby social, environmental and economic goals are simultaneously satisfied. Based on an unbalanced panel of semi-intensive shrimp farms containing primary-source information at pond level for the period 1994, 1996–1998 in northwest Mexico, this paper assesses farm performance indicators adjusted to incorporate environmental impacts. This 4-year time series coincides with a switch in the species reared in commercial shrimp farms from white shrimp (first 2 years) to blue shrimp, as a consequence of viral disease outbreaks in the former species which impacted operations in Mexico in 1995 and 1996. Therefore, efficiency and productivity can be measured and the results can be analyzed in correspondence with three events: use of white or blue shrimp in operations; the effect of experience of working with one species after many years (white shrimp) and to initiate a learning curve with a new species (blue shrimp) after 1996; and the effect of the viral outbreak on production performance. Using an input distance function approach, total factor productivity (TFP) and technical efficiency (TE) using both traditional (T) and environmentally adjusted (EA) indicators were examined. TFP was reduced in 1996–1998 compared to 1994, due to a technological regression as reflected by increased input-intensive production technology resulting in an increase in undesirable outputs. The learning curve resulting from a shift from white shrimp to blue shrimp production species resulted in higher FCRs, water exchange and pollution emissions, despite increasing shrimp yields. In all years except 1994, EA TE and EA TFP were lower than the traditional TE and TFP scores. TE and TFP had an opposite behavior than yields in this period of time. In order to improve the technological change (TC) component of TFP in light of stable TE scores, increased government assistance in disseminating technological know-how is necessary to improve TFP at a faster rate during the transition period.

Intake and discharge nutrient loads at three intensive shrimp farms

This study was conducted to help provide a framework for Australian regulation of shrimp farm siting and discharges. Monitoring of farm water usage, and intake and discharge water quality was conducted at three commercial intensive shrimp farms, chosen to represent different operating environments, latitudes, cultured species and management styles. Weekly samples were taken over 3 years, for 3–12 months at each farm, to investigate intake and discharge concentrations and loads of total suspended solids (TSS), total nitrogen (TN) and total phosphorus (TP). Mean water exchange was 1.4 ML ha−1 day−1 (about 10% day−1) at the first farm studied and 0.5 ML ha−1 day−1 (about 3.6% day−1) at the others. Farm mean discharge concentration varied as follows: TSS, from 36.9 to 119 mg L−1; TN, from 2.1 to 3.1 mg L−1 and TP, from 0.22 to 0.28 mg L−1. Farm mean intake concentrations were from 11% to 91% of equivalent mean discharge concentration (for TN at Farm B and TSS at Farm C respectively). Mean net discharge loads, related to area of production ponds at each farm, varied as follows: TSS, from 4.8 to 85.7 kg ha−1 day−1; TN, from 1 to 1.8 kg ha−1 day−1 and TP, from 0.11 to 0.22 kg ha−1 day−1. The highest net loads of TSS, TN and TP were all from the farm with the highest water exchange rate, located on a coastal river, and studied during a year of high rainfall with associated poor water quality. These results can be used to help predict likely discharge characteristics for new shrimp farms, and provide a benchmark against which to evaluate future improvements in shrimp farm environmental management.

Reproductive readiness of the shrimp Litopenaeus vannamei grown in a brackish water system

The reproductive readiness of the marine shrimp Litopenaeus vannamei (formerly Penaeus vannamei) cultured in brackish water was characterized by applying morphological, physiological, and molecular tools. The shrimp were cultured on two commercial shrimp farms in brackish water that was pumped from artesian wells that tap into a geothermal aquifer. The shrimp populations exhibited a bimodal growth curve with the females being significantly bigger than the males at the end of the growout period. Some male shrimp started to develop spermatophores about 6 months after the first post-larval (PL 0) stage, and some with developed, normal-looking, white spermatophores were observed 8 months after PL 0. The sperm count in these males was 10.1×10 6±5.8×10 6 cells per compound spermatophore, and 81.6±19.8% of the cells were spiked. Melanization of the males, which eventually affected about a third of the male population, first became evident before the appearance of white spermatophores. Female ovaries were transparent and appeared to be arrested in a previtellogenic stage. However, beyond a weight/age threshold of 20 g/8 months, some of the ovaries had become opaque and the vitellogenin gene was found to be expressed in the ovary—but not in the hepatopancreas—of 7 out of 10 females. A unique case of a 46.8 g female with a fully developed ovary that was found in the brackish-water-held broodstock is reported.

Characterization of intake and effluent waters from intensive and semi-intensive shrimp farms in Texas

Two commercial shrimp farms in south Texas were evaluated for influent and effluent water quality from June to October 1994. The intensive farm, Taiwan Shrimp Village Association (TSV) had an average annual yield of 4630 kg ha−1 while the semi-intensive farm, Harlingen Shrimp Farm (HSF), had a yield of 1777 kg ha−1. The study had three objectives: (1) to compare influent and effluent water from the intensive and semi-intensive shrimp farms, (2) to show which effluent water-quality indicators exceeded allowable limits, (3) to indicate inherent problems in farms operated with water exchange and summarize how findings from this study led to changes in farms' management that limited potential negative impact on receiving streams. Water samples were collected and analysed twice a week for the TSV farm and once a week for the HSF farm. Samples were analysed for dissolved oxygen (DO), salinity, pH, ammonia-nitrogen (NH3-N), nitrite-nitrogen (NO2-N), nitrate-nitrogen (NO3-N), total phosphorus (TP), total reactive phosphorus (TRP), five-day carbonaceous biochemical oxygen demand (cBOD5), total suspended solids (TSS) and settleable solids (SettSols). Most of the effluent constituents showed fluctuations throughout the sampling period often related to harvest activity. Effluent pH at TSV was lower than influent values but within the regulatory requirements set by Texas Commission of Environmental Quality (TCEQ), formerly known as Texas Natural Resource Conservation Commission (TNRCC). HSF effluent pH values were higher than its influent, but still within TCEQ limits. Effluent DO mean levels were generally below the regulatory daily mean requirement, with values at TSV often below those for influent. Effluent nutrient concentrations and net loads were generally higher at the intensive shrimp farm, with NH3-N mean concentrations above the daily mean set by the TCEQ on several occasions. Effluent TSS concentrations were higher than influent for both farms, with daily mean values above the TCEQ limit. The two farms presented similar TSS concentrations despite their different stocking densities. However, TSS total net load and net load per hectare were higher at the intensive farm. The semi-intensive farm presented higher cBOD5 concentrations and net loads despite its lower stocking density, with daily mean values above the TCEQ limit. The cBOD5 net load at TSV presented negative values indicating higher load at the influent than at the effluent. Analyses showed no evidence of self-pollution between influent and effluent at the two farms. The high feed conversion ratio (FCR) values (2.3 and 2.7 for the intensive and the semi-intensive farm respectively) suggest that better feed management is needed to reduce nutrient and solid net loads release from the two farms. The data obtained from this study resulted in several modifications in design and management of the two farms that reduced the potential negative impact on receiving streams. A brief summary of the improvement in selected effluent water-quality indicators at the intensive shrimp farm is provided.