Comparison of microbial community structures in intensive and extensive shrimp culture ponds and a mangrove area in Thailand

ABSTRACT:   A pelagic bacterial community structure was examined in experimental intensive shrimp culture ponds that have a shrimp–mangrove complex aquaculture system, an extensive shrimp culture pond and a mangrove area in Thailand by denaturant gradient gel electrophoresis analysis of polymerase chain reaction amplified partial 16S rRNA genes. Bacterial community structure in the intensive shrimp culture ponds was distinguishable from that of the mangrove area. In the extensive shrimp culture pond, the bacterial community structure resembled that in the mangrove area, but bacterial abundance was as great as that in the intensive shrimp culture ponds. Among the intensive shrimp culture ponds, the bacterial community structure was different between a closed culture system and a shrimp–mangrove complex culture system. Moreover, the bacterial community structure in mangrove planted ponds was close to those in the intensive shrimp culture ponds when shrimp culture was conducted, but it was close to those in the mangrove areas without shrimp culture. These results suggest that intensive shrimp culture with shrimp feed input affects the bacterial community structures in pond water.     

Phosphorus budget in shrimp aquaculture pond with mangrove enclosure and aquaculture performance

ABSTRACT:   An experiment in which water was circulated between shrimp aquaculture ponds stocked with 10 000 or 20 000 PL-15 stage Penaeus monodon , and mangrove enclosures each planted with 476 Rhizophora mucronata per enclosure, was carried out at the Samut Songkhram Coastal Aquatic Research Station, Faculty of Fisheries, Kasetsart University, Thailand. Shrimp survival rate was significantly higher ( P  < 0.001, Fisher's exact test) in ponds where 10 000 larvae was stocked and water was exchanged with the mangrove enclosure, compared with the control pond with no water exchange, over the 136 day experimental period. Phosphorus transport to the mangrove enclosure was estimated to be 0.41 kgP and 0.18 kgP over the experimental period and change in phosphorus content in mud was reduced there compared with the control pond. A load reduction effect to the environment was confirmed in this aquaculture system with mangrove enclosure compared with the phosphorus budget in the control pond, and 6.2 or 8.9 ha of mangrove area was estimated to be required by 1 ha shrimp ponds to fully process the phosphorus.     

Integrated shrimp-mangrove farming systems in the Mekong delta of Vietnam

In recent years, mangroves have been seriously threatened by shrimp culture development in the Mekong delta of Vietnam. As one way of protecting the mangroves, efforts have been made to develop shrimp-mangrove integrated farming systems through State Forestry Fisheries Enterprises (SFFEs), involving a participatory approach. The present study investigated the shrimp-mangrove farming systems in Ngoc Hien district at the southern tip of the Mekong delta through a detailed farm-level survey, including technical, environmental, social and economic factors. A total of 161 shrimp-mangrove farms on the east and west coasts of Ngoc Hien district were surveyed. The results showed that on the East coast of the delta, the pH of the bottom soil, the water alkalinity, gate width ratio (ratio of gate width to pond area), pond age and mangrove density, and flooding level of ‘flat’ (flat is where the mangroves are planted) in the dry and rainy seasons were significantly correlated with shrimp pond yields. On the west coast, the pH of the bottom soil, dissolved inorganic phosphorus, ditch area, and flooding level of ‘flat’ were found to be significantly correlated with shrimp pond yields. An economic analysis, based solely on the economic returns from shrimp culture showed that the farming systems with a mangrove coverage of 30-50% of the pond area gave the highest annual economic returns. The results demonstrate a better economic return to farmers who maintain mangroves in their farming systems.     

The use of mangrove wetland as a biofilter to treat shrimp pond effluents: preliminary results of an experiment on the Caribbean coast of Colombia

The potential benefit of integrating mangrove and shrimp farms to protect ponds against erosion, to enhance the productivity of supply water and also to treat pond effluents has been pointed out previously. Agrosoledad, a 286‐ha shrimp farm located on the Caribbean coast of Colombia, was constructed behind a 1‐km‐wide mangrove area. Farm effluents are partially recirculated through a 120‐ha mangrove wetland used as a biofilter. A 3‐month study compared the concentrations of suspended solids and inorganic nutrients in the supply canal, the pond drainage and the biofilter. Suspended solids increased in pond drainage compared with supply water, but they were drastically reduced in the biofilter. In contrast, dissolved inorganic nitrogen and phosphorus concentrations were not different in supply water and pond drainage, but they increased in the biofilter because of the presence of a large marine bird community. Additionally, a significant decrease in dissolved oxygen and pH was observed in the biofilter. The study demonstrated the efficiency of the system to eliminate suspended solids from the effluent. However, nutrient dynamics showed that the possible use of mangrove wetlands as biofilters for effluent treatment will be less predictable than expected.     

What is the ecological footprint of aquaculture after 5 decades of competition between mangrove conservation and shrimp farm development?

1. Among the several threats to the conservation of mangrove ecosystems in most South Asian countries, shrimp farming is predominant. Since the introduction of shrimp farming in Sri Lanka in the 1980s, mangroves on the island’s north-western coast have been continually cleared to create new shrimp farms, leading to a decline in the social-ecological services provided by the mangrove ecosystems.
2. Using aerial (1973) and satellite (1996–2020) images, this study assessed areal changes in mangroves and shrimp farms in the Pambala-Chilaw lagoon complex and Ihala Mahawewa, as well as the ecological footprint of shrimp farming in the study area.
3. Mangroves around the Chilaw lagoon had decreased in areal extent by 45% from 1973 to 2020 of which 92% of this change was attributed to shrimp farming. There was, however, a decrease in the areal extent of shrimp farms from 2001 to 2020, and a corresponding increase in mangroves from 2006 to 2020.
4. The ecological footprint of shrimp farming was assessed by comparing the expected surface ratios with those recorded for shrimp farms with mangroves and surface water bodies in the study area from 1973 to 2020. The results showed that the current shrimp farming was unsustainable (i.e. high ecological footprint).
5. While the results support the current view that there is cause for cautious optimism with mangrove conservation (as evidenced by an increase in mangrove areal extent), it also reveals that semi-intensive shrimp farming in Sri Lanka and probably other similar tropical countries is unsustainable.
6. If immediate actions such as effective regulation of shrimp farming activities and mangrove restoration are not taken, the mangrove ecosystem will continue to decline.

     

The Potential Use of Mangrove Forests as Nitrogen Sinks of Shrimp Aquaculture Pond Effluents: The Role of Denitrification

A generalized nitrogen budget was constructed to evaluate the potential role of mangrove sediments as a sink for dissolved inorganic nitrogen (DIN) in shrimp pond effluents. DIN concentrations were measured in pond effluents from three semi-intensive shrimp ponds along the Caribbean coast of Colombia between 1994–1995. Mean NH₄⁺ concentrations in the discharge water for all farms were significantly higher (67 × 12 μg/L) than in the adjacent estuaries (33 × 8 μg/L). Average NH₄⁺ concentrations in the pond discharge over all growout cycles were similar, representing an approximate doubling in relation to estuarine water concentrations. In contrast, NO₂^-+ NO₃^- concentrations were similar in both pond effluent and estuarine waters. Dissolved inorganic nitrogen loading of the ponds was similar. The estimated reduction of DIN in pond effluents by preliminary diversion of outflow to mangrove wetlands rather than directly to estuarine waters would be × 190 mg N/m² per d. Based on this nitrogen loss and depending upon the enrichment rate, between 0.04 to 0.12 ha of mangrove forest is required to completely remove the DIN load from effluents produced by a 1-ha pond.     

Profitability evaluation of resource allocation for growing redtail and Chinese shrimp

A farming survey was conducted to evaluate the profitability of resource allocation for producing redtail shrimp, Penaeus penicillatus (Alock) and Chinese shrimp, P. chinensis (Osbeck). Data on production costs and total revenue according to different harvest sizes of shrimp species were collected based on 108 individual ponds operated by 25 surveyed shrimp farmers. The results indicated that growing Chinese shrimp to a marketable size of 12 g was the most profitable management strategy. The profits could be maximized by integrating small-scale farms to a 12.41 ha optimal farming area when the available resources remained the same as those for a 10 ha farm.     

Socio-economic impacts of shrimp culture

Farmed shrimp contributed 27% of total world shrimp production in 1995 with a volume of 712 000 tonnes. Undoubtedly, the shrimp culture industry earns valuable foreign exchange for developing countries and generates jobs across the industry from fry gatherers to growers and processors. However, grave socio-economic consequences – including conversion, expropriation and privatization of mangroves and other lands; salinization of water and soil; decline in food security; marginalization of coastal communities, unemployment and urban migration; and social conflicts – have followed in the wake of, shrimp farm development in the Philippines and other tropical countries. The paper focuses on mangrove ecosystems: the valuation and cost-benefit analysis of their goods and services, and the mangrove-offshore fisheries connection. Research gaps in these areas and the need to internalize the ecological and socio-economic costs (‘externalities’) of shrimp farming are highlighted. Other recommendations include mangrove conservation and rehabilitation, enforcement of existing legislation, and introduction of environment-friendly aquaculture within the broader framework of community-based, integrated coastal area management, e.g. the traditional, extensive polyculture ponds in Indonesia.     

Coastal wetlands of the northern Gulf of California: inventory and conservation status

• 1. Above 28°N, the coastline of the northern Gulf of California is indented at frequent intervals by negative or inverse estuaries that are saltier at their backs than at their mouths due to the lack of freshwater inflow. These ‘esteros’ total over 215 000 ha in area and encompass mangrove marshes below 29°N and saltgrass (Distichlis palmeri) marshes north of 29°N. An additional 6000 ha of freshwater and brackish wetlands are found in the Colorado River delta where fresh water enters the intertidal zone.
• 2. The mangrove marshes in the Gulf of California have been afforded some degree of protected status in Mexico, but the northern saltgrass esteros do not have priority conservation status and are increasingly becoming development targets for resorts, vacation homes and aquaculture sites.
• 3. We conducted an inventory of the marshes using aerial photography and satellite images, and evaluated the extent and type of development on each marsh. We reviewed the available literature on the marshes to document their vegetation types and ecological functions in the adjacent marine and terrestrial ecosystems.
• 4. Over 95% of the mangrove marshes have been developed for shrimp farming. However, the farms are built adjacent to, rather than in, the marshes, and the mangrove stands are still mostly intact.
• 5. The majority of saltgrass marshes above the mangrove line are still relatively unspoiled. However, resort and vacation home development is taking place on land surrounding them.
• 6. We recommend a system of protected reserves incorporating the pristine wetlands, along with water quality management and buffer zones for the more developed esteros. The saltgrass marshes should be considered for conservation protection, similar to the protection given to the southern mangrove marshes whose value has already been recognized.

Copyright © 2006 John Wiley & Sons, Ltd.     

Ecological footprint for assessment of resource use and development limitations in shrimp and tilapia aquaculture

We review estimates of the spatial ecosystem support required to run a typical semi-intensive shrimp farm in a coastal mangrove area in Carribean Colombia, and to produce food inputs and process wastes for large-scale industrially managed tilapia cage culture and small-scale, semi-intensive tilapia pond farming in Lake Kariba, Zimbabwe. The tilapia farming is discussed in relation to the pelagic kapenta, Limnothrissa miodon (Boulenger), fishery and to inshore fisheries in the Lake. The results show that a semi-intensive shrimp farm needs a spatial ecosystem support—the ecological footprint—35 to 190 times the surface area of the pond, mainly mangrove area. Based on the analysis, we conclude that shrimp farming in Colombia is already utilizing close to the full support capacity of its coastal environment. In intensive tilapia cage farming, the ecological footprint for feed production is 10 000 times larger than the area of the cages. In contrast, a tilapia pond farm maintained on offals from fisheries, agriculture and households depends very little on external ecosystem areas. As long as there is a direct market for human consumption of all kapenta caught in the Lake, fish cage farming based on fish meal from kapenta would be doubtful from ethical, ecological as well as resource management points of view, even if it was economically feasible.     

Estimates of Bottom Soil and Effluent Load of Phosphorus at a Semi-intensive Marine Shrimp Farm

A phosphorus budget for a single crop was prepared for a 685‐ha semi‐intensive shrimp farm that consistently has produced about 3000 tonnes/yr of black tiger prawn, Penaeus monodon. Phosphorus inputs were shrimp stock, 0.31 kg/ha; triple superphosphate, 1.38 kg/ha; incoming water, 25.8 kg/ha; and feed, 65.3 kg/ha. Phosphorus outputs were harvested shrimp, 5.43 kg/ha, and outflow for water exchange and draining, 42.7 kg/ha. The high clay‐content soil in pond bottoms adsorbed 45.2 kg/ha of phosphorus. Water was taken from and released back into the same estuary and bay. The phosphorus contribution of shrimp farming to the receiving water body was the difference between the amount of phosphorus in effluent and that in the incoming water, which was 16.9 kg/ha. Bottom soil accumulated 67.8% of phosphorus added to the ponds. Another estimate of soil phosphorus uptake based on the relationship between cumulative phosphorus applied to ponds as fertilizer and feed and soil phosphorus concentration suggested that 63.2% of fertilizer and feed phosphorus had accumulated in pond bottoms. The farm effluent phosphorus load was 23.5 tonnes/yr. The estuary and bay system has an estimated volume of 4.8 × 10⁹ m³, and the annual phosphorus input from the farm had a concentration equivalent of 0.005 mg/L, and there were no other major inputs of phosphorus. The estuary and bay are flushed by freshwater inflow and tidal action, and the farm input is not likely to cause eutrophication.     

A closer look into shrimp yields and mangrove coverage ratio in integrated mangrove-shrimp farming systems in Ca Mau,Vietnam

Shrimp aquaculture is the biggest source of export income in Vietnam. However, the development of the shrimp poses a serious threat to coastal mangroves by converting coastal mangroves into shrimp farms. Much effort has been made to replant mangroves and reduce the impacts of shrimp farming on the environment, and maintaining mangrove coverage at 30–50% of total farm area has provided the highest benefits in the integrated mangrove shrimp model. In this study, we re-examine the benefits of forest cover on the survival and yield of tiger shrimp (Penaeus monodon) in the integrated mangrove shrimp farming systems in Ca Mau province, Vietnam. The study found positive linear correlations of log transformed survival and yield of tiger shrimp with forest cover of the forms: Ln (survival)?=????1.39?+?0.038?×?forest coverage (r²?=?0.22; p value?=?0.0007); Ln (yield)?=?3.55?+?0.026?×?forest coverage (r²?=?0.16; p value?=?0.004). The households with high forest cover (i.e.,?>?45%) also had 1.07?±?0.29 and 1.39?±?0.36 (CI 95%, p value?=?0.000) kg ha^?1 higher yield per night harvest than those with medium and low forest cover, respectively. As a result, households with high forest cover have higher benefits than those with lower forest cover. Our findings together with previous published studies lead to the recommendation that farmers maintain mangroves in farming systems for better economic and environmental benefits.

     

A review on the morphology, molecular characterization, morphogenesis and pathogenesis of white spot syndrome virus

Since it first appeared in 1992, white spot syndrome virus (WSSV) has become the most threatening infectious agent in shrimp aquaculture. Within a decade, this pathogen has spread to all the main shrimp farming areas and has caused enormous economic losses amounting to more than seven billion US dollars. At present, biosecurity methods used to exclude pathogens in shrimp farms include disinfecting ponds and water, preventing the entrance of animals that may carry infectious agents and stocking ponds with specific pathogen-free post-larvae. The combination of these practices increases biosecurity in shrimp farming facilities and may contribute to reduce the risk of a WSSV outbreak. Although several control methods have shown some efficacy against WSSV under experimental conditions, no therapeutic products or strategies are available to effectively control WSSV in the field. Furthermore, differences in virulence and clinical outcome of WSSV infections have been reported. The sequencing and characterization of different strains of WSSV has begun to determine aspects of its biology, virulence and pathogenesis. Knowledge on these aspects is critical for developing effective control methods. The aim of this review is to present an update of the knowledge generated so far on different aspects of WSSV organization, morphogenesis, pathology and pathogenesis.     

Effect of water exchange with mangrove enclosures based on nitrogen budget in <Emphasis Type="Italic">Penaeus monodon</Emphasis> aquaculture ponds

ABSTRACT:   A model experiment in which water was circulated between shrimp aquaculture ponds (Ponds 1, 2, and 5), and mangrove enclosures (Ponds 3 and 4), was carried out at the Samut Songkhram Coastal Aquatic Research Station, Thailand, from March through July 2003. Five ponds with a size of 40 m × 20 m and 1.5 m deep were used for this experiment. Ten thousand shrimp larvae Penaeus monodon at the PL-15 stage were stocked in Ponds 1 and 5, and 20 000 larvae were stocked in Pond 2. Mangrove Rhizophora mucronata (476 trees) had been planted in each of Ponds 3 and 4 in July 2002. Approximately 30% of the water in Ponds 2 and 5 was moved to the mangrove enclosures by siphon (Ponds 3 and 4, respectively) every Thursday, and the same amount was returned to the shrimp ponds by pump every Monday over the 136-day experiment. Shrimp incorporated 30.3, 25.6, and 33.7% of the input nitrogen as feed in Ponds 1, 2, and 5. Since 2.02 kg N in Pond 2 and 0.76 kg N in Pond 5 was transported to the mangrove ecosystem, and 4.26 kg N in Pond 2 and 3.98 kg N in Pond 5 was retained in water and mud, it was estimated that between 2.1 and 5.2 unit areas of mangroves is required to remove the nitrogen remaining in the aquaculture pond.     

Productivity benefits of selectively breeding Black Tiger shrimp (Penaeus monodon) in Australia

Advances in the domestication and selective breeding of Australian Black Tiger shrimp, Penaeus monodon, opens the opportunity for world producers to reconsider the benefits of farming this species. Just over a decade ago this species was the world's most farmed shrimp species, however, difficulty in its domestication, in part, led to the widespread establishment of Penaeus vannamei (Pacific White shrimp) as the most farmed shrimp species in the world. This study empirically evaluates the productivity benefits of commercially domesticating P. monodon against production from wild broodstock of the same species. The evaluation compared the relative production from commercial ponds stocked with the progeny of wild P. monodon broodstock and ponds stocked with the progeny of domesticated stocks. The production data were from 164 ponds of domesticated stocks and 30 ponds of wild stocks, collected over 4 years (2009–2013) from two separate farm sites of the same Australian shrimp farming company. The wild stocks were sourced from the east coast of Australia. The results suggested that the productivity of the selectively bred stocks was 39% greater compared with production from wild stocks given equivalent amounts of feed and other inputs. Furthermore, productivity was additionally enhanced depending on the choice of feeds and whether stocking took place in September rather than later in the year (i.e. in early spring rather than late spring/early summer in the Southern hemisphere). This suggests that there is significant potential to further enhance the productivity of P. monodon farms via integrating advances in domestication, feeds and management practices.     

Intensification of Shrimp Culture in Earthen Ponds in South Carolina: Progress and Prospects

Experiments on the intensive cultivation of Pacific white shrimp, Penueus vunnumei, in ponds in South Carolina were begun in 1985 at the Waddell Mariculture Center. A preliminary study involved two 0.1 ha ponds stocked at an average of 43 postlarvae/m², with management practices based on those used in Taiwan for intensive pond culture of Penueus monodon. Harvest yields averaged 6,757 kg/ha for one crop, demonstrating the technical feasibility of such intensive culture of P. vannumei. In 1986, 2.5 ha of ponds at the Waddell Center (six ponds totaling 2.0 ha at 40 postlarvae/m² and two totaling 0.5 ha at 60/m²) yielded a total of 13,606 kg (5,442 ke/hn). These results were obtained even though aeration and water exchange rates were substanthlly reduced and South Carolina experienced its worst heat wave and drought. This served as a pilot-sde, proof-ofconcept test. Tank studies in 1985 and 1986 showed little effect of stocking density on shrimp growth rate at densities of 20–100 animals/m². This was confirmed in ponds in 1987 when no differences in growth rates were observed at densities of 20–100 postlarvae/m². Harvest biomass increased directly with stocking density in all trials, reaching a maximum of 12,680 kg/ha/crop at 100 shrimp/m² in 1987. Initial attempts to intensify production in the nascent South Carolina shrimp farming industry occurred in 1986, when approximately 32 ha of private ponds were stocked at densities of 10–32 postlarvae/m². Farm harvests increased with stocking density, with maximum yield of 3,656 kg/ ha/crop. This trend toward intensification in the private sector is continuing, and in 1987 maximum harvests from private ponds were 5,050 kg/ha from a 0.3 ha pond and 4,625 kg/ha from a 1.5 ha pond. Prospects for further implementation of intensive culture in the private sector appear excellent, with yields of ≥ 10,000 kg/ha/crop expected from private farms within the next few years.     

Introduction to the design of coastal aquaculture systems in Taiwan

The traditional culture of shellfish in the coastal waters of Taiwan has a long history. The culture area was limited to the sandy beaches of the south and southwest coast. In the past decade, due to the shortage of land resources and water pollution, coastal water aquaculture has been extended to intertidal rocky areas and the sublittoral zone. Concrete ponds have been constructed on the intertidal zone of the rocky coast specifically for culturing such species as small abalone, Haliotis diversicolor supertexta, grass shrimp, Penaeus monodon, grouper Epinephelus sp. etc. Fish culture in floating cages and oyster culture on floating long-lines and rafts are also practiced. This paper presents details of construction designs, with emphasis on utilizing water circulation, construction costs and wave resistance. Some examples are selected to illustrate the layouts used and the problems faced.     

Intensive Culture Potential of Penaeus vannamei

Tank and pond rearing studies were conducted to assess the potential for intensive culture of Penaeus vannamei in South Carolina. Postlarvae were stocked in intensive nursery tanks at 500/ m². Growth and survival were compared for shrimp reared in control fiberglass tanks and in tanks with artificial substrates (fiberglass screen). Addition of substrate improved survival (82% versus 58%), but not growth. Juvenile shrimp (mean weight, 1.3 g) from the nursery trial were stocked into 6 m diameter tanks at densities of 10, 20 and 40/m². Growth rate was inversely related to stocking density, with mean sizes of 33.9, 32.5, and 26.7 g attained at the low, medium, and high densities respectively after 168 days. At harvest, standing crop biomass averaged 225.6, 442.0, and 685.4 g/m² for the three densities. To further test the intensive culture potential, two 0.1 ha ponds were stocked with hatchery-reared postlarvae at densities of approximately 40 and 45/m². The ponds were managed intensively using paddlewheel aerators and water exchange averaging 16–17%/day. The ponds were harvested after 138 and 169 days and yielded 6,010 kg/ha of 16.7 g (mean weight) shrimp and 7,503 kg/ha of 17.9 g shrimp, respectively. Average production was 6,757 kg/ha with a food conversion of 2.51. These data suggest good potential for intensive pond culture of P. vannamei in South Carolina and other areas of the continental United States.     

Compensatory growth and feed restriction in marine shrimp production,with emphasis on biofloc technology

In Brazil, studies and production of penaeid shrimp in a biofloc technology (BFT) system are recent, but the results point to a promising future. Research with feed restriction inducing compensatory growth in shrimps has been shown to be a technique that allows a saving of around 25% in the use of feed for shrimp production. It also allows the reduction of costs with salaries and adapts shrimp farming to the world demand for environmentally friendly production, with the reduction of nitrogen and phosphorus levels in its effluents, as well as lower water use in shrimp farming. In crustaceans, it has been shown that after a period of feed restriction, the animals show a pronounced compensatory growth when they return to a sufficient food source. Studies with the penaeid shrimp Litopenaeus vannamei reported the ability of the species to obtain a complete compensatory growth after short feeding periods (1 to 3 days) followed by feeding; These short periods of fasting presented a greater efficiency in the feed conversion besides the decrease in the concentration of phosphorus present in the aquatic environment, coming from the excreta. The adoption of a restriction program in the feeding using BFT may contribute to a reduction in operating costs, reduction of metabolic nutrients dissolved in water, and, consequently, an increase in the number of cycles in which the same water can be reused for production reducing production costs and improving productivity indices in shrimp farming.