Effects of Shrimp farming on Mangroves

SWES 474/574Pamila Ramotar, Ashlee Rhudy and Thomas Benson

Contents•Introduction

•Impacts of shrimp farming

•Shrimp diseases

•Benefits of Aquaculture

•Mitigating effects

•Conclusions

Introduction • Mangrove forests support a wealth of life, from

crustaceans to people, and most importantly the health of the planet.

• Forests mangroves form are among the most productive and biologically complex ecosystems on Earth.

• Mangroves are evergreen trees and shrubs that are well adapted to their salty and swampy habitat.

• They having breathing roots (pneumatophores) that emerge from the oxygen-deficient mud to absorb oxygen.

• Their location combined with their low

perceived value makes mangrove forests prime targets for shrimp farm development.

• Mangroves provide nursery grounds for fish and shrimp

• One of the greatest threats to mangrove survival comes from shrimp farming.

• At first glance, shrimp might seem the perfect export for a poor country in a hot climate

• Rich countries have an insatiable appetite for it (shrimp has overtaken tuna to become America's favorite seafood),

• The developing world has the available land and right climate to farm it.

• A prime location for shrimp ponds, though, happens to be the shore zone occupied by mangroves, marshes or mainly salty flats

• • The relative to low ecological value of tropical and subtropical

marshes and salt flats, have been conceived as coastal wastelands with low ecological and economic value.

• This has led to of loss of marshes through land development or modification for use in shrimp farming.

• Few attempts have been made to value salt marshes in economic and ecological terms

• To compound matters, shrimp farmers typically abandon their ponds after a few crop cycles (to avoid disease outbreaks and declining productivity) and move to new sites, destroying more mangroves as they go.

Mangrove depletion is associated with shrimp aquaculture in Asia and Central America.

•Large areas of mangrove wetlands have been converted into milkfish and shrimp farms and includes:

• in the Philippines (205,523 ha) (Chua 1992)

•Indonesia (211,000 ha) (Chua 1992).

•69,400 ha in Thailand (Dierberg and Kiattisimkul 1996)

•102,000 ha in Vietnam (Primavera 1998)

•6500 ha in Bangladesh (Primavera 1998)

• 21,600 ha in Ecuador (Alvarez and others 1989)

•11,515 ha in Honduras (Stonich 1995, De Walt and others 1996).

Impacts – General • The siting locations for shrimp pond

construction;

In extensive systems farms are located near the shore line to take advantage of the tide to collect post larvae, large hectares of mangroves are destroyed.

• the management and technology applied during the operation of shrimp ponds;

• the size or scale of the production and the surface dedicated to it, and;

Depend on whether the farms would be extensive, semi intensive and intensive based on the systems used it would determine the management and technology used.

Impacts – General

• Seepage of brackish water from the culture ponds into groundwater supplies

• The impact associated with intensive shrimp culture is the seepage of brackish water from the culture ponds into groundwater supplies and adjacent rice paddy fields.

• In some locations in Thailand, new shrimp pond construction occurs behind mangrove zones where freshwater wetlands and rice-growing areas are affected by surface and subsurface saltwater intrusion generated by pumping groundwater to the ponds.

• This leads to social costs, such as a reduction in domestic and agricultural water supplies, decreases in fish production, further marginalization of coastal fishermen, and displacement of labor

• The use of groundwater has resulted in land subsidence.

Impacts – Effluents and Shrimp Pond

• Effluents from shrimp ponds are enriched in suspended solids, nutrients, and biochemical oxygen demand (BOD) with concentrations largely depending on whether the management is extensive, intensive or semi intensive

• Studies have clearly shown that BOD, ammonia, chlorophyll a, and total suspended solids increase with stocking density

• extensive shrimp ponds produce few wastes, semi intensive ponds produce intermediate waste loads.

• the degree of intensification, i.e., higher stocking density ,use of water, feeds and fertilizers, produces an increased waste load.

• When effluents derived from agriculture, industry, and municipal areas are combined, sources of good quality water are sometimes scarce.

• When weather and tidal conditions (i.e., cloudy days, low winds, and neap tides) are combined, the result is a critical degradation of water quality in the shrimp ponds and the adjacent estuarine/lagoon waters.

Impacts – Capture of Wild Post larvae and Wild Shrimp Stocks

• Mortality of shrimp fry bycatch, loss of mangrove ecosystems, and genetic degradation of native populations may all contribute to a decline in biodiversity .

• During the 1980s and 1990s, about 35% of the world's mangrove forests had vanished.

• Shrimp farming was a major cause of this, accounting for over a third of it.

• Mangroves, through their roots, help stabilize a coastline and capture sediments; their removal has led to a marked increase of erosion and less protection against floods.

Shrimp Farming and disease• Its an aquaculture business used to raise

shrimp for human consumption

• World production is close to 800,000 metric tons, about 30% from shrimp raised on farms in more than 50 countries.

• It is estimate that farmed shrimp will account for more than 50% of total global production within the next five years.

• While approximately 99% of farmed shrimp are raised in developing countries, almost all of it is exported and consumed in rich, industrial countries - the US, Western Europe, and Japan.

• Since 1993 shrimp farming has encountered many issues that is believe to be viral diseases and is the main reason for the collapse of the industry.

Cultured SystemsThere are three types of systems used to raised and culture shrimp. •Intensive culture system: the shrimp are raised in high density and insensitively managed tanks and ponds

•Semi-intensive system: the shrimp are raised in moderate densities with some management in cages and ponds

•Extensive systems: Shrimp are raised in low density ponds or tanks with little management in natural bodies of water

In Intensive and some semi–intensive systems prevention and treatment of disease is possible, however because of the high density of these systems it aids the development and transmission of the diseases.

In extensive systems treatment is impractical.

Diseases • Shrimp are susceptible to

protozoa, fungi, bacteria, and viral diseases.

• Antibiotics can be used to combat protozoa, fungi and bacteria caused diseases

• 11 different virus disease of shrimp

• Consisting of three parvo-like,

2 reo-like, toga-like virus, and many baculoviruses

• The major pathogen in china is IHHNV (hypodermal and hematopoietic necrosis virus), which is a parvo-like virus that causes high mortality rates in juvenile shrimp

This picture shows Shrimp with IHHNV disease which is seen in the bent rostrums

• They found that there is an occurrence with affected areas and the nutrient content of the estuary

• Due to less rain and run-off the salinity of the estuaries is high and in range to grow bacteria

• Also the decrease in river flow cause nutrients to build up in the estuaries causing nutrient loading. This picture shows shrimp with the white spot virus.

Measures taken to prevent disease

• Disinfecting the farming ponds before stocking

• Enriching nutrition in the estuaries• Improving ecological conditions• Improving water quality (grow in low

salinity water) • Supplying high quality feeds to the

shrimp • They also use polyculture

Polyculture

• The main system used is the shrimp-fish system.

• This helps because the fish eat the sick

and infected shrimp stopping disease transmission and improving the balance in the ecology of the pond.

• Problem: The fish may cause shrimp survival to be low.

Capture of wild postlarvae• Wild fry provides seed for many

shrimp farms• Collection of wild fry can lead to

bycatch waste which hurts local fish populations

• Can have devastating effect on weaker ecosystems

•Aquaculture is a sustainable global seafood source•Important economic role in developing countries • Provides millions of jobs worldwide•Little to no effect on local marine populations

Benefits of aquaculture

Benefits Continued•Aquaculture can reduce pressure from commercial fishers

•Applicable to a variety of fish and crustacean

•Year round production provides room for world population growth

Sustainable aquaculture

• Can be obtained through practices that are environmentally no degrading, economically viable and socially acceptable

• Proper management and regulations are key

• Biggest inhibitor is lack of knowledge worldwide

Mitigating the impacts - Effluent

• The polyculture of bivalve mollusks, fish, and shrimp, using pond water to feed oysters, mussels, and seaweed in the effluent streams

• Use of shrimp farm effluents to irrigate salt tolerant crops. Glenn and others (1991) and Brown and others (1999) found that various plants in low salinities (Salicornia bigelovii, Atrilplex, Distichlis) and high salinities (Suaeda esteroa) remove nitrogen from shrimp effluents effectively.

Mitigating the impacts - Shrimp pond

The alternatives for use are:

• To convert to salt ponds

• Culture of other species (shellfish and crabs)

• To restore the ponds for halophyte and/or mangrove plantings.

Mitigating the impactsPond Designs

• Improved pond designs (Dierberg and Kiattisimkul 1996, Sandifer and Hopkins 1996), construction of wastewater oxidation–sedimentation ponds,

• Reduction of water exchange rates are also examples of actions to mitigate water quality deterioration.

• Improving the method for feed supply (Pa´ez-Osuna and others 1998)

• Improve the nutrient composition of the feed (Avnimelech 1999) could be an effective strategy for lowering the load of nitrogen and phosphorus released into the environment.

• Another alternative is to use mangrove wetlands as filters of pond effluents prior to their release into adjacent waters.

Mitigating the impacts - Capture of Wild Postlarvae and Wild Shrimp

Stocks

• Regulate wild fry by catch by establishing:

1.suitable sites,2.periods, 3.catch effort4.stimulating the use of hatchery post

larvae.

Conclusions • Shrimp farming has caused social dislocation,

ecological change, and environmental destruction that is arguably worse

• Serious environmental problems include the destruction of coastal wetlands, water pollution, disruption of hydrological systems, introduction of exotic species, and depletion and salinization of aquifers.

• Most critical social problems identified by local peoples is the loss of communal resources - including mangrove areas, estuaries, and fishing grounds - that local people depend on for both subsistence and commercial economic activities.

Best Management practices 1. Pond preparation2. Good quality seed selection3. Water quality management4. Feed management5. Health monitoring/Biosecurity6. Pond bottom monitoring7. Disease management8. Better Harvest and post-harvestPractices9. Record maintenance/Traceability10. Environmental awareness and instituted educational programs helps to promote suitable shrimp farming

Income from pre-existing livelihood activities like fishing and farming may be affected negatively by the loss of habitat and environmental degradation.

Benefits related to broadening the economic base of rural areas, generating local employment, enhancing food security, and conserving local environments

Mangrove protection laws are enacted in many countries

New farms are usually of the semi-intensive kind, which are best constructed outside mangrove areas

There is a trend to create tightly controlled environments in the farms, with the hope to achieve better disease prevention

• Waste water treatment has attracted attention; modern shrimp farms have effluent treatment ponds where sediments are allowed to settle at the bottom and other residuals are filtered.

• Low-intensity polyculture farming for some areas are recommended

• Mangrove soils are effective in filtering waste waters and tolerate high nitrate levels,

• The industry has also developed an interest in mangrove reforestation

References• Alongi, D. M., K. G. Boto, and A. I. Robertson. 1992. Nitrogen and phosphorus cycles. Pages 251–292 in A.

I. Robertson and D. M. Alongi (eds.), Tropical mangrove ecosystems. American Geophysical Union Press, Washington, DC.

• Alvarez, A., B. Vazconez, and L. Guerrero. 1989. Multi-temporal study of mangrove, shrimp farm and salt flat areas in the coastal zone of Ecuador, through information provided by remote sensing. Pages 141–146 in S. Olsen and L. Arriaga. (eds.), Establishing a sustainable shrimp mariculture industry in Ecuador.

• Boto, K. G. 1992. Nutrients and mangroves. Pages 138–145 in D. W. Connell and D. W. Hawker (eds.), Pollution in tropical aquatic systems. CRC Press, Boca Raton, Florida.

• Boyd, C. E., and J. W. Clay. 1998. Shrimp aquaculture and the environment. Scientific American 278:58–65.

• Boyd, C. E., and L. Massaut. 1999. Risks associated with the use of chemicals in pond aquaculture. Aquacultural Engineering 20:113–132.

• Alongi, D. M., K. G. Boto, and A. I. Robertson. 1992. Nitrogen and phosphorus cycles. Pages 251–292 in A. I. Robertson and D. M. Alongi (eds.), Tropical mangrove ecosystems. American Geophysical Union Press, Washington, DC.

• Alvarez, A., B. Vazconez, and L. Guerrero. 1989. Multi-temporal study of mangrove, shrimp farm and salt flat areas in the coastal zone of Ecuador, through information provided by remote sensing. Pages 141–146 in S. Olsen and L. Arriaga. (eds.), Establishing a sustainable shrimp mariculture industry in Ecuador.

• Boto, K. G. 1992. Nutrients and mangroves. Pages 138–145 in D. W. Connell and D. W. Hawker (eds.), Pollution in tropical aquatic systems. CRC Press, Boca Raton, Florida.

• Boyd, C. E., and J. W. Clay. 1998. Shrimp aquaculture and the environment. Scientific American 278:58–65.

• Boyd, C. E., and L. Massaut. 1999. Risks associated with the use of chemicals in pond aquaculture. Aquacultural Engineering 20:113–132.

• Boyd, C. E., P., Munsiri, and B. F. Hajek. 1994. Composition of sediment from intensive shrimp ponds in Thailand. World Aquaculture 25:53–55.

• Brown, J. J., and E. P. Glenn. 1999. Management of saline aquaculture effluent through the production of halophyte crops. World Aquaculture 30:44–49.

• Brown, J. J., E. P. Glenn, K. M, Fitzsimmons, and S. Smith. 1999. Halophytes for the treatment of saline aquaculture effluent. Aquaculture 175:255–268.

• Dierberg, F. E., and W. Kiattisimkul. 1996. Issues, impacts, and implications of shrimp aquaculture in Thailand. Environmental Management 20:649–666.

• Flaherty, M., and C. Karnjanakesorn. 1995. Marine shrimp aquaculture and natural resource degradation in Thailand.Environmental Management 19:27–37.

• Glenn, E. P., J. W. O’Leary, M. C. Watson, T. L., Thomas, and R. O., Kuehl. 1991. Salicornia bigelovii Torr: An oilseed halophyte for seawater irrigation. Science 251:1065–1067.

• Hopkins, J. S., P. A. Sandifer, M. R. DeVoe, A. F. Holland, C. L. Browdy, and A. D. Stokes. 1995. Environmental impacts of shrimp farming with special reference to the situation in the continental United States. Estuaries 18:25– 42.

• Hopkins, J. S., R. D. Hamilton, P. A. Sandifer, C. L. Browdy, and A. D. Stokes. 1993. Effect of water exchange rate on production water quality, effluent characteristics and nitrogen budgets of intensive shrimp ponds. Journal of the World Aquaculture Society 24:303–320.

• King, S. E., and J. N. Lester. 1995. The value of salt marsh as a Sea defence. Marine Pollution Bulletin 30:180 –189.• Lightner, Donald V. "Diseases of Cultured Penaeid Shrimp." CRC Handbook of Mariculture: Crustancean Aquaculture.

2nd ed. CRC, 1993. 393-444. Print.• Martı´nez-Cordova, L. R., M. A. Porchas-Cornejo, H. VillarealColmenares, J. A. Caldero´n-Perez, and J. E. Naranjo-

Paramo. 1998. Evaluation of three feeding strategies on the culture of white shrimp Penaeus vannamei Boone 1931 in low water exchange ponds. Aquacultural Engineering 17:21– 28.

• Pa´ez-Osuna, F., S. R. Guerrero-Galva´n, A. C. Ruiz-Ferna´ndez, and R. Espinoza-Angulo. 1997. Fluxes and mass balances of nutrients in a semi-intensive shrimp farm in north-western Mexico. Marine Pollution Bulletin 34:290 –297.

• Pa´ez-Osuna, F., S. R. Guerrero-Galva´n, and A. C. Ruiz-Ferna´ndez. 1998. The environmental impact of shrimp aquaculture and the coastal pollution in Mexico. Marine Pollution Bulletin 36:65–75.

• Pa´ez-Osuna, F., S. R. Guerrero-Galva´n, and A. C. Ruiz-Ferna´ndez. 1999. Discharge of nutrients from shrimp farming to coastal waters of the Gulf of California. Marine Pollution Bulletin 38:585–592.