Issues in Ecology Number 8 Winter 2001 ronment.In chile.for example Whether aquaculture salmon can be farmed along with depletes or enhances net fish sup a type of red alga that removes olies in the future will depend to large amounts of dissolved nitro a large extent on how markets gen and phosphorous wastes for resources are managed.The from salmon cages The effluen absence of reaulations or price output from salmon farming is disincentives on coastal pollution thus used to nourish a seaweec by fish farms,for example,limits crop.and the added revenue from mollusk farming and slows the the sale of the seaweed more thar adoption of non-polluting tech pays for the extra infrastructure nologies by other marine needed for the integrated system aquaculture systems f government policies more,government subsidies to required fish farms to internalize the ocean fisheries sector ofter the environmental costs of waste prevent farmed fish from unde discharges that is,by making cutting the market age treatment mandatory wild-caught fis at least unt then re eries are ully depl fitable. fish can replac ats app for of ies in st Shrimp ponds along the southern coast of Thailand (Photo:N.Kautsky) must be addressed in order to continu ed subsidies to the oce make these fisheries sector currently approach 20 to 25 percent of gross fisheries enue globa may pre ent increas Promoting sustainable aquaculture atches of wild fish in the shor ed farr Long-term growth of the aquaculture industry de production did not result in reduced capture levels despite 30 pends on both ecologically sound practices and sustainable to 50 percent declines in the international nrices for four of resource management.Governments can encourage such the five main species of wild salmon (chinook coho pink practices by stringently regulating the creation of new farm- and chum)during the 1990s.Salmon catches worldwid ing facilities in mangroves and other coastal wetlands,es- actually rose by 27 percent between 1988 and 1997.Simi tablishing fines to minimize escapes of fish from aquaculture larly,despite rapid growth in alternative farmed fish such as pens,enforcing strict disease control measures for the move. tilapia.wild capture of hake and haddock has remained rela ment of stock,and mandating effluent treatment and in- tively stable during the past decade pond recirculation of wastewater. Many aquaculture opera Finally,perhaps the largest unknown for both the tions have adopted such practices even in the absence o private nd public sectors is the future availability of fres strict government policies,especially with the heightening of water sites for aquaculture production. easing scarcity ent years. of freshwater esou rces could severely limit the farming o such policie ofte politically enforce suc is constraint or uure grow ate in the indu er systems makes even mor signif impro on the h urgent to 04 ulture systems tha ecologically and socially sound Mandate for the Futur the ro atio ng the e Aquaculture is an industr of oc and the proc of coastal ecosystems. is cear.however.that if aquaculture is to fufill its long-t10 Issues in Ecology Number 8 Winter 2001 Whether aquaculture depletes or enhances net fish sup￾plies in the future will depend to a large extent on how markets for resources are managed. The absence of regulations or price disincentives on coastal pollution by fish farms, for example, limits mollusk farming and slows the adoption of non-polluting tech￾nologies by other marine aquaculture systems. Further￾more, government subsidies to the ocean fisheries sector often prevent farmed fish from under￾cutting the market for wild-caught fish, at least until ocean fisheries are fully depleted. Whether farmed fish can replace or provide market alternatives for ocean catches will depend sig￾nificantly on the economics and policies of fisheries in various na￾tions. High fixed costs of fishing fleets, labor considerations, and continued subsidies to the ocean fisheries sector — subsidies that currently approach 20 to 25 percent of gross fisheries rev￾enue globally — may prevent increased aquaculture production from lowering catches of wild fish in the short term. In the case of salmon, for instance, increased farm production did not result in reduced capture levels despite 30 to 50 percent declines in the international prices for four of the five main species of wild salmon (chinook, coho, pink, and chum) during the 1990s. Salmon catches worldwide actually rose by 27 percent between 1988 and 1997. Simi￾larly, despite rapid growth in alternative farmed fish such as tilapia, wild capture of hake and haddock has remained rela￾tively stable during the past decade. Finally, perhaps the largest unknown for both the private and public sectors is the future availability of fresh￾water sites for aquaculture production. Increasing scarcity of freshwater resources could severely limit the farming of herbivorous fish such as carps and tilapia. This constraint on the future growth of freshwater systems makes it even more urgent to develop marine aquaculture systems that are both ecologically and socially sound. Mandate for the Future Aquaculture is an industry in transition, and we will continue to evaluate trends as the field develops. Already it is clear, however, that if aquaculture is to fulfill its long-term ronment. In Chile, for example, salmon can be farmed along with a type of red alga that removes large amounts of dissolved nitro￾gen and phosphorous wastes from salmon cages. The effluent output from salmon farming is thus used to nourish a seaweed crop, and the added revenue from the sale of the seaweed more than pays for the extra infrastructure needed for the integrated system. If government policies required fish farms to internalize the environmental costs of waste discharges — that is, by making sewage treatment mandatory — then integrated systems that re￾duce the waste stream would be even more profitable. Some ca￾veats apply: Human health con￾siderations now limit the market￾ability of mollusks raised in the waste stream from intensive fish farming areas, and such concerns must be addressed in order to make these types of integrated systems economically viable. Promoting Sustainable Aquaculture Long-term growth of the aquaculture industry de￾pends on both ecologically sound practices and sustainable resource management. Governments can encourage such practices by stringently regulating the creation of new farm￾ing facilities in mangroves and other coastal wetlands, es￾tablishing fines to minimize escapes of fish from aquaculture pens, enforcing strict disease control measures for the move￾ment of stock, and mandating effluent treatment and in￾pond recirculation of wastewater. Many aquaculture opera￾tions have adopted such practices even in the absence of strict government policies, especially with the heightening of environmental concerns in recent years. In poor countries, however, such policies are often neither politically enforce￾able nor economically and socially feasible. Despite significant improvements in the industry, many ecologically sound technologies remain on the shelf and underused in the field. This is an arena where external funding agencies such as development banks can play a stra￾tegic role by encouraging the development and financing the implementation of sustainable aquaculture technologies, the rehabilitation of ecosystems degraded by aquaculture, and the protection of coastal ecosystems. Shrimp ponds along the southern coast of Thailand (Photo: N. Kautsky)