In New Brunswick, where factory farmed salmon have largely replaced wild salmon, aquaculture immediately conjures up an image of unsustainable economic specialization. Over 100 fish farms now dot the coastline, using the Bay of Fundy as a sink for their waste.
In contrast,fish and crustaceans have been farmed sustainably in Asia for at least 3000 years. However, rising global demand for seafood has led to the development of new technologies and culture systems and pressure to for specialized production similar to that found in New Brunswick. But, unlike New Brunswick, there are active attempts to develop more sustainable alternatives. An interesting example aimed at increasing both economic productivity and ecosystem resilience is captured in the photo below of a rice/shrimp farm in Soc Trang province in the Mekong Delta during the wet season. In the dry season the rice fields are filled with brackish water and the farmers produce a crop of shrimps. Early in the next wet season the fields are flushed with freshwater and the next rice crop is planted. This dual crop strategy is sustainable and has positively transformed the economy of the region.
This example is described in detail in Troell, M. 2009. Integrated marine and brackishwater aquaculture in tropical regions: research, implementation and prospects. In D. Soto (ed.). Integrated mariculture: a global review. The abstract of the publication does a nice job of outlining the key ideas involved:
While the concept and practice of integrated aquaculture is well-known in inland environments particularly in Asia, in the marine environment, it has been much less reported. However, in recent years the idea of integrated aquaculture has been often considered a mitigation approach against the excess nutrients/organic matter generated by intensive aquaculture activities particularly in marine waters. In this context, integrated multitrophic aquaculture (IMTA) has emerged, where multitrophic refers to the explicit incorporation of species from different trophic positions or nutritional levels in the same system. Integrated marine aquaculture can cover a diverse range of co-culture/ farming practices, including IMTA, and even more specialized forms of integration such as mangrove planting with aquaculture, called aquasilviculture. Integrated mariculture has many benefits, among wich bioremediation is one of the most relevant, and yet is not valued in its real social and economic potential although the present document provides some initial economic estimates for the integration benefits derived from bioremediation. Reducing risks is also an advantage and profitable aspect of farming multiple species in marine environments (as in freshwaters): a diversified product portfolio increases the resilience of the operation, for instance when facing changing prices for one of the farmed species or the accidental catastrophic destruction of a crop. Yet such perspectives are far from been considered in mariculture where, on the contrary, there is a tendency to monoculture.