Part of the IAF editorial panel, Dom has a PhD in Nutritional Sciences from the University of Guelph, Canada.
Today he teaches various undergraduate and graduate courses on animal nutrition and agriculture at the University of Guelph. Between 2007 and 2009, he coordinated the “Paris Semester”, a study abroad program for undergraduate students at the University of Guelph.
He serves on a number of international committees, including the US National Research Council Committee on Nutrient Requirements of Fish and Shrimp.
See all of the Aquaculture view columns here.
November - December 2013
Environmentally sustainable aquaculture production: a nutritionist’s perspectiveRearing fish and crustaceans in an intensive manner involves the transformation of dietary inputs into fish biomass. This process generates waste, which in many cases can be difficult to contain and recover. The release of waste into aquatic ecosystems by aquaculture operations may result in nutrient enrichment of these ecosystems which, in turn, can potentially lead to environmental changes.
In North America and Europe, the potential (or hypothetical) environmental impacts that can be brought on by aquaculture have been a major issue raised (and highly publicised) by a number of environmental non-governmental agencies (eNGOs), environmental activists and various competing end-users (e.g. recreational users). I have always felt that the aquaculture sector constitutes an easy target in the popular press due to its status as a relatively new industry (a new kid on the block!). I also believe that aquaculture has been targeted because a relatively small number of fish farming operators, notably salmon cage culture operations on the east and west coasts of Canada and the USA, are located in what can be described as ‘playgrounds’ for city dwellers.
Nonetheless, there is no point having sour grapes and we must effectively and ethically address challenges head on. There is a growing consensus around the world that aquaculture operations, notably those operating in sensitive areas, should act in increasingly environmental and socio-economically sustainable manners.
The origins of waste
Nutrition plays a very important role in the types and amounts of waste released by aquaculture operations. The release of solid waste is mainly a function of the digestibility of the feeds served to the animals, and the release of dissolved wastes is mainly a function of the metabolism of absorbed nutrients by the fish. Consequently nutrient mass balances and nutritional strategies, respectively, offer direct and effective ways of predicting and managing waste output by aquaculture operations.
The stakeholders in the aquaculture industry can globally be described as good environmental stewards. Very significant reductions in waste outputs per unit of biomass produced have been achieved over the past few decades by commercial aquaculture operations, notably in Europe and the Americas. Significant changes have started to take place, or are expected to take place, in the rest of the world. Further reduction in waste outputs are currently being achieved through the fine-tuning of feed formulations, judicious use of feed additives, and the processing or refining of ingredients. Numerous ongoing R&D efforts may also contribute to the development of effective strategies for further reducing the waste outputs of aquaculture operations.
The real impacts of waste
It is important to note that the ‘release of waste’ by aquaculture operations cannot be systematically equated with ‘deleterious environmental changes’, as it is frequently assumed in much of the documentation of eNGOs, the popular press and even the scientific literature on aquaculture. For example, a large scale research effort on the impact of freshwater aquaculture at the Experimental Lakes Area of Ontario, Canada led by Dr. Cheryl Podemski (Fisheries and Oceans Canada) convincingly demonstrated that environmental impacts induced by rainbow trout cage culture in an ultra-oligotrophic lake were actually very largely positive, notably the for usually-fragile native (wild) lake trout (Salvelinus namaycush) populations. An overview of the project can be found at the following URL: http://www.dfo-mpo.gc.ca/science/publications/article/2007/27-09-2007-eng.htm
This great research project, as well as other similar studies, showed that the types and potential magnitude of the ‘environmental changes’ are highly dependent on the biological, chemical, and physical characteristics of the receiving ecosystems. Different water bodies will react differently to the influx of the same amount of certain wastes (e.g. solid organic matter, solid or dissolved nitrogenous or phosphorus wastes).
Besides being driven by complex interactions between biological, chemical, and physical factors, the perception of these changes will also be dependent on numerous socio-economic factors. For example, a slight increase in primary productivity (e.g. microalgae) or secondary productivity may be perceived negatively in areas where tourism and recreational activities are significant. The same increases in primary and secondary productivities could potentially be perceived as neutral, or even beneficial, in areas where environmental degradation has already taken place, or in regions where the natural productivity of water bodies is limited, and wild fish and invertebrate harvests play important roles in the regional economy. The expectations and value systems of the various local stakeholders play a great role in the definition of ‘assimilative capacity’ and ‘environmental impacts’. These parameters are not as objective as they are often assumed to be.
Several studies have shown that the estimation of waste outputs from aquaculture operations can quite easily be done with nutrient mass balance models. However, the assessment and prediction of the potential environmental impacts associated with the release of waste from aquaculture operations represent a much greater challenge which generally requires a multidisciplinary approach (a team composed of fish biologists, limnologists, benthic habitat specialists, oceanographers, modellers, nutritionists etc.), as well as great effort and investments.
Engaging in the dialogue
I feel that the aquaculture nutrition community should play a more important role in the ongoing dialogue about the real impacts of aquaculture operations. We need to seek to engage the public in healthy and realistic dialogue. A popular bumper sticker in the parking lot of my university is “If you ate today, thank a farmer!” This very simple message conveys effectively that food production is not merely an ‘accessory’ activity. It is essential to our daily survival and standard of living. It is at least as important (in the greater scheme of things) than leisurely endeavours, such as holidaying, boating, water skiing, surfing or sport fishing. I am always a bit disappointed by how few eNGOS are truly engaged in raising awareness of the very broad and profound impacts on aquatic ecosytems caused by sprawling development of housing or recreational infrastructure around bodies of water. I guess you don’t really want to bite the hand that feeds you …
Agree, disagree? Any suggestions of topics? Let me know at email@example.com, or in the comments below.