How can we create a more sustainable aquaculture industry?

In our previous posts, we looked at conservation issues regarding aquaculture – things such as the spreading of disease, the destruction of habitat, the excessive harvesting of ocean resources, etc.  So, the question is: what needs to be done in order to create a healthy, more sustainable aquaculture industry?

It’s highly unlikely that aquaculture will continue to grow at its current rate, or even develop into its full potential if goals and strategies are not put in place to efficiently monitor natural ecosystems.  These ecosystems are crucial to the life of the industry.  Recognizing the need to create a sustainable form of aquaculture, Naylor (2000) suggested four goals that, if implemented, will only be beneficial to the industry.  These goals, quoted from Naylor’s review article, are:

           

1.     “Expansion of the farming of low trophic level fish.”

Nearly 80% of all aquaculture production worldwide consist of herbivorous species (Naylor 2000).  These species include things like molluscs, carp and tilapia.  Since these species are herbivores, they do not need to be fed fish meal, which results in a net gain in fish supplies worldwide.  If more farming of herbivorous species were conducted, fish stocks would be less affected (Baily 1997).

However, it is not that easy.

Due to consumer demand, the number of farmed carnivorous species such as salmon and shrimp is only increasing.  These species require an input of fish meal in their diets which affects wild fish stocks.  Apart from that, farmers are starting to add fish meal and fish oil to the diet of herbivorous species to increase weight gain.  To reverse this trend, more studies have to be conducted into how to feed aquaculture species using other substances, such as vegetable oils.  This leads directy into our second goal.

2.     “Reduction of fish meal and fish oil inputs in feed.”

There are two major downfalls of the use of fishmeal:  First of all, feed is the largest production cost for the aquaculture industry.  Secondly, the continued use of feed puts pressure on, and declines, wild fish species (Naylor 2000). As stocks diminish, and aquaculture grows, the prices of feed will only increase, reducing the profitability of the industry.  So, researchers are actively looking for new, more affordable feed that has less of a conservation impact by looking into such things as soybeans, meat byproducts (blood and bone) and microbial proteins (Tacon 1994).  While some types of aquaculture have reduced their use of fish meal significantly, such as the salmon industry, the effort has to be made across a greater portion of the industry as a whole.

3.     “Development of integrated farming systems.”

One of the easier ways to create a more sustainable aquaculture industry is to merge more types of farming into a type of farming known as polyculture.  In polyculture, different types of species (phytoplankton filter feeders, zooplankton filter feeders, herbivores and bottom feeders) are grown together, each utilizing the others wastes and nutrients.  These types of farms require less land (since multiple farms are merged), less money (since there is less of a cost for food) and they efficiently utilize resources that are naturally provided to them.

We know that this form of farming can work because some of the most widely cultivated fish are grown in polyculture farms in Asia: the silver carp, the bighead carp, the grass carp and the common carp (Naylor 2000)

The question that needs to be asked is: if four of the most widely cultivated species can be farmed together, why isn’t this type of farming being used for species such as salmon and shrimp?  Combining these species would only increase productivity and reduce costs as well as pollution.

4.     “Promotion of environmentally sound aquaculture practices and resource management.”

Perhaps the most important goal of creating sustainable aquaculture is efficiently managing our natural resources and creating ways that reduce practices that are environmentally unsafe.  If more consequences were imposed upon individual farms, for example by implementing fines if fish escape or increasing land taxes to reduce large land use, then negative environmental impacts could be avoided. 

The industry could also promote environmentally sound aquaculture by ensuring wastewater is recycled or cleaned and establish restrictions on mangroves and wetlands that limit their use for farms.

These four goals are very broad and also very difficult to implement.  However, in order to fulfill aquaculture’s long term potential, everyone must share this vision and these goals.  Current aquaculture practices are putting pressure on wild fish stocks and harming the environment.  Changes need to be made and these goals show that there are many ways to do it. 

-Brandon and Mark

References

Baily, C (1997). Aquaculture and basic human needs. World Aquaculture 27:28-31

Naylor, R.L., R.J. Goldburg, J.H. Primavera, N. Kautsky, M.C.C. Beveridge, J. Clay, C. Folke, J. Lubchenco, H. Mooey, M. Troell (2000). Effect of aquaculture on world fish supplies. Nature 405:1017-1024. 

Tacon, A.G.J (1994). Feed ingredients for carnivorous fish species: Alternatives to fishmeal and other fishery resources. Food and Agricultural Organization, Rome.