by Zachary Lehmann

Fish farming has been in the news a lot in recent years, or at least in the news a big recreational fisherman, like myself, might read. While many people may have heard of fish farming and its negative environmental effects, few people outside the industry really understand why it is so harmful.

To fully understand the negative impacts of fish farming, we need to start at the beginning—what is fish farming and how did it come into being? Fish farming is a form of aquaculture where fish are raised commercially in tanks or enclosures and are artificially provided with food sources.

The demand for fish products has grown steadily as fish and fish protein have gained popularity in the food and health markets. As a result, fisheries have become overfished, leaving both commercial and recreational fishermen to struggle with regulators to protect their favorite species and fishing holes.

As more and more restrictions are placed on harvesting free-range fish populations, the number of commercial fish farms is increasing. In 2008, the Food and Agriculture Organization reported global returns of fish farming to be at 33.8 million tons of fish worth approximately $60 billion.

Fish farming is currently a profitable, booming industry, but as the industry grows so do the adverse environmental effects.

Initially fish farming appeared to be a natural solution to the overfishing problem. Rearing fish in artificial enclosures eliminates the need to harvest wild fish from the natural fisheries, making both consumers and fishermen happy. Unfortunately, natural ecosystems are never easy to reproduce in ways that are both economically feasible and environmentally sustainable. Aquaculture infrastructure becomes expensive quickly, and there are strict space and water quality requirements that must be met to properly house the fish and produce maximum growth.

Healthy fish grow the fastest and therefore yield the most profit for a farm. However, the density of fish raised in these farms far exceeds the densities of fish found in the wild, leading to numerous problems with disease. Overcrowding stresses the fish, reducing their growth rates and increasing the spread of disease, which ultimately makes the farm less profitable. It is simply not economically feasible to rear fish populations in artificial enclosures for large-scale commercial use.

Given these issues, the industry quickly made the obvious move to farm fish in open water. Open water fish farm installations are usually a series of nets or cages suspended in oceans, lakes, and rivers. The constant flushing of the open water eliminates the costs associated with the upkeep of water quality; however, the population density in these installations is still very high and leads to rampant disease transmission. Open water fish farms often become a highly concentrated area of disease that is barely separated from the native populations by a thin net or mesh. Furthermore, the solid waste of such high concentrations of fish covers areas of the ocean or lake floor, disrupting or completely destroying the natural fish and invertebrate habitat.

While this paints a bleak picture for the fish farming industry; in actuality, the situation is even worse. Genetic manipulation of fish species has led to gene-enhanced fish grown in open water farming installations. If grown in isolated tanks, these fish pose no threat to the natural DNA strains of fish species, but in open water enclosures, the altered genetic material is impossible to contain. As a result native wild fish are not only exposed to disease and water pollution but also are threatened by unnatural genetic alteration.

Genetically modified fish are larger and are more likely to attract mates; however, they also are less likely to produce offspring that survive until adulthood. In addition, biologist Rick Howard of Purdue University has shown that genetically modified fish crowd out native fish on spawning beds. Spawning beds are small depressions created by fish for depositing and fertilizing eggs. Larger fish in general are able to better defend territories, ensuring their spawning beds are fertilized before others. Because gene-enhanced fish are larger, they are able to drive off native fish from prime spawning bed locations, preventing native genetic material from being passed on to the next generation. The specific effects of genetically enhanced fish populations interbreeding with native fish species are still unknown, but many experts predict the results could decimate local fish populations.

While the evolution of modern fish farming practices seems reasonable and straightforward, closer examination exposes significant and serious ecological issues. With market demands on fish products continuing to rise, there is little economic incentive for fish farmers to heed the concerns of environmental activists especially when the associated costs are higher.

That isn’t to say people are not trying to stem the tide of genetically enhanced fish farms. Many activists are speaking out against current industry practices and calling to light the degradation of natural fish stocks. As an avid fisherman, I am optimistic that the popularity of free range and organic food markets will help to turn the tide on destructive aquaculture practices before it is too late.