Case Study: How Can Aquaculture Affect Natural Ecosystems?
In many aquaculture operations, fish and seafood are raised in pens that are close to shore in marine environments, like in the picture to the side. Raising fish in concentrated settings can affect the natural ecosystem in which they are located. For example, increased nutrients are released into the surrounding water from uneaten food and the wastes produced by the fish. This can cause local algal blooms that affect the surrounding natural ecosystem. Shellfish (clams and oysters) are especially susceptible when oxygen levels in water drop too low. Net pens anchored near shore also allow the spread of diseases, antibiotics, and other pollutants into surrounding ecosystems.
( http://www.fishaq.gov.nl.ca/aquaculture/ )
Sea lice, parasites that infect both farmed and wild fish, have affected salmon raised in aquaculture pens around the world. Sea lice are also a threat to wild salmon where salmon fishing is an important part of the economy. Scientists estimate that in the early 2000s, sea lice associated with salmon farms near Vancouver Island accounted for 90% of the deaths of juvenile wild salmon after deaths rom other known causes were counted. A new approach to treating farmed salmon for sea lice has reduced the impact of sea lice on wild populations. There are still concerns, though, that the sea lice are becoming resistance to the parasite treatment.
Another way that near-shore aquaculture operations may affect natural ecosystems is through escaped fish. For example, many of the salmon species raised in farms are not native to the waters in which they are raised. Sooner or later, some of these fish escape. When Atlantic salmon from aquaculture escape into the Pacific Ocean, they compete for food with the wild pacific salmon. In other areas, escaped fish may compete with wild individuals for mates, disturb habitats, or become invasive.
Currently, about 60% of all aquaculture production takes place in freshwater ecosystems and production is growing rapidly. Aquaculture of freshwater species typically involved the construction of ponds, which allows for the close management of fish, shrimp, or other species. The environmental impacts of freshwater aquaculture are similar to those of marine systems. An excess of nutrients from wastes and an escape of species, are also issues in freshwater aquaculture. In addition, freshwater aquaculture involves the conversion of land to new use. Often the lands involved are mangrove swamps or other wetlands that many people believe should be protected. Mangrove swamps and other wetlands are important habitats for juvenile fish and other seafood, as well as a location of nutrient cycling.
Research and Analyze
1.
Research aquaculture operations in the Atlantic Provinces. What types of fish/seafood are farmed there? In what quantities? What are some of the advantages and disadvantages of aquaculture operations in these provinces? Have these operations affected the sustainability of nearby aquatic ecosystems? If so, how?
Communicate
1.
Make suggestions for how aquaculture operations can be run sustainably.
Jackson , Ann, Ellen Murray , et al, et al. Environmental Science: A Canadian Perspective. 1. Whitby: McGraw-Hill Ryerson, 2013. Print.