Negative Impacts
Sustainability is the key issue here, and with feed conversion ratios (feed to tuna growth) of approximately 10:1 or higher, though this is purely a consequence of the carnivorous diet and high metabolic costs of the species. Removing tuna from the wild before they have spawned is another obvious impact, which hopefully the closed life cycles of SBT at Clean Seas will alleviate some of the pressure on declining stocks. Tuna farms are point sources of solid waste onto to the benthos and dissolved nutrients into the water column. Most farms are more than a kilometre off the coast, thus the deeper water and significant currents alleviate some of the impact on the benthos. Due to the high metabolic rates of SBT, low retention rates of nitrogen in tissue is seen, and there are high environmental leaching of nutrients (86-92%).
Other environmental impacts include the use of chemicals on the farms, which can leach into the surrounding environment. These include antifoulants to keep the cages free from colonial algae and animals, and therapeutants to deal with disease and parasitism. Toxicants, such as mercury and PCBs (polychlorinated biphenyls), can build up over time, particularly through the tuna feed, with some evidence of contaminants being more elevated in farmed fish than in wild stocks.
Read more about this topic: Southern Bluefin Tuna
Famous quotes containing the words negative and/or impacts:
“There is no reason why parents who work hard at a job to support a family, who nurture children during the hours at home, and who have searched for and selected the best [daycare] arrangement possible for their children need to feel anxious and guilty. It almost seems as if our culture wants parents to experience these negative feelings.”
—Gwen Morgan (20th century)
“We are no longer in a state of growth; we are in a state of excess. We are living in a society of excrescence.... The boil is growing out of control, recklessly at cross purposes with itself, its impacts multiplying as the causes disintegrate.”
—Jean Baudrillard (b. 1929)