This theory postulates that iron from the volcanic ash fertilizes the sea and enhances excessive growth of phytoplankton thus providing food for zooplankton and small fishes, which in turn become food for salmon. This theory explains why there is excessive growth of salmon in rivers of British Colombia and Canada following a volcanic eruption, which occurred on the Kasatochi Island. This theory sparks a lot of controversies internationally as to whether or not to fertilize the sea with iron to boost dwindling fish stocks.
Supporting this theory, the population of salmon fishes in 2009 was very low as compared to the excessive numbers in 2010 in Fraser River in British Columbia. The leading proponent of this theory who is also an eminent fisheries research scientist, Tim Parsons argues that ash from volcanic eruptions contains iron which indirectly enhances the excessive growth of salmon. Other fisheries scientists support Parsons’s school of thought because of his great experience in oceanic sciences that earned him a medal from the Canadian government. Another research scientist, David Welch says that practical determination of the salmon growth is by checking seasonal growth of scales and comparing 2010 and 2008 growth if there are any significant differences in their growth.
Opponents of the theory such as Carl Walters dismiss the arguments saying that the theory is as good as any theory meaning there is nothing new or interesting about it. He further argues that the practical determination of the seasonal scales will not give a significant difference to support the theory. Since salmon fishes depend on zooplankton and small fishes as their food, it is, therefore, unrealistic to attribute their bloom just one month after volcanic eruption because of the growth of zooplankton and small fishes take several months to a year to reproduce even though there is evident phytoplankton bloom. Moreover, if the volcanic eruption is the cause of the salmon glut experienced in the Fraser River, the same scenario should replicate itself in another place where volcanic eruptions are prone.
Scientific research has confirmed that iron is a necessary mineral for the growth of phytoplankton; the primary producer of food in the sea or ocean. Phytoplanktons are food to small fishes and zooplankton, which in turn form the main food of the salmon fishes. The low population of the salmon fishers in the Northern Pacific Ocean is due to the limited amount of iron in water but recent volcanic eruptions and dust from Asian deserts are increasing the concentration of iron in the North Pacific Ocean. The theory is credible because, in places where volcanic eruptions had occurred, there was a subsequent increase in the population of salmon several years after.
Although the theory gives a plausible biological explanation for the excessive growth of salmon in the North Pacific Ocean, it will prompt fish industries to add iron deliberately into the oceans to increase fish reproduction posing unforeseen danger in marine life. There is a fear that big companies formulated the hypothesis for them to dump huge amounts of iron into the sea as a means of regulating climate. However, for the theory to be credible the volcanic ashes must be rich in iron and spread ashes to oceanic regions that have a limited concentration of iron. The eruption needs to occur in summer and spring for the phytoplankton to receive enough sunlight for their growth and stimulate the growth of zooplankton and small fishes, which are the food that promotes salmon glut.