By: Dana Sackett
Successful marine protected areas (MPAs) have helped to improve many fisheries. What, may you ask, helps those successful MPAs be successful? Well, there are a number of things that need to be considered to effectively pick a site and implement an MPA. Some of these include fish biology, politics, societal needs, and economics. However, there is one factor that can also affect the success of an MPA that is seldom considered: pollutants.
In marine systems, ocean currents can move and disperse pollutants without regard to MPA boundaries, influencing the very thing we use to determine MPA success: fish growth and survival. Pollutants can reduce fish growth, condition, and survival as fish divert energy away from everyday biological processes (for example tissue growth, energy used to obtain food, avoid predation and guard habitat) to defend against the pollutant.
Because pollutants reduce fish growth and survival and MPAs increase fish growth and survival by preventing fishing, what then do you think would happen in an MPA that has been contaminated with pollutants for an extended period of time?
This is a question we are asking ourselves in Hawaii where an uninhabited island called Kaho`olawe (pronounced ko-o-la-vay) was used as a testing area for explosive military devices and live-fire military training (naval bombing, air-to-surface missiles, live-fire drills) from 1941, after the attack on Pearl Harbor, until 1994. It was in 1994 when the United States Government transferred ownership of Kaho`olawe to the State of Hawaii, who in turn established the Kaho`olawe Island Reserve (KIR), protecting the waters surrounding the island from fishing.
Explosive-related pollutants (e.g., TNT) have been linked to reduced growth and survival in fish, and degrade relatively slowly in the environment. Also, many sites with explosive-related contaminants continue to hold unexploded ordinances. Consequently, testing sites for explosive devices often continuously release toxic pollutants to the environment over extended periods of time.
So at Kaho`olawe the question becomes, what has a bigger impact on the growth and survival of fish in a population, legacy pollutants from years of military explosives or the removal of fish from fishing? We hypothesized there would be more and larger fish inside KIR compared to outside despite the decades of explosive-related contaminants because fishing likely has a much bigger influence on fish growth and survival than legacy contamination.
What would your theory be? Tell us what you think and why in a comment below.
References and more:
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3 Comments Add yours
I have no background in marine biology but I would hypothesize that long-term exposure to legacy pollutants could damage the affected fish population’s genetic potential which may in turn affect fertility and the survival of its spawn. Worse yet, some legacy pollutants might even create a health hazard to people (or animals) consuming the affected fish. (I am thinking of mercury poisoning in traditional fishing grounds of Northern Quebec Cree during the flooding of the area around James Bay.) Over-fishing will definitely diminish fish stocks but to allow a marine protected area to reproduce damaged or potentially toxic fish could be equally harmful.
Very good points Brenda! You also bring up an important thought, the type of pollutant and level of toxicity is very important to answering this question. Here TNT and other explosive contaminants are not bioaccumulative the way mercury is and so eating the fish would not be a problem. However, if this were a more toxic contaminant such as mercury the answer may be very different.
Explosives are sometimes used as a method of capturing fish, especially in developing nations. This method of capturing fish is very destructive on the habitat, and this current study that you are conducting may also reveal further detriment associated with the use of explosives. Be sure to write a follow up post when the research has been conducted and let us know the outcome.