The disasters left in the wake of the BP Gulf of Mexico oil spill are too numerous to count and seem to be growing daily. But since this area of the Gulf is considered a sportfishing paradise, I wondered how the oil would affect big fish.
I asked Matt Rigney, a New England recreational fisherman who is working on a book about the decline of the large offshore fish (marlin, bluefin tuna and swordfish), In Pursuit of Giants: One Man’s Global Search for the Last of the Great Fish (Viking/Penguin, 2011). Rigney just returned from a visit to the Gulf, where he spoke to scientists at the University of Southern Mississippi Gulf Coast Research Laboratory. Below, he lists five ways the oil spill could affect the Gulf’s sportfish.
1. Immediate mortality of existing adults and juveniles of various species, including not only the sportfish but their prey. The impact on pelagic (offshore) adults and juveniles would apply only to those that can’t get away from the spill–either because they’re not fast enough or because they get boxed in by it. At any rate, to kill adults means you’re killing spawners. How many generations would they have engendered? If a lot of adult pelagics are being impacted, this could arguably have long-term population effects. Same with juveniles who will never live to breed.
Another impact of the spill is that it will affect the offshore sportfish’s prey. If the food sources are widely impacted, what effects will this have? One example would be populations of game fish prey that may not be able to move out of the area quickly enough not to be hit by the oil or its hydrocarbon components. These fish will likely either die or be contaminated through ingestion. The questions are, how severely will they be contaminated, where will toxins reside in their bodies, and will those toxins be passed on to predators?
2. Mortality of this year’s eggs, sperm and larvae. This is important because it’s like during war time, when you lose a whole generation of young men. If large portions of a spawning class are lost, what impact will this have on stock populations in the future? For every egg lost that would have become an adult, how many generations are lost from that one adult? Will you see a short or prolonged dip in population numbers for various species? For species like the bluefin tuna, the loss of a significant portion of this year’s class of eggs and/or larvae could be disastrous. Their population numbers are already precarious.
The other thing to consider is that the oil is affecting the actual sargassum (floating vegetation) that provides a critical nursery habitat for a wide range of pelagic creatures. The sargassum traps oil sheen and oil clumps. Can the sargassum survive this? What if a lot of this nursery habitat is lost? Even if the weed can survive, how long will it go on being toxic, and what about all the small creatures that live in it?
3. Deformities and mutations for those creatures exposed to less intense levels of toxins over time, or to short but intense levels that don’t kill them. Could oil-induced deformities produce mutations or chronic conditions that weaken a species? It may be that we can’t know without studying this, but it’s a concern.
4. Toxins entering offshore food web (and therefore our food web). GCRL scientists told me that a number of species are able to sequester toxins in the liver. They can survive being poisoned, within reason. But even if they sequester the toxins, if they’re eaten, those toxins get passed on to the predator. And on up the food chain. Will offshore predators be eating tainted food? For how long? To what effect? Where do predators sequester toxins (liver, skin)? Does this mean some food from Gulf will be unsafe? If it’s in the food chain, how long will humans have to consider the question of contamination of any seafood taken from the Gulf of Mexico?
5. The range of unknowns. The fact is, and most scientists would tell you this, the impacts of the oil spill–severity, duration, scope–are simply unknown. Another unknown is the potential balancing effect of the massive closure of U.S. offshore commercial and sport fishing. Think of how many fish are not being harvested by commercial or sport fishing right now because both are shut down. It’ll be interesting to see if there’s an up-tick in adult pelagic fish populations or size in the coming years as a result of the fish being spared of fishing pressure this year–although they certainly have other problems.
Image: Matt Rigney
