Tuesday, June 11, 2013

The Inexhaustible Sea

“Probably all the great sea-fisheries are inexhaustible; that is to say that nothing we do seriously affects the number of fish …” - Thomas H. Huxley, 1884
Image courtesy of panda.org

       Comprising over 70 percent of the earth’s surface and home to 97 percent of life found on earth, the ocean is as vast today as it was at the turn of the 20th century. It’s where life originated and it continues to sustain organisms both in its waters and on land. Indeed the attitude that the ocean would always provide is still held by many to this day. But the world has changed a great deal since Huxley’s time, and as technology has advanced, humans have become experts at exploiting the earth’s natural resources. The aftermath of such extractions can clearly be seen on land in the form of polluted rivers and streams, clear-cut forests, and greenhouse gas emissions, but we tend to assume that the ocean is so immense and powerful that it’s indestructible; our negligence would only be diluted in its deep blue waters.
       From our terrestrial vantage, the ocean still looks in good shape. It’s still the same color as it always was, and trash has only visibly accumulated in a few places like the Great Pacific garbage patch and along the coastlines. But if you could peer beneath its surface, a different picture would emerge. Marine life is facing a whole host of stressors including pollution, rising ocean temperatures, and ocean acidification. But to date, the biggest pressure on marine ecosystems has come from overfishing
Image courtesy of Seaplex
Trash accumulations in the Pacific Ocean

       Increasingly sophisticated methods of locating fish in their aquatic habitats are being employed across the globe. Fish schools are being detected using sonar, aircraft is tracking their migrations, and GPS monitored buoys designed to attract particular species, known as “fish aggregating devices,” have left virtually no fish out of reach. Yet despite the technological sophistication, the extraction methods are remarkably haphazard and wasteful. Take for instance bottom trawling, a particularly destructive technique for collecting popular bottom dwelling seafood like shrimp and cod by using weighted nets to scrape the ocean floor. The nets scoop up everything in their path, from endangered fish to centuries-old corals. It is common practice for trawlers to sweep the same areas on a regular basis, allowing nothing to grow in their wake.
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Aerial Image of Trawling Paths
Image courtesy of Glogster.com
Seafloor, Before and After Trawling

       These methods of extraction are highly unselective and result in massive amounts of bycatch, a term that sounds so inconsequential it’s easy to ignore. What bycatch consists of is more difficult to overlook: sea turtles, sea birds, dolphins, whales, sharks, corals, non-target fish, and others. More often than not, these creatures are left to suffocate on fishing vessels before being thrown back overboard, dead. It’s estimated that as much as 90% of what is caught in trawling nets is tossed back into the sea (1). Adding to the waste, almost a third of what is brought to land isn’t even consumed by humans. This portion is used to feed farm-raised fish and terrestrial dwelling livestock or gets used in the production of pet food and fertilizer (2).
Image courtesy of Richard Herrmann, SeaPics.com/PEW
Bycatch: California sea lions hang trapped in a gill net off the coast of Baja California, Mexico in the Pacific Ocean
       Even the bycatch figures from so-called sustainably-caught fish are troubling. The “Sustainably-Caught” label issued by the Marine Stewardship Council, an international nonprofit organization, was developed to give consumers a choice in where their seafood comes from. However, the organization has come under recent criticism from environmentalists and marine biologists for relaxing their standards in order to keep pace with the growing demand for more responsible sourced seafood. Steve Campana who heads the Canadian government’s Shark Research Laboratory has been following the practices of Swordfish fisheries in Nova Scotia, where the label had been issued. He said that the long-line boats accidentally catch tens of thousands of sharks every year and on average, almost two sharks are killed for every swordfish snagged (3).

Image courtesy of WomenWorkingForOceans.org
Long line shark bycatch

       The extent of the overfishing problem wasn’t entirely clear until as recently as 2001, when a study was published in Nature examining the global fish harvest figures. What official data showed was that annual global harvest had been increasing annually. However, it also showed something peculiar. While global harvests were increasing, local catch rates were decreasing as fisheries were collapsing worldwide. But how could this be? What researchers discovered was that China was over-reporting their catch data for political purposes. So instead of catching more and more every year, the world had really been catching less and less, and the decline had probably begun in 1988 (4).
       After this striking revelation, the urgent need for actual scientific data on the state of fisheries became clear. But scientists needed a way of quantifying fish populations, and this is no small feat. As fisheries scientist John Shepherd puts it, “Counting fish is just as easy as counting trees, except they’re invisible and they move.” (5). Boris Worm, a Marine Research Ecologist and Associate Professor at Dalhousie University in Nova Scotia led a team of scientists that took on the task. They looked at data collected from Japanese fishing boats that use long baited hook lines and found that in the 80’s about one out of every 10 hooks caught a fish compared to only one out of a hundred in 2002. The study published in Nature in 2003 found that 90 percent of large predatory fish such as marlin, large cod, large sharks, tuna and swordfish had disappeared. Graphs prepared from the data showed long declining slopes representing the percentage of fisheries that had collapsed. If you were to extrapolate the graphs, you would see that they bottom out at around the year 2048. This means that if current harvest rates continue, we can expect that all of the species we currently consume will have collapsed within the very near future (6).
Image Courtesy of sciencemag.org
Collapse of global fisheries since 1950

       Today, 70 percent of the world's marine fish stocks are fully fished, overfished, depleted or recovering, according to the Food and Agriculture Organization of the United Nations (7). As some of our more enjoyed delicacies like the Bluefin tuna are becoming harder to access, fishermen are now turning to less desirable, smaller species. While we don’t know exactly what the implications of removing all of these fish are in terms of the health of the ocean’s ecosystems, what we do know is that ecosystems are highly complex and interdependent. 

       In the National Geographic Wild broadcast, A Life Among Whales, it was illustrated just how interconnected ocean ecosystems can be by recalling the chain of events that occurred after fisherman decided whale’s were threatening the fish supply and their numbers thus needed to be reduced. As local whale populations drastically declined, their predators, the killer whales, began targeting other prey like seals. Seals then began declining and killer whales moved on to sea otters. With the decimation of the sea otter population, urchins and other otter prey exploded and began destroying kelp forests in which fish lay their eggs. With fish larvae now exposed, they were easily eaten by numerous marine species and in the end, a sharp decline in fish stocks occurred ruining the livelihood of many fishermen. This is a well-defined example of how reducing the numbers of certain species can have unexpected and unintended consequences. Biodiversity data indicate that there is little redundancy in the ocean’s ecosystems making it particularly vulnerable to damage. The trend is that as one fish species declines, the overall biodiversity of its ecosystem declines with it (8). Eliminate all or most large fish species and you threaten to unravel entire marine ecosystems.
       It’s been shown time and time again that diverse ecosystems are productive ecosystems. Considering that a billion people rely on fish as their primary animal protein source, continuing with business as usual by fishing the ocean to death will inevitably have catastrophic political, social, and economic consequences. And this comes at a time when global warming and other man made problems are threatening future food securities as well.
       So what can be done to avert the impending collapse of the ocean’s ecosystems? Clearly, fishing must be reduced and some of the ocean must be protected to provide marine life with a safe place to recover their populations. Scientists have recommended we protect at minimum 10 percent and ideally 30 percent of the ocean. Today, only one percent was protected, a far cry from the recommendations and startling reminder of the inaction of governments taken on behalf of industry (9). There is a need to revisit the rules of what should be considered sustainable and implement them through enforceable legislation. We should continue pressuring governments into taking real action on these issues, but in the meantime, we mustn’t act as complacent consumers waiting for them to do so. Instead, we must take responsibility for our own role in the problem by learning new ways to eat and either reducing or cutting out seafood consumption altogether. We must educate others and ourselves on the issue and lead by example. If we ever hope to have our fisheries return in the future, we need to move past old assumptions that the ocean, the life-blood of our planet, is limitless and will always provide. Until their numbers are able to recover, fish can no longer be considered a renewable resource.

Image courtesy of TheTerraMarProject.org

Works Cited:

1) http://www.cnn.com/2013/03/22/world/oceans-overfishing-climate-change
2) http://factsanddetails.com/world.php?itemid=2196&subcatid=340
3) http://www.npr.org/2013/02/11/171376509/is-sustainable-labeled-seafood-really-sustainable
4) journal.nafo.int/J23/caddy.pdf
5) http://www.huffingtonpost.com/cathy-erway/the-pescatores-dilemma_b_246373.html
6) http://www.sciencemag.org/content/314/5800/787.abstract
7) http://www.fao.org/docrep/009/y5852e/Y5852E02.htm#ch1.1
8) http://www.globalissues.org/article/171/loss-of-biodiversity-and-extinctions#DecliningOceanBiodiversity 

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