Habitat destruction. Pollution. Over exploitation. All terms that have been echoed through the vast literature over and over again, and which are being institutionalized in our understanding of the world around us. Once again, my friends, we must apply the deleterious effects of these atrocious activities to yet another beautiful group of creatures, those belonging to the super order Selachimorpha under the subclass Elasmobranchii (for simplicity sake, we’ll call them sharks). It has been shown that population levels of sharks have been experiencing precipitous declines for many decades.
While all activities that impact the shark populations are of importance, the largest driver (and possibly most important) is that of over exploitation. Over harvesting sharks, especially for their fins, has decimated species abundances, resulting in losses anywhere from fifty percent to complete collapse.
Many laws and regulations, including up-listing of all ray species and more shark species on CITES, have been instituted in efforts to reduce the over harvesting of sharks, especially for their fins. Unfortunately, the fact remains that the sale and trade of fins is an extremely lucrative business, and illegal fishing persists. Another factor contributing to this issue is that local store owners in areas of sale/trade are often unaware of regulations, largely due to negligent enforcement.
The economic benefits of harvesting sharks, both for their fins as well as other parts, is nothing to scoff at, reaching well over $600 million dollars a year according to a recent study. However, the use of sharks in ecotourism is an expanding market the world over, and has proven to be a lucrative one at that. Indeed, one study indicates just how quickly the business is growing, and how its generated profits are likely to exceed those from harvesting sharks in the coming years. As you can guess, this use of sharks for recreation purposes is a way of life for many people, and often represents a large economic driver for the communities involved with it.
While the economic losses that would be associated with the loss of sharks are certainly of importance, perhaps more important is that of the ecological implications that will ensue. The loss of a top predator in any ecosystem is often associated with many detrimental environmental effects. First off, it could elicit a trophic cascade, which Terborgh et al. say occurs when “a perturbation at one trophic level propagates through lower levels with alternating positive and negative effects.” There are many instances where trophic cascades have occurred, wreaking havoc on the ecosystem, and sometimes constituting a restructuring of the communities of organisms there. Consider how, in the classic example of Yellowstone National Park, the removal of the top predators (wolves) from the ecosystem in the early 1900’s resulted in an explosion of herbivore species that were, until then, held at bay, and this resulted in the decimation of plant species. However, reintroduction of the wolves in the mid-1900’s allowed for a balance to be struck, and the entire ecosystem is back to functioning well once again. Perhaps an example that aligns much better with the issue at hand is the loss of apex predator shark species in northwest Atlantic coastal regions. This removal allowed prey ray and skate populations to markedly increase, essentially eliminating the scallop bed, and ultimately lead to the loss of “century-long scallop fishery.”
Fishing down the food web has also been a concern of researchers for several decades now. This scenario implies that once all of the large predatory fish are depleted, or at least populations fall so low as to make fishing them economically unviable, fishermen will move down to the next trophic level, and so on through the entire ecosystem. This process was evident with regards to terrestrial ecosystems, considering the loss of the megafauna in recent history (recent in terms of the geological time scale), we’ve simply applied it to the oceans now.
This article may leave the reader with a sense of doom and gloom in regards to this issue; however, recent reports and new technology may help to dispel this feeling of dread. Awareness advertisements featuring well-known figures, such as Yao Ming and Jackie Chan, have prompted decreased demand for shark fin soup in areas such as China and Southeast Asia. Additionally, new research in the field of forensics is coming to the fore, and presents a possibility to combat the illegal fishing of sharks through tracking the origins of shark fins, as well as other products. Finally, recent reports from the National Oceanic and Atmospheric Administration (NOAA) indicated that, at least off the East Coast of the United States, the populations of shark species have been rebounding in the past couple of years. While still far from desirable abundance levels, these all provide stepping stones for the future of the sharks, lending to some a notion of there being light at the end of the tunnel. However, this all still depends on you, the lay public, deciding to opt for or against that next bowl of delicious shark fin soup. Where will your allegiance lie?