Keeping Sharks in Perspective
Well, it’s Shark Week and that time of the summer when everyone is thinking about sharks. Unfortunately, the information given to the public about sharks through Shark Week shows, TV news, and other media outlets tend to present a wide array of mixed messages while attempting to provide the public with the latest information about sharks. For instance, we often hear that shark populations have drastically declined due to overfishing and habitat loss, but the occurrence of shark bites on humans is rising. How can that be? We hear impassioned messages about the importance of sharks in the marine environment and their high ecological value, but subtly behind these messages is one that promotes a fear of sharks, typically focusing on their potential danger to humans. So, why should people care enough to want to restore their populations? How do we reconcile these rather contradictory messages? Well, it all starts with good information and a bit of perspective.
For years we’ve been told that many shark populations have significantly declined due to overfishing, bycatch and habitat loss. Sharks, in general, are more susceptible to being over harvested than other species of fishes that we like to eat because of their life histories (e.g., grow slowly, take a long time to reach sexual maturity, produce relatively few young) and cannot be harvested or managed the same way as these other species. These effects of overfishing, pollution, and habitat loss were recognized several decades ago in the U.S. and as a result a wide range of state and federal regulations (e.g., Clean Water Act - 1972, Clean Air Act -- 1973, Marine Mammal Protection Act – 1973, Magnuson-Stevens Act – 1976, California Marine Life Protection Act – 1999, CA banning of nearshore gillnets – 1994) were put into place in order to restore marine habitat and rebuild depleted populations.
A leopard shark meanders through Big Fisherman's Cove on Catalina Island. Photo courtesy of Chris Lowe.
So, despite an ever growing U.S. human population, increased coastal development, and demand for seafood, have these regulations helped? While the global picture for sharks is bleak, I would say shark populations are doing better in U.S. waters. It has been a slow recovery process, but I think we can see many positive results of these regulations. For example, there is growing evidence that coastal shark populations off California are recovering over the last 15 years. One sign of ecosystem recovery is the return of apex predators to an environment. Many shark populations (e.g., leopard sharks, soupfin sharks, thresher sharks, and even white sharks) off the coast of southern California were previously impacted as the result of direct fishing or bycatch. State banning of nearshore gillnets and better regulation of offshore drift gillnets in the mid 1990s have helped these populations to recover. The remaining commercial fisheries have made great strides in reducing bycatch of sharks and other unintended catch and now fishers are making a living.
But, just reducing fishing pressure isn’t enough to allow these populations to recover, there has to be plenty of food available to sustain them as well. The increase in the white shark population along the California coast has likely not only been due to protecting the young ones from being landed in coastal fisheries, but the simultaneous recovery of their food as the result of better water quality and habitat restoration. For example, young white sharks that spend their first summers along southern California coastal beaches eat stingrays, dogfish, and other coastal fishes, all of which are readily abundant. Adult white sharks like to eat marine mammals like seals and sea lions. Protection of marine mammals and better management of commercial fisheries from the 1970s – 1990s has enabled seal and sea lion populations to recover better than biologists could have imagined. Although it has taken a long time to see some of the positive effects of these costly commitments to restore our marine ecosystems, it is encouraging to see that we were able to recognize these problems, acknowledge the importance of conserving these animals and find solutions to enable their populations to recover.
Photo courtesy of Chris Lowe.
Of course, this is not the case everywhere and many shark populations are in serious trouble. Many countries have not done a good job of regulating their fisheries and their shark populations in other parts of the world are decreasing at alarming rates. Hopefully, the lessons we have learned and costs we have paid can serve as an example.
So, while many people may be excited to hear that our shark populations are increasing, others may be a bit wary of this good news. It’s important to maintain perspective. Will the increasing number of white sharks along our coast pose a greater threat to people? It’s hard to say. The problem is we really don’t know why sharks occasionally bite people. While we are certainly not their natural prey, with more people going in to the water than ever before and the number of sharks increasing, it is likely the number of incidences will increase. Nevertheless, the probability of being bitten by a shark is still extremely low and the reality is that you are at far greater risk driving to the beach. If you’re not worried about driving to the beach, then you shouldn’t be worried about sharks. In fact, you should be excited to know that things are getting better and it’s because more and more people care about a healthy ocean.
Chris Lowe PhD., is a marine biology professor at California State University Long Beach and Director of the university’s shark lab. Many of the research projects conducted by the lab have ventured to locations like Tahiti, Enewetak Atoll, and Baja, Mexico with funding from the Office of Naval Research and National Geographic Society. A leading expert on great white shark populations, Lowe has over 60 publications to his credit, and studies movement patterns of large sharks in the Northwestern Hawaiian Island, movement patterns of gamefish in marine refuges, and the bioenergetics of near shore gamefish.