The government of Western Australia recently announced a plan to kill great white sharks that come close to popular swimming beaches, resulting in justifiable outrage from the scientific and conservation communities. I’ve written before (here and here) about why this is a bad idea that will harm a species in need of protection without making the ocean significantly safer for humans, and won’t rehash the details here. Instead, I want to focus on a claim recently made in support of this plan by Paul Mulshine, best known for taunting environmentalists by stating that shark fin dumplings would taste better if only more sharks were killed.
In a recent blog post on the subject, provocatively titled “Aussie’s common-sense approach to great white sharks has shark huggers’ jaws flapping” , Mulshine makes a lot of wildly inaccurate claims about great whites, shark attacks, and shark conservation.
“A shark’s just a big fish. And we humans kill millions of fish every day so we can eat them.”
No one is claiming that sharks aren’t fish, Paul. The issue is that they are a fish with a drastically declining population worldwide. They are considered Threatened (specifically, “Vulnerable”) by the IUCN Red List. They are listed under CITES Appendix II, are protected under Australian law (listed as Threatened under the Environmental Protection and Biodiversity Conservation Act) and are currently being considered for protection under the U.S. Endangered Species Act. So yes, great white sharks are fish, but they’re species of fish that we need to protect so that they don’t go extinct.
Also, there’s a difference between killing fish to eat (which can also have severely negative consequences on the ocean) and killing members of a Threatened species because people are afraid of them and governments don’t want to take basic preventative measures to reduce the risk of shark attacks.
“Never mind killing sharks; these guys oppose even the netting off of beaches to prevent them from eating humans.”
This asinine comment shows that Mulshine hasn’t bothered to learn the first thing about the subjects he’s yelling about. Shark nets are not a barrier that unobtrusively prevents sharks from approaching a beach. They don’t even fully surround beaches. Instead, they work by killing sharks (as well as sea turtles, sea birds, and marine mammals) and reducing local populations. In essence, Mulshine has just said “environmentalists not only object to killing sharks, but they object to killing sharks!”
The post (along with his earlier posts) is full of similar idiotic nonsense that I won’t go into further for fear of getting so frustrated that I’ll yell at my computer. However, I want to address an important point that Paul Mulshine has made before and repeats here. He incorrectly claims that sharks are actually not ecologically important at all and removing them will have very small consequences for the ocean’s food web. Specifically, he said:
“the best scientific study yet published on the topic says that there is little evidence that removing sharks from the food chain would have much effect at all.”
First of all, please note the ridiculous and all-too-common tactic of referring to “the only study out of dozens on the subject that even peripherally agrees with my point” as “the best scientific study yet published”.
Mulshine at no point actually says which study he’s referencing, but from the description I assume he’s referencing this one ( The Role of Sharks and Longline Fisheries in a Pelagic Ecosystem of the Central Pacific, available here). I’ll briefly describe the study and its conclusions here, but I encourage anyone interested to read the full paper.
The team of scientists, which includes Pew Fellow Dr. Timothy Essington(who Mulshine interviews in support of his claims), ran a series of ecological models to determine the hypothesized impacts of shark population declines to a pelagic food web. Their conclusion was “in general, analysis of the Central North Pacific model reveals that sharks are not keystone predators.” This quote is essentially the basis of Mulshine’s entire argument- one study concluded that a few specific species of sharks in one specific geographic region are not keystone predators, therefore no shark in the world is ecologically important at all and we should kill more of them.
It’s worth noting that the original paper itself includes the following caveats:
1) The authors explicitly acknowledge that other scientists who have done similar research in different systems found that sharks are ecologically important to some of those systems.
“When perturbed through a keystone predator test… [many other similar] models also produce strong ecological responses to the removal of sharks.”
2) While sharks were found to not be terribly important in the specific system they studied, this obviously doesn’t mean that sharks can’t be ecologically important elsewhere.
” Logically, we should expect that systems will differ in the relative importance of sharks based on their abundance, trophic position, and prey.”
3) Although sharks weren’t found to be ecologically important here, that doesn’t mean we shouldn’t worry about their populations and try to protect them.
”The conservation of sharks centers on two main issues. One of them is focused on biodiversity arguments and the unique evolutionary history expressed in the lineage of sharks. That, alone, is a strong and significant basis for concerns about fishery effects on shark populations.”
In other words, the paper itself completely undermines the point that Mulshire is trying to make using the paper!
I asked Dr. Essington about how his research was represented in Paul Mulshire’s article, and he provided the following statement:
”Suffice it to say that Paul took many of my statements quite out of context, as I was simply explaining to him my paper (which compares sharks to tunas, two very different life histories). It seems to me that this has little relevance in coastal communities (moreover, I did point out areas where we would expect sharks to be important – say when they consume species with low productivities; these comments were excluded from the interview). Do I think sharks are always critical important? Of course not, neither does any ecologist. Do I think we can predict the impacts of species removals? Nope. Still, that’s quite a different conclusion than ‘sharks are never important’.”
If anyone is interested in learning more about the ecosystem-wide effects of the loss of sharks, there is a great deal of literature on the subject that I can recommend. I’d particularly encourage you to read the best scientific study yet published on the topic (see what I did there?), a global review of the devastating effects of the loss of predators in both marine and terrestrial systems. One of the co-authors is… you guessed it, the very scientist Paul Mulshire uses as “proof” that scientists don’t think anything bad happens when we get rid of predators, Dr. Timothy Essington.