Last August, two petitions were sent to the National Marine Fisheries Service from three conservation organizations (the Animal Welfare Institute, WildEarth Guardians and Friends of Animals). The petitions (available in their entirety here) requested that four species of skate be listed as “threatened” or “endangered” under the Endangered Species Act, and requested that critical habitat for these species be designated and appropriately protected. These species are the thorny skate, barndoor skate, winter skate, and smooth skate.
Due to both a directed fishery (skate wings are used for lobster trap bait, and also for food for a primarily-overseas market that includes Europe) and bycatch in bottom fisheries , Northwest Atlantic populations of these species have experienced serious declines in recent years. While some skate species have rebounded (for reasons that are not entirely clear), The thorny skate remains particularly threatened- the IUCN Red List considers the subpopulation off the Northeastern U.S. coast to be Critically Endangered. It is illegal for U.S. fishermen to keep thorny skates they catch (and has been since 2004), but they are commonly taken as bycatch in fisheries for the other skates and groundfish.
“After reviewing the information contained in the petition and information readily available in our files, we conclude that the petition fails to present substantial scientific or commercial information indicating that the petitioned action concerning barndoor, smooth and/or winter skate may be warranted…We find that the petitions do not present substantial scientific information indicating the petitioned actions may be warranted. Accordingly, we will not initiate a review of the status of thorny skate at this time.”
The National Marine Fisheries Service listed several reasons why they believe these skates should not be listed under the Endangered Species Act.
1) There is no evidence that the U.S. subpopulation of thorny skates is reproductively isolated from other subpopulations, which resulted in NMFS examining the species as a whole rather than the subpopulation that the IUCN Red List considers Critically Endangered. While the NMFS response acknowledges that ”in the United States, surveys indicate that the population is at a historically low level”, it points out that “millions of thorny skate exist and their distribution ranges across vast areas on both sides of the North Atlantic”. In other words, a drastically reduced population isn’t that bad if there are still lots of animals remaining. The IUCN Red List made a similar point- their analysis considers the entire global population of thorny skates “Vulnerable” (again, they consider the subpopulation off the Notheastern U.S. to be “Critically Endangered”).
The IUCN Red List explains why they focus on different subpopulations of thorny skates:
“Tagging studies (Templeman 1984b for the northwest Atlantic, Grand Banks (Canada); Walker et al. (1997) for the northeast Atlantic) suggest that Thorny Skates are rather sedentary, as most (85%) were recaptured less than 90 km from the initial capture point (some after twenty years at liberty). This information along with differences in size of egg capsules (Templeman 1984a), and the great latitudinal differences in size (length) at sexual maturity among the areas sampled, led Templeman (1987) to conclude that no large-scale migrations of thorny skates occurred between the sampled areas.”
These points were cited by the petitions, and in response, NMFS replied:
“Contrary to the petitioner’s assertions, there is no evidence of reproductive isolation of any subpopulation of thorny skate across the North Atlantic Ocean. Connectivity across broad geographic regions reduces the overall risk of extinction, and buffers the potential impacts of fishing mortality on thorny skates.”
2) There is no evidence that bottom trawling negatively impacts the ecosystem in a way that affects the population of these skates. While many scientists consider bottom trawling to be among the most destructive fishing gears in use today, equivalent to cutting down a forest and killing everything in it in order to capture rabbits, NMFS needs specific data showing that the fishing gear will negatively impact the parts of the ecosystem that these skates need to survive. Specifically, there is no evidence that trawling in the region is “degrading benthic habitat structure and affecting the availability of the skate’s prey as well as the skate’s ability to avoid predators.” In contrast, the IUCN Red List recommends that in order to protect thorny skates, managers should “reduce bycatch by closing and/or reducing fishing effort (particularly otter trawling) in areas of high thorny skate concentration.”
3) I’ll present the last one verbatim: “While it is reasonable to predict that climate change will result in some changes to the habitat of thorny skate, sufficient information is not presented or otherwise available to indicate that climate change, or other natural or manmade factors, may be causing the species to be threatened or endangered. We conclude that the available information does not lead a reasonable person to conclude that thorny skates are threatened or endangered due to one or more of these factors at this time.”
The NMFS report noted that if more research becomes available ( including studies demonstrating reproductive isolation between subpopulations, negative effects of climate change on the populations of these animals, negative effects on skate habitat as a result of trawling gear, and the effects of disease on skate populations), they would reconsider listing these species under the Endangered Species Act. Masters Thesis, anyone?
In the meantime, no clear plan is in place for the New England Fishery Management Council to address the lack of thorny skate recovery relative to other species, and a proposed fishery increase could result in even higher thorny skate bycatch mortality.