91AV

James Sulikowski, Ph.D., professor in the 91AV’s Department of Marine Sciences, was recently awarded two grants from the National Oceanic and Atmospheric Administration (NOAA) for a combined amount of more than $493 thousand. Both grants will fund studies aimed at providing positive impacts for both the commercial fishing industry and the environment.

The first grant will support Sulikowski’s efforts to quantify and reduce post-release mortality for Dusky sharks that are unintentionally caught during commercial pelagic longline fishing. Pelagic longline (PLL) gear consists of a mainline (five to forty miles in length) with approximately 20-30 hooks per mile. Although the PLL fishery is highly regulated, PLL gear does interact with non-target species, such as the Dusky shark, one of the bycatch species of the PLL fishery. The Dusky shark is listed as a prohibited species by NOAA, and laws have banned the targeting of them for capture since 2000.

According to Sulikowski, Dusky sharks are one of the most vulnerable shark species in the western North Atlantic Ocean due to this incidental catch, and even small incidental mortalities associated with capture could have drastic effects on their populations.  Failure to reduce fishing mortality for Dusky sharks could impose further gear or area closures in Dusky shark habitats or, in extreme circumstances, support an endangered species listing for the species.  Sulikowski warns that this would impose a high economic burden on resident pelagic longline vessels that are unable to travel outside of high use Dusky shark habitat and may even force some boats to stop fishing.  

In order to fill this research need, Sulikowski and his colleagues from the University of Maine (Walt Golet, Ph.D.), New England Aquarium (John Mandelman, Ph.D.) and NOAA (Lisa Natanson, Ph.D., William Driggers, Ph.D., Eric Hoffmayer, Ph.D.) propose to evaluate the post-release mortality of Dusky sharks captured by pelagic longline gear using a high rate pop-up satellite archival tag. These tags will allow for the post release survival of Dusky sharks captured in PLL to be monitored and linked to biological, physical and capture variables in order to develop a set of “best” practices that can be used to reduce the observed levels of mortality of dusky sharks in the PLL.

The second grant will fund a study to determine the post-release mortality rate for Atlantic cod that are accidentally caught in lobster traps in the Gulf of Maine. According to Sulikowski, Atlantic cod has been a principal component of the New England groundfish fishery since the 17th century. However, in recent decades this species has experienced considerable declines in population and is presently estimated to be at historically low biomass levels. Due to this, recreational fishing for cod is prohibited, and the commercial quota has been significantly reduced.

“While these management efforts are in place to facilitate the recovery of cod,” said Sulikowski, “the mortality rates of cod and other fish that are discarded as bycatch after capture is one of the most significant issues affecting marine fisheries management.  Understanding discard mortality rates -- among other management goals -- is important to calculating total fishing mortality and stock biomass, which aid in the development of biologically acceptable catch limits for a given fishery.” 

Discard mortality (DM) rates are rarely known for many fisheries, and the development and implementation of accurate quantitative methods to estimate DM rates under realistic fishing conditions are scarce, Sulikowski said. Consequently, management utilizes conservative (“worst-case scenario”) DM estimates when data are lacking, which has direct bearing on fishery catch limits and can result in area/time closures. As such, Sulikowski believes that accurate DM estimates are of dire importance for the successful management of any fishery.

In order to avoid this potential worst case scenario, Sulikowski, with colleagues from the New England Aquarium  (Mandelman) and Micah Dean, M.S. (Massachusetts Division of Marine Fisheries), will evaluate the physical injury to Atlantic cod immediately following capture by standard lobster gear under fishery-dependent conditions. These mortality data will subsequently be applied to the broader sample of assessed cod to derive robust discard mortality rates applicable at the fishery-wide scale. In addition, best practice recommendations will be determined to enhance survival of cod captured in lobster gear by examining injury and fishing-related factors contributing to mortality so that both mortality and interactions can be reduced in this fishery.