Mitigating the Impact of Commercial Fishing on Thorny Skate in the Gulf of Maine

Thorny skate (Amblyraja radiata) are a bottom-dwelling species that can be found in the cooler, deeper waters of the Gulf of Maine. These skate can be identified by the sharp thorns that cover the top-side of their bodies and are used as protection from predators.

In the Gulf of Maine, these skate have been subject to direct and indirect commercial fishing pressures by three of the major fisheries—Northeast Multispecies, Monkfish, and Atlantic Sea Scallop. These fisheries use bottom-tending gear such as otter-trawls, dredges, and gillnets and have either directly targeted thorny skate for the meat on their wings or have incidentally captured and discarded these animals as bycatch.

Thorny skate are sensitive to these types of fishing pressures because aspects of their life history, such as low reproductive output, make it difficult for the population to withstand high fishery removals. Unfortunately, this susceptibility led to a significant decline in thorny skate biomass in the Gulf of Maine and prompted the species’ listing as a prohibited (zero-possession, mandatory-release) species by the New England Fishery Management Council in 2003.

Despite this management measure, these skates continue to be commonly captured and discarded in commercial fisheries and still remain one of the most overfished stocks in the Gulf of Maine with a population level near historic lows.

The effectiveness of any fishery landings prohibition policy is predicated upon one simple question: does the species survive after being released/discarded?

It is also valuable to understand the aspects of the capture-and-handling process, such as haul/soak durations or handling methods, which can influence mortality, along with when and where the species is at highest risk of fishery interactions. Given its dire population status and sensitivity to fishing mortality, the importance of answering these questions for the thorny skate cannot be overstated because even low- to moderate-incidental mortality rates may prevent population recovery.

In 2016, research scientists from the Anderson Cabot Center for Ocean Life began a collaborative study—funded by the NOAA Bycatch Reduction and Engineering Program—to better understand the thorny skate discard mortality rate in the Gulf of Maine commercial otter trawl fishery (see below for list of collaborators).