Research Shows Dogfish Management Based On Flawed Data

March 22, 2006

Release from: Susan West
Outer Banks Sentinel (North Carolina)

Research conducted under the North Carolina Fishery Resource Grant Program shatters assumptions used by the National Marine Fisheries Service (NMFS) in the management of the spiny dogfish fishery.

In a report presented to an audience of fishermen and fisheries managers in New Bern last week, Roger A. Rulifson of the Institute for Coastal and Marine Resources at East Carolina University said that his research showed that NMFS’ estimates of spiny dogfish mortality rates are too high.

NMFS estimates that 50 percent of dogfish caught in trawls, 75 percent caught in gillnets, and 100 percent caught by hook and line do not survive capture and release. The federal agency uses those figures in the stock assessment models that form the basis for management plans and regulations.

Rulifson’s research showed an initial mortality rate of zero percent for spiny dogfish captured in trawls and 17.5 percent for those caught in gillnets. The study did not look at hook and line mortality.

In fish held in observation cages for 48 hours, the trawl mortality rate remained zero and gillnet mortality increased to 33 percent.

The report concluded that most spiny dogfish “survive trawl-induced stress and injury.”

Rulifson said that the mortality rate for gillnets represented “the maximum mortality rate expected in a winter gill net fishery” because gillnets used in his research remained in the ocean for periods much longer than those typically used by fishermen.

Twenty-six percent of the dogfish captured in the project’s trawl tows displayed gillnet markings. Rulifson explained that that figure was significant because it showed that at least one-fourth of the fish had survived prior capture by gillnets, offering another indication that the rates used by NMFS are too high.

He noted that the mortality rates established through his research were lower than those found in a summer study completed in 2003 in Massachusetts that also contradicted the rates used by NMFS. Rulifson believes that difference might be explained by the minimal change in temperature between the ocean and the decks of fishing boats in winter.

In the 1990s, the dogfish fishery was a valuable winter fishery for commercial fishermen on the Outer Banks. Fishermen entered the fishery at the urging of NMFS when the federal government helped develop markets for a species considered under-utilized in the 1980s.

Although dogfish never became popular in America, lucrative overseas markets developed in England where it was called rock salmon and used in fish and chips. It was also used for schillerlocken, a cured product popular in Germany and France.

In 1997, managers classified the species as overfished and regulations that went into effect in 2001 curtailed the directed fishery, allowing only minimal amounts to be harvested as bycatch in other fisheries. North Carolina commercial fishermen, however, report an abundance of dogfish that often interferes with bluefish and gray trout fishing.

Commercial fishermen Chris Hickman of Hatteras and Eddie Newman of Swan Quarter worked with Rulifson and his research assistants.