In 1999, Dr. Dvora Hart came to the NEFSC to work on sea scallops. During that same fishing year, just over 21 million pounds of sea scallops - worth about $115 million dollars - were landed in the Northeast by the U.S. sea scallop fishery.

Dvora Hart, Woods Hole, 2006. NOAA Photo by George Liles

Dr. Dvora Hart spent a lot of time visiting with her family on Cape Cod before actually landing a job in Woods Hole. “I spent a year in the Environmental Sciences Division at Oak Ridge National Laboratory working on stream ecology. A few years later I took a job at Tel Aviv University in Israel, where the most interesting thing I did was on Sea of Galilee/Lake Kinneret food webs,” said Hart. “I like to say I came up from the streams, to the lakes, and finally made it to the ocean!”

Since that time, annual landings have more than doubled and ex-vessel revenues (what’s paid to vessels in the initial sale of the catch) have roughly tripled, making the sea scallop fishery one of the most valuable in the U.S. and catapulting New Bedford to the top of the nation’s most valuable port list. This year, there’s a good chance the fishery will attain new record highs.

What happened?

“The truth is that strong recruitment in the Mid-Atlantic and smart fishery management have made the difference,” said Hart.

In December 1994, three areas on or near Georges Bank were indefinitely closed to all gear capable of taking groundfish, including sea scallop gear. Portions of these areas encompassed historically productive sea scallop beds that were then largely depleted, creating defacto closure areas for sea scallops, although the boundaries were not drawn for that purpose. The experiment was on.

“Within a few years, it was evident from our annual NMFS summer sea scallop dredge surveys that these beds were recovering. By 1998, a large biomass of scallops existed in the Georges Bank closed areas,” said Hart.

In 1999, fishery managers created the first controlled access sea scallop fishery inside the Georges Bank closed areas, allowing scallopers to fish in a portion of Closed Area II. During the five-month opening, participants harvested $36 million in landings, which accounted for nearly one-third of the total U.S. ex-vessel revenues from the sea scallop fishery in 1999.

“This demonstrated not only how quickly scallops could recover during closures, but also how large individuals could get, and how lucrative the harvests could be. The fleet began to think more seriously about the benefits of using systematic closures, in addition to controlling effort in the open areas,” said Hart.

In hindsight, said Hart, the initial Georges Bank bonanza probably led to the notion that there was a “spillover” effect from the closures. The idea was that eggs produced by the animals building up in the closure area would be transported into the adjacent open areas, thus also increasing scallop abundance there. More than a decade later, during which time scallop management measures have included a series of closures, the story comes into better focus.

“The spillover effect for sea scallops from Georges Bank is a myth,” said Hart.

“Although biomass increased rapidly inside the Georges Bank closure areas, the incoming numbers of young scallops did not really increase overall,” said Hart. Despite several short-term fishery openings of the scallop beds inside the closed areas since 1999, Georges Bank sea scallop landings have only recovered to the historic average. “The more traditional tools of effort control, such as days-at-sea limits and ring size increases, have probably done as much, if not more, to restore Georges Bank sea scallop harvests to more typical levels than have closed areas,” she said.

“The actual story for the sea scallop fishery across the northeast shelf has more to do with controlling fishing effort, and exceptional productivity in the Mid-Atlantic together with the rotational closures in this area than with the Georges Bank closures,” Hart concluded.

In 1998, the Mid-Atlantic sea scallop resource was depleted, but an area off Virginia Beach and another south of Hudson Canyon off New Jersey had promising numbers of small scallops. “These two areas were closed for three years to allow small scallops to grow up, but the results we got were quite different in each area,” Hart said.

Typical circulation of water on Georges Bank and along the Mid-Atlantic Coast.

The Virginia Beach area was pretty much a failure. “It wasn’t a very productive area to begin with. Scallop biomass increased in the first closure year, but declined after that,” said Hart. Also, fishing other than scalloping was allowed in the area. Hart said the lesson of this closure was to “make the area larger to promote better enforcement, and do not put closure areas at very edge of the sea scallop’s distributional range.”

The Hudson Canyon closure area fared much better. When reopened, yields and biomass were well above those previously observed in this area. What was really interesting, though, was what happened to the south of the closure area.

Water currents within Hudson Canyon are generally southerly and run parallel to the coast. At about the same time that biomass increases were occurring in the Canyon, numerous small scallops were also detected in an area to the south of the Canyon, dubbed “the Elephant Trunk” because of the shape of its depth contours.

“There may indeed be a spillover effect from the buildup of biomass in the Hudson Canyon area, essentially what people thought might happen on George Bank but did not,” The difference may be because a gyre exists on Georges Bank which retains scallop larvae on the Bank. The currents in the Canyon, on the other hand, potentially push larvae to the south.

The Elephant Trunk area was closed in 2004. When it reopens in January 2007, it is expected to produce a historic high in landings, perhaps resulting in more yield from this one small area than was typically harvested from the entire resource prior to the last few years. “We saw strong recruitment in 2005 southward of the Elephant Trunk, so the pattern may be repeating itself” said Hart, “and this area is set for closure in 2007.”

A large number of two-year old recruits (2001 year class) were observed south of Hudson Canyon closed area on the 2003 NMFS survey, in what became the Elephant Trunk closed area. NOAA photo.

In all cases, Hart says, the fishery boom must be attributed to coupling closures with management measures that control overfishing. “Management measures have actually worked for sea scallops. The reduction in days fished, increased ring size, reduced crew size, and rotational closures, combined with the strong productivity in the Mid-Atlantic have caused overall sea scallop yields and revenues to go way up.”

Hart has been working on developing an even better rotational closure scheme, one that optimizes revenues and stability in the fishery. “One idea is to use averaging of population growth over several years to arrive at an optimal harvest rate. This would better account for natural variability in population growth.” Her work indicates that six- to nine-year closures would produce the highest yields - if areas were closed on a regular schedule. “But this obviously has to be tempered by the cost of waiting for the openings and the displacement of fishing effort during the closures,” said Hart.

Another idea is not to close areas on a regular schedule, but to only implement closures to optimize yield from large cohorts. A cohort is all the animals born in a given year. “Cohorts with relatively large numbers of individuals would be protected using closures until they grew to larger sizes, and we would not worry very much about smaller cohorts,” explained Hart.

To get a better understanding of stock conditions and improve the timeliness of what we know about abundance, Hart said digital imaging will be the next big break through. “The NMFS sea scallop resource dredge survey provides biological samples from the population and also generates a highly reliable index of relative abundance. However, the survey provides less information about physical habitat and absolute abundance,” she said.

Recent experiments have been conducted using video cameras, mounted on a pyramid-shaped support frame and dropped near the ocean bottom to capture images of scallops on the bottom. “Within the camera’s field of view, about 3 square meters, one can see almost 100% of the scallops larger than 80 millimeters -- just over 3 inches – as well as their habitat. “In other words, we can get absolute abundance estimates for larger sea scallops, plus a good picture of the substrate,” said Hart.

On the other hand, the video “drop camera” images do not detect smaller scallops, and are not a reliable way to determine the exact size of scallops pictured. Each drop surveys a much smaller area than a dredge tow. One video drop covers about 3 square meters, while one dredge tow covers 4,500 square meters.

Digital still cameras, towed behind a ship or mounted in a submersible, may significantly improve what imaging can provide to improve surveys. Hart has been working with a group of researchers who are developing an underwater towed instrument for assessing sea scallops on the bottom. The system flies a digital camera off the bottom, taking several photos per second. The work is funded through the sea scallop set aside research program, which is authorized under the Sea Scallop Fishery Management Plan.

Rather than the one image derived from the video drops, the digital camera’s flight generates a strip of pictures to piece together. “The digital camera system has the large area coverage of a dredge, and provides absolute counts like the video drop camera,” said Hart. The digital images also have better resolution and less distortion than video images.

“Right now we are working on a way to aggregate information from these images,” said Hart. "Next year, we intend to conduct paired experiments using both the dredge and the digital still camera set-ups,” she said.

In the short term, Hart sees a bright future for the sea scallop fishery. “With the reopening of the Elephant Trunk area in 2007, landings should exceed 70 million pounds for a number of years. This harvest level is more than three times as great as the annual yields obtained prior to the recent scallop boom. Long-term, landings of 50 million pounds are probably sustainable,” she said.

Despite this rosy outlook, some problems remain. Presently, any vessel can obtain a general category scallop permit, which allows the vessel to land 400 pounds of scallop meats per day. The scallop boom, coupled with declines in many other fisheries, has enticed many to enter the general category fishery.

Hart worries about the resource impacts of the unrestrained addition of effort into the sea scallop fishery. “Shrimp vessels from the Gulf of Mexico, as well as vessels from the Northeast that formerly fished for squid or groundfish, have switched to general category scallop fishing,” noted Hart. “Unchecked, such increases in fishing effort have the potential to reverse much of the progress that has been made in the past decade.”

The New England Fishery Management Council is currently working on an amendment to the scallop management plan to control effort in the general category fishery. The amendment could be implemented by the start of the 2008 fishery.

Posted September 14, 2006