The IUCN/SSC Shark Specialist Group
Shark News 8: December 1996
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Spiny dogs - Is History Repeating Itself?
Mistaken identity: in confusing a shark for a fish, fishermen and managers in the NW Atlantic have squandered a once-abundant resource
Michael Rivlin
Perhaps it's their name - dogFISH -that's led to the confusion on the part of fishermen and managers. Or perhaps it's their modest size. Whatever the explanation, US NW Atlantic fishermen have been allowed to fish spiny dogfish Squalus acanthias as though they were teleosts, without paying heed to the axiom that a sustainable, directed shark fishery is an oxymoron ... especially one that proceeds in the absence of management.
As a result, although a directed US domestic fishery in the NW Atlantic for the sharks began only in the late 1980s, there is overwhelming evidence that the seemingly inexhaustible stock of dogfish - once regarded as nuisance 'trash' fish, and then as the 'underutilised' last refuge of beleaguered fishermen - are either near collapse or veering in that direction. At the very least, they have been impacted to a point at which it will take them years to recover.
Swollen fleet
Dogfish life history - long life, late maturation, and low fecundity comparable to other sharks - makes them especially susceptible to fishing pressure. Females spawn at age 10 to 20 years, and give birth to an average of 6 to 10 pups after a gestation period of 16 to 22 months - a maturation period rivalling that of the Indian elephant. The maximum reported age for females is 40 years, 35 years for males.
In the NW Atlantic, the sharks follow a seasonal north-south migration route. Dogfish head to waters off North Carolina in the fall and return to the Mid-Atlantic in the spring, eventually concentrating in waters between Cape Cod and Nova Scotia. An ever-expanding US fleet of small gillnetters and hook-and-liners now fish for dogfish during the summer. The fleet of somewhat larger boats that follows the dogfish south to Maryland in the winter has grown just as rapidly.
Two factors account for the fishery's rapid rise. Steadily increasing prices paid by Europeans, who buy virtually the entire catch of dogfish, have in recent years made the sharks a lucrative catch. This was combined with the New England groundfish collapse that left fishermen scrambling for fish to put in their hold. With mature females moving inshore to bays and estuaries during the summer, dogfish were one of the few as-yet-unregulated species accessible to smaller boats shut out of most other fisheries.
In 1990 annual dogfish landings, which had been averaging about 4,500 mt, climbed sharply to 14,900 mt, and by 1993 had shot up to 20,400 mt - a level of fishing mortality five times that of the late 1960s. Landings for 1994 and 1995 have remained steady.
In addition, discard rates - imprecisely monitored as are many aspects of this unregulated fishery - are nonetheless estimated to be very high. A 1993 study showed discard mortality to be 2/3 or more of reported landings, and other estimates say the rate may equal or exceed actual landings.
The impact of this high fishing mortality is reflected in changes in stock size, composition, and catch per unit effort (CPUE). According to a National Marine Fisheries Service (NMFS) 1994 stock assessment, although stock biomass was about 4-5 times that of the late 1960s, the spawning portion of the biomass had not increased since the late 1980s.
In addition, scientists and fishermen estimate that between 1993 and the present CPUE has decreased by 30% to 50%. A NMFS study of catch effort by Gulf of Maine gillnetters confirms this almost 50% decrease. Gillnetters who could once fill their boats before noon now use two to three times more net, with mesh two inches smaller than they employed previously, and still can't achieve catches they once had.
Females targeted
Compounding the problems associated with fishing on a long lived, late maturing species with low fecundity, dogfish swim in schools segregated by size and, for the larger individuals, by sex. This behavior has made them especially vulnerable to a fishing fleet that, until recently, pursued only the largest fish - mostly mature females - preferred by the European market that buys about 95% of the catch.
Swept area estimates of fishable biomass - fish greater than 80 cm and virtually all females - which had increased threefold from 1968 to 1988, have declined more than 10% since then. And there is significant evidence that the structure of the population has shifted towards smaller, immature females and males. The average size of dogfish in commercial landings and in the NEFSC trawl survey has declined by about 5 cm since 1982. As a result, according to Michael Hopper, a veteran dogfish buyer formerly with Worldwide Seafoods, larger European processors have been forced to accept smaller fish than they would have 2-3 years ago. The minimum weight of seven pounds once demanded by buyers has dropped down to four pounds, and the average size of the sharks landed has continued to decrease from eight to six lbs.
Experts had predicted that stricter groundfish regulations would drive hordes of otter trawlers in search of new fishable stocks into the dogfish fishery. However, according to Hopper, landings may have peaked in 1995, and he predicted that by 1997 they would begin to fall. In addition, the buyer thinks that the fishermen's realisation that dogfish stocks are diminishing accounts for the fleet size peaking and stabilising at 1995 levels. "This is not a growth segment of fishing industry anymore," observes Hopper.
Despite these question marks over the fishery's future, some regional fishery council members and fisheries managers persist in portraying the fishery as it once was - rolling out welcome mats instead of posting warning signs.
For example, a Massachusetts Governor's Seafood Task Force program to stimulate interest in alternate species includes dogfish on its list of 'underutilised' species. And while the focus of the campaign is on developing a market for small, currently discarded males - probably in value-added products that will minimize the public's overwhelming rejection of 'cape shark' - stimulating participation is the last thing this fishery needs.
Spiny dogfish being removed from gillnet, New Bedford, MA. Photo: Michael Rivlin.
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Scientists ignored
Some NMFS scientists and management council staffers have been saying for the last couple of years that if there is any chance of saving the NW Atlantic stock and establishing a sustainable fishery, a fishery management plan (FMP) must be implemented as soon as possible. The 1994 "Report on the 18th Northeast Regional Stock Assessment Workshop" issued by NMFS' Northeast Fisheries Science Center in Woods Hole concluded that if the fishery was allowed to continue without control, "the stock will eventually decline." And in 1995, NMFS termed the stock "fully utilised."
But as recently as early 1996, the Mid-Atlantic and New England Fishery Management Councils recommended postponing development of such a plan - in part because important scientific findings were not available to policy makers.
Opponents to a management regime argued that dogfish were a detriment to groundfish recovery, and that if anything they should be fished down rather than built up. Dogfish, they said, were at fault for the groundfish crisis. And if not exactly to blame, then their very presence made groundfish recovery impossible. One of the few scientific facts every New England fisherman and manager has learned is that the ratio of dogfish and skates to groundfish on Georges Bank is now 75% to 25% - exactly the inverse of what it was in past years.
Dogfish are opportunistic feeders, and their diet does include a variety of commercially valuable species. However, according to Dr Mike Fogarty, chief of the food chain dynamics investigation at the Northeast Fishery Science Center, his soon-to-be-released, multi-year study indicates that attempts to thin dogfish populations are based on faulty assumptions. Fogarty says that, when compared with other species, dogfish are relatively unimportant predators on cod and haddock. "If you removed all the dogfish from the system," states the ecologist, "I wouldn't expect that it would have a big impact on groundfish."
Fogarty's studies have revealed that dogfish do prey heavily on herring and mackerel. However, he points out that many other predators, including cod and hake, feed on the same prey. In addition, Fogarty notes that "because dogfish are so highly migratory, the effects on any part of the coastline are transient and temporal." Removing dogfish, concludes the scientist, probably would not have an impact on herring and mackerel either.
Fogarty acknowledges that dogfish do compete with groundfish for food, and that more locally abundant food supplies could conceivably increase the recovery rate for cod and haddock. But he observes that stocks of herring and mackerel are so plentiful that availability of prey isn't a limiting factor and so concludes that groundfish populations are likely unaffected by the large concentrations of dogfish.
Fogarty has been presenting his findings to fishery council members, and has apparently made an impression on some individuals. In November 1996, the Mid-Atlantic Fisheries Management Council restarted the delayed dogfish management process.
Michael Rivlin,
401 E 89th Street, New York NY 10128, USA
Fax: (+1) 212.996.4152, email: mrivlin@pipeline.com
Michael Rivlin is a journalist and former field editor of National Fisherman who frequently writes about commercial fishing and marine conservation issues. First North American Print Rights © 1996 MICHAEL RIVLIN
Pacific Coast Catastrophe Brewing
With a fleet of Pacific Northwest fishermen searching for a substitute species after the late 1980's salmon collapse, fisheries managers seem oblivious to unregulated, directed dogfish fisheries that have begun developing along the Washington, Oregon and California coasts and in Puget Sound.
Washington landings have crept up steadily, from around 3 million lbs in 1990 to around 6.8 million lbs in 1995. Oregon and California fisheries are in incipient stages, but growing rapidly, However, at present there is no talk of instituting a management plan and no stock assessment data being gathered which would aid in developing such a plan.
For a recent lesson in what intensive fishing can do, Pacific Northwest residents can look up the coast to British Columbia, where dogfish landings have fallen from an average of 9 million lbs in 1985-1989 to an average of 4 million pounds in 1990-1995. A similar boom-and-bust pattern was seen in
British Columbia during a fishery for vitamin-A rich dogfish livers
that, six years after its 1943 peak, had reduced fishable biomass 75%.
In November 1996, the Mid-Atlantic Fisheries Management Council restarted the delayed dogfish management process. The Council should be adopting an information document in December that will solicit public comments early in the new year. This is the first step in the long and difficult process toward the drafting and implementation of a Fishery Management Plan for spiny dogfish, which can be accelerated by input from the scientific and conservation communities. Comments should be submitted to:
David Keifer, Executive Director
Mid-Atlantic Fisheries Management Council
Federal Building, 300 South New Street
Dover, DE 19901, USA
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