30. The Agony of Recovery: Scientific Challenges of Spiny Dogfish Recovery Programs
Paul J. Rago and Katherine A. Sosebee
Abstract.—Following intense harvests by distant-water fleets before 1975, populations of spiny dogfish Squalus acanthias in the Northwest Atlantic increased steadily in abundance during the mid-1970s and 1980s. Peak abundance in the early 1990s was short-lived as the United States commercial fleet began a large-scale fishery on mature female dogfish. Between 1989 and 1999, approximately 250,000 metric tons of female spawning stock was removed, reducing the stock to about 30% of BMSY levels. Abundance of male dogfish, however, was relatively unaffected by the fishery. The average size of mature female dogfish declined by more than 10 cm and the average length of juveniles declined as well. Recruitment during 1997 to 2003 was the lowest in the 1968–2006 time series. Recruitment in 2006 was low despite a very high catch rate of mature females in the spring survey by the Northeast Fisheries Science Center. The ratio of mature male to females increased from about 2:1 prior to the directed fishery to about 7:1 by 2001.
Under federal fisheries management, the rebuilding plan eliminated the directed fishery and has allowed a limited, bycatch-only fishery. Efforts to rebuild populations are complicated by (a) the residual abundance of males and immature females; (b) concerns about ecosystem function; (c) high rates of discarding; and d) an apparent shift in spiny dogfish distribution from offshore to inshore areas during the past 5 years. Projection models suggest that recovery of dogfish poses significant management challenges owing to the current non-equilibrium size and sex composition of the stock, transient effects of a 7-year string of low recruitment, slow growth, and the difficulties of implementing an appropriately selective fishery.