Dismissing dogma? What do we really know about the spiny dogfish, Squalus acanthias, population in the US western north Atlantic Ocean

No abstracts are to be cited without prior reference to the author.

The status of the spiny dogfish (Squalus acanthias) stock in the US portion of the Northwest Atlantic has become a contentious issue. Distributed from Maine to Florida, this species was once considered to be the most abundant shark throughout its US range. As a result of reported declines below biomass threshold levels, in early 2000 the Mid-Atlantic, New England Fishery Management Councils, and Atlantic States Marine Fisheries Commission implemented a management plan which imposed annual quotas and possession limits for vessels fishing in both Federal and State waters. Because of characteristics such as slow growth, extended gestation period, small litter size, and a spawning-stock biomass (SSB) below threshold levels as recent as 2005, the spiny dogfish population was not anticipated to rebound for more than a decade. Recent Northeast Fishery Science Center (NEFSC) survey data, however, suggest a fourfold increase in SSB has occurred between 2005 and 2009. Based on the aforementioned life-history characteristics, this substantial increase in biomass is considered to be biologically unrealistic. Preliminary data are presented to support hypotheses that are divergent to common paradigms it is hypothesized that: (i) the biologically unrealistic increases in SSB may be caused, in part, by a substantially more active vertical movement pattern that prevents this species from being effectively captured by NEFSC otter trawl surveys, and (ii) the gestation period of spiny dogfish may be less than the proposed 22 months and that there may also be regionally different reproductive cycles across this species’ US range.