Age Structure Response of Principal Groundfish to Marine Protected Areas in New England

• Main Author: Chawarski, Julian
• Format: Text
• Language: unknown
• Published: DigitalCommons@UMaine 2017
• Subjects: Fisheries; Gulf of Maine; Atlantic Cod; Age Structure; MPAs; Marine Protected Areas; Biology; Marine Biology; Bris; Stige; atlantic cod; Gadus morhua
• Online Access: https://digitalcommons.library.umaine.edu/etd/2853; https://digitalcommons.library.umaine.edu/context/etd/article/3919/viewcontent/M_ChawarskiJulian_Final.pdf

Atlantic cod (Gadus morhua), yellowtail flounder (Limanda ferruginea), and haddock (Melanogrammus aeglefinnus) were once dominant species in the New England fisheries economy, together accounting for over half of the landings value of groundfish. Over the last several decades, all three species have experienced dramatic shifts in spawning stock biomass (SSB) with current estimates for cod stocks at 3% and 7% of target biomass (Gulf of Maine and Georges Bank stocks, respectively), a strong contrast to haddock stocks that are nearly fully recovered (NEFSC 2014, 2017). As principally demersal species, they are easily targeted by trawl and gillnet, the former representing the majority of landings in New England waters. Now considered a choke species for the entire groundfish fleet, the current state of cod may signal the demise of other fish stocks if management measures are not adjusted. Despite a 2010 shift from input controls to a mixture of input controls (i.e., year-round closures) and output controls (i.e., hard quotas), along with yield-based stock assessment reference points, the outcomes for these key groundfish have been confounding. Some suggest that the failure to account for age structure of populations in management may underplay the value of old fish, those which are generally removed by commercial fishing (Le Bris 2013, Secor 2015, Stige et al. 2017). Age truncation, vulnerability to overoptimistic assessment, and increasing amplitude of climate oscillations all put the recovery of certain species at risk (Berkeley 2004, Pershing et al. 2015). One of the key management changes enacted with the Sustainable Fisheries Act of 1996, was the implementation of year-round closures throughout New England waters. Heralded as a backstop to uncertainty, these temporary Marine Protected Areas impart a conservative management approach with the simple goal of reducing overall mortality. Nearly 25 years after the first areas were closed to fishing, research has been inconclusive about the effects on the groundfish ...