Developing management options to deal with spasmodic recruitment in Atlantic redfish

Fri, November 9, 2018 11:00 AM - 12:00 PM AQUATIC ECOSYSTEMS RESEARCH LABORATORY (AERL). Speaker: Murdoch McAllister
Associate Professor; Institute for the Oceans and Fisheries, UBC

Location: AERL Theatre (120), 2202 Main Mall, UBC

Some marine fish stocks are known for large interannual variation in cohort strength. This can create challenges for the assessment and management of fisheries for such stocks. An extreme example of this can be found in Atlantic redfish (Sebastes mentella and S. fasciatus) in the Gulf of St. Lawrence and Laurentian Channel. Landings fluctuated between 30-140 kt between the 1960s and 1990s but dropped to 3-10 kt since then due to sharp declines in abundance. Following over 20 years of low abundance and recruitment, and, in 2010, designation by COSEWIC of these two stocks as endangered and threatened, these stocks produced in 2011 the largest cohorts seen in the history of the fishery, i.e., 488x and 22x the historic average. The arrival of these large cohorts has sparked interest in new long-term management plans for the fishery. I will review a recent collaboration with Fisheries and Oceans Canada and fishery stakeholders to develop a management strategy evaluation (MSE) for this fishery. We used simulation modeling to evaluate different management procedures (MPs) for setting future catch limits while accounting for several sources of uncertainty. We found that catch limits set using an abundance index for larger sized redfish mostly avoided overfishing and allowed stable harvests of about 20-60 kt in the next two decades, depending on the MP that was simulated. MPs that included maximum caps to catch limits gave lower but less variable catches, longer periods of large catches (≥40 kt), and had lower risks of overfishing than uncapped MPs. The most influential uncertainties were over the magnitudes of historic catches, future recruitment and natural mortality for redfish. Industry stakeholders that had questioned past assessments were in contrast cooperative and supportive of the MSE process and results.