Research Document - 2016/048
Assessing the status of the cod (Gadus morhua) stock in NAFO Subdivision 3Ps in 2015
By R. M. Rideout, D. W. Ings, B. P. Healey, J. Brattey, M. J. Morgan, D. Maddock Parsons, M. Koen-Alonso, and J. Vigneau
Abstract
The status of the cod stock in the Northwest Atlantic Fisheries Organization (NAFO) Subdivision 3Ps was assessed during a Fisheries and Oceans Canada (DFO) Regional Peer Review Process meeting held October 20‑22, 2015. Stock status was updated based upon information collected up to spring 2015. Principal sources of information available for the assessment were: a time series of abundance and biomass indices from Canadian winter/spring research vessel (RV) bottom trawl surveys, inshore sentinel surveys, science logbooks from vessels < 35 ft., logbooks from vessels > 35 ft., reported landings from commercial fisheries, oceanographic data, and tagging studies.
Total landings for the 2014‑15 management year (April 1‑March 31) were 7,166 t or just 54% of the Total Allowable Catch (TAC), and this marks the sixth consecutive season that the TAC has not been fully taken. The 2015‑16 fishery was still in progress at the time of the meeting. The removals through recreational fishing are unknown since 2007, but based on previous estimates are thought to be a small fraction (~ 1%) of the commercial landings.
Estimates of abundance and biomass from the DFO RV spring survey have been relatively stable over the past seven years (except for a high value in 2013 apparently influenced by a year-effect), with abundance being slightly higher than it was in the early 2000s and biomass being generally lower than it was in the early 2000s. The 2015 survey was dominated by young fish which are not yet of commercial size. Sentinel gillnet catch rates have been very low and stable since 1999. Sentinel linetrawl catch rates have been below average for the past six years and the 2014 catch rate was the lowest in the time series. Gillnet catch rates from logbooks of vessels < 35 ft. have been generally stable since 1999 but increasing to slightly above average in 2014. Linetrawl catch-rates decreased over 2006‑10, but subsequently increased and are presently at the time‑series average.
Estimates of Spawning Stock Biomass (SSB) derived from a survey-based (SURBA) cohort model increased considerably over 2009‑12 but have since declined. The 2014 and 2015 estimates are approximately 1.4 times higher than the limit reference point (LRP), and the stock is currently in the ‘cautious zone’ according to DFO’s Precautionary Approach (PA) Framework.. The probability of being below the LRP in 2015 is low (~0.05). Recruitment has improved over the last decade with most cohorts at or above the time-series (1983‑2014) average. In particular, indications are that the 2011 and 2012 cohorts are strong. Estimated total mortality has generally been increasing since 1997 to near the time-series maximum. Over 2012-14, it averaged 0.65 (48% annual mortality), which is high especially considering that reported landings have been about half of the TACs over this time period.
Projection of the stock to 2016 was conducted assuming mortality rates will be within ±20% of current values (2012‑14 average). Projection scenarios indicate that the 2016 SSB will increase from the 2015 estimate, with median 2016 relative SSB projections ranging from 1.7 to 2.1. In each of the scenarios, the probability of being below the LRP in 2016 is low (≤ 0.05).
Despite short-term projections for stock growth, there is reason for concern for 3Ps cod going forward. Although recruitment has recently been good, mortality is very high and hence the long-term contribution of these year classes to the fishery and spawning biomass is still uncertain. The spawning biomass is composed almost entirely of young fish, with the current age at maturity being the lowest recorded in the time series. Recent biological data suggest fish growth rates are low and that fish condition is poor. In recent years, cod in 3Ps have been feeding heavily on lipid-poor prey such as snow crab and other invertebrates. The combination of these biological data with the recent rise of warm-water species such as white hake is suggestive of broad changes in the 3Ps ecosystem and perhaps reduced cod productivity.
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