Évaluation des stocks de sébaste à longue mâchoire (Sebastes alutus) de la Colombie-Britannique en 2023

Abstract

Results below are reported as medians (with 90% credibility intervals in parentheses). Status The probability that the female spawning stock biomass (B) at the beginning of 2024 is greater than the limit reference point (LRP, 0.4BMSY, which is equilibrium biomass at maximum sustainable yield) and upper stock reference (USR, 0.8BMSY) is > 0.99 for all three Pacific Ocean Perch subareas (5ABC, 3CD, and 5DE), placing all three stocks in the Healthy zone. Current stock status (B2024/BMSY) is 2.0 (1.1, 3.5) in 5ABC, 2.8 (1.3, 5.8) in 3CD, and 2.9 (1.5, 5.7) in 5DE. Stock status for 3CD has greater uncertainty than for the other two stocks. The probability that the exploitation rate (u) in 2023 was below the exploitation rate at maximum sustainable yield was greater than 0.96 for all three stocks. Therefore, the exploitation rate in all three areas is below the maximum removal reference rate of uMSY. Trends Annual stock status (Bt/BMSY) for Pacific Ocean Perch has been fluctuating above the USR from 2014 to 2024 in 5ABC, has been trending upward above the USR from 2007 to 2024 in 3CD, and trending strongly upward above the USR from 2014 to 2024 in 5DE. Stock size in the beginning of 2024 relative to unfished female spawning biomass (B2024/B0) is estimated to be 0.50 (0.33, 0.77) for 5ABC, 0.71 (0.36, 1.3) in 3CD, and 0.72 (0.43, 1.3) in 5DE. Ecosystem and Climate Change Considerations A low-recruitment worst-case projection was made by simulating an arbitrary 50% recruitment reduction for over 20 years from 2015 to 2034. This simulation showed little difference from the base run projections at the levels of catch investigated. Stock Advice All constant-catch policies tested showed very low risk (P < 0.01) of breaching the equilibrium reference points based on maximum sustainable yield (MSY) (LRP, USR, Removal Reference) over the next 10 years for the base run. Decision tables based on B0 reference criteria showed a probability P(B2034 > 0.2B0) of 0.93 at the highest catch evaluated in each subarea, and P(B2034 > 0.4B0) exceeded 0.5 in 3CD and 5DE for all catch policies and exceeded 0.5 in 5ABC for catches at 2,550 tonnes per year or lower. The probability of projected spawning biomass being greater than current spawning biomass, P(Bt > B2024), indicated that, for all years from 2025 to 2034, the projection probabilities vary among the three stocks. 5ABC is projected to increase while 3CD is projected to decline, even at zero catch, and 5DE is projected to remain constant at all evaluated catch levels.