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Trajectories of spawning and vulnerable biomass relative to virgin levels, Bt / B0 and Vt / V0 respectively, over time, shown as the medians of the MCMC posteriors for the base-case model run.
Source publication
Pacific Ocean Perch (Sebastes alutus, POP) is a commercially important species of rockfish that inhabits the marine canyons along the coast of British Columbia. The status of POP in Queen Charlotte Sound, British Columbia, is assessed under the assumption that it is a single stock harvested entirely in Pacific Marine Fisheries Commission (PMFC) maj...
Contexts in source publication
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... 4 shows the posterior distributions of the reconstructed vulnerable biomass by year, together with the estimated historical catches. Figure 5 compares the trajectory of the estimated medians of vulnerable and spawning (mature females only) biomasses relative to their unfished values. These results demonstrate a slow decline in biomass from 1940 to 1960, followed by an increasing biomass caused by fish entering the population after a large recruitment event around 1952 ( Figure 6). ...
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... effect can be seen in Figure 6, with elevated recruitments lying on either side of the modal year, resulting in a summed overall increase on the order of 5 to 20 times the long-term average recruitment. Each of these events resulted in increases in the reconstructed vulnerable and mature biomass levels ( Figure 5) as these fish matured or became old enough for capture by the fishery. ...
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... the prior mean was raised to 0.07 and the CV increased to 20% (Figure E.46), the model converges on a higher M for both sexes, but the mean of the posterior is 3% less than the prior mean for females and 5% greater than the prior mean for males, while the M posterior CV is less than 10% for both sexes. However, this model generates a significant amount of autocorrelation in a number of parameters, including both M parameters (Figure E.59). Similar results are obtained from a model using a uniform prior on M (no expectations, Figure E.47), with the mean of the posterior distribution for M just below 0.07 for females and at 0.075 for males with a CV near 10% for both sexes. ...
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... in previous rockfish stock assessments, this assessment depicts a slow-growing, lowproductivity stock. It was severely depleted by the mid-1970s from commercial fishing by foreign fleets ( Figure 5). It appears that this early fishery was sustained from a strong recruitment event that occurred in the early 1950s ( Figure 6). ...
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... median of B2017 /B0 is estimated to be 0.27 with 90% credible interval of (0.18, 0.42) and the median exploitation rate is 0.056 (0.033, 0.085) ( Table 2). The median Bt /B0 has remained fairly constant just above 0.25 for the past 10 years ( Figure 5). Examination of the decision tables (Table 3 to Table 5) and Figure 11 confirms that current catch levels are below the model predictions of surplus production, with catches around 2,750 t/year resulting in biomass predictions with P(B2022>BMSY) ≈ 0.5. ...
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... Arrowtooth Flounder predominates in POP tows (24%), followed by POP (19%), Yellowtail Rockfish (8%), and Dover Sole Microstomus pacificus (7%). Midwater POP tows captured predominantly Pacific Hake Merluccius productus (Figure C.15). ...
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... traces show acceptable convergence properties (no trend with increasing sample number) for the estimated parameters ( Figure E.25), as do diagnostic analyses that split the posterior samples into three equal consecutive segments ( Figure E.26) and the check for autocorrelation in the parameters out to 60 lags ( Figure E.27). Some of the parameters (e.g., ...
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