Bayesian Age-Structured Model - Goodness of Fit - Among the 4 models compared, the M4 performed better in both Deviance Information Criterion (DIC) and retrospective errors (Table 8.1.1) for the base case, and also had the lowest DIC across a range of data sensitivity runs (Table 8.1.2). The DIC value of M4 is much lower than the other 3 models, and the retrospective error, both one year retro and Mohn’s retrospective error are much smaller than the other 3 models. This suggested that M4 is the most appropriate model and the weakfish population is nonstationary as reflected in M variation over time, and spatial asynchrony. - Statistical Catch-at-Age Model (ASAP) - Goodness of Fit - ASAP showed strong patterning in some of the residuals for total catch and index values (Figures 8.2.1 – 8.2.10). ASAP estimated lower catch in the beginning of the time series and higher catch in the later years, especially for the commercial fleet. It also predicted higher index values than observed in the early part of the time-series and lower index values in later years for several indices, most notably the composite young-of-year index. - Depletion-Based Stock Reduction Analysis (DBSRA) - This model failed to produce credible results. See Section 7.3 Depletion-Based Stock Reduction Analysis for more discussion of the approach. - Virtual Population Analysis (VPA) - The VPA model appeared to struggle with the updated data, resulting in F estimates that were at the bounds. The VPA model estimated higher total abundance, recruitment, and SSB at the beginning of the time-series than the ASAP model with either the 2009 base data or the 2016 base data (Figure 8.4.2). The VPA also showed the peak of abundance, recruitment, and SSB in the mid1990s, instead of at the beginning of the time-series as the ASAP runs do. However, all three models showed more similar estimates in the last ten years. The VPA and the ASAP with the 2009 base data were slightly more optimistic about trends in N, SSB, and F than the 2016 base model, but all agree that the population is at very low levels compared to the early part of the timeseries. - Current Overfishing, Overfished/Depleted Definitions - Currently, there is no overfishing definition for weakfish. The SSB target and threshold were set at SSB30% and SSB20%, respectively, such that the target represents a level of SSB that is 30% of an unfished stock. If the stock were to be below the SSB threshold, it would be considered depleted. - Depleted Status - Under conditions of time-varying natural mortality, there is no long-term stable equilibrium population size, so an SSB target is not informative for management. The Weakfish TC recommends an SSB threshold of SSB30% = 6,880 MT that is equivalent to 30% of the projected SSB under average natural mortality and no fishing. When SSB is below that threshold, the stock is considered depleted. SSB in 2014 was 2,548 MT, below the SSB threshold, indicating the stock is depleted (Table 9.2.1, Figure 9.2.1). SSB has been below the threshold for the last 13 years. - Overfishing/Total Mortality Status - The TC recommends the use of total mortality benchmarks to prevent an increase in fishing pressure when F is low but M is high. When Z is below the Z target, F reference points can be used to assess overfishing status. Z in 2014 was 1.11, above the Z target, but below the Z threshold, indicating total mortality is still high but within acceptable limits (Table 9.2.1, Figure 9.2.2). Z was above the threshold from 2002-2013.