Measures of Overall Model Fit - For landings, the base model fit the longline fishery the closest (standardized residual = 0.0127, Fig. 4.1.1.c, d), the commercial hook-and-line fishery next (standardized residual = 0.2290, Fig. 4.1.1.a, b), headboat next (standardized residual = 0.7562, Fig. 4.1.1.e, f) and MRFSS/MRIP last (standardized residual = 0.8311, Fig. 4.1.1.g, h). For discards, there were no discards for the commercial longline fishery; therefore, the base model fit the headboat fishery the closest (standardized residual = 0.2249, Fig. 4.1.2.c, d), the commercial hook-and-line fishery and MRFSS/MRIP were fit almost equally well (standardized residuals = 0.9691 and 0.9762, Fig. 4.1.2.a, b and 4.1.2. e. f). As is frequently the case, the model fit the indices less well. The NMFS-UM Reef Visual Census had the closest fit (standardized residual = 0.3775, Fig. 4.1.3.a, b), the commercial hook-and-line index was next (standardized residual = 1.0176, Fig. 4.1.3.c, d), followed by the commercial longline index (standardized residual = 1.0652, Fig. 4.1.3.e, f), followed by the fishery independent monitoring survey for recruits (standardized residual = 1.5221, Fig. 4.1.3.g, h), the next index was the MRFSS/MRIP index (standardized residual = 1.7334, Fig. 4.1.3.i, j), followed by the Riley’s Hump index on spawning fish (standardized residual = 1.8085, Fig. 4.1.3.k ,l), the poorest fit was to the headboat index (standardized residual = 2.1292, Fig. 4.1.3.m, n). The plots of age compositions for landings are shown in Fig. 4.1.4, discards (Fig. 4.1.5), and indices (Fig. 4.1.6). - Total and Spawning Stock Biomass - Table 4.4 lists the total biomass at the beginning of the year, spawning biomass at the beginning of May, and the exploitable biomass at the beginning of the year based on overall selectivity. The total biomass of Mutton Snapper declined to a low in 1994 and then has been increasing ever since (Table 4.4, Fig. 4.4). Spawning biomass shows a similar pattern with a low in 1994 and then higher levels afterwards. Exploitable biomass consists of those fish that can be harvested legally and has accounted for about 60% of the total biomass (1981-2013 average 58%). The exploitable biomass has varied little over the years but also reached a low in the early 1990s and then has increased. The decline in exploitable biomass in 2012 as 2013 but not in spawning biomass may reflect the low recruitment in 2010 and 2011. The spawning biomass retrospective pattern was minimal with a slight tendency to increase as more years were added to the analysis (Fig. 4.4.c). - Fishing Mortality, Landings, and Discards - The total fishing mortality rates for age-3 fish has been variable, peaking in 1984 at 0.40 per year, and then the rate declined reaching a low of 0.08 per year in 2001 and then increased again to 0.27 per year in 2008 (Table 4.6.1, Fig. 4.6.1a). The larger error bars in the early years reflects the lack of age samples from the fleets. The fishing mortality rate in 2013 was 0.18 per year. Recreational fisheries account for most of the mortality on Mutton Snapper (Headboat in 2013 was 0.02 per year and MRFSS/MRIP was 0.15 per year) while the commercial fisheries accounted for about 0.01 per year (Fig. 4.6.1b). As a reasonableness check, we calculated a total mortality of 0.24 per year using landings-weighted ages (3-40 years) from 2011 – 2013 with a Chapman-Robson catch curve (Chapman and Robson 1960, Murphy 1997). With an average natural mortality for ages 3-40 years of 0.11 per year, the fishing mortality from the catch curve was 0.13 per year. The geometric mean fishing mortality from ASAP for the same years was 0.12 per years. While there are different assumptions involved with the two methods, the similarity is encouraging. The retrospective pattern in fishing mortality rates was minimal (Fig. 4.6.1.d). The fishing mortality rates for discards shows that few fish older than four years are released alive (Table 4.6.2). - Benchmark / Reference Points - For Mutton Snapper, the Council’s chose F30% as a proxy for the fishing mortality rate producing maximum sustainable yield/Overfishing Limit and the equilibrium spawning biomass associated with F30% as the biomass measure (SSBF30%). Because of the uncertainty in the estimate of fishing mortality in the terminal year, typically the geometric mean of the most recent three years is used to indicate the current fishing mortality rate (Fcurrent) and that value was 0.12 per year in the base model. With an estimate of F30% (MFMT) of 0.18 per year; the F-ratio was 0.66 indicating that Mutton Snapper was not undergoing overfishing. The estimated spawning biomass in 2013 was 2,354 mt and the equilibrium spawning biomass at F30% was 2,109 mt for a biomass ratio of 1.13 indicating that for the base run, Mutton Snapper was not overfished. The Minimum Spawning Stock Threshold, MSST = (1-M)*SSB F30%, was 1,877 mt and had a MSST biomass ratio of 1.27. For age-4 being fully selected instead age-3, the numbers were MFMT = 0.20 per year and Fcurrent was 0.12 per year for an F-ratio of 0.62. The biomass and yield numbers are the same as with age-3 being fully selected. A phase plot of the F-ratio on the biomass ratio from the MCMC simulations is in Fig. 4.8.1. None of the F-ratios from the MCMC outcomes were greater than 1.0 and only 6.2% of the SSB-ratios were less than MSST and 24.3% were less than the SSB at F30%SPR. Plots of static and transitional spawning potential ratios by year indicate that SPR has been increasing since the middle 1990s which coincides with the increase in minimum size to 16” TL for retention in 1994 (see F.A.C. chapter 68-14 in Florida FWC 2015) in state waters of Florida and in federal waters of the South Atlantic region (SAFMC 1994, Amendment 7 to the Snapper Grouper Fishery Management Plan). In 1999, regulations for federal waters for many reef fish were made compatible with Florida regulations (GMFMC Reef Fish Amendment 16B, 1999), but the impact on biomass trends of these regulations was less apparent on Mutton Snapper biomass.