Last updated on 27 March 2018
The most recent benchmark stock assessment for red grouper in the Northern Gulf of Mexico was conducted through the Southeast Data, Assessment, Review (SEDAR) process with data through 2013 (SEDAR 2015). The data and assessment team consisted primarily of federal agency staff with additional representation from state agencies, universities, environmental groups, and scientific and advisory bodies of the Gulf of Mexico Fishery Management Council. The review panel consisted of members from the Center for Independent Experts (CIE) and the GMFMC Scientific and Statistical Committee (SSC). The preferred model was developed using Stock Synthesis 3 (SS3), an integrated statistical catch at age model used widely in the US and internationally. Input data included commercial and recreational harvest and discards plus a “fleet” to account for red tide mortality, four fishery-dependent and three fishery-independent indices of abundance, sector specific age and length composition data, and other biological information. Fishery and index selectivity was modeled for each fleet and index separately. Uncertainty in model results was investigated using a range of sensitivity runs to evaluate assumptions regarding data inputs and model configuration, plus a retrospective analysis. Projections across a range of fishing mortality rates investigated harvest and stock status over a 17 year time horizon (SEDAR 2015).
Last updated on 23 January 2018
Biological reference points were first established for Gulf of Mexico red grouper through the Generic Sustainable Fishery Management Act Amendment (GMFMC 1999), which recommended managing the stock based on spawning potential (SPR) as a proxy MSY-based reference points. A 2002 stock assessment determined the stock was overfished, resulting in a Secretarial Amendment that refined the biological reference points and implemented a 10-year rebuilding plan (GMFMC 2004). Annual catch limits and targets (ACL, ACT) were established for three years under the Secretarial Amendment, and have been re-evaluated regularly and adjusted appropriately (GMFMC 2008)(GMFMC 2011)(GMFMC 2016). GMFMC (2008) also established sector allocation of the ACL as 76% commercial and 24% recreational. A peer reviewed stock assessment in 2015 determined that red grouper in the Gulf of Mexico are not overfished and overfishing is not occurring. Applying established harvest control rules to the biomass estimates from this assessment resulted in increases to allowable harvest levels that were considered excessive (GMFMC 2016). A more conservative ACL was set, with sector specific ACTs determined as 95% of the commercial ACL and 92% of the recreational ACL based on an accepted ACT/ACL buffer determination strategy (GMFMC 2016).
Last updated on 23 Jan 2018
Biological reference points based on spawning potential ratio (SPR) were established for Gulf of Mexico red grouper through the Generic Sustainable Fishery Management Act Amendment (GMFMC 1999), but were revised to MSY-based reference points through Secretarial Amendment 1 (GMFMC 2004). During the 2015 stock assessment, stock status was evaluated relative to the MSY-based reference points, but the peer review panel recommended reverting back to SPR-based reference points due to uncertainty in fitting the spawner-recruit relationship necessary to estimate MSY reference points (SEDAR 2015). Stock status in the 2015 assessment was therefore evaluated using a biomass target of 30% of maximum spawning potential (SSB30%SPR; measured in terms of fecundity), a minimum stock size threshold (MSST) of (1-M)*SSB30%SPR, and a corresponding fishing mortality threshold that achieves the biomass target at equilibrium (F30%SPR) (SEDAR 2015). The assessment reports these values as F30%SPR = 0.204, SSB30%SPR = 1,203,500 eggs, and MSST = 1,035,000 eggs (SEDAR 2015).
Last updated on 27 March 2018
Terminal year spawning biomass (measured in fecundity) was estimated as SSB2013 = 2.223 million eggs, relative to the biomass target of SSB30%SPR = 1.204 million eggs (SEDAR 2015). The estimated fishing mortality in the terminal year of the assessment of F2013 = 0.121 is approximately 59% of the fishing mortality threshold of F30%SPR = 0.204 (SEDAR 2015). Results of the benchmark assessment indicate terminal year SSB exceeds the SSB target, and fishing mortality is well below the threshold, suggesting the stock is not overfished and overfishing is not occurring. Commercial landings increased in 2014, but declined to previous levels in 2015 and 2016, and have remained below the ACT in all years since the terminal year of the assessment (NMFS 2017).
Last updated on 27 Mar 2018
Spawning biomass (total fecundity) was relatively stable during the first decade of the stock assessment time series, fluctuating without trend between approximately 1.15 billion and 1.22 billion eggs from 1986 to 1997. Beginning in 1998, spawning biomass rose steadily to over 1.92 billion eggs by 2005. A red tide event occurred in 2005, causing significant mortality, which resulted in an abrupt decrease in spawning biomass back to pre-1998 levels. Since then total fecundity has increased rapidly, reaching a time series high of 2.25 billion eggs in 2012. Spawning biomass in the terminal year of the assessment was estimated at SSB2013 = 2.22 billion eggs.
Fishing mortality shows a generally inverse trend compared to spawning biomass. Harvest rates were generally stable around F = 0.2 during the early years of the assessment, but declined by approximately 50% from the early 1990s to early 2000s. The red tide event caused a spike in mortality (attributed to fishing) to over 0.47. Following the spike, mortality rates resumed their previous decline, reaching a time series low of F = 0.07 in 2010 before rising slightly in subsequent years. Terminal year fishing mortality is estimated as F2012 = 0.108.
Quota monitoring results for commercial red grouper are provided back to 2004 (NMFS 2017). From 2004 to 2010, landings generally declined from a high of 5.5 million pounds gutted weight (lb gw) (2,495.5 t) in 2004 to a low of 2.9 million lb gw (1,315.8 t) in 2010. In 2011, commercial landings increased to 4.8 million lb gw (2,177.9 t) and have fluctuated without trend between this value and 5.6 million lb gw (2,540.8 t) through 2016 (NMFS 2017).