GDAR01 Gulf of Mexico Blue Crab
The Gulf States Marine Fisheries Commission (GSMFC) has completed a Gulf-wide assessment of the blue crab populations in the Gulf of Mexico. The regional assessment has been completed through the GSMFC's Gulf Data, Assessment, and Review (GDAR) Program as GDAR01. Each of the five state marine resource agencies provided blue crab experts and analysts to develop abundance indices for use in surplus production models. Much of this work was influenced by assessments already completed in Louisiana, Florida, Texas, and the Chesapeake Bay.
The assessment is the culmination of a year-long effort to gather all of the available data from the commercial fishery, the recreational fishery, and the individual state agencies' independent sampling for blue crabs.
The final GDAR01 Assessment Report, with the GDAR01 Reviewers' Report included, is available as an Adobe PDF file. Please cite the Assessment Report as:
VanderKooy, S. (ed). 2013. GDAR01 Gulf of Mexico Blue Crab Stock Assessment Report. Gulf States Marine Fisheries Commission. Ocean Springs, MS. GSMFC Number 215. 313p.
The coding for both the modified catch-survey and the surplus production models are available as an RTF file at http://www.gsmfc.org/pubs/IJF/GDAR01/GDAR01 Model Code.rtf
The blue crab, Callinectes sapidus, has the broadest latitudinal distribution of all the Callinectes species, ranging from Nova Scotia and Maine to northern Argentina and is found throughout the US Gulf of Mexico (GOM). Based on tagging and genetic investigations, two potential management populations may exist in the Gulf of Mexico: a Florida or "Eastern GOM stock" occurring along the Florida coast to Apalachee (centered in Tampa Bay), and a "Western GOM stock" occurring from central Texas to Apalachicola Bay and centered in Louisiana. Using this population structure, we provide quantitative analyses on the status of the Western and Eastern stocks through 2011.
Total reported commercial blue crab landings in the Gulf have increased from less than one million pounds in the late 1800s when landing statistics were first collected, to approximately 18 million lbs prior to World War II. Landings increased markedly in the late 1950s with introduction of the wire trap that replaced traditional trotlines by the mid-1960s. The increased availability of raw product associated with adoption of the wire trap stimulated processing capacity and market development, and landings continued to rise through the 1980s. Record landings of 78 and 79 million pounds occurred in 1987 and 1988, respectively. Although landings continue to fluctuate, a general downward trend in Gulf-wide landings began in 2000 and has continued through 2010. Natural and anthropogenic events as well as changes in management measures may have directly influenced landings. These include a number of catastrophic hurricanes and the sinking of BP's Deepwater Horizon oil platform off Louisiana in 2010 that closed most of the north-central GOM to harvest during the most productive portion of the fishing season.
Fishery-independent estimates of abundance for both juvenile and adult stocks have shown either decreasing or steady trends throughout the last two decades while commercial landings have declined. The Western stock has undergone a strong decline in juvenile abundances since the mid-1980s, and a decline in adult abundances from the mid-1980s until the mid-1990s, after which it has remained relatively stable. Eastern stock adult abundances have shown a similar trend (declining through the mid-1990s and stable since), while the juvenile abundance has been relatively stable since the late 1980s. In both stocks, the abundances have experienced substantial variability from year-to-year, and in the case of the Eastern stock, these abundances typically peak in years following high rainfall.
In this assessment, we employed two separate modeling approaches to address the GOM stocks. The primary model was a modified catch-survey analysis similar in structure to those used in previous blue crab stock assessments (Chesapeake, Louisiana, Florida, Delaware), while the supporting model was a surplus production model. The estimated MSY from the base model configuration was 164 million individuals for the Western GOM stock and 23 million individuals for the Eastern GOM stock, where fisheries on both stocks have landed less than the MSY for the majority of the time series. The Western GOM stock experienced overfishing in 1999 and 2002, while the Eastern GOM stock experienced overfishing in 1996 and 1998. The base model found that both stocks are currently neither overfished nor undergoing overfishing, although the Western stock is in a depressed state and approaching an overfished limit.