Fishery-dependent stock assessment of crayfish in the eastern Atchafalaya River basin, Louisiana

ABSTRACT Objective The wild crayfish harvest in the Atchafalaya River basin (ARB) is the largest in North America. However, there have not been extensive crayfish stock assessments in the ARB due to minimal harvest regulations, a lack of population data and reporting from harvesters, and the enormous ARB spatial scale. The purpose of this research was to obtain a crayfish stock assessment in the eastern ARB by partnering with a local crayfish processor that purchases crayfish from harvesters throughout the ARB. Methods Crayfish harvest data were collected in 2018 and 2019 from harvesters and included the number of traps fished, total weight of crayfish collected, and ARB spatial zone where crayfish were harvested (upper, middle, or lower). Crayfish species, sex, carapace length, and male reproductive form were examined weekly from three subsamples of at least 400 individuals from different harvesters in each zone (1,200 crayfish · week−1 · zone−1). A minimum of 100 female red swamp crayfish Procambarus clarkii were collected monthly from three different harvesters in each zone (900 females/month; 300 females/zone) to determine ovarian maturation. Results In 2018, the lower zone had a significantly lower mean weight of crayfish per trap, and red swamp crayfish in the upper zone had a shorter mean carapace length. The atypically large ARB flood pulse in 2019 contributed to the reduced mean crayfish harvest and red swamp crayfish carapace length observed compared with 2018. Smaller-mesh traps used by harvesters in the upper zone influenced mean crayfish size and weight per trap. Sexually mature female red swamp crayfish increased after May, with 50% population maturation at the beginning of July. Conclusions These results provide novel, high-quality fisheries-dependent data for the stock assessment of the ARB crayfish fishery. The effects of trap mesh size, flood pulse dynamics, and female maturation on the fishery provide baseline data for resource managers and future management decisions on the crayfish fishery.