Modeling potential consequences of climate-driven sex reversal on Southern and Summer Flounder population dynamics

Objective

We investigate the interacting effects of fishery selectivity and sexual dimorphism by using the fisheries for Southern Flounder Paralichthys lethostigma and Summer Flounder P. dentatus as case studies. In both species, females are larger than males, and temperature-sensitive sex determination can lead to an increased proportion of males at sexual differentiation in warmer temperatures.

Methods

We developed a size-, age-, and sex-structured population dynamics model for each species to understand how temperature-induced sex reversal will interact with harvesting to impact population productivity. We considered scenarios with realistic sex ratios and varying levels of fishing pressure.

Result

Our models of these species show that population egg production, abundance, biomass, and catch will all be constrained if sex ratios at differentiation become more male-biased. For both species, climate-induced changes to the sex ratio in early-life stages could have a greater impact on relative catch than fishing mortality. We demonstrate that the spawning potential ratio may not be sensitive to climate-induced changes in the sex ratio unless we account for changes in the sex ratio at differentiation in the historic baseline reproductive potential.

Conclusion

These findings underscore the importance of utilizing sex-specific stock assessments for species with temperature-sensitive sex determination mechanisms.