The consequences of size‐selective fishing mortality for larval production and sustainable yield in species with obligate male care

Size-based harvest limits or gear regulations are often used to manage fishing mortality and ensure the spawning biomass of females is sufficiently protected. Yet, management interactions with species9 mating systems that affect fishery sustainability and yield are rarely considered. For species with obligate male care of eggs, it is possible that size-specific harvest of males will decrease larval production. In order to examine how size-based management practices interact with mating systems, we modeled fisheries of two species with obligate male care, Symphodus melops (corkwing wrasse) and Ophiodon elongatus (lingcod) under two management scenarios, a minimum size limit and a harvest slot limit. We simulated the population dynamics, larval production, and yield to the fishery under a range of fishing mortalities. We also modeled size-dependent male care to determine its interaction with management. In both species, the slot limit decreased yield by less than 12% at low fishing mortalities; at higher mortalities, individuals rarely survived to outgrow the slot and spawning potential decreased substantially relative to unfished levels. The spawning potential decreased less when managed with a slot limit if we included a positive feedback between male size, care, and hatching success, but the benefit of implementing the slot depended both on the relative proportions of males and females selected by the fishery and on our assumptions regarding male size and care. This work highlights that the effects of size- and sex-selective fisheries management can be nuanced and produce counter-intuitive results.