Using life-history information to identify management priorities within an emergent multi-species grey mullet fishery

Three grey mullets are native to the United Kingdom: Chelon labrosus , Chelon ramada , and Chelon auratus, for which there is an emergent fishery. These species are managed under a broad grey mullet fishery, but aspects of the life-histories of these populations remain undetermined. The fishery has never been formally assessed. For each species, this research i ) investigated their life-history, ii ) quantified relative fishing pressure, and iii ) investigated their relative vulnerability to overfishing. Grey mullets were collected from commercial fisheries along the southern coast of England. Fish were weighed, measured, and ages were assigned by counting scale annuli. Maturity was determined through macroscopic inspection of gonads. Fecundity was estimated for ripe females using the gravimetric method. Length and age at maturity were estimated from logistic models on maturity ogive data. Age-length relationships were investigated using von Bertalanffy growth models. Catch curves were used to estimate relative mortality rates, from which the exploitation ratio was calculated. A productivity susceptibility analysis (PSA) was applied to investigate the relative vulnerability of each species using a scenario-based approach: i ) data collected in this study only, ii ) best-case, and iii ) worst-case scenarios. The PSA suggests that C. labrosus are most vulnerable to overfishing, despite not being explicitly targeted by the fishery, partially due to being the least productive species (long-lived with late sexual maturation and limited fecundity). This research demonstrates that individual species respond differently to fishing pressure, and managing groups of species under a broad fishery may disproportionately impact the most vulnerable species.