Seasonal dynamics of the reproductive effort and first maturity of Chinese hat snails Trochita trochiformis (Born, 1778) in Guerrero, Mexico: Towards a sustainable fishery management

The Chinese hat snail Trochita trochiformis is a valuable gastropod for artisanal fisheries on the southeast coast of Guerrero, in the Mexican Pacific. The knowledge of the reproductive biology of this species is of the utmost importance to assess the renewal capacity of natural stocks, thus ensuring sustainable management strategies, particularly in the case of this heavily exploited resource. Here, we investigated gametogenesis, reproductive effort and the size at first maturity of T. trochiformis over a 2-year cycle using qualitative and quantitative histological techniques. Gonad development was classified into 6 different stages for both males and females, ranging from immature to spent sexual structures. Moreover, the first records of protandric sex reversal were reported for this species. Snails were able to reproduce throughout the year, with maximum peaks of gonad development occurring during winter at minimal sea surface temperatures of around 27 °C; whereas spawning and short periods of gametogenic inactivity were observed with rising temperatures (27 °C to ∼31 °C) through spring and summer. The results suggest that female gonads have superior breeding capacity than males, yielding the highest oocyte quality during winter. Shell diameter at first maturity (SD₅₀) was estimated for the first time for this species at 44.8 mm for females, and 45.4 mm for males. Therefore, females are prone to overfishing since nearly 12 % of males changed to females after adult size in this study. Based on these results, two management measures could be applied: 1) a banning period from December to February during the season of greatest reproductive effort, and 2) an initial minimal capture size of ∼45 mm, thus allowing the snails to spawn at least once during the reproductive cycle.