Size at sex change in the protandric hermaphrodite <scp>Patagonian</scp> blenny <i>Eleginops maclovinus</i> (<scp>Cuvier</scp>, 1830) in central‐southern <scp>Chile</scp>

Hermaphroditic fish species show low resilience to fishing exploitation, as alterations in sex ratio or size at sexual transition have direct implications for population fitness. The Patagonian blenny is a protandric hermaphrodite of economic importance in Chile, where basic knowledge of its life-history traits remains scarce. Using individuals collected from the artisanal fishery, we estimated the proportion of females at length (P_F) for this species in Chile through histological analysis, and compared our findings with those of previous studies conducted in the southeast Pacific and southwest Atlantic. A total of 301 individuals were collected during March and from July to October 2022, of which 189 gonads were submitted to histological analysis. P_F was estimated using a generalised linear model with a binomial error distribution. Histological analysis indicated that females possess a group-synchronous gonadal development, whose reproductive season occurs during autumn-winter. The sexual transitional phase occurs between 30 and 40 cm in total length (L_T). The fitted ogive of P_F did not differ significantly between macroscopic and histological methods (p > 0.05). However, temporal and spatial variations in P_F were evident when compared to previous studies conducted on both the Pacific and Atlantic sides. In Chile, this study revealed a decrease in the size at sexual transition for this species from 41.6 cm L_T in 1974-1975 to 35.7 cm L_T in 2022, highlighting the need for a monitoring system and the implementation of appropriate management measures.