Reproductive dynamics of the sea cucumber Holothuria arguinensis: Biological insights to support fisheries management

Sea cucumbers, a crucial component of benthic ecosystems, are increasingly studied for their ecological significance and economic value. With rising demand leading to overexploitation, species such as Holothuria arguinensis in the NE-Atlantic have become new targets for fisheries. Understanding their reproductive biology is crucial for effective and informed management and conservation efforts. This study examines the reproductive cycle of H. arguinensis in an unexploited population along the southwestern coast of Portugal over 18 months, with monthly samplings and concurrent environmental data collection. The study found a balanced sex ratio (1:1) with no significant sexual dimorphism in size, though females had significantly higher gonad weights and gonadosomatic indices (GI), indicating greater reproductive investment. Reproductive activity peaked from April to July, aligning with longer photoperiods and higher seawater temperatures. The size at first maturity was 204 mm for males and 203 mm for females, suggesting early maturity. Environmental analysis showed that photoperiod positively affects GI, while higher temperatures trigger spawning events. Peaks in chlorophyll-a corresponded with spawning, suggesting phytoplankton biomass may cue reproduction. This study also highlights differences and similarities among populations, prompting whether additional variables or more complex interactions shape reproductive cycles beyond photoperiod, temperature, and phytoplankton biomass. These findings underscore the need to protect larger, fecund individuals to maintain population resilience and ensure sustainable harvesting. Furthermore, they reinforce the importance of research on reproductive drivers and management. This research provides critical data for developing fisheries management and conservation strategies for H. arguinensis in the NE-Atlantic, ensuring the species' long-term sustainability.