Reproductive timing and intensity in a Galápagos intertidal mollusc are modulated by thermal phases.

The decline in finfish fisheries has increased the harvesting of coastal invertebrates, particularly molluscs. To understand how the endemic Galápagos chiton Radsia goodallii withstands harvest pressure, its reproductive traits were assessed on San Cristóbal Island across three El Niño thermal phases. Reproductive timing, duration, and intensity were found to vary significantly across thermal conditions, with a distinct cycle and peak gonadal investment approximately every four months. Reproductive intensity was highest during the cooler El Niño phase, whereas the duration of gonad maturity extended during warmer periods. Shifts in timing were evident in the onset of reproductive activity across phases. A male-biased sexual asymmetry in gonadal investment, combined with a higher number of females, suggested low sperm competition and potentially influenced male reproductive effort. Larger individuals exhibited greater reproductive capacity, indicating size-related reproductive optimization. Although a tropical species, R. goodallii displayed reproductive patterns more typical of temperate species, likely shaped by the Galápagos' unique oceanographic conditions. These findings improve understanding of the species' reproductive strategy and offer practical management insights, such as setting minimum catch sizes to protect juveniles until maturity or enforcing seasonal closures during reproductive peaks to support sustainable harvesting.