The present study describes a remarkable caudal regeneration capacity of Physiculus cyanostrophus, a benthopelagic fish from the twilight zone. This trait reveals the ability of this particular morid to survive attacks that would be lethal in other species. In teleosts, the most widespread sublethal predation is confined to scale-eating and fin-nipping by specialized predators. In P. cyanosytrophus the larger sized individuals the greatest amount of tissue loss occurred in the caudal region (maximum 28 vertebrae, corresponding to 45% lost body length). The amount of regenerated tissue was independent of body losses and ranged between 5 and 19% of total length for the entire range of sizes. The frequency of regenerated individuals in the population increases with ontogeny (16.8–67.5%). Tissue losses represent a significant allocation of costs in terms of growth and offspring production. Nevertheless, regeneration capability decreases mortality in the large breeding females of a population, maximizing maternal fitness.