Egg loss in females of two lithodid species following different return-to-the-water protocols

Abstract

Coastal waters of the southern tip of South America have sustained a mixed king crab fishery since the 1930s, with two target species: the southern king crab Lithodes santolla and the stone crab Paralomis granulosa. The fisheries are managed with the so-called 3S rule (Sex, Season, and Size) and females mustbe returned to the water. In king crabs, fecundity can be reduced by several mechanisms, but those related to fishing activities are only partially known. In this article, we tested experimentally whether egg loss is caused by the return of L. santolla and P. granulosa ovigerous females to the water. To do so, we performed experiments for each species with a 3 × 2 different return-to-the-water conditions: free fall, ramp, or a no-fall (control), with or without previous aerial exposure of females. Our experiments demonstrate that free fall impacts, similar to the normal practice in the fishery of the Beagle Channel,result in egg loss in both the species. Female L. santolla lost more eggs if females were exposed to air prior to the dropping. Also, eggs with more developed embryos were likely to be lost as a result of tumbling. In both the species,the use of a ramp for the returning of crabs to water caused an egg loss similar to those of the experimental controls. In P. granulosa fecundity from three areas with different fishing effort suggest that the return of females to the water may be a negative effect that could be detected at a populationlevel. To our knowledge, this is the first study that demonstrates the egg loss of female crabs returned to the water in a fishery.