Effects of fishery practices on fecundity of two lithodid crab species of commercial interest in Southern South America

Abstract

The fishery of Lithodes santolla is the second most productive lithodid crab fishery in the world and in southernmost South America is considered a mixed fishery due to its co-occurrence with Paralomis granulosa. Fishing takes place in Argentina and Chile, where regulations restrict to land only males larger than a legal size, but with variable fishing seasons. All females and small males must be returned to water. Both species have long periods of embryogenesis. Individual fishers operate on a small geographic scale, following lithodid crabs which are typically confined to channels, fjords or straits. Therefore females can be fished and discarded on multiple occasions throughout egg-bearing period. We studied the effect of the fishing practices on the fecundity of L. santolla and P. granulosa. First, we experimentally evaluated the effect of seven repeated return-to-water simulations in different conditions: aerial exposition or aerial exposition followed by a free fall (FF) or ramp. Secondly and only in L. santolla, we tested the effect on the egg-loss of different stocking densities followed by a FF return-to-water. Finally, we estimated the fecundity at the beginning and at the end of the egg-bearing period in females of L. santolla. The FF produced a high egg-loss and did not increase with the trial repetitions in L. santolla. Female P. granulosa showed a similar egg-loss pattern for all treatments, and overall lost fewer eggs than female L. santolla. In P. granulosa except for the FF, the trial repetition produced an increase in the egg-loss. In L. santolla there was no effect on the egg-loss due to stocking densities. Based on the field studies, fecundity of L. santolla decreased during the egg-bearing period. This study demonstrated the effects of repetitive fishing events on the fecundity in two lithodid species of commercial interest.