Emerita analoga, an Anomura marine benthíc crab of the Peruvian coast maerozoobenthos ís one of the organisms that the RIBEN monítors to determine the influenee of "El Niño" events. Sampling was carried out biweekly in San Jase beach (Lambayeque) from April 1996 to July 1998. Cephalotoraxic length (Le mm) and total weight (g) was registered. The ovígera mass was weighed, and a portion of 0,05 9 was used for eggs and breeding count lo estimate fertility and eontribution of breeding. The data were processed statistically comparing the indíviduals of April 96 -Mareh 97 with those of April 97 July 98 ("El Niño 1997-98"). The fertility of ovigera females in stadium Ov-1 range from 983 to 17517 (mean 5782), and from 1 100 to 18210 (mean 8534) eggs, for the periods April 96-Mareh 97, and "El Niño", respeetively. This significant differenee was also evident tor Ov-2; however, in relatíon to the sizes in which fertility inerease with the increment of Le, "El Niño 1997-98" had a negative effect. The fertility -Le regressíons were different, being the fertility of E. anafoga affected negatívely by the "El Niño 1997-98"; in a same way, it influenced negatively in its condition (weight-Iength). "El Niño 1997-98" affected the given breeding positively, beca use during the pick of this event E. anafaga presented another reproductive period that has allowed a good reeruitment and the recovering of the population that had disappeared.
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