Changes in parasite-chaetognath species assemblages in the Mexican Central Pacific before and during El Niño 1997-1998.

We investigated the seasonal and interannual changes in diversity, abundance, and prevalence of chaetognaths and their parasites collected monthly during 1996-1998 in the Mexican Central Pacific. We tested the hypothesis of a positive relationship between abundance and species richness of chaetognaths and their parasites, and investigated the influence of the 1997-1998 El Niño event on this host-parasite interaction. Of the 9 chaetognath species collected in the present study, only 7 were found to be parasitized.