Initial six-year expansion of an introduced piscivorous fish in a tropical Central American lake

Two populations of the piscivorous fish Gobiomorus dormitor (the 'guabina') were examined in two separate crater lakes in Nicaragua, Central America. At Lake Apoyo, G. dormitor were introduced in May 1991 by local fishermen and have invaded successfully; at Lake Xiloa, the population is naturally occurring. To provide baseline life history data for G. dormitor in both lakes and to test hypotheses related to population growth and invasion success, this study aimed to (1) document and define the population growth and depth distribution of the fish through video transects in Lake Apoyo; (2) compare diet composition between lakes; and (3) compare life history parameters between lakes, including relative growth rates and reproduction. Videotaped transect studies, designed originally to examine cichlid breeding, began in both lakes in 1990 and have documented the subsequent increase of G. dormitor. Yearly means generally fit the exponential growth model. G. dormitor foraged mainly in shallow waters in Lake Apoyo and preyed mostly upon the atherinid Melaniris cf. sardina throughout seasons. In Lake Xiloa, cichlid fry constituted the majority of the diet overall and cannibalism was more common, although this trend varied with the cichlid breeding season. Relative growth rates were significantly different, based on otolith mass regressions on standard length. Lake Apoyo G. dormitor generally behaved as a successful invading species, displaying exponential growth, year-round reproduction, and higher foraging success than the natural population of Lake Xiloa. Further research is planned to explore the G. dormitor invasion when the population becomes integrated into the community.