Initial Six-year Expansion of an Introduced Piscivorous Fish in a Tropical Central American Lake

Two populations of the piscivorousfish Gobiomorusdormitor (the ‘guabina’) were examined in two separate crater lakesin 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 ratesand reproduction. Videotaped transect studies, designed originally to examine cichlidbreeding, began in both lakes in 1990 and have documented the subsequent increase of G. dormitor. Yearly means generally fit the exponential growthmodel. G. dormitor foraged mainly in shallow waters in Lake Apoyo and preyed mostly upon the atherinid Melaniris cf. sardina throughout seasons. In Lake Xiloa, cichlidfry constituted the majority of the diet overall and cannibalismwas more common, although this trend varied with the cichlidbreeding season. Relative growth rateswere significantly different, based on otolithmass 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.