Life history variation in introduced populations of the Mayan cichlid, Cichlasoma urophthalmus, in the Everglades

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Jay M. Savage, Committee Chair


Life history strategies were described for three introduced populations of the Mayan cichlid, 'Cichlasoma' urophthalmus in the Florida Everglades. The three populations represented three distinct habitat types recently invaded by the Mayan cichlid: freshwater sawgrass wetland, freshwater flooded cypress forest, and brackish mangrove canal. Fish were collected monthly using cast-nets over an 18 month period in 1996--7. Somatic growth rates, condition, and female reproductive allocation were compared across the three populations, and to published data from Mexican studies.Somatic growth rates of adult size fish were compared using otolith mass-body length relations. These results suggest that cypress forest fish exhibited faster growth. Abiotic and biotic factors were evaluated as potential explanations for the observed differences in growth rate. The differences among the populations could not be explained by geographic proximity, hydrologic similarity, water temperature, salinity, length-frequency distributions, or age composition. Although dietary differences could not be excluded, higher growth rates in the cypress forest population were attributed to either a life history strategy of reduced gonad investment, or a new population effect of intra-specific competitive release.Fulton's K condition factor was used to determine somatic condition for each adult fish sampled. Condition factor varied seasonally both within and across sites, and increased with rising water levels. Overall, condition was highest in the cypress forest population. The brackish mangrove population showed the least seasonal fluctuations, but exhibited markedly lower condition than the other populations. Condition factor was also calculated for fish collected in an earlier Mexican study at Celestun Lagoon, Yucatan. Condition factor of Mexican fish was about 20% higher than that of the Florida fish.Female reproductive allocation strategy was compared using fecundity counts and oocyte size measurements. Fecundity varied across sites, with higher fecundity at the cypress and mangrove populations. Comparisons were complicated by the lack of linear length-fecundity relations at the sawgrass and mangrove sites. Oocyte diameter was highest for the sawgrass population. Thus, there appears to be a trade-off between oocyte size and number, with the sawgrass females allocating their resources differently from the other populations.


Biology, Ecology; Biology, Entomology; Agriculture, Fisheries and Aquaculture

Link to Full Text