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In the presently reported study, we estimated length--weight relation (LWRs) for seven species of freshwater fishes from Central America. Samples were collected using seines from 60 sites across Nicaragua, Costa Rica, and Panama during field expeditions conducted between 1997 and 2012. The fishes were preserved and transported to the lab, where their total weight (W) was measured (to nearest 0.0001 g) and standard lengths were taken (to nearest 0.01 mm). Data were collected from four livebearers (Poeciliidae), Alfaro cultratus (Regan, 1908), Phallichthys amates (Miller, 1907), Poecilia gillii (Kner, 1863), and Priapichthys annectens (Regan, 1907); the cichlids (Cichlidae), Parachromis dovii (Günther, 1864) and Parachromis managuensis (Günther, 1867); and a silverside (Atherinopsidae), Atherinella hubbsi (Bussing, 1979). Estimates of parameter b ranged from 2.936 (A. hubbsi) to 3.696 (P. gillii), while estimates of parameter a ranged from 1.7 x 10-6 (P. gillii) to 1.9 x 10-5 (P. managuensis). Parameter b estimates were greater than three, consistent with allometric growth, with the exception of P. annectens, P. managuensis, and A. hubbsi, for which t-tests failed to reject the null hypothesis of isometric growth. Our results provide the first LWR information for five (71%) of these species and may prove useful for data imputation or estimating the biomass of poeciliid, cichlid, and atheriniform fishes in Central American rivers in the future. [ABSTRACT FROM AUTHOR]

One of the original goals of phylogeography was to use genetic data to identify historical events that might contribute to breaks among communities. In this study, we examine the phylogeography of a common livebearing fish ( Poecilia gillii) from Costa Rica. Our goal was to determine if phylogeographical breaks in this species were congruent with previously defined boundaries among four fish community provinces. We hypothesized that if abiotic factors influence both community boundaries and genetic structuring in P. gillii then we might find four clades within our focal species that were geographically separated along community boundary lines. Similarly, we expected to find most of the genetic variation in P. gillii partitioned among these four geographical regions. We generated DNA sequence data (mitochondrial cytochrome b and nuclear S7 small ribosomal subunit) for 260 individuals from 42 populations distributed across Costa Rica. We analysed these data using phylogenetic (parsimony and likelihood) and coalescent approaches to estimate phylogenetic relationships among haplotypes, patterns of gene flow and effective population size . Contrary to our expectations, we did not find four monophyletic groups that mapped cleanly to our geographical community provinces. However, one of our clades was restricted to a single province, suggesting that common earth history events could be responsible for both genetic structuring in P. gillii and fish community composition in this area. However, our results show a complex pattern of gene flow throughout other regions in Costa Rica where genetic structuring is not predicted by community province boundaries. [ABSTRACT FROM AUTHOR]

Pesticide chemical residues in water samples and biomarker responses in transplanted fish were used to monitor environmental hazards of pesticides in Palo Verde National Park (Costa Rica). The Costarican fish, Parachromis dovii (Ciclhidae) and Poecilia gillii (Poecillidae), were selected as sentinel species. Contaminant analyses detected up to 15 different pesticide residues in water with hexachlobenzene (2261 ng l(-1)), phorate (473 ng l(-1)), epoxiconazole (314) and bromacil (117 ng l(-1)) being the compounds found in higher concentrations. Biomarker responses evidenced impacts on cholinesterase activities in transplanted fish at Barbudal site probably due to the presence of organophosphate insecticides such as phorate. High enzyme activities of glutathione S-transferase and catalase and elevated levels of lipid peroxides were also observed at a site impacted by rice fields (Cabuyo); those effects could be associated with the presence of hexachloro benzene and triazole fungicides. In general, P. dovii biomarkers were affected to a greater extent than those of P. gillii in fish transplanted to sites associated with agriculture, which suggests the former species is a good candidate for future surveys.