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Reproductive and morphological indicators of the fish Gambusia puncticulata (Poeciliidae) in very polluted sections of Almendares River, Cuba. The Almendares River watershed covers a large portion of Havana city. Human activities have negative impacts over it. We studied the alteration of biological processes in fish from polluted sites. Stressor-based cumulative effects assessment was applied at individual level in Gambusia puncticulata (Poey, 1854). Three sites of Almendares River were sampled monthly from July 2006 to June 2007. Length and weight of females, and condition factor for both sexes, were higher in the impacted sites. An increase of food supply due to eutrophication can explain why fishes are heavier and longer at polluted sites. Gonadosomatic, specific fecundity index and embryo numbers were significantly higher on the reference site. The Hepatosomatic index was higher in females from the most contaminated sites. Differences in δ 13 C and δ 15 N among contaminated and reference sites suggest that the food source is not the same.

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The Almendares River is the largest river draining the area around Havana City, Cuba. The watershed is heavily populated and industrialized, which has had a significant impact on the flow and water quality of the river. The main goal of this study was to analyze the spatial variability in dietary habits, nutrient flow (using stable isotope ratios δ(15)N and δ(13)C), and mercury (Hg) levels along the Almendares River upstream and downstream of point-source discharges using localized fish Gambusia puncticulata. Stomach contents of G. puncticulata were similar among these sites. However, mean δ(15)N values ranged from 6 to 18 ‰ across sites and were lower in fish from downstream than upstream sites, suggesting localized influences of nutrient inputs along the river. δ(13)C values were between -22 and -25 ‰, except at a mid-basin site (-26 to -27‰), indicating that fish relied on similar carbon sources at most sites. Total mercury concentrations ranged from 0.04 to 0.49 μg/g wet weight whole body and were unrelated to the among-site differences in δ(15)N, but Hg exceeded the threshold considered to be protective of fish health (0.2 μg/g ww whole body) in the majority of fish from all sites but one. Results of this study indicate that although the dietary habits of this species do not vary across sites, tissue differences in δ(15)N, δ(13)C and Hg show little movement of this species among sites. Localized effects of human activities on nutrients and metals may be affecting the health of this species and posing a risk to other consumers in the ecosystem.

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