Sublethal effects of environmental concentrations of caffeine on a neotropical freshwater fish.

Caffeine is a contaminant frequently detected in water bodies. Growth trends in both human population and caffeine consumption per capita are expected to exacerbate the occurrence of caffeine in freshwaters. Yet the effects of caffeine on native fish fauna are poorly understood. We exposed larvae of an endemic Neotropical catfish (Rhamdia quelen) to a range of caffeine concentrations for 30 days. We found that larvae exposed to the highest concentration (16 mg L-1) showed skeletal deformations and reduced growth. We further compiled measured environmental concentrations of caffeine in surface freshwater globally and performed a risk assessment. Our analysis points to a low risk to R. quelen and equally sensitive fish species in ~90% of the freshwater ecosystems considered in our analysis. The risk quotient is higher in freshwater ecosystems of South and Central America, where R. quelen is endemic. Although the ecotoxicological risk is currently low in most places, increased caffeine consumption, exacerbated by the lack of sanitation, is expected to increase caffeine concentrations in many parts of the world, posing a threat of sublethal morphological effects to local fish species.

Effects of pH on the incubation and early development of fish species with different reproductive strategies.

Fish reproduction in natural environments tends to occur in conditions, including extreme pH values, ideal for the survival of offspring. In this context, the purpose of this study was to assess the influence of pH on both survival and early development of two fish species, Astyanax lacustris (short-distance migrating fish) and Piaractus mesopotamicus (long-distance migrating fish), with different reproductive strategies. Our experiments were divided into two tests (incubation and larviculture) at five pH levels. First was incubation through a water recirculation system using 2 L incubators followed by larviculture using a 2.5 L aquarium. pH had no influence on the hatching rate of A. lacustris eggs, but affected the yolk-sac diameter, while the newly-hatched larvae had some skeletal disorders. For P. mesopotamicus, pH influenced the hatching rate and perivitelline space, while the newly-hatched larvae had several skeletal disorders. The larviculture of A. lacustris revealed no effect on the survival rate, but the analyzed morphometric variables indicated significant differences between the treatments. An acidic pH negatively influenced the survival rate of P. mesopotamicus, and all morphometric variables also varied significantly between the treatments. We concluded that both the survival and development of A. lacustris and P. mesopotamicus revealed different responses at pH levels during incubation and larviculture tests.