Population Dynamics of Introduced Sunfish Species to Tropical Reservoirs

Three species of sunfish (redear, redbreast, and bluegill) were introduced in Puerto
Rico’s reservoirs decades ago to expand anglers’ opportunities and as forage for
predator species. Since 2006, we have been monitoring these fish via boat mounted
electrofishing. For many years, all sunfish species had shown “stable” populations.
However, in recent years a rapid decline, particularly in redear sunfish, which
previously was extremely abundant, was detected. In some reservoirs, the redear
sunfish CPUE decreased from 27 fish/hour (2006) to 10 fish/hour (2012) while in
others, they have practically disappeared, declining from 20 fish/hour (2006) to 0
fish/hour (2013). The same trend has been observed with the two other sunfish
species that have disappeared from the majority of the monitored reservoirs. Two
potential explanations are provided. The first - predation on sunfish eggs and
juveniles and competition for food by the invasive Red Devil cichlid. The second -
overharvest of sunfish for human consumption.