Non-native Pumpkinseed fish (Lepomis gibbosus) are likely to become invasive in England under conditions of climate change, according to a study to be published in a forthcoming issue of the Journal of Fish Biology.
Emily Fobert and coauthors used ambient temperature and heated experimental ponds to examine the competitive interactions between introduced Pumpkinseed and native European perch (Perca fluviatilis) in England, and to determine how these interactions are likely to change under increased temperatures predicted by current climate change models.
Carrying out their experiments in six artificial ponds located at Tanyard Fisheries in East Sussex, the authors experimentally heated three ponds and maintained the other three at ambient temperatures.
The authors stocked each of two sets of ponds (one heated and one unheated) with an equal biomass of fishes in one of three treatments: perch alone, sunfish alone, and both species (with exactly half of the total biomass for each species).
The fishes had been individually tagged and their sizes and weights monitored over the course of the experiment. After 14 days, all the fish in the pond were killed and their gut contents analysed. This experiment was repeated three times.
The authors failed to find any evidence that the Pumpkinseed adversely affected growth in perch in either the present day (ambient) or predicted climate change (heated) environments. There was also no evidence that the two fish species were directly competing for food; both species fed predominantly on midge larvae when maintained alone, but the perch switched to a diet consisting of less optimal prey (microcrustaceans) when maintained together with Pumpkinseed.
The authors caution that the failure to demonstrate any negative effects of competition in their experiments does not mean that it does not exist. The time scale of the experiments may have been too short, and the effects of different stocking densities were not tested. They anticipate the Pumpkinseed to become invasive in England under warmer temperatures associated with climate change.
For more information, see the paper: Fobert, E, MG Fox, M Ridgway and GH Copp (2011) Heated competition: how climate change will affect non-native pumpkinseed Lepomis gibbosus and native perch Perca fluviatilis interactions in the U.K. Journal of Fish Biology doi:10.1111/j.1095-8649.2011.03083.x
Why not take out a subscription to Practical Fishkeeping magazine? See our latest subscription offer.