It’s common to hear of non-native fish species like Asian carp invading Canada’s fresh-water systems, but it turns out our country also has a few aquatic invaders of our own living abroad. One of these species is the pumpkinseed sunfish.

“The pumpkinseed is native to Canada and the U.S., but not to Europe, where it has been introduced or spread to some 30 countries,” says Dr. Michael Fox, professor emeritus in the Trent School of the Environment and Biology department, who recently completed a research project on the invasiveness of the pumpkinseed with Dr. Gordon Copp ‘76, a Trent alumnus and adjunct to Trent’s Environmental & Life Sciences graduate program. Now principal scientist in fish biology and non-native risk analysis at the Centre for Environment, Fisheries and Aquaculture Science in Lowestoft, England, Dr. Copp is a visiting professor at Bournemouth University in southern England.

Invasiveness depends on location

These pretty and sometimes pesky little fish got overseas through various ways, means, and purposes. In France, for instance, they were introduced as a potential aquaculture species for food, whereas in England they were imported as an ornamental fish for ponds. In other European countries, they were introduced as pet fish for aquariums or as prey for other imported fish species like largemouth bass, another North American fish.

As for their invasiveness, that depends on location.

“They’re not necessarily invasive everywhere,” says Prof. Copp. “The pumpkinseed is invasive in countries like Spain and Portugal, where they tend to displace some of the native species, maybe eat their food or even their young, but in England their impact is relatively benign so far.”

Model for predicting potential invasiveness

Thanks to a multi-year NATO Collaborative Research Grant, Professors Fox and Copp developed a model for predicting the invasiveness of freshwater fishes, focusing on the pumpkinseed.

“The NATO-funded network was interested in looking at how existing non-native species would respond to climate change, and the pumpkinseeds, with their biology and the females’ reproduction response to local conditions, temperature and other factors influenced our choice,” says Prof. Fox.

The model was developed with the idea that the potential invasiveness of a fish population could be predicted by modeling the average rate of juvenile growth (body length at the end of the second year of life) against the mean age at first maturity of that population.

“Aside from the model itself, one of the unique things about this approach was that it may have been the first time anyone tried to predict the invasiveness of a population, as opposed to the species generally,” explains Prof. Fox.

“We had pretty good success in predicting populations that would be non-invasive, but our predictions for populations that would be invasive were less than 60% correct,” says Prof. Fox.

One of the reasons for this is the fact that the model used the growth and maturity characteristics of the invaders, rather than the original populations.

“Populations adapt to changed conditions in the water where they are introduced, and continue adapt after their original introduction,” explains Prof. Fox. More data on source populations would be needed to generate more accurate predictions.

The work lays a critical foundation for future researchers with the time and funding resources to eliminate the sources of data variation and for government agencies to develop potential screening tools to manage invasive species.

Fondly recalling Trent professors

Prof. Copp fondly remembers his Trent professors who helped shape and establish his career.

“I did not study fish while at Trent but Professor Perce Powles, who was Trent’s only fish biologist at the time, helped in my attempt to catch some common carp for an environmental chemistry project, and I cited at least one of his journal articles in my subsequent research,” he says. “And Professor David Lasenby taught the limnology course, and Professor Nighswander, who taught electron microscopy. It’s thanks to these two professors that I learned to write scientific papers and carry out independent scientific research.”

Prof. Copp continues his close ties with his alma mater as the founder of the British Isles chapter of the Trent Alumni Association.