Are Chaoborus larvae more abundant in acidified than in non‐acidified lakes in Central Canada?

Abstract

Eriksson et al (1980) hypothesized that the abundance of certain macroinvertebrate predators, such as larvae of the phantom midge Chaoborus, should increase in acidified lakes because of the elimination of fish. To examine the influence of pH and presence of fish on Chaoborus abundance, we surveyed Chaoborus populations in 33 lakes in Ontario, Canada which ranged in pH from 4.5 to 7.4. Chaoborus larvae were not more abundant in the acidified lakes that were devoid of fish than in the remaining lakes. Therefore, we concluded that pH and presence of fish are not prime determinants of total Chaoborus abundance in Canadian Shield lakes. We hypothesized that significant increases in Chaoborus abundance should only be anticipated when fish populations are eliminated by acidification of relatively nutrient rich lakes.