Water_Wolves

Jeff Green | Feb 03, 2005

Feature article February 3, 2005

Contact Us

by Gray Merriam

Before Christmas there was a round of appointments to the Order of Canada by the Governor General in Ottawa. In town to receive one of those awards was Dr. David Schindler, Killam Professor from the University of Alberta in Edmonton. A few years earlier, he had received the Stockholm Water Prize, the world equivalent of a Nobel Prize for ecologists. He knows his stuff!

Through the hard work and good reputations of people like Joe Slater, David Taylor and Susan Brandum of the Friends of the Tay Watershed, Dr. Schindler made time during his official visit to Ottawa to spend three hours in Perth in discussions with environmental volunteers from this area.

In response to one question, Dr. Schindler expressed concern that the fisheries in freshwater lakes across Canada were in a serious decline due both to commercial fishing and to significantly increased pressure from sports fishing. He speculated that our freshwater sports fisheries might decline just like the offshore cod fishery did. Many things have increased the pressure from sports fishing on our freshwater fish stocks: more leisure time for fishing, high-tech fish finders, modern tackle technologies, rapid access to fishing locations, promotion of frequent ultra-high pressure fishing from tournaments with misguided notions that catch and release prevents impacts on both mortality and reproduction.

Fishing differs from most of our sports harvesting of wildlife in that fishing takes mostly predators. Most other wildlife taken are herbivores. Dr. Schindler sees important effects from our reduction of the number of predator fishes. By reducing the predators, we reduce the mortality they cause to their food fishes. This greatly increases the proportion of smaller, minnow-sized fishes. These smaller fish species generally feed on invertebrates such as crustaceans scuds, ostracods and the like. These little animals commonly feed by filtering the water to sieve out small animals and plants such as algae. With increased numbers of small fish because too many of their predators have been removed, fewer algae will be removed by the invertebrates.

If your lake is receiving more than the normal inflow of nutrients due to human activities and, at the same time, we humans are driving the number of predatory fish down to previously unknown low numbers, both of our actions could help to increase the numbers of algae in your lake. Yes, Dr. Schindler suggested that taking pike, pickerel and both species of bass or reducing their success in reproduction could also be a cause of the abnormal population of algae that you dont like along your lakeshore.