Variables associated with the use of chemotherapeutic agents on trout farms in Ontario, Canada

Abstract

This study investigated whether certain farm-level variables were related to the use of chemotherapeutic treatments by Ontario, Canada trout producers. Several treatment outcomes were examined in each of two fish-size categories (10 cm or less and over 10 cm), including: (1) the likelihood of initiating any treatment; (2) the frequency of treatment initiation; (3) the likelihood of using any preventive treatments; (4) the likelihood of initiating more than half of all treatment regimens for preventive reasons. Data were obtained by personally interviewing 62 farmers who in total marketed 91% of the farmed trout produced in Ontario in 1990. Producers with more years of fish farming experience or those with no more than one full-time equivalent person working with the fish were less likely to have initiated treatment in either size category than were those with less experience or more workers. In addition, farmers producing fewer fish or those running specialized hatcheries or vertically integrated operations were less likely to have ever treated fish that were 10 cm or less in size than were those with larger farms or growout-only operations. Treatment frequency increased significantly if farmers had used preventive treatments. Also, among farmers who did treat 10 cm or smaller fish, those with more years of farming experience tended to initiate fewer treatments. Farmers with hatcheries or vertically integrated farms were less likely to have initiated any preventive treatments in 10 cm or smaller fish than were those with growout-only operations. Members of the Ontario Aquaculture Association were less likely than non-members to have initiated more than half of their treatment regimens in 10 cm or smaller fish for preventive reasons. Farmers who had lower water flows per 10 cm or over fish tended to rely more heavily on preventive treatments in this size group of fish than did those with higher flows per fish.