. The Canadian field-naturalist. 1982 RUBEC AND QADRI: BULLHEAD IN OTTAWA RiVER 11 stations in the upper river, lower river, and near Hawkesbury. The back-calculated lengths at each annulus varied between different year classes of the same population as well as between the six stations. The growth was highest the first year followed by smaller increments in succeeding years. The back-calculations from the three sections of the Ottawa River have been compared to studies else- where (Table 4). The growth of Brown Bullhead in the lower Ottawa River was similar to acid polluted environments in the
. The Canadian field-naturalist. 1982 RUBEC AND QADRI: BULLHEAD IN OTTAWA RiVER 11 stations in the upper river, lower river, and near Hawkesbury. The back-calculated lengths at each annulus varied between different year classes of the same population as well as between the six stations. The growth was highest the first year followed by smaller increments in succeeding years. The back-calculations from the three sections of the Ottawa River have been compared to studies else- where (Table 4). The growth of Brown Bullhead in the lower Ottawa River was similar to acid polluted environments in the Monongahela River, West Virgi- nia (Redd 1970). The growth in the upper river and near Hawkesbury was generally higher than that observed in the United States and Czechoslovakia (Tables 4 and 5). Growth of Brown Bullhead in the upper Ottawa River was similar to those from Lake Washington (Table 4). However, L=« calculations (Table 5) indicate that Washington State fish (Imamura 1975) have the potential to attain a larger size. The growth of youth bullheads in Oklahoma was very high (Table 4) but the L°^ value calculated (Table 5) is probably too high due to the lack of older fish in the sample (Finnell et al. 1956). Bullheads from Riviere du Nord (Phaneuf 1974), a tributary of the Ottawa River, exhibited a lower growth rate than those in the Ottawa River. Bullheads within any age group exhibited a large range in size indicating that the population consisted of both fast and slow growing individuals (Table 6). The large overlap in lengths of bullheads of different ages made the determination of age groups from length frequency distributions impractical. However, the fact that the mean lengths of the sampled bull- 400- 300- E E o 200- 100- (208)_r^(43l). P- Upper river Jf.^O Hawkesbury ^§(24)* Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations m
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