Age Determination and Biological Studies of Northern Pike Esox Lucius Linnaeus 1758 from Lobstick Area, Smallwood Reservoir, Labrador

Wheeler, John Paul (1980) Age Determination and Biological Studies of Northern Pike Esox Lucius Linnaeus 1758 from Lobstick Area, Smallwood Reservoir, Labrador. Masters thesis, Memorial University of Newfoundland.

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Abstract

A sample of 415 northern pike was taken from below Lobstick structure, Smallwood Reservoir, during the summers of 1977 and 1978. Four methods of age determination, scales, opercula, cleithra and otoliths, were compared to determine if different methods provided comparable ages for the same fish. Analysis of covariance showed significant differences between empirical and back-calculated age-length regressions using scales, opercula and cleithra; there were no differences using otoliths. Otoliths were used to study age and growth of pike from Lobstick. The maximum age recorded was 15 years, with 49% of the fish in the 7 and 8 age-groups. The fish ranged in length from 9.3 to 87.5 cm, with a mean fork length of 62.0 cm. The weight increased as the 3.0634 power of the length. Coefficient of condition values of mature fish, sampled from June to September, were highest in early June and lowest in late June. Instantaneous total mortality rates, calculated from a catch curve, were higher for females (0.37) than for males (0.32). The overall sex ratio was close to 1:1. Males were predominantly (50%) mature by age 5, or at 40 cm, females by age 8, or at 60 cm. Observation of ovaries of mature pike indicated that all pike did not spawn each year. Fecundity estimates of fish 51.0 to 87.5 cm in length ranged from 5732 to 62,000 with a mean of 28,016. Of the 86 stomachs examined for food contents, 62% were empty. Whitefish was the principal item (64%) where food was present.

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