Research Document - 2014/013

Comparing Age, Growth, and Mortality of Brook Trout (Salvelinus fontinalis) sampled from Seven Lakes on the Northern Peninsula, Newfoundland to assess the efficacy of established regulations for Ten Mile Lake

By R. C. Perry and D. G. Keefe

Abstract

The following report describes a comparative study of seven brook trout (Salvelinus fontinalis) lakes located on the Northern Peninsula of Newfoundland and Labrador, Canada. Six of the lakes are currently managed under a generic, island wide, management regime. The seventh, Ten Mile Lake, was placed in a special trout management area (STMA). The STMA was created in response to concerns that the brook trout population in the pond had collapsed with anecdotal evidence suggesting small catch size and low catches rates. In the STMA the harvest was severely limited. The angling season for Ten Mile Lake was shortened to 45 days in the summer, and the ice fishing season was eliminated. The STMA has been in place since 2004. Prior to the creation of the STMA baseline data was not collected and therefore it is difficult to determine whether the STMA was warranted or, if a collapse did occur, the extent of the recovery. We performed a cross-sectional comparison among the seven lake’s Catch per Unit Effort (CPUE), growth rates and mortality to determine the relative status of Ten Mile Lake. Our comparison revealed that three of the seven sampled ponds had a catch composition with overall mean sizes that were larger than Ten Mile Lake. When we compared fish size-at-age, brook trout aged three and four were significantly smaller in Ten Mile Lake when compared to five of the other six lakes. Using least square regressions and an index of growth rate derived from incremental otolith growth, we determined that Ten Mile Lake brook trout had the lowest mortality and growth rates of the seven sampled lakes and it had the oldest age structure. Using the derived otolith growth chronology, we determined that the Ten Mile Lake population’s growth rates have been slowing subsequent to 2004. Additionally, gill net catch rates among the seven lakes did not appreciably differ. We conclude that Ten Mile Lake has similar catch rates and composition to other popular fishing locations near its vicinity. Due to the low mortality and slowing growth rate, we believe brook trout population density for Ten Mile Lake may be increasing. The decreasing growth rates are likely in response to the increasing population density. Recommendations are made to increase the length of the angling season.

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