Research Document - 1999/056

The effect of water temperature on angling catch of Atlantic salmon in the Upsalquitch River.

By F. Mowbray and A. Locke

Abstract

There is little doubt that mandatory catch and release has reduced angling mortality of multi-sea winter Atlantic salmon, but there continues to be concern that mortalities might result from angling or handling stress, especially in years of warm water temperatures. Closure of angling fisheries in warm weather has been proposed as a management solution. However, closure would be ineffective if angling effort and/or catch per unit effort at high temperatures were very low. Atlantic salmon angling catch, effort and catch rates at four Crown angling reserves located on the Upsalquitch River, New Brunswick, were examined in relation to morning water temperatures at a barrier fence located upriver. The analysis included one cold year (1992) when only one day with morning temperature ³ 20 oC was recorded at the barrier fence, two years of moderate temperatures (1993-94; 25% and 8% of morning temperatures of 20 oC, respectively) and one unusually warm year (1995; 97% of morning temperatures recorded at Morrissey Rock trapnet ³  20 oC). Morning temperature (0800 h ± 1 h) was found to be a reasonable surrogate for minimum daily temperature. Maximum daily temperature generally occurred in late afternoon. Catch per unit effort was slightly lower on days with morning temperatures ³  20 oC in two of the three years when angling occurred at these temperatures, but the high level of effort resulted in substantial catch. In 1995, the warmest year studied, 67% of the angling effort and 55% of the angling catch were recorded on days with morning temperature ³  20 oC.

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