Research Document - 2009/074

Atlantic Salmon (Salmo salar) and Smallmouth Bass (Micropterus dolomieu) Interactions in the Magaguadavic River, New Brunswick

By J.W. Carr and F.G. Whoriskey

Abstract

Data from 15 years (1994-2008) of backpack electrofishing surveys of juvenile Atlantic salmon habitat in the Magaguadavic River, New Brunswick were reviewed to document occurrences of smallmouth bass. We also examined datasets from salmon smolt monitoring stations (1999-2009) and from the head-of-tide fish ladder trap (1992-2008) in this river for captures of bass. Bass were found at 55% (N=23) of the juvenile salmon habitat sites. The species co-occurred with juvenile salmon at various electrofishing sites annually, except in 2001 and 2003. On average, the species co-occurred at 35% (range: 0 to 89%) of the electrofishing sites sampled over the 15 year period.  Bass were found throughout most of the main stem riffle-run habitat and in 45% (N=15) of the tributaries sampled. In the tributaries, the majority of the bass were young of the year and 87% of those sites were within 100 metres of a lake, reservoir, or the river’s main stem. Body sizes (lengths) were generally similar between salmon and bass at most electrofishing sites and salmon outnumbered bass in most cases. However, larger bass were found in the river’s main stem and near commercial salmon hatcheries. Bass were found in 1^st and 2^nd order streams as small as 2 m wide. However, they did occur more frequently in 3^rd to 5^th order streams and they apparently avoided spring fed areas. Bass occasionally co-occurred with salmon smolts at trap sites during the spring monitoring periods, and were also captured at the head-of-tide fish ladder. In addition to smallmouth bass, one exotic largemouth bass (M. salmoides), the first record for this species in the Maritimes Provinces, was captured in the Magaguadavic system in 2006.

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