Spatial and Temporal Movements of White Sucker: Implications for Use as a Sentinel Species

Abstract White suckers Catostomus commersonii are widely distributed in rivers of North America and often used in environmental monitoring. The species' value as a sentinel has been questioned because some populations are known to travel long distances during spawning migrations and therefore can be exposed to multiple environments. The movements of white suckers in a 65‐km reach of the Saint John River, New Brunswick, were studied from 2001 to 2003 using radio and acoustic tracking and analyses of stable isotope ratios. Individuals maintained small home ranges in the river from summer to late winter, averaging 2.6 river kilometers [rkm] or less each year. During the spring spawning season, upstream and downstream movements to three tributaries occurred. Distances traveled were up to 40 rkm and averaged 9.2 rkm (SD = 11.0). Two males used separate tributaries within a spawning period, and there was evidence that spawning may not take place every year. Stable isotope results confirmed that white suckers maintained a high fidelity to well‐defined reaches in the main river outside the spawning period. These results indicate the importance of distinct, limited habitats and connectivity of habitats for white suckers in large rivers and support the hypothesis that white suckers reflect localized environmental conditions and can be used as a sentinel.