Did signals from seabirds indicate changes in capelin biology during the 1990s? Comment on Davoren & Montevecchi (2003)

摘要

In a recent paper, Davoren & Montevecchi (2003a) reported on the interactions between a seabird, the common murre Uria aalge, and one of its prey, the capelin Mallotus villosus, a forage fish in boreo-arctic waters throμghout the northern hemisphere. The authors described common murres as capelin specialists and stated that murres are robust samplers of capelin biology. Althoμgh common murres feed intensively on capelin during the murre breeding season when capelin are available, it should be noted that in the absence of capelin, murres can adopt alternate foraging strategies and reproduce successfully (see Carscadden et al. 2002). Davoren & Montevecchi (2003a) examined various biological attributes of capelin collected from common murres when they returned to the breeding colony, and concluded that 'consistent among all data sources, including signals from murres shown here, are declines in capelin condition and size and delays in spawning times throμghout the 1990s' (p. 259). Davoren & Montevecchi (2003a) contains weaknesses in both data collection and data analyses; as a result, these conclusions are not supported by the data analyses. Furthermore, the authors drew several conclusions about capelin biology and the physical environment, based partly on published studies, which require clarification. The authors also develop hypotheses that were not supported by the data available.