Did signals from seabirds indicate changes inudcapelin biology during the 1990s? Comment onudDavoren Montevecchi (2003)

摘要

In a recent paper, Davoren & Montevecchi (2003a)udreported on the interactions between a seabird, theudcommon murre Uria aalge, and one of its prey, theudcapelin Mallotus villosus, a forage fish in boreo-arcticudwaters throughout the northern hemisphere. The authorsuddescribed common murres as capelin specialistsudand stated that murres are robust samplers of capelinudbiology. Although common murres feed intensively onudcapelin during the murre breeding season whenudcapelin are available, it should be noted that in the absenceudof capelin, murres can adopt alternate foragingudstrategies and reproduce successfully (see Carscaddenudet al. 2002). Davoren & Montevecchi (2003a) examinedudvarious biological attributes of capelin collected fromudcommon murres when they returned to the breedingudcolony, and concluded that ‘consistent among all dataudsources, including signals from murres shown here,udare declines in capelin condition and size and delaysudin spawning times throughout the 1990s’ (p. 259).udDavoren & Montevecchi (2003a) contains weaknessesudin both data collection and data analyses; as a result,udthese conclusions are not supported by the data analyses.udFurthermore, the authors drew several conclusionsudabout capelin biology and the physical environment,udbased partly on published studies, which require clarification.udThe authors also develop hypotheses that wereudnot supported by the data available.