Scale-dependent correlation of seabirds with schooling fish in a coastal ecosystem

Abstract

The distribution of piscivorous seabirds relative to schooling f ~ s h was investigated by repeated censusing of 2 intersecting transects in the Avalon Channel, w h c h carries the Labrador Current southward along the east coast of Newfoundland. Murres (primarily common murres Uria aalge), Atlantic puffins Fratercula arctica, and schooling fish (primarily capelin .Mallofus villosus) were highly aggregated at spatial scales ranging from 0.25 to 15 km. Patchiness of murres, puffins and schoohng flsh was scale-dependent, as indicated by significantly higher vc~ridnce-to-mean ratios at large measurement distances than at the minimum distance, 0.25 km Patch scale of puffins ranged from 2.5 to 15 km, of murres from 3 to 8.75 km, and of schoohng flsh from 1.25 CO 15 km. Patch scale of birds and schooling fish was sirmlar m 6 out of 9 con~parisons. Correlahon between seabirds and schooling birds was significant at the minimum measurement distance in b D L I ~ of 12 comparisons. Correlation was scale-dependent, as inlcated by sigruficantly higher coef1i:ients at large measurement &stances than at the minimum distance. Traclung scale, as indicated b) Lhe maxlmum significant correlation between birds and schooling fish, ranged from 2 to 6 km. Our analysis showed that extended aggregations of seabirds are associated with extended aggregatlons of schooling fish and that correlation of these marine carnivores with their prey is scale-dependent.