MARINE ECOLOGY - PROGRESS SERIES Mar. Ecol. Prog. Ser. Published September 18 Scale-dependent correlation of seabirds with schooling fish in a coastal ecosystem David C. Schneider & John F. Piatt Newfoundland Institute for Cold Ocean Science, Memorial University of Newfoundland, St. John's, Newfoundland A1B 3x7, Canada ABSTRACT: The distribution of piscivorous seabirds relative to schooling f~sh was investigated by repeated censusing of 2 intersecting transects in the Avalon Channel, whch 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 DLI~ of 12 comparisons. Correlation was scale-dependent, as inlcated by sigruficantly higher coef1i:ients at large measure- ment &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. INTRODUCTION Marine buds form aggregations that range from a few metres to tens of ldometres in lateral extent. Aggregations ranging from 5 to 50 km in chord length have been reported in the Bering Sea (Schneider 1982, l n d e r et al. 1983, Woodby 1984), the California Cur- rent (Briggs et al. 1984), and the Benguela Current (Schneider & Duffy 1985). The existence of these aggregations suggests that seabirds may be correlated with prey at a similar scale, but this has not been tested directly. We investigated the distribution of murres (pnmanly the common murre Uria aalge) and Atlantic puffins Fratercula arctica relative to schooling fish at Witless Bay, the site of a major seabird colony in the northwest Atlantic. This colony consists of 3 closely spaced islands on the western side of the Avalon Channel, a relatively deep (>l50 m) nearshore trough that funnels the inshore arm of the Labrador Current southward along the east coast of Newfoundland. Capelin spawn along this coast from late June into mid-July (Temple- man 1948), and during this period they are the most O Inter-Research/Printed in F. R. Germany abundant schoohng f~sh nearshore. Capelin are the most important prey in the diets of murres and puffins at Witless Bay (Mah3ney 1979, Brown & Nettleship 1984, J. Platt unpubl, riata). We investigated variability in the abundance of birds and schooling hsh by malung repeated surveys of 2 transects at Witless Bay during the summer of 1984. Our objectives were tc, determine (1) whether variabil- ity in the abundance of birds and schooling fish was scale dependent; (2) whether birds and fish were loc- ally correlated; and (3) whether correlation was scale- dependent. METHODS Surveys were made 3long an offshore transect run- ning eastward from Green Island into the Avalon Channel and along a coastal transect running parallel to the coastline from Bay Bulls to Cape Broyle (Fig. 1). The offshore transect was surveyed 4 times and the coastal transect was surveyed 3 times during the sum- mer of 1984. Bird counts were nljde from a 12 m fishing vessel