Predator-prey interactions of common murres (Uria aagle) and fish in the northwest Atlantic : foraging strategies on multiple scales

• Main Author: Davoren, Gail K.
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2001
• Subjects: Canada; Common Murre; Northwest Atlantic; Uria aalge; uria
• Online Access: https://research.library.mun.ca/1589/; https://research.library.mun.ca/1589/1/Davoren_GailK.pdf; https://research.library.mun.ca/1589/3/Davoren_GailK.pdf

The Northwest Atlantic ecosystem is currently undergoing changes in species interactions and ocean climate. Capelin (Mallotus villosus ), the dominant forage fish in the ecosystem, is the main prey item of marine birds, mammals and piscivorous fish. In the 1990s, spawning capelin were small, spawned later, shifted their distribution southerly to non-traditional areas compared to historical accounts, and abundance estimates have varied widely. During these changes and divergent biomass estimates, this research was initiated. The focus of this thesis is the multi-scale behavioural interactions of marine predators and prey: a marine diving bird, the common murre ( Uria aalge ), and its main prey species, capelin. This study integrates both colony-based and vessel-based techniques. I showed that some aggregations of capelin are stable in space and time on a number of scales: fine- (1-100 m; minute-hour), coarse- (1-100 km; day-week) meso-scale (100-1000 km; annual), allowing murres to use memory to locate prey at sea during different periods during their annual cycle. Social foraging techniques appeared to be important on fine- and coarse-scales (local enhancement, network foraging) while no evidence was found for social foraging techniques over larger spatial scales (Information Center Hypothesis). Spatial scales at which murres tracked capelin were highly variable, as found in other studies examining predator-prey interactions of mobile organisms. The tracking scales of murres to capelin were smallest during the breeding (0.8-5.1 km) and pre-breeding periods (3.1-8 km), compared to post-breeding (6.0-50.0 km). This variability in spatial associations between predators and their prey was likely due to different energetic requirements, locomotory constraints and search strategies used among these periods. Inter-colony comparisons of provisioning behaviour by murres revealed low feeding rates of chicks at the largest murre colony in eastern Canada relative to a smaller colony, which resulted in the lowest average ...