Hot spots of predators and prey on multiple spatial and temporal scales in the marine ecosystem of the Northwest Atlantic

No abstracts are to be cited without prior reference to the author.

Forage species lie at the core of complex marine food webs, providing essential linkages among trophic levels. High-density aggregations of forage species (hot spots) allow the maximization of energy transfer between upper and lower trophic levels. Capelin, (Mallotus villosus) the dominant forage fish in the Northwest Atlantic ecosystem, is the major prey item of marine birds, mammals and fish. We examined the distribution of capelin and their main avian predator, common murres (Uria aagle), throughout the year from 1998 - 2002. Vessel-based surveys revealed the locations of persistent hot spots of capelin on multiple spatial and temporal scales: fine- (1-100 m; minute-hour), coarse- (1-100 km; day-week) and meso-scale (100-1000 km; annual). Fine-scale studies revealed the bio-physical characteristics used by capelin to select habitats, resulting in the persistence of capelin schools within hot spots. Meso-scale behavioural studies indicated that avian predators, might use a mixed strategy to relocate hot spots: memory at broad-scale and social foraging at fine scales. Overall, persistent hot spots of capelin allowed predators to maximize prey encounter rates, while minimizing search efforts for prey. Conservation of such hot spots is essential to maintain the stability of food webs and, thus, they are critical areas for protection.