Co-occurrence and aggregation of marine birds and mammals in Monterey Bay, California, USA

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 387:295-303 (2009) - DOI: https://doi.org/10.3354/meps08082 Co-occurrence and aggregation of marine birds and mammals in Monterey Bay, California, USA Laird A. Henkel* Office of Spill Prevention and Response, California Department of Fish and Game, 20 Lower Ragsdale Drive, Suite 100, Monterey, California 93940, USA *Email: lhenkel@ospr.dfg.ca.gov ABSTRACT: Patterns of spatial and temporal co-occurrence or avoidance among different species of marine birds and mammals can provide insights into the degree to which these top predators compete for prey. I conducted at-sea surveys in nearshore waters of Monterey Bay, California, USA, and used a randomization technique to assess co-occurrence patterns of marine birds and mammals in 1 km transect segments. As expected, strongest positive associations were among members of 3 different foraging guilds: pursuit-divers, surface-feeders, and plunge-divers. Within guilds, pursuit-divers exhibited marked avoidance of one another (negative co-occurrence), although surface-feeders often co-occurred with each other. The study was conducted during 2 yr, 1999 and 2000; during 2000, when predator abundance was greater and prey abundance may have been decreased, pursuit-divers exhibited more avoidance of one another than in 1999. These data suggest that competition reduces foraging ability for pursuit-diving species, making it more profitable for them to disperse more widely, whereas surface-feeding species (primarily gulls) benefit from flock foraging under most conditions. Larger animals tended to frequently co-occur, while the smallest member of each guild tended to avoid other species, indicating competitive exclusion of smaller predators. KEY WORDS: Seabirds · Marine mammals · Co-occurrence · Overlap · Niche · Segregation · Aggregation · Competition Full text in pdf format PreviousCite this article as: Henkel LA (2009) Co-occurrence and aggregation of marine birds and mammals in Monterey Bay, California, USA. Mar Ecol Prog Ser 387:295-303. https://doi.org/10.3354/meps08082 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 387. Online publication date: July 28, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.