Record Details
Cross-scale analysis of the Pribilof Archipelago, southeast Bering Sea, with a focus on age-0 walleye pollock (Theragra chalcogramma)
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Cross-scale analysis of the Pribilof Archipelago, southeast Bering Sea, with a focus on age-0 walleye pollock (Theragra chalcogramma) |
| Names |
Ciannelli, Lorenzo
(creator) |
| Date Issued | 2002 (iso8601) |
| Note | Access restricted to the OSU Community |
| Abstract | Age-0 pollock are the most abundant small pelagic species around the Pribilof Archipelago, composing more than 90% of both the local numerical abundance and the fish biomass abundance. Due to a favorable combination of physical and biological conditions, it is likely that age-0 pollock experience enhanced feeding and growth around the Pribilofs. However, age-0 pollock are also subject to high predation risk owing to the high numbers of groundfish, seabirds and marine mammals that reside around these islands. The relative benefit that age-0 pollock might experience from enhanced feeding compared to the negative effects of predation is as yet unclear. This study seeks to understand the outcome of bottom up and top down forces on age-0 pollock ecology, by exploring environmental variability around the Pribilof Islands and associated traits of age-0 pollock population ecology. Ecological variables considered here are age-0 pollock distribution, their growth, energy content and mortality from predation. Results indicate that both predation (i.e. groundfish distribution) and energetics (i.e. habitat-dependent potential for growth) affect the meso-scale (1 to 10 km) variability of age-0 pollock distribution. Local hydrographic features, and particularly water temperature, can mediate the importance of either factor, by affecting groundfish distribution and age-0 pollock physiology. Additionally, the hydrographic features associated with the frontal structure around the islands significantly influence the energy content and the foraging impact of age-0 pollock on their prey. Foraging impact and consequent food limitation risk also varies according to age-0 pollock size, due to the pronounced changes in diet and metabolism that juvenile pollock typically undergo during early life. Results of a mass-balance ecosystem model applied to the community around the Pribilof Islands show that Chrysoara malanaster, a prevalent scyphomedusae, causes about 60% of the total age-0 pollock predation mortality, while groundfish cause about 30%. These findings prove useful in understanding the role of the Pribilof ecosystem both as a juvenile pollock nursery area and as an ecosystem nested within the larger Bering Sea. Different hypotheses are discussed and further considerations are made on the general role of oceanic archipelagos nested within larger ecosystems. |
| Genre | Thesis |
| Topic | Fish populations -- Alaska -- Pribilof Islands |
| Identifier | http://hdl.handle.net/1957/38600 |
