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ผู้เขียน หัวข้อ: Primary productivity and the carrying capacity for herring in NE Pacific marine  (อ่าน 2262 ครั้ง)
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« เมื่อ: มกราคม 23, 2010, 07:45:36 PM »

Primary productivity and the carrying capacity for herring in NE Pacific marine ecosystems

R. Ian Perry *, Jacob F. Schweigert
Fisheries and Oceans Canada, Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, BC, Canada V9T 6N7

Progress in Oceanography 77 (2008) 241–251
Available online 26 March 2008

Keywords:Alaska,Annual surplus production,British Columbia,Carrying capacity,Pacific herring,
Primary productivity

a b s t r a c t
The carrying capacity for Pacific herring (Clupea pallasi) and its relationship to primary productivity was
examined for eight populations in the NE Pacific and eastern Bering Sea. Data on biomass (ages 3 and
older) and catches of herring in British Columbia (Georgia Strait, west coast Vancouver Island, Central
Coast, Queen Charlotte Islands, Prince Rupert) and Alaska (Sitka, Prince William Sound, eastern Bering
Sea) during the second half of the 20th Century derived from analytical stock assessments were used
to calculate annual surplus production of herring. There was considerable interannual variability in herring
productivity among all populations, however, only three (Georgia Strait, Prince Rupert, Prince William
Sound) showed significant differences in mean productivity on decadal time scales (productivity
regimes). Carrying capacity for the most recent productivity regime for each population was estimated
using the Schaefer surplus production model. Mean annual primary productivity was estimated from
remotely-sensed (SeaWiFS) chlorophyll data for British Columbia and Sitka ecosystems, and from
in situ chlorophyll data for Prince William Sound and the eastern Bering Sea. The carrying capacity for
herring populations in the NE Pacific ranged from 28,000 to 250,000 tonnes, and to 325,000 tonnes in
the eastern Bering Sea. When considered on the basis of their distributional area, the west coast of Vancouver Island and Georgia Strait populations had the highest carrying capacity per unit area (9.3–
13.8 tonnes km2) and the eastern Bering Sea had the lowest (0.7 tonnes km2). There is a significant
positive linear relationship between the productivity of herring populations at carrying capacity and primary productivity on a per unit area basis. Although similar direct relationships have been observed
between phytoplankton standing stock (as chlorophyll biomass) and total catches of resident fish populations from these regions, such a direct relationship was unexpected between primary productivity and herring carrying capacity because of multiple trophic pathways and other factors (e.g. spawning habitat) which should limit the carrying capacity for individual populations of particular species of fish. These results may be used to forecast potential responses of herring in NE Pacific ecosystems to global changes in ocean productivity.
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