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Demersal fish and invertebrate biomass in relation to an offshore hypoxic zone along the US West Coast
Author(s) -
KELLER AIMEE A.,
SIMON VICTOR,
CHAN FRANCIS,
WAKEFIELD W. W.,
CLARKE M. E.,
BARTH JOHN A.,
KAMIKAWA DAN,
FRUH ERICA L.
Publication year - 2010
Publication title -
fisheries oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 80
eISSN - 1365-2419
pISSN - 1054-6006
DOI - 10.1111/j.1365-2419.2009.00529.x
Subject(s) - hypoxia (environmental) , benthic zone , demersal zone , oceanography , demersal fish , fishery , biomass (ecology) , environmental science , mesopelagic zone , bottom water , oxygen minimum zone , invertebrate , pelagic zone , biology , fishing , geology , oxygen , upwelling , chemistry , organic chemistry
In August 2007, as part of the NOAA National Marine Fisheries Service (NMFS) West Coast Groundfish Bottom Trawl Survey, we examined the biomass of demersal organisms in a known hypoxic area off the Oregon coast. Although observed each summer, the intensity of hypoxia has varied annually (2002–2007) with the greatest temporal and spatial extent noted in 2006. In 2007 we identified the geographic extent of the hypoxic zone and sampled 17 stations along two depth contours (50 and 70 m) within the area. A Sea‐Bird SBE 19 plus equipped with a dissolved oxygen (DO) sensor was attached to the bottom trawl to monitor oxygen concentration during each tow. Bottom DO concentrations at all stations were hypoxic with means along the tow tracts ranging from 0.43 to 1.27 mL L −1 . Total catch per unit effort (ln CPUE, kg hectare −1 ) and species diversity (number of species, N ) were significantly and positively related to oxygen concentration along the hypoxic gradient. In addition, CPUE (natural log‐transformed) for eight fish species and five benthic invertebrate species were significantly and positively related to bottom oxygen concentration within the hypoxic region. Condition factors for five fish species, as well as Dungeness crab ( Cancer magister ) increased with increased bottom oxygen levels along the hypoxic gradient. Historical catch (2003–2006) within the hypoxic zone indicates that biomass was significantly lower in 2006, the year with the lowest bottom DO levels, relative to other years.