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Yearling juvenile coho and Chinook salmon were sampled on 28 cruises in June and September 1981-85 and 1998-07 in continental shelf and oceanic waters off the Pacific Northwest. Oceanographic variables measured included temperature, salinity, water depth, and chlorophyll concentration (all cruises) and copepod biomass during the cruises from 1998-07. Juvenile salmonids were found almost exclusively in continental shelf waters, and showed a patchy distribution: half were collected in ∼5% of the collections and none were collected in ∼40% of the collections. Variance-to-mean ratios of the catches were high, also indicating patchy spatial distributions for both species. The salmon were most abundant in the vicinity of the Columbia River and the Washington coast in June; by September, both were less abundant, although still found mainly off Washington. In June, the geographic center-of-mass of the distribution for each species was located off Grays Harbor, WA, near the northern end of our sampling grid, but in September, it shifted southward and inshore. Coho salmon ranged further offshore than Chinook salmon: in June, the average median depth where they were caught was 85.6 and 55.0 m, respectively, and in September it was 65.5 and 43.7 m, respectively. Abundances of both species were significantly correlated with water depth (negatively), chlorophyll (positively) and copepod biomass (positively). Abundances of yearling Chinook salmon, but not of yearling coho salmon, were correlated with temperature (negatively). We discuss the potential role of coastal upwelling, submarine canyons and krill in determining the spatial distributions of the salmon. [ABSTRACT FROM AUTHOR]

Populations of the sand crab, Emerita analoga, are well established on the California coast. However, populations in Oregon occur sporadically and appear to be restocked by larvae drifting north from California. Due to increased northward transport in winter during El Niño events, we would expect that larval recruitment to northern populations should be higher during these periods. This hypothesis was tested by comparing larval abundances between non-El Niño and El Niño years, 1997 and 1998, respectively. In 1997, larval abundances and seasonality were similar to historical data from 1969–71. First zoeal (Z1) stage larvae were present during these summers, but in low numbers, indicating that E.analoga spawned off the coast of Oregon. In 1998, strong larval recruitment from the south occurred, demonstrated by a large number of fifth zoeal stage (Z5) larvae collected off Oregon in April and May. The large numbers of Z1 found in summer 1998 indicate that the Z5, which arrived from California earlier that spring, successfully recruited to adulthood and reproduced. These data indicate that Oregon E.analoga populations are probably dependent on larvae travelling from California in the Davidson Current. It follows that this species could be used as an indicator of coastal current fluctuations such as those seen during El Niño events. [ABSTRACT FROM PUBLISHER]

Both simple and more complex lower trophic ecosystem models were applied to the near shore pelagic zone of the California Current System. The ecosystem models were a simple nitrogen–phytoplankton–zooplankton (NPZ) model derived from that of Edwards et al. (J. Mar. Res. 58, 37–60, 2000), and a modified version of the more complex PICES North Pacific Ecosystem Model for Understanding Regional Oceanography (NEMURO), which includes both nitrogen and silicate cycles, as well as multiple phytoplankton and zooplankton components. These models were framed within two simplified physics models, similar to those constructed by Newberger et al. (J. Geophys. Res. 108 (3), 3061, doi:10. 1029/2001JC001182, 2003). The first physics model was a zero-dimensional closed system, used for structural analysis of the biological models. The second was a one-dimensional (horizontal, with no vertical structure) cross-shelf model of the mixed layer, used to examine the biological response to upwelling. The predictions of the two biological models within the one-dimensional physical framework were compared with observed nutrients, chlorophyll, and zooplankton on the Newport Hydrographic Line. Equilibrium behavior of the zero-dimensional models was similar to that in previous studies; differences between the models resulted primarily from differences in the density dependence of mortality. Both models were found to be highly sensitive to the same four parameters: source nitrate concentration, maximum grazing rate, zooplankton Ivlev constant, and zooplankton mortality rate. In the cross-shelf case, both biological models had a similar timing of phytoplankton response to upwelling, but maximum phytoplankton concentration and zooplankton dynamics differed, with the simpler NPZ model resulting in lower dissolved nutrients but higher plankton densities than the modified NEMURO model. While the modified NEMURO model provided a slightly better overall fit to observations, neither model was able to fully capture observed phytoplankton and zooplankton dynamics. [Copyright &y& Elsevier]

The zooplankton of the northern California Current are typically characterized by an abundance of lipid-rich copepods that support rapid growth and survival of ecologically, commercially, and recreationally valued fish, birds, and mammals. Disruption of this food chain and reduced ecosystem productivity are often associated with climatic variability such as El Niño events. We examined the variability in timing, magnitude, and duration of positive temperature anomalies and changes in copepod species composition in the northern California Current in relation to 10 tropical El Niño events. Measurable impacts on mesozooplankton of the northern California Current were observed during seven of 10 of these events. The occurrence of anomalously warm water and the response of the copepod community was rapid (lag of zero to 2 months) following the initiation of canonical Eastern Pacific (EP) events, but delayed (lag of 2-8 months) following 'Modoki' Central Pacific (CP) events. The variable lags in the timing of a physical and biological response led to impacts in the northern California Current peaking in winter during EP events and in the spring during CP events. The magnitude and duration of the temperature and copepod anomalies were strongly and positively related to the magnitude and duration of El Niño events, but were also sensitive to the phase of the lower frequency Pacific Decadal Oscillation. When fisheries managers and biological oceanographers are faced with the prospect of a future El Niño event, prudent management and observation will require consideration of the background oceanographic conditions, the type of event, and both the magnitude and duration of the event when assessing the potential physical and biological impacts on the northern California Current., (© 2015 John Wiley & Sons Ltd.)