GLOBEC: Mesoscale euphausiid and whiting distribution in the CCS and their relationship to environmental conditions
G.L. Swartzman, B. M. Hickey [Univ. Washington]

This proposed project addresses the Retrospective aspect of the U.S. GLOBEC Announcement of Opportunity. We will analyze acoustic and supporting hydrological and topographic data collected in summer 1995 and 1998 by the National Marine Fisheries Service with an eye to examining the spatial distribution of euphausiid patches and fish shoals as they relate to bottom topography, upwelling, current velocity, stratification and phytoplankton biomass. Additionally, we propose participation in and analysis of data collected in 2001 in the same area (Monterey CA to Queen Charlotte Islands. B.C., Canada). We will examine a series of hypotheses concerning the possible association of large euphausiid patches near the shelf break north of Cape Blanco, Oregon with minimum alongshore and onshore-offshore currents, large phytoplankton biomass and upwelling-driven currents directed towards the shelf break. We will also test hypotheses about the proximity of euphausiids with a major predator fish, Pacific whiting and how it changes south to north of Cape Blanco, the possible enhancement of euphausiid density along the edges of submarine canyons, and the effect of El Niņo on both euphausiid and whiting distribution and abundance. The analyzed data will form a baseline data set for use by ongoing and proposed GLOBEC monitoring and process studies.

FIRST YEAR WORK

We propose to use acoustic data collected by the National Marine Fisheries Service during summer 1995 and 1998 (Figure 1) to map and study the distribution of euphausiid patches and fish shoals along transects from Monterey, CA to Queen Charlotte Islands, BC. We will first identify shoals of fish and patches of plankton in the water column using image thresholds and morphological filtering (Swartzman et al., 1994) and pixel by pixel subtraction of echo-sounder images at two frequencies (38 and 120 kHz). The species composition of the acoustically identified fish shoals will be assessed using Methot and Anchovy trawl samples. The species composition of the acoustically identified plankton patches will be estimated using BONGO net sample data collected along the survey route. Hydrodynamic data collected on the same cruises, including Acoustic Doppler Current Profiler (ADCP), temperature and salinity with depth (CTD and XBT data), bathymetry (acoustic bottom detection), and surface temperature (AVHRR images) and fluorescence (SeaWIFS images for 1998 only) will be acquired. We will analyze the ADCP and CTD data to produce time and depth averaged current velocity vectors, and to compute the upslope convergence rate (the velocity component of current in the upslope direction, perpendicular to the shelf break, divided by the distance from the shelf break). We will also resolve the mesoscale current properties to identify time periods of upwelling or downwelling. The satellite image and current data will be melded to enhance evidence for upwelling and downwelling as well as to identify such mesoscale hydrological features as eddies and filaments. Hydrological and bathymetric data will be fused with fish and plankton distributions, for purposes of exploratory data analysis and data communication. We will use an acoustic data viewer, FishViewer, to overlay environmental data on the acoustic data using the onshore-offshore survey transects (Figure 1) as units of display. We will use 4-D data draping methods to display data layers for fish and plankton abundance, depth, currents, surface temperature and fluorescence as baseline data for process and monitoring studies conducted in the CCS north and south of Cape Blanco, OR. During the first year of study we will begin testing hypotheses concerning the spatial relationship of large (3-10 km in width), high-density, euphausiid patches, observed along the shelf break during the 1995 survey (Figure 2), to local upwelling, onshore currents, and alongshore currents and to the spatial distribution of fish shoals.

This page was last updated on March 15, 2007.

Maintained by:
Hal Batchelder
College of Oceanic and Atmospheric Sciences
Oregon State University
Corvallis, OR 97331-5503
phone: 541-737-4500; FAX 541-737-2064