Hydroacoustic krill abundance monitoring


Euphausiid crustaceans, commonly known as “krill”, represent a primary food resource for pelagic fish, seabirds and marine mammals in the California Current ecosystem. To understand dynamics in fisheries and marine wildlife populations, it is critical to obtain, analyze and share data on the distribution, abundance, and life history attributes of krill in this ecosystem. We have processed hydro-acoustic surveys across the entire California Current Ecosystem - from Port Angeles, Washington to San Diego, California.

We used the EchoView software to process echo-sounder data. A set of algorithms are used to distinguish krill from other signals. Processed Nautical Scattering Coefficient (NASC) values are integrated vertically from a depth of 400 m to 10 m below the surface.

Cruises were conducted between March and August from 2000 to the present.

Modeling krill distribution and abundance


With respect to ecosystem-based management and protection (e.g., design of marine protected areas), it is important to understand, and if possible predict, the abundance and spatial distribution of key mid trophic level prey species.  Krill are an integral component of the California Current Ecosystem (CCE) that support commercially valuable as well as protected species.  It has been postulated that krill have affinities for particular bathymetric and hydrographic habitats (i.e. canyons, isobaths, fronts), but it is unclear how these factors collectively influence krill aggregations.  We surveyed the spatial distribution of krill using hydroacoustics in central-northern California and modeled their distribution in relation to bathymetric slope, distance from shelf break/canyon heads and fronts, phytoplankton/chl-a concentrations, and sea-surface height anomalies (eddy structures) using a Regional Ocean Modeling System (ROMS) coupled to an ecosystem model (CoSINE; Ocean Modeling Group, Santora et al. 2013), as well as an Individual-Based Model (IBM) parameterized for Euphausia pacifica (Dorman et al. 2005).  The model also outputs spatially-explicit distributions and can be used to understand "hotspot" formation.  This project has been supported by the NASA Research Opportunities in Space and Earth Sciences (ROSES) program and California Sea Grant.

"Hotspots" of productivity and trophic transfer in the open ocean


Understanding spatial variation in biological activities is critical to the ecosystem approach to management, especially for marine spatial planning.  In this project we are using satellite remotely-sensed data on phytoplankton (proxied by chlorophyll-a concentrations) and shipboard acoustic surveys of zooplankton (krill) and visual observations on marine birds and mammals to test the hypothesis that "hotspots" of phytoplankton, krill, and consumers co-vary spatially in the California Current.  We define "hotspots" based on the persistence of elevated values of chl-a, krill, and marine bird density in space and time.  We are modeling chl-a and krill "hotspots" in relation to seafloor and coastal topographies and water mass characteristics, and contours of seabird densities in relation to krill and chl-a concentrations.  Satellite imagery provides a holistic perspective on productivity in this large marine ecosystem which is not available by other means, yet provides key information on spatial variability in ecosystem properties of significance to upper trophic level species of management and conservation concern.  Our ecosystem-wide analyses have revealed open ocean "hotspots" within the California Current that appear to be of special biological significance and warrant future research, monitoring, and possibly protection to maintain and/or enhance ecosystem functions, such as feeding interactions of top predators.  This project has been supported by the Resources Legacy Fund Foundation, the Marisla Foundation, and NOAA's California Current IEA Program.

Information about the KrillCam is coming soon.