GLOBEC - A comparison of the effects of coastal upwelling on the population dynamics and vital rates of the euphausiids Euphausia pacifica and Thysanoessa spinifera in the north
ern California Current, north and south of Cape Blanco, OR
William T. Peterson [NOAA Northwest
Fisheries Science Center and Oregon State University,
Hatfield Marine Science Center and
the Cooperative Institute for Marine Resource Studies]
The project proposed here is directed at describing the population dynamics of two of the GLOBEC target organisms, the euphausiids Euphausia pacifica and Thysanoessa spinifera. The project will involve sampling at biweekly intervals along a transect line off the central Oregon c oast at Newport, OR for the purpose of describing temporal variations in euphausiid abundance, recruitment, vital rates and production. This high-frequency sampling program will be supplemented with bimonthly cruises with sampling along four transect lin es: two off Oregon (Newport and Coos Bay) and two off northern California (Crescent City and Eureka) during GLOBEC Long-Term Observations Program (L-TOP) cruises. Data from these survey cruises will provide information on spatial variations in euphausiid biomass, numerical abundance, vital rates and production in the waters throughout the GLOBEC study region (Newport OR south to Eureka CA). The project proposed here has four objectives:
All of the above data will be passed to one of the GLOBEC modelers (H. Batchelder, Univ. of California at Berkeley) who is devel oping an individual-based model for both euphausiid species; the proposed work is presented in the context of examining the relationship between the ecology of euphausiids and salmonid growth and survival.
We will sample along the Newport OR hydrographic line (44° 40'N) once in January, biweekly from February through October, and monthly in November and December for a total of 21 cruises. Most of this work will be done from a 55' coastal research ves sel. We will visit stations 1, 5, 10, 15, 20, 25, and 30 miles from shore during the daytime and do CTD casts, make secchi depth measurements, take water samples from the surface and 10 m for chlorophyll and nutrients, and sample the zooplankton with a l ight-weight 60 cm Bongo net with 202 m mesh hauled vertically from 100 m to the surface. At night on the return leg, we will sample at the 25, 20, 15, and 10 mile stations for juvenile and adult euphausiids using 70 cm 333 m mesh Bongo nets towed over t he upper 50 m of the water column. At the 25 and 15 mile stations, live euphausiids will be collected by suspending a 1-m diameter 333 m mesh net at a depth of 20 m and sampling as the ship drifts. Adult female euphausiids will be sorted from the catch and incubated for measurement of egg production rates. The preserved samples from these 21 cruises will be enumerated by euphausiid species and developmental stage and will be used to describe seasonal cycles of abundance of each life cycle stage. Previ ous sampling off Newport at biweekly intervals has demonstrated that large phytoplankton blooms in summer associated with event-scale relaxation of upwelling lead to bursts in euphausiid egg production; cohorts are generated at this time. For those perio ds when a cohort is clearly identifiable, we will calculate stage-specific developmental rates. From the density estimates of each developmental stage, we will calculate rates of recruitment and mortality and, through length-frequency analysis, we will c alculate growth and production rate.
Five of the 21 cruises along the Newport Line will be carried out as part of the U.S. GLOBEC Long-Term Observations Program. Presently, we are funded to conduct cruises five times per year along transect lines off Newport OR. Three of these cruises also include transect lines off Coos Bay (43° 13'N), Crescent City CA (41° 54'N) and Eureka CA (40° 54'N). We have prepared a renewal request to continue this work. If funded, we will sample euphausiid s with vertical net tows to 100 m using 60 cm Bongos 202 m mesh nets (for larvae) both day and night, with a 1 m2 MOCNESS with 333 m mesh over several depth strata and with 70 cm 333 m mesh Bongo nets at night for juveniles and adults (along the Newport L ine only). In addition, females will be collected for egg production measurements as described above at two stations along each transect line during each of the five cruises. The purpose of this work is to study spatial variations in euphausiid biomass, spatial variations in density of euphausiid eggs, larvae, juveniles and adults, and spatial variations in euphausiid egg production rates off central Oregon and northern California, north and south of Cape Blanco (43° N latitude). The contrast betw een euphausiid population dynamics north and south of Cape Blanco is of particular relevance to GLOBEC because coho salmon that reside in ocean waters and return to rivers north of Cape Blanco are declining in abundance, while those that reside in ocean w aters and return to rivers south of Cape Blanco have relatively high growth and survival rates. Our data will contribute to the GLOBEC goal of determining if there are differences in biomass and production of GLOBEC target species in these contrasting co astal regions. All of this work will be repeated in each of five years allowing us to document interannual variations in the population dynamics and production of the two dominant euphausiid species, Euphausia pacifica and Thysanoessa spinifera< /I>.
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