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Updated June 17, 2001 |
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Comparative study of the dynamic population, secondary productivity, and reproductive ecology of the euphausiids Euphausia pacifica and Thysanoessa spinifera in the Oregon upwelling region |
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Jaime G�mez-Guti�rrez |
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College of Oceanic and Atmospheric Sciences, Oregon State University, 104 Ocean. Admin. Bldg. Corvallis, OR 97331-5503 USA. E-mail: [email protected] |
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Introduction |
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This Ph.D. dissertation proposal is focused on comparing the seasonal abundance, population dynamics, vertical distribution, secondary production by body growth and egg production, egg hatching success, and egg sinking speed of the euphausiids Euphausia pacifica and Thysanoessa spinifera from the Oregon coast population. |
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The Oregon upwelling region is inhabited by about 10 to 12 euphausiid species. The euphausiids Thysanoessa spinifera and Euphausia pacifica are the dominant species accounting for about 95% of euphausiid abundance and biomass. The biology, ecology and population dynamics of E. pacifica have been extensively studied during the last 40 years, particularly in their larval development and morphogenesis (Ross 1981, Knight 1984, Rumsey and Franks 1999), fecundity (Ross et al. 1982, Iguchi and Ikeda 1995, 1999), growth rate (Smiles and Pearcy, 1971, Brinton 1976, Ross 1982, Bollens et al. 1992, Tanasichuk, 1998a), molting rate (Dexter, 1977), vertical distribution (Bollens et al. 1992), population dynamics (Brinton, 1976, Tanasichuk, 1998a), and feeding rates (Ohman 1984, Dilling et al. 1998, Passow and Alldredge 1999). However, T. spinifera has received much less attention, and relatively little is known about its biology and ecology in the North Pacific (Summers 1993, Tanasichuk 1998b). I plan to do a comparative study of both species in their biology and ecology in the Oregon upwelling region. Detailed knowledge about population parameters of those euphausiid species is essential to answer some of the basic questions about the importance of euphausiids to energy flow through the Oregon pelagic ecosystem or the importance of seasonal or long-term climate effects on variations in euphausiid populations. Large seasonal environmental changes make it necessary for species to develop strategies in recruitment/overwintering survival of poor conditions and maintain the stocks on a stable level. Key parametes of the life cycle like sex ratio, breading season, appearance of eggs and larvae will be studied as well as functional characteristics like mortality, growth and recruitment. |
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Important NOTE: I propose a dissertation of three major chapters, but as in any scientific research the final number of chapters and their topics could change according the results obtained. |
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Chapter 1. Seasonal and interannual abundance variation, and population dynamics of the euphausiids Euphausia pacifica and Thysanoessa spinifera along the Newport Hydrographic line, Oregon USA (1970-1972). |
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Objectives |
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Determine the cross-shelf, seasonal, and year-to-year variability of abundance of all the life-stages of E. pacifica and T. spinifera during 1970-1972 along the Newport Hydrographic line (NH1-NH60) (see figure 1). This line was sampled every two weeks during 1970-1971 and monthly during 1972. |
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Estimate the seasonal and year-to-year variability of secondary productivity due to body growth of E. pacifica and T. spinifera during 1970-1972 along the Newport Hydrographic line using cohort analysis. |
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Chapter 2. Egg production, hatching success, and egg sinking speed of the euphausiids Euphausia pacifica and Thysanoessa spinifera from the Oregon coast populations. |
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Objectives |
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To know the biometry, morphology, embryology, and development time of the eggs of Euphausia pacifica and Thysanoessa spinifera. |
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To estimate the egg production rate (EPR) and female weight-specific growth rate attributable to egg production of Euphausia pacifica and Thysanoessa spinifera for LTOP and Mesoscale cruises. |
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To determine the vertical distribution and cross-shelf distribution of eggs and early larval stages of Euphausia pacifica and Thysanoessa spinifera from the Sun Flower line (45�N) during 1977-1978. |
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Determine the egg sinking rates of Euphausia pacifica and Thysanoessa spinifera under laboratory conditions. |
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Determine the mortality rate of euphausiid eggs using demographic methods from the Sun Flower line (45�N) during 1977-1978. |
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See the proposal approved by the Mamie Markham award 2001-2002. Hatfield Marine Science Center |
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Most samples from this chapter will be collected on board the RV Elakha. See also the zooplankton pump |
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Chapter 3. Egg and larval dispersion of the euphausiids Euphausia pacifica and Thysanoessa spinifera associated with mesoscale variability in the Oregon upwelling region. |
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Objectives |
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Determine the horizontal distribution and dispersion patterns of the eggs, early larval stages, and females stage IV of T. spinifera and E. pacifica in the Oregon upwelling region during April to September 2000. There are five oceanographic surveys carried out by the L-TOP program and the Mesoscale variability research programs. Here I show an example of sampling stations during the Mesoscale II (July-August 2000) |
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Locate temporally and spatially the main spawning regions of both species and associate the mesoscale variability with larval dispersion patterns. |
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To do the coupling of an individual-based population dynamics model off the euphausiids Euphausia pacifica and Thysanoessa spinifera to a 3D circulation model in the Oregon upwelling region. This part of the chapter strongly depends on the model circulation developed by COAS physical oceanographers, so this still as a tentative objective. |
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Links to research programs |
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U.S. GLOBEC Northeast Pacific |
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Researchers from GLOBEC |
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Coho and Chinook salmon landing time series |
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Who said that to be a zooplanktologist is easy? |
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