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Strait of Georgia Ecosystem Modelling (STRATOGEM)

The Strait of Georgia is a semi-enclosed sea on Canada's west coast. In recent years this ecosystem has undergone many changes. In particular, many once productive fish stocks have declined or collapsed. Although these changes are due in part to increased environmental impacts by humans (fishing, pollution etc.), a growing body of evidence suggests that some of these changes are also linked to ocean climate.

STRATOGEM is a new NSERC Strategic Project involving researchers from UBC, UVic and the Institute of Ocean Sciences (DFO). We will combine field sampling with ecosystem modelling to explore links between winds and the Fraser River outflow on the supply of nutrients that drives plankton production in the Strait of Georgia. Variations in plankton production are believed to be an important factor in determining variations in the production of many commercially valuable fish.

Our field sampling will involve (i) using automated oceanographic instruments to sample water and plankton along the various BC Ferries routes that cross the Strait of Georgia, and (ii) conducting monthly oceanographic cruises in the Strait of Georgia from a high-speed hovercraft operated by the Canadian Coast Guard. Using the oceanographic data we collect, in conjunction with historical data collected in the Strait, we will use a series of ecosystem models to simulate the interactions between physics and biology in the Strait. From these models we will develop a series of "rules" to help fisheries managers evaluate the oceanographic "state of the Strait" in a given year so that environmental data can be incorporated into ecosystem management plans.

We began our field work in April 2002. To see the data we have collected so far, and to find out more about the project, visit the STRATOGEM website.


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Climate Change and Zooplankton Dynamics in the Strait of Georgia

Neocalanus plumchrus is the dominant calanoid copepod in the Northeast Pacific during spring and early summer. Like many calanoids, Neocalanus plumchrus (Neocalanus hereafter) spends much of the year at depth in diapause. Adult Neocalanus spawn at depth in late January - early February and naupliar stages rise through the water column during late winter/early spring. The later developmental stages (e.g. C2's through C5's) occupy the surface layers of the NE Pacific and the Strait of Georgia (SoG hereafter) for about only about 100 days each summer. During this time, however, Neocalanus is a major grazer of phytoplankton stocks, and represents a critical food source for many fish species, including several speices of juvenile salmon.

It has recently emerged that, relative to historical trends, the timing of the peak abundance of Neocalanus in the surface waters has shifted back by about 60 days in the NE Pacific and by about 30 days in the SoG. The underlying cause of this shift remains unclear, but it seems to be linked to recent warming of ocean temperatures, perhaps coupled to changes in the developmental timing of Neocalanus . Coincident with this shift there has been a dramatic decline in the survival of many once productive salmon stocks in the SoG . We have recently undertaken a new field program to determine whether the SoG Neocalanus population is reproducing at the same time and reproducing at the same rate as it did in the past. In the coming years we plan to extend this effort to also consider the population dynamics of other coastal zooplankton species in an attempt to determine whether the sort of changes observed in the Neoclanus population are occurring in other species, too.


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Ecology of Larval Fish

Turbulence and Larval Fish Feeding : In the late 1980's it was proposed that, by increasing encounter rates with prey, microscale turbulence is of net benefit to planktonic predators such as larval fish and copepods. Over the past several years (in collaboration with Pierre Pepin and Bill Leggett) I have conducted a field program in coastal Newfoundland designed to test various aspects of this theory. We have found that not only can turbulence increase feeding success in larval fish, but under certain conditions it also leads to a shift in prey selectivity (from smaller to larger prey under increasing turbulence).  

Otolith Microstructure and Larval Growth : We use otolith microstructure to examine daily growth patterns of larval fish (in much the same way that forest biologists us tree rings to examine annual growth patterns in trees). Many researchers have attempted to correlate the width of the daily bands with the temperature and feeding conditions experienced by the larvae. One of our most interesting findings is that the pattern of otolith growth on the days immediately prior to capture is most likely the result of the environmental conditions experienced by the larvae 5-8 days earlier . Most recently, we have coupled our field observations of larval fish and their zooplankton prey with a circulation model to examine mesoscale patterns in larval growth, and how feeding and growth will respond to changes in environmental conditions.


Recruitment of Larval Fish to NE Pacific Seamounts : There are about 25 seamounts in the NE Pacific with summits shallower than 500m. Many are dominated by various rockfish ( Sebastes ) species. It remains unclear, however, how these populations are maintained. Physical oceanographers have recently identified a new class of eddy, known as Haida eddies , that carry coastal waters from the west coast of the Queen Charlotte Islands into the open NE Pacific. Since adult rockfish are not generally found offshore, it may be that Haida eddies function as an offshore transport corridor for larval and juvenile rockfish and provide an important connection between coastal populations and seamount populations in the NE Pacific. We have collected larval rockfish (and other fish species) from two Haida eddies since 2000. Our goal is to compare the elemental structure of otoliths from these larvae to archival rockfish otoliths from NE Pacific seamounts to determine whether any seamount rockfish originated in coastal waters. For more details, have a look at the poster we presented at the10th Annual PICES Meeting. Also of note is that one of these shallow seamounts, Bowie Seamount , is about to be designated a Marine Protected Area by Fisheries & Oceans Canada, in recognition of its isolated fish populations and the fact that it represents a unique environment within Canadian waters.