Chum and Coho Stream Ecology Project

Measuring young coho helps researchers elucidate interactions between eggs and carcasses of spawning chum and their use in streams by juvenile coho.

Spawning salmon in the Pacific Northwest make an important nutrient contribution to coastal, freshwater and riparian ecosystems, interacting with mammals, birds, fish and amphibians.  Many salmon runs are also very depressed. The documented decline in salmon abundance in the Pacific Northwest over the last century has drawn a lot of attention to conservation needs, both for salmonids themselves, but also for the stability of ecosystems relying on these energy inputs.

Field crew from the collaborative research effort between Raincost, SFU and Heiltsuk Fisheries lug the morning's equipment into a study site. Above: SFU's Alison Page and Raincoast/Heiltsuk Fishery's Doug Brown.

Raincoast’s Chum and Coho Stream Ecology Project is part of a larger research program with Simon Fraser University that focuses on the interactions between salmon and their environments. Long term field studies and experiments have been set up in order to understand how various human impacts on salmon and their habitats translate into population declines and recovery, and how these also affect the many species of freshwater and terrestrial plants and animals linked to nutrients and food web interactions involving salmon.

This project has set out to study one remarkable salmon interaction – the feedback loop between spawning chum salmon and juvenile coho salmon hatching and rearing in freshwater streams. Chum carcasses and eggs provide very high energy nutrients during the short growing season for juvenile coho, and have been found to affect various aspects of growth, body condition and survival. The success of juveniles in stream environments is a particularly

PhD student Michelle Nelson and Dr. John Reynolds measure water features that help characterize small streams.

important component of population dynamics of coho salmon, because unlike most other salmonid species, coho rear in freshwater streams for 1-3 years before they migrate to the sea.  This dependence on stream environments makes coho particularly susceptible to human disturbance, which has led to serious population threats in some areas. It is thought the seasonal availability of spawner nutrients may be critical to the population regulation of stream-rearing juvenile coho.

The field work for this project is based from Raincoast’s field station on Denny Island in the Great Bear Rainforest. This is the traditional Territory of the Heiltsuk First Nation, our project partners through the Heiltsuk Fisheries Program who help undertake spawner counts in the fall.

Setting traps to capture juvenile salmon. Once counted and measured, the fish are released.

To date, four field seasons have been completed (spring and fall, 2007 and 2008). Field seasons involve detailed stream assessments, juvenile census, and sample collection of various plant and animal material.  So far, 4000 person-hours have gone into the capture and collection of over 2000 juvenile salmon along with hundreds of terrestrial and aquatic invertebrate samples.  We have 25 watershed study sites, including many small, previously unstudied streams. Laboratory work is now in progress, which involves detailed invertebrate community measurements, fish stomach content analysis, isotope analysis, and analysis of coho age structure using scales and ear bones (otoliths).

This research will serve two purposes. First, it will advance our general understanding of the role of trophic cascades and feedback loops in ecosystem dynamics.  Second, it should help inform more holistic management of salmon and their habitats – an objective that has been underscored as a high priority by local communities and conservation groups, and set out as a key strategy in the Canadian government’s Wild Salmon Policy.