Dynamics of southern resident orcas and salmon

“No fish; no black-fish.” That’s how the First Nation saying translates, says Ken Balcomb. When there are no salmon in the Salish Sea, there are no resident orcas.

Has modern marine science reached the point that it, too, could articulate so elegantly the ecological dynamics of the Pacific Northwest’s endangered icons — Pacific salmon and the southern resident killer whales that prey upon them? We at Beam Reach aspire to find out — by mashing up data sources (from the Fraser and the Columbia rivers) with our own observations of the Salish sea (at the Lime Kiln lighthouse in the San Juan Islands) in this single plot, updated daily.

Our initial choice of data sources is motivated by the amazing result of Hanson et al., 2010 — southern residents prey almost exclusively on Fraser River Chinook salmon during the summer months. This led us to what we believe are the longest, most-continuous measures of returning adult Chinook, discharge, and temperature on the Fraser River: the Chinook test fishery at Albion and the discharge (flow) and temperature monitoring station ~75 km upstream at Hope (1912-present). The Albion test fishery provides daily adult Chinook catch-per-unit-effort (CPUE) for a standard (1200′, 8″ mesh) net deployed in the river by fishing vessel(s). The Hope station generates flow in cubic meters per second (m^3/s) and temperature in degrees Celsius (oC). See map below for measurement locations.

View Lime Kiln ocean observatory in a larger map

Salish Seas study site and measurement locations.

Our second data search was focused on the Columbia River due to growing evidence that southern residents seek the biggest, fattest fish returning to other West Coast rivers during the non-summer months. This idea is supported by scarce historic sightings, along with satellite tracks, prey samples, and acoustic detections obtained by Brad Hanson and colleagues in recent years. We obtained daily counts of adult Chinook at the Bonneville dam (Chinook/day) and flow measurements at the USGS monitoring station at the Dalles ~50 km upstream (1878-present, converted to m3/s and oC).