Beam Reach

2013: the year southern ‘resident’ killer whales were transient

The year 2013 was an exceptionally unusual one in the world of southern resident killer whales and Pacific salmon. Most noticeably, the southern residents returned to the Salish Sea later than normal, raising concerns among conservationists. Throughout the summer, researchers and whale watch operators noted that the whales were present less than normal and the duration of their visits to the Salish Sea were abbreviated.

Meanwhile, the Chinook salmon runs on the Fraser plummeted while 80-year record returns were counted on the Columbia at the Bonneville dam fish ladder. Combined with new evidence from satellite tags that the southern residents are focused on Columbia salmon during the spring months, the sighting patterns of 2013 may indicate a transition for the urban estuary known as the Salish Sea — from one with “resident” orcas to one with southern “transient” fish-eating orcas.

Killer whale trends

Based on data from the Orca Network sighting maps from the past decade (see figure below), records were set or tied in 2013 for the least number of days spent by southern residents in the historic core of their summer habitat (the west side of San Juan Island in Haro Strait). The SRKWs were seen only once in March and not at all in April. Even more shockingly, they showed up only 5 times in May (a record low) and were observed 15 times in June, a low level not seen since 2001.

The same data show downward trends in monthly sightings over the last decade. With the exception of a high in 2011, the March prevalence has been flat or decreasing. There are stronger, more continuous downward trends in April and May sightings.

We used the OrcaMaster database maintained by The Whale Museum to look for trends in sighting “gaps” — the number of consecutive days between sightings of J pod members within the Salish Sea.   Val plotted running averages of 2013 gaps versus a historic average (1992-2012) and found that in the spring of 2013 sighting gaps were 2-5x longer than the average.  Only during and after September of 2o13 did the gap return to a normal duration.  (Maybe we should look at trends in Salish Sea chum run?)

Historic trends in J pod sighting gaps (Val Veirs, using R and ggplot)

Chinook trends

One way to characterize the foraging conditions the SRKWs experienced in 2013 within the Salish Sea and on the outer coast is to examine the Chinook salmon counts from the Fraser and Columbia rivers. The Albion test fishery on the Fraser provides a proxy for the abundance of Fraser Chinook, the primary prey of SRKWs in the Salish Sea from spring through the summer . The fish counts at the Bonneville dam on the Columbia are a proxy for the abundance of Chinook on the outer coast of Washington.

As marine naturalists like Jane Cogan and Monika Wieland have pointed out, 2013 was an exceptionally bad year for Fraser Chinook returns. The fish arrived late and the cumulative returns were well below this historic average and only slightly better than in the worse year on record, 2012.  The highpoint of the 2013 run was the peak around the 3rd week of August that may also be related to a pulse of Chinook recorded in the first two weeks of July off southern Vancouver Island (in the Area 20 test catch fishery).

In contrast, adult and jack Chinook abundance in the Columbia River has been on the rise for the past couple decades, with 2013 standing out as a record-setting year for adult Chinook.

Daily Chinook counts at Bonneville show that while most of the record-setting abundance was due to the fall run, the spring run also had peaks well above the 10-year average.

The spring run passed Bonneville from late April to late May, 2013.  This timing is consistent with the timing of the spring Columbia Chinook run in 2012.  Since Bonneville dam is about 200 km upstream from the river mouth and adult Chinook swim at about 0.5 m/s, we could expect that the returning Columbia Chinook were in the ocean at least until about a week before they reached Bonneville ( 200,000 m / 0.5 m/s = 400,000 seconds = ~5 days).  So where were the southern residents in March and April of 2013, since they weren’t being sighted in the Salish Sea?  We don’t know about J and L pods, but the satellite tag deployed on K25 indicates the likely position of K pod (up until April 4).

The answer is: during March, 2013, K25 was spending a lot of time going back and forth along the continental shelf of Washington (and to a lesser extent Oregon) with a track that centered on the mouth of the Columbia River.

We need to know more about when the returning Columbia fish are on the continental shelf and accessible to the southern resident killer whales.  But these salmon trends from the region’s biggest rivers combined with migratory patterns of the orcas strongly suggest that the southern resident killer whales may be happy to move their “residence” to wherever the eating is best!  Perhaps we are watching them become southern transient fish-eating killer whales?!

Anecdotal observations of orca-salmon interactions

When the fish-eaters were around during the summer of 2013, they displayed some unusually aggressive foraging. A (potential) prize Chinook salmon was taken off a derby fisherman’s line and became the focus of a KPLU radio story and an impressive photo of the one that was eaten away…

The part that didn’t get (taken) away. (credit: Kevin Klein)

This local predation event was a first for Washington State (as far as we know), though it was comparable to one by Alaskan fish-eating killer whales. In the video below, the Alaskan whales were foraging amongst fishing vessels and happened (probably visually) upon a large hooked Chinook. (Mute your speakers if you don’t want to hear angry and amazed fishermen cursing.)

Later in the summer of 2013, back in Washington, a whale watch captain obtained this video of southern resident killer whales pursuing a large (likely Chinook) salmon alongside the boat —

Could these uncommon foraging observations indicate that the southern residents were having a tough time finding enough to eat in the Salish Sea?  We’d be interested in hearing from local fishers about how often they’ve had fish taken off their lines by Southern Residents.  Monika assures us though that it is common to observe SRKWs pursuing salmon around and underneath whale watching boats, so maybe we should attribute the second video to more typical foraging and take it as evidence that orca-salmon interactions in the fall of 2013 were more typical than earlier in the year.