David Welch, PhD Kintama Research Services Ltd General Outline
1. Juvenile Year – Smolt Migration After Leaving the Fraser i) Strait of Georgia ii) Beyond– The Continental Shelf Migration
2. Immature Year(s) – Life in the Open Ocean(?)
3. The Return Migration (Mature Sockeye)
4. Survival– Where Can it Change? Sockeye Life History Stages Alevin Fry
Smolt The Marine Immature Phase: 1 1 2 /2 ~ 3 /2 years of a 4~5 year life Male span
Mature Female BC Sockeye Geography
Alaska
Bering Sea
SE Alaska (Panhandle)
Q. Charlotte I/Haida Gwaii Queen Charlotte Sound Aleutian Islands Strait of Georgia Juan de Fuca Gulf of Alaska Strait North Pacific Ocean The Known Ocean Distribution of B.C. Sockeye 1. Juvenile Marine Migrations
A) Strait of Georgia B) Coastal Shelf Northwards
Key Point: There are a mixture of migratory & non- migratory sockeye populations with different behaviours : Most Fraser River sockeye stocks migrate north—rapidly Harrison Lake sockeye remain as long-term residents; Rivers & Smith Inlet (Central Coast) sockeye may remain as residents of Queen Charlotte Sound Fraser Sockeye Trends in Productivity: Harrison Lake vs All “Others”
Figure shows time trend of productivity since 1951. Of 19 stocks, only Harrison Lake shows increased productivity in the last 20 years Harrison Lake sockeye have both a radically different marine migration and different marine survival pattern to other Fraser River stocks Where known, this will be contrasted in this presentation The Early Sea Migration
Research using nets to catch juvenile sockeye salmon found that most migrated north. A small component migrated through Juan de Fuca Strait to the south. POST Telemetry array validated and refined this (See later) Timing
Fraser sockeye are near the southern limit of the distribution. They migrate out of their natal lakes in late April~early May Acoustic tag data indicate that they reach the mouth of the Fraser River in ca. 4 days (Cultus Lake) to 8 Chilko Lake days (Chilko Lake) Cultus Lake At 8.6 km/day, they then reach the north end of Vancouver Island, 400 km distant, in another 400/8.6=46 days The average Strait of Georgia/Johnstone Strait/Queen Charlotte Strait residency is thus 1.5 months This makes the mean date of entry into Queen Charlotte Sound as mid- late June. Strait of Georgia Residence Times:
The 2009 failed runs DFO July Strait of Georgia Survey
of Fraser sockeye had 100 largely left southern y = -3.372x + 13614 BC by late June 80 R² = 0.504 Only the extreme tail end of the migration 60 was left in July– except for Harrison 40
20 July Sockeye Catch (CPUE) CatchSockeye July
0 Jun-11 Jun-21 Jul-1 Jul-11 Jul-21 Jul-31 Trawl Survey Dates Fraser Juvenile Sockeye (All Stocks)
May-June October-November
July-August February-March West Coast Vancouver Island Sockeye
May-June October-November 60 60 May-June Oct-Nov
SEAK SEAK 56 56 GOA GOA NBC NBC QCI QCI
CBC CBC
52 52 Latitude (ºN) Latitude
Latitude (ºN) Latitude WCVI WCVI
48 48
WA WA
44 44 160 154 148 142 136 130 124 160 154 148 142 136 130 124 Longitude (ºW) Longitude (ºW)
July-August February-March 60 60 July-Aug Feb-March
SEAK SEAK 56 56 GOA GOA NBC NBC QCI QCI
CBC CBC
52 52 Latitude (ºN) Latitude
Latitude (ºN) Latitude WCVI WCVI
48 48
WA WA
44 44 160 154 148 142 136 130 124 160 154 148 142 136 130 124 Longitude (ºW) Longitude (ºW) Harrison River Sockeye
May-June October-November 60 60 May-June Oct-Nov
SEAK SEAK 56 56 GOA GOA NBC NBC QCI QCI
CBC CBC
52 52 Latitude (ºN) Latitude
Latitude (ºN) Latitude WCVI WCVI
48 48
WA WA
44 44 160 154 148 142 136 130 124 160 154 148 142 136 130 124 Longitude (ºW) Longitude (ºW)
July-August February-March 60 60 July-August Feb-March
SEAK SEAK 56 56 GOA GOA NBC NBC QCI QCI
CBC CBC
52 52 Latitude (ºN) Latitude
Latitude (ºN) Latitude WCVI WCVI
48 48
WA WA
44 44 160 154 148 142 136 130 124 160 154 148 142 136 130 124 Longitude (ºW) Longitude (ºW) Late Summer-Strait of Georgia Dominated by Harrison L. Sockeye Almost all
juvenile other Fraser Strait of Georgia other A Strait of Georgia C sockeye Trawl survey Fraser River Trawl survey River 3% September 13-24, 2008 1% November 19-21, 2008 collected in n = 207 n = 60 September ~ November trawl surveys are Harrison River sockeye Since Harrison Harrison River River Harrison 99% 97% sockeye do Strait of Georgia other B Gulf Islands other Fraser D not migrate Trawl survey Fraser Trawl survey River 2% September 16-25, 2009 River 4% November 17-19, 2008 north, the one n = 110 n = 108 anomalous (and highly productive) stock is the one that stays Harrison in the Strait of River Harrison 96% River Georgia. 98% Early Summer Juvenile Sockeye Abundance (BC Coastal Waters) 2008 Fraser smolts only 2007 in slightly higher 2008 abundance than 2007 Fraser smolts June Hecate Strait catches show little evidence of the expected 20-fold difference in catch numbers or the proportion that are Fraser sockeye First Autumn at Sea The Offshore Migration? Juvenile salmon migration pathways- September~Early December Catches Key Point: juvenile salmon remain strictly on-shelf for many months Red circles show regions where salmon are caught Yellow crosses show zero catches 200m & 1,000m depth contours shown Juveniles never leave the shelf Data is for all salmon species combined Juvenile salmon distribution in October (All species)
Young salmon enter the Juneau ocean in April-May
Smolts could swim 2,000 km by October; Fraser sockeye therefore don’t move off-shelf but remain on the shelf for extended periods Vancouver At least some have taken Island up residence? Alaskan Peninsula Salmon Distribution (Late November - Early December; All Species)
Bering Sea
10% of juveniles caught (Aleutians) off-shelf, 7 December 1997 2nd & Later Years of Life at Sea Few Juvenile & Immature BC Sockeye in the Bering Sea (Autumn)
Only a few BC/SE Alaska sockeye (all stocks combined) Sockeye Migration— The Open Ocean
Very little data was available to construct this conjectural model of movements, owing to technical limitations of 1960s tagging technologies Stock specific movements of Fraser River sockeye are unclear, but there is evidence that different sockeye stocks are in different places in the offshore (next slide) Offshore Distribution in June
Offshore Limits to the Sockeye Distribution—And Possible Implications of Global Warming
Current & Doubled CO2 Projected Thermal Distribution-- Sockeye December 7ºC Isotherm
July 14ºC Isotherm Maturation & the Return Home The Migration Around Vancouver I Food & Survival Gulf of Alaska Zooplankton Changes Large-scale ocean changes can occur both coastally and offshore Brodeur & Ware showed that the both Gulf of Alaska plankton and pelagic fish and squid abundance doubled in the 1980s; these are 1956–1962 sockeye prey. The 1980s was a period of rapid increases in Fraser sockeye abundance Plankton measurements for the most recent decade are difficult to compare with prior data (but see next slide) 1980–1989 The 2010 Fraser Sockeye Return 2009 vs 2010 Adult Return Years Animation of Cultus Lake Sockeye Migration (“Strait of Georgia Survival”) (2007 Smolt Release) Cultus Lake Sockeye & 2009 Fraser Sockeye Collapse 2004 2005 2006 2007
2007 Outmigrating Smolt Survival (±95% Confidence Intervals) Survival as high or higher than in prior years~ So where did the 2009 adult sockeye fail to survive? Most Mortality of Tagged Smolts Occurred After Leaving Queen Charlotte Strait
Salmon per Survivor (Mortality) 30 28.0
25
20
15
10
5 3.6
0 Cultus Lake - Queen Queen Charlotte Strait- Charlotte Strait Adult Return Summary – Migration & Distribution Smolts travel long distances along the continental shelf before eventually migrating to the offshore North Pacific Ocean The offshore distribution of BC sockeye is thought to be mainly in the Gulf of Alaska The offshore phase of the life history is least well understood, but abundant sockeye stocks from the Bering Sea co-occur here, as well as other BC stocks that did not collapse in 2009. (2010 reports are that high sockeye returns occurred across the North Pacific) Summary - Migration Fraser sockeye stocks (other than Harrison) migrate out of the Strait of Georgia Most take the northern route and migrate at 1 body length/second (8.5 km/day for 10 cm smolts) They migrate 400 km through the Strait of Georgia, Johnstone Strait/Discovery Passage, & Broughton Archipelago to reach Queen Charlotte Sound in ca. 40 days Harrison Lake sockeye (increasing in productivity) are an anomaly—they migrate to sea soon after birth, remain long periods in the Strait of Georgia, and then apparently exit via Juan de Fuca Strait and overwinter on the west coast of Vancouver Island. Long-term residence in the Strait of Georgia (&/or not migrating north through Johnstone Strait) is thus associated with higher marine survival. A General Thought & Caution Adult returns generally thought to be determined “early in the life history” As a result, there is a tendency to assume that events early on determine adult returns (this makes the research easier, by allowing a narrower (and simpler) focus) Though a common assumption, there is little data to support it! An important point for the Commission to remember that a survival drop to 1/10th its normal value can reduce adult returns to 1/10th as well– no matter where in the life history it happens This simple point is often overlooked, because biologists assume that most mortality happens very early in the life history. This assumption is almost never tested.