Harmful algae & Fraser sockeye – liveblog

Dr. Jack Rensel, Rensel Associates Aquatic Sciences (works with Puget Sound fish farmers on permitting/etc., but not BC farmers)

Harmful Algal Blooms and Possible Effects on Fraser River Sockeye Salmon

11:04 Intro

Much of this talk is based on co-author Nicola Haigh’s 10-year sockeye database.

Target algae of interest: Heterosigma akashiwo, HAMP database

11:06 Background

Heterosigma is a microflagellate that kills farmed fish in Puget Sound, BC, and beyond (but not Korea).   Associated with eutrophication and sometimes kills plankton.  Migrates vertically up to 15m depth, cysts in silty sediments, sometimes blooms over entire basins for long periods (>1 week).

11:12 Initiation of blooms

Initiation often in S Straits of Georgia (and sometimes Bellingham Bay, or Case Inlet).  There are U.S. fish farms nearby in the San Juan area and near Vancouver.  Association with neap tides and southward pulsing dynamics in Straits of Georgia and Haro Strait.

11:17 Wild fish exposure

Some think wild fish will escape by swimming under when cells raft on surface, but cells can be mixed down and continue to be toxic to fish.  Sockeye are surface oriented, both as adults and as juveniles (near-shore).  Since farmed fish in 15m deep pens are dying, it is likely that wild sockeye are at risk, too.

11:19 Fraser River sockeye

Most important stock on the west coast (CA-BC).  They have 4-year predominant life cycle with juveniles readring 1 winter in lake prior to out-migration followed by 2 winters at sea.  Most smolts leave Fraser in May/June; adults return July and August.  Most juveniles migrate out northward, but some go south.  All stick close to coast and many go through the Gulf Islands (Groot and Cooke, 1987; map indicates minimal use of the San Juans).

August 2009 news: deep crash of Fraser River sockeye.  Why?  Total run peaked at ~24M in 1994; ~2M in 2007.  From Pacific Salmon Commission escapement data (1952-2007).

11:25 Harmful Algae Monitoring Program (HAMP) database

Sampling areas on outer and inner Vancouver Island.  Frequent occurrence of blooms in BC, while we go years without blooms in Puget Sound.  2007 saw a huge increase in blooms relative to previous decade.

11:29 Looking for correlations

Comparing time series of marine survival fraction (e.g. from Chilco stock total run size) and bloom index (e.g. S. Georgia Strait sampling area) the smoking gun is Chilco stock inversely correlated with bloom index in S Georgia Strait, and to a lesser extnt in Queen Charlottes and Broughton Archipelago.

What about Puget Sound?  Looking at years in which we had large blooms in both PS and BC, followed two years later by low run sizes.  A mystery is that there are no PS reports of major fish kills during large bloom periods (though at least some dead wild salmonids have been reported in every major bloom reported).

Prior to 1980, most adult sockeye came in through Straits of Juan de Fuca.  Northerly diversion rate has increased since (from ~20% coming in through Johnstone Strait to ~70%).

David Welch did a nice study of tagged smolts, but had to raise to bigger size and they swam through bloom areas in just a few days.  Wild smolts likely hang out longer in shallow, near-shore areas, increasing their exposure risk.

11:42 What is changing?

Masson and Cummins, 2007 show that Strait of Georgia is warming (~2C since 1970) throughout water column.

Warmer springs => earlier blooms => into juvenile sockeye timing

Nitrogen loading from human society increasing; Newton and Van Voorhis, 2003, shows that Possession Sound and Admiralty Inlet are nutrient sensitive.  Human population around Salish Sea is near 4M now, there are many combined sewer overflows (especially around very dense Vancouver), and Victoria won’t treat fully until 2020.

11:47 Monitoring and mitigation

Need ORCA buoys around Puget Sound

Clay is effective in Korea for flocculation; maybe could help in combination with the Solarbee circulators being used in East Coast estuaries.

Chilco stock should be tagged somehow.

Make better use of satellite data, e.g. NOAA CoastWatch Aqua MODIS

11:48 GIS demo shows how satellite data can contextualize tracks of fish migration.

11:55 Alternative hypotheses

Food web problems?

Sea lice (not a problem in PS due to lower salinity).  Contested, but HABs may pre-dispose smolts to sea lice infection.

11;57 Conclusion

HABS are unlikely to be sole cause of long term decline of sockeye recruit per spawner, but may be a major component of smolt loss, especially in 2006 and 2007.

Long term R/S decline since 1989 points to ecosystem oscillation or change.

12:00 Thanks

Mike LaPointe acknowledged for data from Pacific Salmon Commission.

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