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When I bought my place (Pickering Passage) a few years ago it was packed with Manila and littlneck clams. I think it was 2 or 3 winters ago when I found hundreds of clams lying on the surface alive but definitely not healthy. They couldn't dig back down into the substrate. Birds got many of them, then rock crabs came in and really tore up the beach. After that, I had essentially no manilas or littlneck clams left (major disaster for this clam eater). Didn't affect the butter clams or other deeper clams. I assume this was due to freezing temperatures during a low-tide cycle. Is this how clams typically respond to freezing? Are there other explanations I should investigate? My attempts a re-seeding have had limited success, and the natural re-seeding is going very slowly. Previous owner said there were always tons of clams on the beach and he never had a similar die-off. Anyone else have this happen?

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Hi Milt,
This is a very good question, and one that many people are likely dealing with. This year we have seen one of the worst clam die-offs in the last 40 years in many parts of south Puget Sound. Oakland Bay had major die-offs. This sort of event is not common, but it does happen. I think your freezing theory may be true. In addition, large rain events that wash lots of fresh water over the clams can lead to die-offs. Do you have a stream that runs over your beach? Re-seeding is going to be difficult without netting because the small clams are so vulnerable. Clams, like crabs, can go through boom and bust cycles that can last a number of years. If you have a small population of clams and a large population of crabs it is going to be difficult for the clams to survive. As you wait for the natural-set clams to recover, my advice would be to seed a patch under some netting, and carefully monitor the natural recruitment of the area around it. Keep us posted how your recovery project progresses.

Thanks - This is great information and I hope other people chime in with their experiences.

I've observed quite a few instances of winter kill this spring in Hood Canal, Sequim Bay, Oakland Bay and Case Inlet. Manilas are very susceptible to winter kill but it can effect native Littlenecks. It does tend to be limited to only the larger clams in my experience. The two events associated with them but not both in every case are night time extreme low tides during sub zero weather and a recent rain episode. Tidelands where the clams are exposed to freezing winds from the east and north are where the worst mortality occurs. Brutal experience to come upon 10's of thousands of recently dead and dying Manila clams in the spring. Puget Sound had a similar major die off in 2001 but on some beaches it can be chronic. The only solution for Manila clams where this happens is to manage your crop intensely. Plan to harvest immediately upon when the clams reach harvest size.....say on a 3 year cycle. You start to increasingly lose mature Manilas to other natural causes anyway after the 3rd year so it's more cost effective in my opinion to harvest them rather than lose them. Harvest and reseed. Don't garden more than you can handle unless you are willing to accept partial or entire losses of your crop. Faster crop rotation also helps water quality as it speeds up nutrient removal. I haven't tried it but covering your Manila beds with a good layer of pacific oyster clusters might provide some insulation. The mortalities I've witnessed haven't been that extreme in the naturally occurring Pacific oyster beds that contain Manilas in Hood Canal. Worth trying maybe.

Not much you can do about assisting the native Littlenecks in returning to your beach as there isn't a seed source yet available. One thing to keep an eye on though is Butter clam recruitment into the area where the natives use to be. A given amount of clam ground can only support so much clam biomass. I've observed several places where a native Littleneck mass mortality has occurred that were rapidly filled in with Butter clams to the point where the beach was saturated with them but there wasn't any room for native Littlenecks to recruit to. There are several beaches where mortality occurred in 2001 that use to be dominated by native Littlenecks that today have few if any but awesome Butter clam populations. Not at all a bad thing if you like Butter clams but if you want native Littlenecks back in those spots you'll have to thin down the Butters to make room. Consider harvesting both Butters and natives on a regular basis also to allow new recruits of both to become part of your native clam population. There's a tendency where natural mortality isn't very significant for stocks of clams to simply become old....think of towns where everyone is older than 50 years and there are no teenagers or new babies.

One last trick you may try for increasing native clam species abundance is to simply place netting down where their habitat is. Don't put down any Manila seed under the netting. I've had some excellent results from this over the years at a number of sites....not all sites but it can work.

I posted my story earlier, but it isn't there. Mine in not a winter kill problem, but something else. I seeded 4000 Manila under netting the first week in July. At this date (Aug 11) I have a 100% mortality. Ugh. My beach has pretty fine sand, native butters and geoducks. I tried to pick an area with coarser sand, but . . .
Any ideas.

BD