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Salmon, warming waters, damns..

901 views 9 replies 8 participants last post by  cabezon 
#1 ·
#3 ·
That story does a decent job of explaining the issues with dams, but like just about every story I read about salmon, it contains a fair amount of BS.

I'm no fan of hatcheries, but it does wild salmon no good to spread misinformation like a claim that hatcheries are to blame for the shrinking Chinook phenomenon. The simple, hard fact (that no journalist will ever print) is that open ocean fisheries (both rec and commercial) are, damn near 100%, the cause of shrinking Chinook. Every year, a small majority of the world's Pacific salmon are harvested in Alaska's marine waters. Naturally, most of the fishing happens there, because that's where all the fish are concentrated. It's reached a point where fish can't survive the 4-5 years it takes to get really big anymore. It seems the fish are adapting to a shorter lifecycle, to ensure that as many fish as possible get to spawn. That's why we (and the orcas) only see much smaller Chinook on the menu today.
 
#6 · (Edited)
Us living in Washington State have been hearing this story for the last several years. Redfish Lake in Stanley Idaho was literally down to one last salmon. It's real dude. Us humans are changing things and not always for the better. Ask one of your old time local Montana friends how the elk hunt has changed over the years...
 
#10 · (Edited)
Hi folks,
There is an interesting article in US Today concerning the recent deaths of gray whales: https://www.usatoday.com/story/news...-dead-beaches-cause-death-unknown/2352505001/. Often mass die-offs of marine mammals are due to a disease outbreak. But this appears to be linked to an environmental factor - likely too many whales and too little food. Gray whales are unique among baleen whales in foraging on benthic (bottom-dwelling) amphipods. These amphipods form dense mats on mud bottoms and filter phytoplankton. The whales scoop up a mouthful of soft bottom and tube mat; they use their baleen plates to force out the mud and swallow the amphipods. While there are gray whales that spend their summers in Puget Sound and B.C. most depend on amphipod mats in the Gulf of Alaska. A tenable hypothesis for these dead, emaciated whales is that the gray whales have exceeded their carrying capacity. But carrying capacity is not a static number but is influences by environmental variabilty too.

Interestingly, the number of humpback whales that wintered in Hawaiian waters last winter were also down substantially from those observed previous years. [But we haven't seen their corpses.... perhaps because they migrate far offshore.] Humpback whales also feed in the Gulf of Alaska but on krill and herring, not amphipods, via bubble-nets and lunge-feeding. But the krill and herring poplations depend on phytoplankton and zooplankton.

And, the salmon and steelhead that are returning to the Pacific Northwest also feed in the Gulf of Alaska. And we all know how poor those returns have been in recent years. I have also heard reports that catches of walleye pollock are down in the Gulf of Alaska (but up in the Bering Strait and Chukchi Sea).

All these fingers point to a large-scale disruption of marine food webs in the Gulf of Alaska. Phytoplankon need light and nutrients to grow. When the surface waters are warm (= blob), the upwelling of nutrients from deeper waters is blocked. So, there is adequate light for photosynthesis but inadequate nutrients for phytoplankton growth.

Meterologists have been able to measure the extent of the blob (or blobs) and attribute the proximate weather conditions that have favored its development (= persistent high pressure) (see https://www.sfgate.com/news/article/Marine-heat-wave-dubbed-Blob-resurges-in-14457808.php). But they have had less success in determining what has caused these atypical long-term high pressure systems. It is tempting to argue "global climate change" as the ultimate cause, but a long historical baseline record for comparison is lacking in the Gulf of Alaska.

At the core of salmon harvest models are counts of the number of redds, and population estimates of the number of smolts that have made it to sea (= freshwater production). Using historical data of growth and survival of smolts once they are in the ocean, these freshwater population estimates are used to predict the number of returning adults when they are due to migrate back few years later (X smolts reaching the ocean convert to Y number of returning adults). BUT these models assume that the current growth and survival conditions in the Gulf of Alaska are similar to from those growth and survival conditions that growing fish have experienced historically. Clearly, the conditions have changed for the worse in the Gulf and the models have badly overestimated the number (and size) of returning fish. The "North of Falcon" decisions that set fishery allocations are made without any DIRECT sampling of the actual number of returning fish, but paper estimates.

Under this scenario, the catch targets in SE Alaska, off Vancouver Is., and off the Washington coast are far too generous. And very few unharvested fish are left to be divided among the tribes (who typically fish their inshore/freshwater "usual and accustomed" areas"), non-tribal commercial fisheries, sport fisheries, and wildlife (aka Southern Resident Killer Whales). All are starving...

Steve
 
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