Will The Sockeye Salmon Withstand This Crisis?

[Hypognosis]

It may be a one-off bad year. It may be part of a long term climate shift.

Whatever your stance on climate change, did your understanding of the workings of nature give you the slightest inkling that cascading problems, like this one, can happen?

http://thkpr.gs/3685149


I sometimes contend that evolution doesn't really happen until there is mass-scale death brought about by environmental crisis. In this example, mass death might be required to assure the survival of just enough of them to assure the species can ride out the crisis.

[Hypognosis]

Thanks for replying, divebuddy. I nearly bumped it after no replies in 5 hours but remembered that this knocks it off the 'unanswered' tab and it really would have got ignored.

i) Yes, hunted to extinction is one possible fate. We came perilously close to losing Cod, not so long ago.

ii) Dying after the eggs are fertilised is part of the normal life cycle. It is all well understood and makes sense in that, having done their one task in life, dying immediately stops them from hoovering up any of the oxygen or food in the stream and also ensures the hatching fry do not get eaten.

What's gone wrong here is that they're dying way before they even reach the spawning grounds.

iii) //OK, but what do you contend at other times.//

Its corollary, which is that, if an environmental niche persists for eons then there is no pressure to evolve and the species occupying that niche will endure with few changes. Crocodile, alligator, coelocanth, sharks, dragonflies, stromatolites and so on. Few visible differences from their fossil equivalents. If a design is a good fit to its environment, then variants (deviants, mutants, if you insist) are more likely to be a substandard fit than to be an improvement.

In the salmon's case, they need to have a heat tolerant variant, to keep that river's population going just for this crisis year and could revert to the norm in generations to come.

I will assume that the species uses other rivers too and will not be utterly wiped out, it is just a substantial chunk of population at stake, being that it is a big river with many tributaries. It could be recolonised after a catastrophe if some fish have adventurous tendencies and do not conform to the "return to river they spawned in" cliché. Finding a depopulated major river would have a major payoff for the lucky few who get to breed there first.


It's early a.m. and I need sleep. Will return to this tomorrow.

[wildwood]

Most salmon species are important commercial species so would not be allowed to die out, saving worldwide catastrophes.
Salmon are easily introduced into other suitable rivers to eventually breed there. Salmon farms will assure that there will always be an viable gene pool available for stock fish.

I feel climate change - man made or natural - will very much affect certain species. Already the polar bears are in steep decline because the disappearing ice floes forces them onto inhabited land, thus in conflict with Man.
Large sections of breeding Emperor penguin chicks/eggs are being wiped out now because the sea doesn't freeze far enough upland.
The presence of foreign insect species in unusual lands is very important. Once established they will be displacing some endemic species and could have a serious effect on commercial cereal crops.

[Hypognosis]

Thanks wildwood.

The more I learn, the more I appreciate how the earth is sorted into areas where the extremes of temperature determine whether it is part of a species' "range".

There is no shortage of ones which are more vigorous and capable of out-competing incumbent alternatives further north (south for antipodeans, obviously). The only thing holding them back being their dislike/poor survival in the colder zones.

UK has a problem with crayfish from similar latitude but opposite side of the Atlantic. Inadvertent introduction, in that case.

Polar bears are, in essence, highly specialised grizzly bears. They are too conspicuous to chase and hunt tundra herbivores and frozen over rivers in Siberia/Canada will not serve up the poundage of meat they need to get by. Things like the salmon run are one-off bounties for them, not part of their regular diet.

Grizzly bears could re-evolve into polar bears, in a future ice age but polar bears have to adapt and de-specialise in order to evolve back into grizzlies.

Evolution isn't plain sailing. Specialisation to the point of extinction, stemming from environmental change, seems to be the norm.

[wildwood]

But to be fair Hypo, without climatic changes over the eons, a lot of species would not have evolved. If for instance, the present temperatures were around a few million years the polar bear would not have evolved because, as you say, it is too conspicuous away from ice floes.

To me, evolution means promotion of the slight genetic alteration within one species that is the most suitable to the everchanging environment, whether this occurs though pressure of a different species or genetic drift is irrelevant. The nomenclatural difference between a polar and grizzly bear is a man made division. The fact that crossing of the two can produce fertile offspring together is proof that they are very closely related and should perhaps be classed as sub-species, not individual species.

[wildwood]

Yeah, and that's what you basically said \_(°¿°)_/.

[Hypognosis]

@wildwood

I only make the distinction because the common conception of evolution is the old-chestnut "predator versus prey" scenario, the logical upshot of which is that faster running herbivores escape often and breed faster offspring then the slowest running predators die off, while the faster tunning predators start to match the speed of the fastest in the herd again.

Both species should be getting faster and faster, as generations go by. I am not sure this is borne out by the data held, to date. Darwin's theory specifies "incremental change" and, after decades of monitoring wildlife it seems that the increments are vanishingly small, so we will need centuries of data to make the first observation.

In actuality, predator species pick off herd members which are vulnerable by virtue of being a calf, so the only scope for evolution of the herd species is how rapidly they become mobile after birth (mere minutes, already) and how rapidly they can grow leg length and strength in order to reach full adult running speed. After that, they have herd protection on their side and lions will sit and let the herd run past, within paw's reach, waiting for one of the right size.

Anyway, it is remarkable how apparently changeless some species can be. There may be pressures we do not yet appreciate as to why ever-faster runners are not favoured. Maybe they need to eat more or need more water, so do not survive the worst famines or droughts. Darwin used the word 'fit' in the sense of hand fitting glove, how well something fits its environment, not physical fitness, in the modern sense of the word.

[wildwood]

The 'little man' was supposed to be one that had its thumb up in agreement. Pity AB has even remove the preview option before posting.

[Hypognosis]

Ah. It does rather look like someone throwing up their arms in exasperation which, I thought, fitted the context.

When you asked "what do you contend at other times", perhaps you were expecting something outlandish and off-message? You seemed let down that my "other times" stuff was boringly mainstream.