N.Wells
Posts: 1836 Joined: Oct. 2005
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Quote | The combined knowledge of all three of these intelligence levels guides spawning salmon of both sexes on long perilous migrations to where they were born and may stay to defend their nests "till death do they part". |
Frankly, you are being foolish. You have at least gone from "defending nests full of young" to defending their nests, but you are still mostly not correct, and for reasons that defy comprehension you keep insisting on talking about salmon in a section about parental behavior and love and marriage. Excepting steelhead trout, in other salmon species most salmon die after spawning (all Pacific and most Atlantic salmon), and they all do little if anything that qualifies as parental care. You might as well claim that humans are instinctively monogamous and cite Donald Trump and Wilt Chamberlain as examples. https://www.youtube.com/watch?v....SPpMciU
More specifically, in all species, the males arrive first and most stake out and defend prime spawning real estate (coarse gravel bars, with currents that are neither too rapid nor too slow, so that the eggs will be oxygenated but not swept away). Some males hang out on the periphery and hope to take over later or steal a quick fertilization at some point. When the females arrive, they pick out good places to lay eggs (thereby choosing their mates in large part by default according to whomever controls the area or is in the vicinity, but there is some courtship and females may drive away some unacceptable males), dig their redds (nests), up to seven, until they run out of eggs. As the females lay their eggs, one or more males approach and start dumping milt (sperm) over the eggs as the female lays them and buries them (she stirs up the gravel at the upstream end of the redd to make another redd, causing gravel to drift over the eggs in the first depression).
Depending on the species and the environment, the female may defend her redd for a while, chasing off other females and other predatory fish species, although she mostly has only two days to (in some species) two weeks to live, and the eggs are going to be developing over the next two to six months, so the mother is mostly not around to defend the nest or protect the young. Mostly the mother hovers over the redd while fanning the water. This may send oxygenated water down to the eggs, which would seem beneficial in early development. The parents are going to die long before the embryoes hatch, but once the embryoes have developed eyes they don't need very much oxygen.
Salmon that spawn on beaches aren't territorial, do no redd defense whatsoever, and tend to mix eggs and spawn from multiple adults all at the same time.
All NW Pacific salmon die after spawning, and about 90% of Atlantic salmon die, although the remaining 10%, nearly all females, head back to the ocean soon after spawning, and may survive through a second spawning run.
In streams, the males defend their territory and thus mating access to females, and will try to chase other males away, although how close the male is to dying, how many other males are around, and local stream conditions may limit his ability to monopolize one or more females. Most commonly, male salmon fertilize the eggs of a few females, and most females get their eggs fertilized by just one male. There is no "til death do they part": nothing approaching marriage, little approaching monogamy, and even less relating to parental care of young, other than the males trying to ensure that they get to be the father. Quite often, after finishing spawning a bunch of males will gather quietly in a quiet pool downstream, and basically wait to die. (They aren't gathering to be social, but because low-velocity water requires less swimming. Notably, those males aren't out defending their nests or hanging out with their womenfolk.)
The young are not at risk of being eaten by other adult salmon (as always, excepting steelhead trout, neither gender eats after entering the stream, and in the Pacific salmon their stomachs have decayed away already).
Nest-building by a female might dislodge previously laid eggs, but the females make a distinct mound and absent crowding other salmon appear to prefer fresh areas (it's less work to fin out a depression if you don't start with a mound: a depression is needed so that flow separation allows the eggs to settle rather than being washed downstream). If there are a lot of females, some females may dislodge previously buried eggs: this can be prevented to a degree by females chasing off other females, but some species in some cases have "wave spawning" where new spawners arrive after the previous lot have finished and died, and re-excavation can be a distinct problem there.
As far as I know, the males and females do not cooperate in building the nests, or defending the territory, or looking after the young.
You are building a fantasy. You can't even be bothered to check out your facts properly. You've gone as far as finding three videos on the internet that vary from ambiguously titled to wrongly titled, and you cite those in support!
Try reading some actual scientific literature before pontificating - something like Groot and Margolis, "Pacific salmon life strategies" would be fine.
Even if crocodilians and salmonids were great parents (although they aren't), the point of your paragraph is nonetheless discredited by the huge number of species that show absolutely no parental care whatsoever: even setting aside plants and fungi, corals, sponges, crinoids, and mollusks tend to be "fire and forget". Octopodes die on spawning, mayflies die after dropping their eggs into rivers and lakes, and cecidomyian gall midges eat their way out of their mother, killing her in the process.
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