Archaeologica.org

Years ago, when I used to take the Nat Geo, there was a report concerning the major quakes that had recently taken place in Alaska, 'The Valley of a Thousand Smokes'. If my memory is correct a major river was dammed as a result, thereby trapping migrant species, such as Salmon on the landward side.
Am I correct in saying that I red a report, somewhere, that they have now lost their migratory instincts?

Roy.

Google doesn't seem to know anything about it.

I have the first 80 years or so of Nat. Geo on DVD so....if you could remember when it was...............


(Asking a lot at our age, I know.!)

Damned if I can Min, it was reported on the BBC here at the time showing Salmon, and I think Seals stuck landwards. Must have been the 60s? or later, certainly not earlier.

Roy.

Roy,

Maybe this can help:

http://earthquake.usgs.gov/earthquakes/ ... istory.php

Nope! I also Googled 'Land Locked Salmon' thinking that might lead to what I saw on TV etc, but it seems that land locked Salmon are quite common.

Roy.

Digit wrote:Damned if I can Min, it was reported on the BBC here at the time showing Salmon, and I think Seals stuck landwards. Must have been the 60s? or later, certainly not earlier.

Roy.

That isn't much to go on, is it?

Not a lot Min, no. The part I was actually interested in was whether Salmon, and perhaps other species, would lose their instinct for migration under those circumstances.
Are the existing land locked Salmon trapped or have they never had access to the oceans.

Roy.

Apparently it is not all that uncommon. I just read where fresh-water salmon are called "trout." (I'm not big on fishing.)

It seems to me that that whole salt water/fresh water thing would be a more immediate problem than migration.

Digit wrote:Not a lot Min, no. The part I was actually interested in was whether Salmon, and perhaps other species, would lose their instinct for migration under those circumstances.
1-Are the existing land locked Salmon trapped
or 2-have they never had access to the oceans.

You're asking two (2) questions.

1-Yes certainly we have a number of examples of this here in British Columbia.

2-makes no sense unless you mean Salmonid ancestors of which no living relatives exist.

You've probably heard of Sockeye Salmon-the landlocked type is called a Kokanee (the name has also been adopted by a local brewery).

The situation can also reverse itself to a degree-some lakes that have regained access to the sea hold both Anadromous Sockeye and Kokanee.

(Note that the Sockeye generally spawn in a river above a lake and the Smolts drop down into the lake to rear for a time before heading off to sea.)

Also Note-it's been a long day I may have some details wrong any other questions Please Fire Away.

2-makes no sense unless you mean Salmonid ancestors of which no living relatives exist.

So were the ancestors fresh water fish or salt water? Salmon exist in most rivers with access to the sea, in suitable latitudes that is, as with eels, but it a rather uncommon life style.
And where the situation reverses itself do they return to the sea as they grow? Do the land locked ones normally die after breeding?

Roy.

Digit wrote:So were the ancestors fresh water fish or salt water?

That is the question-but the answer is still unclear-these days most scientists would say a freshwater fish.

Digit wrote:Salmon exist in most rivers with access to the sea, in suitable latitudes that is, as with eels, but it a rather uncommon life style.And where the situation reverses itself do they return to the sea as they grow?

If I understand your question Yes.

Digit wrote:Do the land locked ones normally die after breeding?

Yes.

The landlocked ones-being deprived of the plenteous micro-nutrients found in Saltwater-are always much smaller than their ocean going cousins but are still hard wired for breeding behaviour.

So called Killie Fish of tropical waters, sometimes called annual fish have a breeding cycle atuned to seasonal pools that dry out. In aquaria some will survive past the year, others won't.
Now with Salmon I once red that some did survive, in British waters I believe that marked fish have returned to breed on three successive occasions.
Dieing after breeding seems a terribly poor tactic.

Roy.

Minimalist wrote:I just read where fresh-water salmon are called "trout."

And didn't the Aral Sea, really a freshwater lake – in mid-Asia! – have a species of freshwater seals? Locked in when the direction of Siberian rivers was reversed during the Würm. I believe it is extinct now.

In any case the Amazon has 2 species of freshwater dolphins (a pink one – the "boto" – and a grey one) whose ancestors were sea mammals. And manatees (3 species, afaik) also apparently have no trouble with either a saltwater or a freshwater environment, living in estuaries and upstream as they do. So adaptation from saltwater to freshwater – at least in mammals – has happened before, and is still happening.

Lake Baikal has fresh water seals.

Roy.

Digit wrote:Now with Salmon I once red that some did survive, in British waters I believe that marked fish have returned to breed on three successive occasions.

Atlantic Salmon don't die neither does Onychorhynchus Mykiss-popularly known as the Steelhead/Rainbow Trout but now classified as a Salmon.

I was going to mention this earlier but thought I might be muddying the waters so to speak.

Digit wrote:Dieing after breeding seems a terribly poor tactic.

Given the staggering numbers they formerly existed in maybe it was the only course of action.