10 replies to this topic

[Neth]

This is a slightly random question, and I might be missing out on something really obvious, but how did fish get into lakes and lochs that aren't attached to the sea?

[Ridder Geel]

Evolution of smaller organisms?

[Neth]

True, but (as far as I'm aware) then (at least) most of the species found in likes are found in rivers too, and lakes that are connected to seas, how did they get there without there being (obvious) ways to get there?

[Beowulf]

I would say tectonic plate drift. The world we see today has not always been around.

[Radspakr Wolfbane]

There are a few different reasons.
Sometimes it could a shift in the landscape like Tectonic plates, sometimes bodies of water were once connected to a larger body of water and got separated during a drought and the third would be from the last Ice age.

There are species that have evolved differently in that kind of environment.
There are 2 fish species in Australia that live close together in separate bodies of water.
The 2 waters were once connected and the fish got split up researchers believe this happened about 10,000 years ago or less.
In the short time the 2 fish species have evolved differently with different colouring and even a physical difference.

[mike_]

Because God made them that way.

[Pasidon]

Har.

Flooding makes new / limited stream paths and fish eggs in animal poo. Lived next to a lake like that a long time ago.

[Neth]

How about lakes formed from glaciation (Corrie lochans/tarns)? They have fish in them, but can't have been in contact with any other water source, and yet still seem to have fish in them (from wat I've researched) could people have put fish in them?

[Pasidon]

I was referring to a short-time span, but that be a good question. In kettle-lakes like that, ancient societies did stock lakes with fish. Early Woodland Native Americans such as Cahokia began the domestication of fish and the creation of artificial lakes. So lots o' cultures around the world began their earliest forms of animal domestication with fish. And also remember, the water levels today were not the same 10,000 years ago... or even 1,000 years ago. The Great lakes are a fairly new, actually. Lakes today may have had fluvial streams going into them, or were part of the ocean itself at one point.

Like the first topic at Revora I could actually put my Archaeology degree to use...

[Neth]

I see, so that's likely a case in lakes formed by glacial erosion? That's what I was really meaning all along. It was a question that came up in my geography class when we were doing Glaciation

[Pasidon]

Usually questions are meant to be answered in class if asked, but the best answer would be ancient fluvial processes creating spawn areas inland. I remember doing a study on a fresh water pond formed from a kettle lake in the middle of Gambia years ago that had fish in it. I took my pickaxe along the dunes and found fish bones very far away from lake, and later tracking the ancient stream that once flowed from it to the ocean. I guarantee I could find the same pattern continued to the Ohio River since the stream existed during the Super Continent, relating to the position of Gambia and the eastern US coast.