How do fishes navigate in the ocean? Because the sea floor is also very deep in the oceans it becomes even harder for them to create a map of the ocean inside their head. For migrating from one ocean to another they definitely need some map in their head. Also not all fish have sonar plus it has limited range and it even makes the job harder as the entire body of water surrounding a fish is constantly evolving
How do they create this map of the ocean inside their head ?
In: Biology
How much of a map *do* they need? Many migratory fish really only need to go north or south depending on the season, and following a coastline is easy. Wikipedia is also telling me that it’s common to follow currents that change with the seasons, which also often flow around coastlines. Some fish have organs that can detect the earth’s magnetic field, which can not just orient them north-south but be used to go in any direction – not that they’re consciously navigating like we’d use a compass, but evolution can give you a fish that knows to swim southeast when the water gets colder, just as much as one that swims pure south.
What makes you think they need a map? All they need to know is how dep their food is likely to be at.
You are asking two questions, of which I can only answer one:
How do fish orient in the deep ocean (e.g. figure out in which direction they’re headed)? With magnetite cells! Salmon have been found to have magnetite-enriched cells in their noses, with which they’re able to sense the magnetic field of Earth. While it seems to work similarily to the magnetic sense of birds like carrier-pigeons, they’re biologically much closer to magnetic bacteria.
In addition, fish are able to sense water pressure and light levels (i.e. depth), as well as temperature, salinity, oxygen saturation and the taste of the water. With all of those, they should be able to get a pretty good picture of “home” and “here”, and presumably a lot of places in between. Then they only need some memory in order to piece together a route from here to home.
I think you should compare it not to how we navigate today using GPS and realistic maps, but instead how the merchant seafarers of antiquity navigated the Mediterranean Sea: They knew that they had to sail towards the setting sun in sight of the coast for a number of days until place A, then from there five more days along the coast to place B, then cross the sea to place C, keep some mountain to the left until arriving at place D, then follow the river until their destination.
I know a stupid amount about odor plumes in water. They can play a big part in how sea animals navigate toward food and away from predators. Sharks in particular (and many fish I assume) use bilateral odor sensing, so they are able to tell by:
1) which side of their “nose” they smell the odor in first
2) how long it takes for the odor plume to reach the other nostril
3) how long the odor plume lasts in either side of their “nose”
In what direction and generally how far away prey might be. They use the same method of moving back and forth while they swim until they catch the scent of something that other animals do.
what should they navigate to, it’s not like fish have their own settlements and megalopolises in the ocean haha
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