Do fish just turnaround and say nope, not for me.
In: Planetary Science
They don’t just get swept down with the current. As you might expect, the fish are pretty good swimmers, and they are able to resist the current quite well to stay in their little habitats. They also will gravitate toward areas where there is less current when they want to chill.
The water intermingles and becomes (I think it’s called) brackish water. The fish that live there adapt for a ways each direction to this water.
In New Orleans, on Lake Ponchatrain, you can drive your boat through bayous and canals into the Gulf of Mexico. I have seen shrimp trawlers in the lake, which is fresh water where the Gulf is salt water. I fished an area in Florida one time where the two waters met, I caught some Reds (salt water) and some catfish (fresh water).
I live a long ways from salt water so some of my info may need corrected, hopefully some salt water folks can add to this.
Pretty much that, yeah. Fish are REALLY good swimmers and most rivers are actually pretty slow-moving, so it is of relatively little consequence to the fish that the river is moving at all. They can overcome the push and swim upstream just as easily as they can swim downstream so they can keep themselves in the same general spot their entire lives with ease.
Most fish don’t really run with the current. Fish like trout stay in freshwater their entire lives, and they tend to stay in the same area throughout their life where there is shelter (i.e., cover) and food, or travel only a few miles one direction or the other throughout their life. They either swim to maintain their place in the current, or they hide by rocks or in areas with low flow. Some fish do move from freshwater to saltwater, like Salmon, who spawn in freshwater and then eventually swim through streams/rivers to saltwater. Since they spawn (i.e., lay eggs) in freshwater, they swim against the flow of the water to get back to freshwater. Some fish have the necessary parts to survive in both freshwater and saltwater, some can only survive in saltwater, and some can only survive in freshwater.
You are exactly right.
The transition between rivers that flow into the sea and the sea is called an estuary. Estuaries are a distinct ecosystem with different wildlife from the coastal water and river.
Whether or not freshwater fish will swim or breed in the estuary depends on the fish. Some avoid it and for some it’s an integral part of their lifecycle. Estuaries are typically placid. Freshwater fish don’t just get dumped into the sea.
Imagine spending your entire life swimming against a relentless current that is pulling you towards your inevitable death.
I have a reef aquarium that has power jets inside simulating constant current, which is good for the corals.
I have at least one fish who will spend *all day* facing the current and swimming against itz staying in place. He sleeps in a calm spot surrounded by rocks.
Fish like to swim, are good at swimming, and are good at staying in one general spot.
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