Freshwater Fishing on Long Island and in New York City.

Murray cod are the most long-lived freshwater native fish in Australia
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Tun-Min Poh: Although most people know that Borneo is a biodiversity hotspot, less people realize that this extends to freshwater fish as well—almost 40% of the freshwater fish species here are endemic to the island. What is more, the Kinabatangan River, the longest in the State of Sabah at 560 km, lies within the most isolated of Borneo’s watersheds. This means that the Kinabatangan has (or maybe had) the highest freshwater endemism on the island. Some species of fish that the local people, the or ‘River People,’ catch for subsistence are found nowhere else in the world.
How long can a freshwater fish live in saltwater
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Fantail guppies are a plentiful, attractive, and inexpensive fish. The diverse colors and patterns on the long tails of fantail guppies make them a beautiful fish to watch as they move around the aquarium. Their graceful appearance is one of the many reasons why freshwater aquarium hobbyists are enchanted by this species. Freshwater fish species by angling, spearing, hooking, longbow, and tip-ups
Photo provided by FlickrThese freshwater monsters, the continent's largest fish, are extremely long-lived
Photo provided by FlickrFeb 18, 2014 - Inventory of Freshwater Fish Species within Big Cypress National Preserve: The Basis for a Long-Term Sampling Program.
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Some of these fish spawn in freshwater and live in saltwater and some live in saltwater and spawn in freshwater.

Most of them require a period of acclimation however. You can't take a rainbow or brown trout that has lived all its life in a freshwater stream or lake and throw it directly into the ocean and expect it to survive very long. However a rainbow or brown trout placed in a river can move gradually from freshwater, through brackish water and into the ocean. In fact some rainbow and brown trout placed in fresh waters that have unimpeded access to the sea (no dams and other obstructions) will spawn in freshwater and live in the ocean, similar to the way salmon do. American eel do the opposite. They spawn and live their early lives in saltwater but move into freshwater as adults.

Bull shark generally live in saltwater and brackish water, but have been known to move upriver into freshwater, but they slowly acclimate themselves as they move along.

I can't think of any fish that can be removed from their usual environment and put directly in another and survive. I'm sure some expert in piscine habits may know of exceptions.

Scientists working in Thailand’s Mae Klong River made a find last week: an enormous stingray that they think is a contender for the largest freshwater fish ever documented by researchers.Freshwater fish are NOT adapted to process high levels of solute in the water and would therefore suffer kidney failure if placed into saltwater. The same process happens when you put soft water freshwater fish into hard water tanks, except the process would take longer.The alligator gar may resemble an alligator when you look at its mouth, but rest assured, it is a fish. This large freshwater fish has a long snout and two rows of fang-like teeth that make it look really scary. The fact that it can reach 10 feet long and 350 pounds makes it even scarier. But, there’s no need to fear because there have been no reports of an alligator gar attacking a human.