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Brackish Water Fish Species

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Brackish water is a widely variable environment, but there are many fish that can tolerate it. In this lesson we'll take a look at what exactly brackish water is and identify some of the fish that call it home.

Phenomenal Fish

Fish are some of the most diverse animals on Earth. They come in an incredible variety of sizes, shapes, and colors. There are fish that eat plants, some that eat other fish, others that eat coral, and some that even suck blood!

But maybe one of the most impressive things about fish is that they can live in so many different environments. Just think about it - there are fish that live in frigid, arctic waters, but there are also fish that live in the toasty waters of the tropics. There are fish that live in shallow pools, as well as fish that live so deep in the oceans that the sunlight doesn't even reach them.

Fish live in diverse habitats and have diverse features, like roughback batfish. What a face!
batfish

Salty Water

But fish also live in waters of different salinity, or amount of salt. Some fish, like catfish, largemouth bass, and bluegills, live in freshwater. This is water with a salinity of less than 0.5 parts per thousand (ppt), meaning that there are x parts of salt per 1000 parts of water. The lower the number, the less salty the water is.

So freshwater is pretty close to zero salt, but the ocean, where fish like tuna, angelfish, and snapper live, is really salty: 35 ppt or greater!

But what about the in-between? Anything that is not freshwater and is also not sea water is called brackish water, and it ranges in salinity from 0.5 - 35 ppt. Many estuaries contain brackish water because they are transition zones from rivers to the sea. But to be clear, there are also freshwater estuaries too (such as the Great Lakes) so salinity is really the driving factor for defining brackish water, not location.

Brackish Water is Variable

Now, if you're a freshwater or saltwater fish that lives in a fairly constant salinity, you've got it pretty good. But if you're a brackish water fish, you live in an environment that is wildly variably and your body needs to be able to adjust accordingly.

Pacific lamprey can tolerate a wide salinity gradient
pacific lamprey

For example, you might live where there are tides or wind that move water in and out, changing the salinity throughout the day. Or maybe you live in a long, narrow creek, where at one end the water is pretty fresh, but at the other end it is very salty.

You'll have to move around to look for food, escape predators, or find shelter, so that means you need to be able to handle salinities that range from very low to very high.

Brackish Water Species

So who are these specially adapted fish? Many are probably familiar; others might surprise you. Fish that live in brackish water for part or all of their lives include:

Though you might not see the shy bonnethead shark, it is a fish that can tolerate brackish water
bonnethead shark

  • Atlantic croaker
  • Atlantic menhaden
  • Bay anchovy
  • Black drum
  • Bluefish
  • Bonnethead sharks
  • Bull sharks
  • Flounders
  • Gars
  • Inshore lizard fish
  • Jumping mullet
  • Killifishes
  • Ladyfish
  • Lampreys
  • Pigfish
  • Pinfish
  • Pipefish
  • Red drum

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