Wednesday, September 3, 2008

Looking for Fish in the Desert

It always amazes me that fish can live in the desert. These little creatures that require water year round are playing an amazing gamble with their lives choosing to live in such a parched area. Haven't they studied the odds? Gambling isn't a safe way to live! 

It turns out that many desert fish species used to live in a lot of water, about 10,000 years ago when huge lakes covered many areas of the Desert Southwest. We live next to the Bonneville Basin, where a huge lake the size of today's Lake Michigan flooded many of the valley bottoms. Many different fish species lived in the lake, but as it dried up, they became restricted to small bodies of water. One such fish species is the least chub (Iotichthys phlegethontis), a tiny minnow-like fish that rarely gets more than two inches long.

I set off one warm morning to help some fish biologists locate these fish. We went to a huge marsh area that has many small springs providing green spots among the more mundane-colored vegetation.

Here is Brooke, ready to measure the depth of the spring as a standard habitat measurement. I want you to notice that the pole she is holding is seven feet tall. The spring is under the thick green vegetation by her feet.

Where's the pole? Look closely, Brooke is still holding it, she's just holding the top of it. The rest of the pole is in the spring, over six feet deep. One wrong step in this marsh and you're literally in over your head.

Take a few steps in another direction and you find the salt marsh stretching off to the distance, as dry as can be. During the spring, a nearby playa fills with water and shorebirds stop by to snack on invertebrates during the migration. 

The scattered pockets of water provide opportunities for diverse vegetation, including these cattails. At selected springs, we lower minnow traps into the water and leave them for three hours.

At the end of three hours we go and pull the traps. Some springs only have predaceous diving beetles and amphipods (also called scuds or freshwater shrimp). But sometimes we have luck and pull out a trap with fish in it. We determine the species and measure the fish before releasing them back into the spring.

Here are two of our catches, a speckled dace (Rhinichthys osculus) and a least chub. Seeing them makes me realize the amazing adaptations the native species have made to live out in the desert. So far their gamble is paying off.

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