When gills build their nests they like to put rocks and large pebbles in their nest to attract a mate. The more "structure" they have the more attractive they are to the opposite sex. Here is a picture of a good gill nest. Perfectly round and easily viewable on a sonar both down image and side image. I have fun looking for their nest beds. You usually find many round bed circles when you find one nest so drop your hooks more than once if you catch one.
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