Because I spend a lot of time on the outer shores catching fish by hook and line, I’m always thinking about how to catch more. I guess this reflects some competitive tendency, but I’d like to think it’s more than that. It seems like every fish I encounter tells a story about something I’m curious about. For example, check out the bright orange spot on the anal fin of this male silver surfperch.
To get you oriented on the above photo, this fish’s head is pointed to the left and you can see the the pelvic fins on the left side, below the belly. That’s quite a splash of color. Is it important for mating success? Now check out the color of the eggs of the Pacific mole crab, Emerita analoga.
This is the underside of a female mole crab. Her head is pointing to the left and the eggs are mostly hidden under a part of her body called the telson. You can see how orange the eggs are, and just about the same color as the spot on the anal fin on the silver surfperch. Below is a hand-posed shot with the telson moved aside to reveal the bright orange cluster of eggs.
Surfperch and mole crabs have a close association on the outer shores. As you might guess, mole crabs are the prey of the surf perch. Crustacean eggs are high in fat, so they are a great food source. I wonder if the orange spot on the silver surf perch is related to this great food source. Surf perch have good vision and internal fertilization, so it just might make sense. I want to find out if surfperch retinas are particularly sensitive to orange wavelengths and if orange would make a good lure color.
I want to thank my friend Mike Westphal for sending me the photos of the mole crab with freshly yolked eggs. We ponder questions like these all the time, so I guess he was happy to do it. Thanks Mike!
Note: I updated the photos and lightly edited the text on September 3, 2017. If you like to color and it’s connections on sandy shores, take a look at these posts: The Color of the Caudal, Fins of Fire, and To Bite or Not to Bite.