exposed on sand; early morning light

Dabbling with Crustacean Competition

I wonder how three similar and closely related surfperch can live together on homogenous sandy beaches. How do they subdivide theoutershores? One solution might be partitioning their food. To study this, I’m learning to identify what they eat; surf perch and their competitors.

A surfperch food item, unidentified, so far
Found in a redtail surfperch stomach, any ideas what it is?

Above is one of the first surfperch food items I ever examined. It remains unidentified, so if you know what it is, I would appreciate hearing from you.

exposed on sand; early morning light
Smooth bay shrimp, Lissocrangon stylirostris
on wet sand
Pacific mole crab, ventral view

Much of the surfperch prey is crustacean. I’ve found lots of smooth bay shrimp, Lissocrangon stylirostris and Pacific mole crabs, Emerita analoga, in the stomachs of surfperch.

Pentidotea, from a surfperch stomach

Pentidotea, an isodpod, is a common food item. I should be able to identify this one by the shape of the telson, but so far I’m stumped. I’m hoping somebody will help me out.

Bright orange glob of tiny crustacean eggs
Crab eggs? Pentidotea for scale

Surfperch can’t resist bright orange crustacean eggs. If you were a fisher, would you consider using orange lures?

Stomach contents in water, a bowl
Goose-neck or leaf barnacles, Pollicipes polymerus

Pollicipes polymerus and Pentidotea affiliate with rocky habitats, so we know surfperch hit the rocks to forage when conditions permit.

On sand
Staghorn sculpin, Leptocottus armatus
on the sand
Sand sole Psettichthys melanostictus

Staghorn sculpin and sand sole arrive on the beaches in summer, just before surfperch give birth to their babies. Are they predators on baby surf perch, or competitors for crustaceans?

Speaking of competitors, here’s something you don’t see every day. An theoutershores reader sent me the following link:

This footage was taken on an outgoing tide, mid-morning on January 6, 2013. I’ve never seen anything like this, but others have, particularly near where this occurred, in San Luis Obispo County, California. It looks to me like these birds are dabbling for crustaceans in the surf. What do you think?

Note: I updated the photos and lightly edited the text on October 21, 2017.

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