On guard

While conducting a snorkel survey last week in a California Central Valley watershed, we were fortunate enough to witness some unusual fish behavior. This prickly sculpin (Cottus asper), normally elusive, was seen popping in and out of a cavity in a submerged tree stump. Upon closer examination, we discovered that it was a male prickly sculpin defending its clutch of eggs.

Like several other fish species (Daddy Daycare and Watchdog or uh… Fish) male prickly sculpin care for the eggs. Normally solitary, in the spring adult males will prepare a nest under a flat rock or solidly embedded woody debris. Males spawn with more than one female and the single egg mass commonly contains eggs from different females, at varying developmental stages (note different colored eggs in the photo above). He will defend the site against intrusions by other males or potential egg predators until the entire egg mass is hatched (15-16 days at 12 °C) (Krejsa 1967). Once the eggs hatch the transparent larvae will drift down river to the first deep pool and the male’s guard duty will be complete.