Hot Tomcod Action 

Welcome to Washed Up's Xucation Channel where we present science education in a format that people will actually watch. In this episode, a lady visits a gentleman and we learn about an interesting fish.

"Hey handsome, bet you can't resist these."

While he fails to resist those, let's discuss the Pacific tomcod (Microgadus proximus). This fish is in the family of true cods, which can be distinguished from other fishes by their three dorsal fins, two anal fins and a single whisker, or barbel, at the end of their chin. (A lot of non-true cods are commonly called "cod," such as "rock cod" for rockfish, and "black cod" for sablefish.)

"Let's see how big you are."

The relevant part of our well-above-average gentleman performer is approximately the size of an average adult tomcod. So, unlike the bigger cod species, there is only a very minor commercial fishery for Pacific tomcod. But they are a somewhat popular sportfish that are often caught from piers. Like other cod, they have delicately flavored flakey white meat. And some people cook them as you would freshwater panfish.

"You deserve a spanking, you naughty boy."

Soft bottoms composed of mud, silt or sand are the substrate that Pacific tomcod associate with, even when they are far above it in the water column. You just don't find them in rocky habitat. Accordingly, young-of-the-year tomcod migrate into near-shore waters, including bays and estuaries with soft bottoms and lower salinity than the open ocean. Overall, they have a very high tolerance for a range of temperatures and salinity. After a period of rearing in shallow waters, they typically migrate to the open sea as adults. But one known exception is Humboldt Bay, where adults inhabit some deeper channels.

"Harder! Harder!"

It seems harder to find washed-up Pacific tomcods than some other common local species. I've only ever found two, and one of those was in the stomach of a washed-up longnose lancetfish. To be sure that the ones I found were not juveniles of the very similar Pacific cod, I measured the distance from the tip of the jaw to the front of the first dorsal fin, and compared that to the overall body length. In my two specimens, the mouth-to-fin length was approximately 25 percent of the total length, where it would be greater than 33 percent in a Pacific cod. (Being a fish biologist isn't as exciting as being a porn star but it's pretty close.)

"Deeper!"

Deeper? Be careful, you two. Anyway, Pacific tomcod occur from Alaska to Central California in surface waters to as deep as 900 feet. In shallower water, scuba divers report seeing spectacular swirling schools of juveniles, especially at night. Like other cod, the Pacific tomcod has many fine sharp teeth, which are ideal for holding onto slippery prey. And a tomcod will eat almost any other critter it can fit into its large mouth, including crustaceans, worms and smaller fish. And they are eaten by almost any critter that can fit the tomcod into its mouth, including larger fish, birds and marine mammals. Because tomcods have no spines in their fins, they probably go down easier than other fish.

"Oh yeah ... oh yeah ... OHHH YEAAAH ...."

Oh yeah, I should mention that tomcod are open-water broadcast spawners, which means the schooling fish spontaneously release their gametes (eggs and sperm) into the water column to mix freely. Whoa! Thanks to our gentleman performer for that somewhat less dignified impersonation of a spawning male tomcod.

And thanks for joining us. Tune in next time when a professional carpet cleaner services a sorority house and we discuss clams.

Biologist Mike Kelly (he/him) is also the author of the book Tigerfish: Traditional and Sport Fishing on the Niger River, Mali, West Africa. It's available at Amazon or everywhere e-books are sold.