spermy prom hair

Last Saturday, I had the pleasure of accompanying some folks as they caught hooligan- these little silver fish that are currently spawning here in the river. I helped to bag them up and in the process, got covered in their sperm (I couldn’t be mad- we did interrupt them mid-spawn with their little zippers down). Afterwards, I tagged along to drop by the local high school prom to check out the dresses (and seeing as I was super excited about this, I’d say I’m adjusting well to small-town Alaskan life). But the highlight of the weekend was being able to tell my mom the next day on the phone “last night I went to the prom and got sperm in my hair.”

Currently, these hooligan fish are swimming up the Chilkoot River here. They’re pretty little silver fish with tones of pinks and purples. They’re pretty general looking, which makes this occasion a perfect opportunity to relay a little general fish morphology.

Fins

Hooligan fins

Fins are the evolutionary answers to fishy locomotion. Pectoral and pelvic fins project from the body and can move in a rotational manner, acting as little steering arms for the fish.

The dorsal fin can occur in one part or two parts, with the more anterior fin always being the primary one and the back one usually being smaller and squishier. In the case of the hooligan, there are two dorsal fins. The dorsal fin(s) act as sails for the fish, slicing through the water with lateral surface area that pushes against the water on either side of the fish. This keeps the fish from tipping over, keeping it right side up. The anal fin functions in balance as well, in charge of more refined adjustments to keep Mr. Fish from tumping over.

Lastly, the caudal (caud being latin for tail) fin is the big daddy in the back that swings from side to side to move the fish forward.

Lateral line

You can peer into the water and see these hooligan swimming against the current in their little groups. They seem to almost have telepathic abilities- knowing and reacting  instantaneously to what their fish friends are going to do. Have you seen those nature shows that show schools of fish all turning and darting in what seems to be perfect unison? How do they do it?

When you look at fish, you’ll notice a faint line that runs down their sides. This is called the lateral line. Lateral lines are actually a series of nerve clumps that act as a composite sensory organ. On the surface, the lateral line is a series of sensory epithelial cells that hook up to the underlying nervous system, which translates the sensations felt by the surface cells to electrical impulses that are sent to the brain. These sensations are caused by minute pressure changes in the fish’s immediate environment. The flick of a neighboring fish’s tail, the opening jaws of a nearby predator, or the creeping legs of a delicious crustacean- the lateral line allows all of these things to be sensed without being heard or seen.

Gills

Gills are NOT underwater versions of lungs. They are entirely different structures from different origins, but do have the shared function of oxygen acquisition. In fact, they are quite superior in this area, what with their countercurrent oxygen exchange and all. Just looking at a fish, you usually don’t get a glimpse of these delicate, feathery gills. They are covered up and protected by a bony covering called the operculum. If you were to snap this off (of a dead fish only, don’t be mean!), you could then see the feathery, vessel-laden projections that serve as oxygen exchange sites for the fish.

So even though fish are slimy, they’re still worth getting to know. Living underwater presents a whole different set of challenges- but not to worry. These little guys have got it covered. Much like I was in their sperm.