Fish on the sand

In the eelgrass beds at the bottom of the intertidal zone, fish dart through the thickets, usually visible only as a flash of movement, a streaking silver shape dashing from shadow to shadow, or a panicked thrash to escape my clumsy foot. They're usually not the fish I see in the upper zones, the sculpins and the flatfish, but they speed away so fast that I haven't been able to recognize any.

This last trip to the low tide line, though, the shallows were littered with dead and dying small fish; I was able to identify three species.

Another Pacific sand lance, Ammodytes hexapterus. These grow to about 11 inches long, so this is a youngster.

In one small area, I counted over 50 of these, all dead, but still fresh, surprisingly still untouched by gulls or crabs. They were all young; the adults spawn and die in mid-winter here. I am wondering what caused this die-off.

A larger sand lance, still alive, but barely. The back is a glittery blue-green, which should help with camouflage in the eelgrass beds, at least from above. At night, they burrow into the sand, to hide from predators.

Mixed with the sand lances, a few darker, larger fish stood out.

Pacific snake prickleback, Lumpenus sagitta. About 8 inches long.

Another. This was still alive, but not able to swim away.

Again, these were young fish; the adults grow to 20 inches long and spawn in the winter.

One more; a beautiful singing midshipman, no longer able to sing.

A steampunk fish, looking as if he were made of riveted plates. Plainfin midshipman, Porichthys notatus, about 8 inches long.

These are night-swimming fish; during the day, they hide under rocks. I found a male, guarding eggs, about this same time three years ago, under a rock at the boat launch. He was fatter and longer than this one.

The "rivets" are lines of photopores, cells that emit light. They may help to attract prey at night. (Although we don't really know that; it's human speculation. We do like to imagine that we understand Ma Nature.)

Belly up, showing the pattern of photopores, and his delicate colouring.

Zooming in to the tail end, to show the little lights, and - look closely - tiny waving three-fingered hands, all in a row.

I didn't pick this one up; some midshipmen have poisonous spines. I'm not sure if this species does, but I'm not risking it.

And I'm left wondering why all these suddenly showed up dead, all at once. The water was clear, it smelled fresh, there was no scum or oil sheen. There is construction going on 'way back at the shore, but that's a full kilometre away. Worrisome.

Fishy business

I'm busy trying to identify a couple of new (to me) fishes that we found on the Boundary Bay beach at low tide.

This one I think I know, at least:

Toadfish on a bed of snails (and probably some hermit crabs)

The other two will wait until tomorrow.

Singing toadfish

... or, under every rock, a new marvel.

I flipped a broken paving stone at the top of the intertidal zone, just off the end of the boat ramp. Here, the shore is rocky and difficult underfoot; long ago, someone laid out a few square pavers, but with time and heavy traffic, they have all broken, and lie helter-skelter among the more "natural" rocks. At high tide, the water covers the end of the ramp, and is about a foot deep over this rocky stretch.

But the tide was going down; the stones were exposed but still wet. Flipping a few disturbed hermit crabs and a handful of green and purple shore crabs. A larger stone, lying not quite flat on the rocks, had a pool of water underneath, and in this pool was a fish.

Plainfin midshipman, Porichthys notatus, aka the singing toadfish.

Detail of the round fins and strong spines on the back.

This was the same species as the one we found out of the water last week at White Rock, and about the same size; approximately 10 inches long.

He  -- it's a male -- wasn't alone. The underside of the rock was covered with a layer of eggs.

A brilliant orange, shining in the sunlight.

Part of the mass of eggs was shimmering and vibrating constantly. I couldn't see what was happening, ...

but the camera could. Look closely. See the eyes? And the translucent , pink, comma-shaped bodies? The're fry; baby fish. Cute!

Singing toadfish come in three types; females, and two different males; they call them Type I males and Type II males.

Type I males are eight times larger in body mass, and have much larger vocal organs. Type II males’ reproductive organs are seven times the size of type I males. Female and type II male midshipman fish can be distinguished from each other by the female’s slightly larger size, and the type II male midshipman’s large reproductive organs. (Wikipedia)

The way it works is this; a large Type I finds himself a nice rock to hide under near the top of the intertidal zone, and digs a nest. When night comes, he starts to sing. (Well, sort of; it's a hum or a buzz. Listen. Whatever you call it, the female likes it.) When a female joins him, she lays her eggs on the underside of the sheltering rock and he fertilizes them. Then she leaves, and he babysits until the eggs hatch and the young fry leave the nest.

And where do Type II males come into it? They are about the size of a female, and their voice is similar to hers. Their mating strategy is to deceive a Type I into mistaking them for females and allowing them to enter his nest. Then the two wait together for a mate; when she arrives, sneaky Type II fertilizes the eggs, and swims away, leaving the cuckolded Type I to do the job of parenting.

These fish are nocturnal; even when they're not brooding, they hide under rocks during the day. At night, they hover over the bottom, laying in wait for prey. On their sides and belly, they have rows of cells which, if their diet includes the right species of copepods, emit light. This may serve as camouflage against the lighter sky, or possibly may attract prey.

The fish at White Rock, showing the lines of photopores.

There's a great photo of eggs and fry on Flickr.
Buzz has photos of a raccoon catching and eating these fish.
A good photo of the photopores and a note about poisonous spines. Warning: hands off!