Archive for November 25th, 2009

There’s a low spot in the meadow that accumulates rain water. What with the weather having been quite wet this summer, this big puddle has been persistent. At it’s deepest spot it is only 6 or 8 inches in depth, however, so I was surprised when I was walking by it recently to see something swimming. Whatever it was darted away from me and into the shallow grasses, where it disappeared. I got around to investigating further this weekend. I dug out my dollar-store net and a bucket and put on my wellies. It took a while to spot the little critter. Finally I saw it zip away into the grasses, where I hovered over it for nearly a minute before my eye was able to pick out the tiny guy. He had already committed himself to such shallow water, there was no further escape, and I soon had him swimming in my bucket.

Once I could get a good look at him, the wee spines on his back made it easy to identify him as a stickleback, probably a Brook Stickleback (Culaea inconstans). This individual was about 35 mm long, but these fish can grow to about 80 mm, with 50 mm being a good average size. They are usually found in the quiet, vegetated waters of small rivers, ponds or lakes with sandy or muddy bottoms. The sticklebacks are part of the order Gasterosteiformes, which includes seahorses and pipefishes. Brook Stickleback eat small aquatic insects and crustaceans, and they in turn are eaten by other fish, birds, salamanders and garter snakes.

These little fish spawn in spring and early summer. The males build a round nest with a single opening and try to lure females inside. The nest is made from algae and other plant materials and stuck together with a mucous-like substance that the male produces in his kidneys. If he’s successful, the female lays her eggs and departs. The male then fertilizes the eggs and defends the nest fiercely from predators. He may fan the eggs to oxygenate the surrounding water. In 8 or 9 days, the young hatch. The male continues to guard them until they are able to swim away to fend for themselves.

How could this fish have found its way to this puddle of water? Perhaps it was carried there while still an egg, on the leg of a wading bird. I decided to release my catch into the larger pond. When I carried the bucket over to the pond, I noticed schools of little fish near the edge of the water. Having my net handy, I reached over and was able to scoop up a sample. These were a different species from my little stickleback.

I placed a few in a glass jar so that I could see them better. They appeared to be a species of shiner. Based on my mini-guide to mini-fish, they may be Bridle Shiners (Notropis bifrenatus), or perhaps the similar Blackchin Shiner (Notropis heterodon). These fish were about a centimeter smaller than my stickleback. Shiners are fish of clear, still, shallow streams and ponds, especially those with submerged aquatic vegetation along the shores and open areas where the fish can school. Spawning generally occurs in late May or early summer. Eggs are laid in clearings around dense vegetation, where they drift down and adhere to the vegetation. The young of the year remain in the vegetation until mid to late summer, when they begin to school, first with other young of the year, and then with adult schools.

Bridle shiners are visual predators and feed only during the day. They hunt for tiny invertebrates in the water column or around vegetation. They don’t do well in turbid, or dirty water as they need relatively clear water to hunt food. They are also poor swimmers, so therefore don’t cope well with changes in water flow. Neither of these characteristics would be helpful in coping with the water in our local stream, so it seems odd that they should be here.

There were other, larger fish visible in the pond, but they quickly zipped away into deeper water. Identifying them will be a good project for next summer.

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