Table of Contents
Sticklebacks are small fish, made easily recognizable by the presence of two, three or more stout free spines on the back in front of the dorsal fin (spines that they can erect or depress at will) and by the fact that each ventral fin is represented by an even larger spine with only one or two rudimentary rays. Some of them have bony plates in the scaleless skin, but others do not.
| KEY TO GULF OF MAINE STICKLEBACKS | |||
|---|---|---|---|
| 1. | Seven dorsal spines or more | — | Nine-spined stickleback, p. 307 |
| Not more than five large dorsal spines | 2 | ||
| 2. | No bony plates on the upper part of the sides, but there is a bony ridge on either side of the abdomen | — | Four-spined stickleback, p. 311 |
| The upper part of the sides are armed with bony plates, and there is a plate in the midline of the belly, but there are no ridges on the sides of the abdomen | 3 | ||
| 3. | Many (28 or more) plates on each side | — | Three-spined stickleback, p. 308 |
| Only 5 or 6 plates on a side | — | Two-spined stickleback, p. 310 | |