Table of Contents
The pompanos are allied to the mackerels; both have deeply forked tails, very slender caudal peduncles, and ventrals situated below the pectorals. And, mackerel-like, most of them have two dorsal fins, the first hard-spined, the second soft-rayed. But they are readily separable from the mackerels by the fact that their first (spiny) dorsal, if they have one, is much shorter than the second (soft rayed) while it may be reduced to a series of very short spines, or even lost altogether in old age. And, except for the leather jacket, they either lack the dorsal and anal finlets so characteristic of the mackerel tribe, or have only one of each at most. They differ further from the mackerels in the number of vertebrae (only 24 as against upward of 30), and in that their premaxillary bones (fixed in the mackerels) are protractile (except in adult Oligoplites), while their anal fin is preceded by two free spines that may either take the form of a permanent finlet or may be lost in old age. Warm seas support a host of species, but none of them is more than an accidental stray to the Gulf of Maine.
| KEY TO GULF OF MAINE POMPANOS | |||
|---|---|---|---|
| 1. | Rear parts of soft dorsal fin, from 7th ray backward, and of anal fin from 6th ray backward are so deeply indented between every two rays as to form a series of 12 to 14 nearly separate low finlets | — | Leatherjacket, p. 380 |
| Rear parts of soft dorsal and of anal fins even-edged, not as series of finlets | 2 | ||
| 2. | Body very much flattened, sidewise; nearly or quite half as deep as it is long to base of caudal fin | 3 | |
| Body moderately stout, less than two-fifths as deep as it is long to base of caudal fin | 6 | ||
| 3. | Back and belly rounded; pectoral fins reach not more than one-third the way back toward the base of the caudal fin | — | True pompanos (genus Trachinotus)[47] |
| Back and belly sharp-edged; pectoral fins reach at least half-way back toward the base of the caudal fin | 4 | ||
| 4. | Second dorsal and anal fins are conspicuously falcate in shape, very high in front, tapering abruptly toward the rear; there are no enlarged bony plates along the lateral line on the caudal peduncle | — | Lookdown, p. 379 |
| Second dorsal and anal fins only moderately high in front, tapering rearward gradually; caudal peduncle with weak bony plates along the lateral line | 5 | ||
| 5. | Upper anterior profile of head concave; ventral fins very small; anterior rays of soft dorsal and of anal not elongate | — | Moonfish, p. 378 |
| Upper anterior profile of head convex; ventral fins as long as head or longer; anterior rays of soft dorsal and anal fins elongate, threadlike | — | Thread fin (probably the young of the Cuban jack), p. 381 | |
| 6. | There is only one well-developed dorsal fin (the soft rayed), the first (spiny) dorsal being reduced to a few short spines, without separate fin membranes | — | Pilot fish, p. 372 |
| There are two well-developed dorsal fins though the first (spiny) is smaller than the second | 7 | ||
| 7. | There is a detached finlet behind the dorsal fin and one behind the anal fin | — | Mackerel scad, p. 374 |
| There are no finlets behind the dorsal and anal fins | 8 | ||
| 8. | There is no finlet in front of the anal fin; and the anal is only about one-half as long as the soft dorsal | — | Rudderfish, p. 373 |
| There is a finlet of 2 short spines in front of the anal fin, and the anal fin is nearly or quite as long as the soft dorsal | 9 | ||
| 9. | The forward part of the lateral line is scarcely arched | — | Goggle-eyed scad, p. 377 |
| The forward part of the lateral line is strongly arched | 10 | ||
| 10. | The breast is naked, except for a small patch of scales in front of the ventral fins | — | Crevalle, p. 375 |
| The breast is covered with scales | 11 | ||
| 11. | The body (to base of tail) is not more than 3 times as long as it is deep; the soft dorsal fin has only 23 to 25 rays | — | Hardtail, p. 376 |
| The body to base of tail is more than 3 times as long as it is deep; the soft dorsal fin has 30 to 35 rays | — | Saurel, p. 377 | |
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[47] None of these southern fish have yet been reported within our Gulf. |
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