[Jordan and Evermann, 1896-1900, p. 2644.]
The yellowtail is right-handed (that is, its eyes are on the right side and its viscera are at the right-hand edge as the fish lies on the bottom), and small-mouthed like the winter flounder, the smooth flounder and the witch. But it is easily distinguished from the first of these by its more pointed snout, thin body, arched lateral line, and more numerous fin rays; from the smooth flounder by the last two characters as well as by the concave dorsal (left hand) profile of its head and by being scaly between the eyes; and from the witch by its arched lateral line, its less numerous fin rays, concave dorsal (left) profile of the head, and especially by lacking the mucous pits on the left (white) side of its head that are conspicuous on the witch (p. 285).
The yellowtail is a comparatively wide flounder, nearly one-half as broad as it is long, with an oval body. The dorsal (left hand) outline of its head is more deeply concave than in any other Gulf of Maine flounder; its head is narrower; its snout is more pointed, and its eyes are set so close together that their rounded orbits almost touch each other. The fact that its mouth reaches scarcely as far back as the eyes, with its small teeth and thick fleshy lips, marks it off at a glance from all the large-mouthed flounders. The dorsal fin (76 to 85 rays) originates over the eyes, its middle rays are the longest. Its anal fin is similar in outline to the dorsal, but is much shorter (56 to 63 rays), and it is preceded by a short, sharp spine pointing forward. The two ventral fins are alike, and each of them is separated by a considerable space from the anal fin. But the pectoral fin on the blind side is slightly shorter than its mate on the eyed side. The scales are rough on the eyed side, but smooth on the blind side.[page 272]
The yellowtail is more constant in color than most of the other Gulf of Maine flatfishes. Its eyed side, including the fins, is brownish or slaty olive, tinged with reddish and marked with large irregular rusty red spots. The caudal fin and the margins of the two long fins are yellow, the yellow tail in particular being a very diagnostic character. The blind side is white, except for the caudal peduncle which is yellowish.
This is a medium-sized flatfish. Several hundred adults caught in gill nets between Cape Ann and Cape Elizabeth (measured by Welsh) ran as follows: Males, average length 15¾ inches, extremes 11¾ inches to 18¾ inches; females, average length 18 inches, extremes 15½ inches to 21¾ inches. This series includes the largest specimens that have ever been reported. A yellowtail 12 inches long weighs about one-half pound; one 15 inches long, about 1 pound; and one 18 inches long about 2 pounds.
A yellowtail is caught in very shoal water now and then: We heard, for example, of several taken in Pleasant Bay, Cape Cod, in 1950. But 5 to 7 fathoms may be set as its upper limit, generally speaking. Thus it keeps to rather deeper water than either the winter flounder or the smooth flounder. On the other hand, most of those caught are at least from no deeper than 50-60 fathoms, and the bulk of the catch is made shoaler than 40 fathoms. We saw many yellowtails trawled by the Albatross III off Marthas Vineyard and Nantucket in 20 to 40 fathoms, in May, 1950, but only 6 in 41 to 50 fathoms, and none in deeper water. Again, in late June 1951, Eugene H averaged about 240 yellowtails per trawl haul, at 26 to 45 fathoms on the western part of Georges Bank, but took only three of them in deeper hauls.
Almost any sandy bottom or mixture of sand and mud suits them, and most of those that Welsh saw taken in gill nets on the Isles of Shoals-Boone Island grounds (p. 274) were over fine black sand between the hard, rocky patches. Rocks, stony ground, and very soft mud are shunned by yellowtails, as they are by most of the other flatfishes.
The yellowtail feeds chiefly on the smaller crustaceans such as amphipods, shrimps, mysids, and on the smaller shellfish, both univalves and bivalves, and on worms. It is also known to eat small fish, but it is not likely that it can catch these often. Its European relative also feeds on sea urchins, starfish, and on algae at times. And it is probable that our yellowtail would be found equally omnivorous were their stomachs examined from various localities. Fish in breeding condition are empty as a rule.
The diet of the yellowtail suggests that it is one of the more sluggish of our flatfishes, and there is no reason to suppose that it ever travels about much after it once takes to the bottom except that it has been described, in Massachusetts Bay, as "inhabiting [page 273] the deep water ... in summer, and approaching the shores in winter," as do various other ground fishes that tend to avoid high temperatures.
If the yellowtails are as stationary as they seem to be, they must be subject to considerable range of temperature from season to season at different depths, in one part of the Gulf or another, from a maximum of about 52°-54° to a minimum of about 33°-36°. And some of them are exposed to still lower temperatures on the Grand Banks, and in the Gulf of St. Lawrence.
The eggs of the yellowtail, artificially fertilized by Welsh in 1912, and hatched at the Gloucester hatchery, were buoyant, without oil globule, spherical, very transparent, and with a narrow perivitelline space. One hundred eggs measured by him ranged from 0.87 mm. to 0.94 in diameter, averaging about 0.9 mm. The surface of the egg is covered with very minute striations, and the germinal disk is of a very pale buff color while alive. The embryonic pigment gathers in three groups shortly before hatching (which takes place in 5 days at a temperature of 50° to 52°); one group on the head, a second group in the region of the vent, and a third group half way between the vent and the tip of the tail. Unfortunately, the fish which Welsh hatched were destroyed accidentally, so we cannot describe the early larval stages. Larvae of 11 mm. are still symmetrical. But the left eye is already visible above the profile of the head at 14 mm. (fig. 139, Grampus specimen), all the fins are outlined, with their rays present in the final number (76 dorsal and 59 anal in the specimen illustrated). Thus, they show enough of the distinctive characters of the adult for positive identification.
The early larval stages of yellowtails and of winter flounders resemble one another closely; in fact, it is probable that some of the young flatfishes pictured by A. Agassiz as winter flounders were yellowtails in reality. But the number of fin rays usually places the larvae in one species or the other after these appear. And the yellowtail does not take to bottom until upward of 14 mm. long, whereas the winter flounder completes its metamorphosis when it is only 8 to 9 mm. long.
Captures of young fish 2 to 4 inches long in February; 2¼ to 4½ inches long in April; 21/3 to 52/5 inches long in May; 3 to 5 inches long in June; and 3 to 61/3 inches in July indicate that the yellowtail grows to an average length of about 5 inches by the time it is one year old. Its subsequent rate of growth has not been traced.
North American continental waters, from the north shore of the Gulf of St. Lawrence, the Labrador side of the Strait of Belle Isle, northern Newfoundland (there are specimens from St. Anthony's in the Museum of Comparative Zoology), and the Newfoundland Banks, southward to the lower part of Chesapeake Bay. It is most plentiful on the western [page 274] half of Georges Bank; in the western side of the inner parts of the Gulf of Maine; on the Nantucket grounds; and off southern New England.
This flatfish is represented in north European waters by the European dab, Limanda limanda, a close ally, from which it is distinguishable by its smaller scales, more pointed snout, more numerous fin rays, and shorter pectoral fins.
We should also mention the deep-water dab (Limanda beanii Goode), for while it has not been taken within the limits of the Gulf of Maine it would not be astonishing to find it on the seaward slope of Georges Bank, for it has been taken westward and southward from Marthas Vineyard in depths of 120 to 896 fathoms. It differs from the rusty dab in a shorter head (occupying only two-elevenths of the total length instead of one-fourth); in the fact that the dorsal (left hand) profile of its snout is convex, not concave; in having only about 64 dorsal fin rays instead of 76 or more; in having only 88 rows of scales along its lateral line instead of 90 to 100; and in the fact that its tail fin is marked with a conspicuous black blotch on the outer rays on each side.
Little was known of the distribution of the yellowtail in our Gulf previous to the introduction of the otter trawl there, for it is seldom seen close inshore; while its mouth is so small that one is seldom caught on hooks as large as those that are used for cod, pollock, or for haddock. But it has proved so abundant since then, in the general region of Nantucket Shoals and in the neighboring side of the so-called South Channel, that about 4,400,000 pounds were landed thence in the most recent year (1947) for which we have information. The western half of Georges Bank as a whole is good yellowtail ground also. But yellowtails seem to be less numerous on the eastern half of the Bank (though generally distributed there), and less so on Browns Bank, as is illustrated by the landings (in pounds) for 1947, as follows: northwest Georges Bank, 930,000; southwest Georges Bank 1,740,000; northeast Georges Bank 210,000; central and southeast Georges Bank 540,000; and Browns Bank 40,310.
Yellowtails are so plentiful on the sandy bottoms in the eastern side of Cape Cod Bay, also, and on Stellwagen Bank, that (with winter flounders) they have long been the mainstay of the draggers that fish there; no doubt the greater part of the 1,150,000 pounds of yellowtails that were reported as taken off eastern Massachusetts in 1947 were trawled on these particular grounds. There are yellowtails in the deeper parts of Massachusetts Bay, too, as Goode and Bean remarked long ago. And since Welsh saw many hundred of them taken in gill nets (not very effective gear for flatfishes) between the Isles of Shoals and Great Boars Head, during March and April of 1913, the yellowtail must be one of the most numerous of its tribe in the western side of the Gulf in general, in suitable depths.
Apparently they are less plentiful, however, around the Gulf to the north and northeast, for the reported catches for 1945 were only about 44,500 pounds for Cumberland County, Maine, which covers Casco Bay and the grounds in its offing; only about 9,000 pounds for Knox and Hancock Counties combined, and none for Washington County in that particular year, though a few hundred pounds have been reported from "eastern Maine" in some other years.
We have taken no yellowtails in the deep basins of our Gulf nor have we heard of any there, probably because of the depth, for the bottom would seem hard enough for them in the eastern trough, at least, even if it is not in the western, or in the bowl west of Jeffreys Ledge. They certainly are uncommon in the Bay of Fundy, too, if not altogether lacking there. And though Huntsman did find a few in St. Mary's Bay, Nova Scotia, United States fishermen bring in only a few hundred pounds from off western Nova Scotia in some years, and none at all in others, though considerable amounts are brought in from the outer Nova Scotian grounds, as mentioned below (p. 275).
Most of the yellowtails that are caught in the inner part of the Gulf of Maine are in 10 to 30 fathoms of water, though they are reported in Shoal water at the mouth of Penobscot Bay; those caught on Georges Bank are in 20 to 45 or 50 fathoms (see p. 272).[page 275]
Trawlers find yellowtails in even greater numbers off the southern New England coast than on Nantucket Shoals, at the proper depths, as illustrated by reported landings thence of about 17¼ million pounds in 1947. And they are moderately plentiful offshore, as far as the offing of New York. But southern New Jersey is about the southern limit to their regular ocurrence.
Turning our attention eastward, we find the yellowtail plentiful all along the outer Nova Scotian banks, where about 2,700,000 pounds were taken in 1947 by vessels from Massachusetts, besides about 2½ million pounds by Canadian vessels.
They are also reported as numerous on the southern part of the Grand Banks from experimental trawling by the Newfoundland Fishery Research Commission, but are "not in any numbers along the Newfoundland coast," so far as is known, though they are recorded from as far north as the Strait of Belle Isle, as already noted (p. 273). They are also distributed generally in the Gulf of St. Lawrence, but no information is available as to their numbers there, for none are reported from the Gulf in the Canadian Fisheries statistics.
The neighborhood of the Isles of Shoals and of Boars Head, at 20 to 30 fathoms, certainly is an important spawning ground for the yellowtails; so, too, the edges of Stellwagen Bank where we have caught spawning specimens. In fact, it is likely that yellowtail eggs are produced in abundance all around the western and northwestern periphery of the Gulf, between the 20 fathom and 50 fathom contours; few, however, in the eastern side, and none in the Bay of Fundy; nor have we found any of its eggs anywhere over depths greater than 50 fathoms. No doubt the yellowtail spawns as actively on the offshore Banks as it does inshore, for though we have not actually found its eggs there we have taken larvae only 7 to 11 mm. long over the western and eastern parts of Georges Bank in July, as well as near Gloucester and near the tip of Cape Cod in July and August.
To the eastward and northward, yellowtail spawn on Sable Island Bank, Banquereau Bank, and the Newfoundland Banks, eggs (no doubt of this species) having been collected on these grounds by the Canadian Fisheries Expedition in 1915. In the opposite direction, it certainly breeds as far westward as New Jersey, for our tow net yielded 88 of its larvae (6.5 to 19 mm. long) 11 miles off Sandy Hook on August 1, 1913; adult fish approaching ripeness have been trawled as far southward as Little Egg Inlet, N. J., in April 1930.
Spawning, Welsh found, begins on the Isles of Shoals-Boone Island ground by the middle of March; and many ripe fish were taken there during the last half of April, but the majority were still green as late in the season as May 8, though others were already spawned out. And spawning must last all summer, for we have trawled many ripe males and females in depths of 17 to 25 fathoms on the edge of Stellwagen Bank at the end of July; have taken eggs indistinguishable from those of the yellowtail in our tow nets in June, July, and August, with one even on September 11; and have taken its newly hatched larvae (6 mm. long) off Race Point as late as August 31. And the individual females evidently spawn over a considerable period of time, for Welsh found that only a small part of the eggs ripened simultaneously.
The yellowtail is one of the most valuable of the flatfishes caught within the Gulf of Maine. It compares favorably in quality with the summer flounder and the winter flounder, but because its body is thinner it brings a lower price to the fishermen. Thus in 1947 the average price, as landed in New Bedford, was about 8 to 9 cents a pound for yellowtails; winter flounders, about 9 to 10 cents a pound; and summer flounders, about 17 to 18 cents a pound. All the yellowtails that are brought in find a ready sale and they make up a large part of the fillet of sole sold to consumers. In 1947 our Gulf yielded between 15 and 16 million pounds of them. But yellowtails live rather too deep to be of any interest to anglers.
 One was taken at 50 fathoms by Albatross II, September 5, 1926, on the northwestern part of Georges Bank, and two of about 10 inches at 90-95 fathoms on the northern edge of Georges Bank, by Cap'n Bill II, August 22, 1952.
 Goode and Bean, Bull. Essex Inst., vol. 11, 1879, p. 6.
 Agassiz, Proc. American Acad. Arts, Sci., N. Ser., vol. 6, 1879, pl. 4.
 Recent records from the Labrador side of the Strait are of one from Barge Bay, July 29, 1910 (Jeffers, Contrib. Canad. Biol., N. Ser., vol. 7, No. 16, 1932, p. 210); and of another taken at Forteau Bay, June 29, 1949, by the Blue Dolphin Expedition, reported to us by Richard H. Backus.
 We have records of one taken off Hog Island, Va., in lat. 37° 41' S. (Bigelow and Schroeder, Bull. U.S. Bur. Fisheries, vol. 48, 1939, p. 340). And it was reported from the southern part of Chesapeake Bay by Uhler and Lugger (Rept. Comm. Fish., Maryland, 1876, p. 95; 2d Ed., 1876, p. 79.)
 Localities are listed by Goode and Bean (Smithsonian Contrib. Knowl., vol. 30, 1895, p. 430).
 To nearest 10,000 pounds.
 Bull. Essex Inst., vol. 11, 1879, p. 6.
 Apart from those that were brought in to Portland by the large trawlers from more distant grounds.
 Landings in 1947 in Massachusetts ports, from grounds westward from Nantucket Shoals, about 12 million pounds; landings in Rhode Island, about 2¼ million pounds; landings in Connecticut, about 3 million pounds.
 About 31/3 million pounds were landed in New York in 1947.
 Albatross II trawled many yellowtails as far southward as the offing of Delaware Bay (lat. 38° 32' N., long. 74° 24' W.) in 12 to 28 fathoms during February, April, and June, of 1929 and 1930.
 The Newfoundland Fishery Research Commission (Rept., vol. 1, No. 4, 1932, p. 110) reports 680 yellowtails taken per 10 hours trawling on Banquereau.
 Frost, Research Bull. 14, Newfoundland Dept. Nat. Resources, 1940, p. 15.
 Welsh obtained many ripe fish there.
 Station 10059, July 9, 1913; and station 10224, July 23, 1914.
 Dannevig (Canadian Fisheries Expedition [1914-15], 1919, p. 17) refers these provisionally to the European dab, which does not occur on our side of the Atlantic. Its egg is indistinguishable from that of the American species.