FISHERIES RESEARCH BOARD OF CANADA BIOLOGICAL STATION, ST.ANDREWS,N.B. General Series Circular No. 43 Aug.1964

Northwest Atlantic UN AS AND

• By S.N. TIBBO and R.A. McKENZIE • of fisheries seems likely since there are still many areas that are relatively unexploited, as for example, the western side of both the North and South Atlantic.

There are five species of tuna (bluefin, yellow- fin, bigeye, and blackfin) and three species of (skipjack, common bonito and false alba- core) in the Northwest Atlantic. They are all simil- ar in appearance especially when they are small and hence are quite difficult to distinguish. How- ever, withoot a cc ur ate identification of the fish, information on the fishery is almost meaningless and NEW Canadian fishery got under way in 1963 hence this Circular has been prepared to assist in A when two enterprising fishermen from Cam- identification and to provide some information on the pobello, New Brunswick, began to fish the offshore distribution of each species. stocks of tuna and bonito in the Northwest Atlantic. These fishermen had tv,,o purse seiners built during All adult and bonitos are large, beaut- the year and in spite of a late star t (August ZO) ifully streamlined fish admirably a dap te d to slip caught 366 tons of bluefin and skipjack before the easily through the water. The bullet-shaped head, season ended. closely-fitting jaws and smooth eyes set flush with the surface suggest that they are capable of great Tunas and bonitos are among the greatest of bursts of speed. Even the fin s fit into grooves or the world's fishery resources but fisheries for them depressions in the body so as not to interrupt the are still in the development stage. This is espec- contour. The tail is crescent-shaped and there are ially so for the Atlantic where large-scale tuna small fins (finlets) between it and the second dorsal fisheries were practically non-existent before 1950. and anal fins. By 1960, however, the catch of tunas and bonitos in the Atlantic amounted to 40 0 million lb or nearly The colour and weight of tunas and bonitos Z0 per cent of the world catch. Continued expansion vary with area and seascin. Other characters used

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(Reprinted from Aug. , 1964 issue of "Trade News" of the Department of Fisheries of Canada) for identification such as eye size, body proportions, Colour. The most colourful of all tunas with length and position of fins, v ar y with the size and a golden band along sides; fins br illi ant yellow, age of fi s h . Identification of young tuna s is ex- especially second dorsal and anal; finlets bright yel- tremely difficult and practically impossible outside low with narrow dusky edges; young fish have whitish of a lab or a to r y because external distinguishing vertical bars or rows of white spots along the sides; characters do not appear until late in life. Ident- colours fade soon after death and yellow disappears. ification of adults of ten depends on a combination of characters rather than on any single character. Distinguishing feature.. The most delicately For example, adult yellowfin have more yellow col- proportioned of all tunas with short head, small girth ouring than any other species but alltunas have some and long tail region; completely covered with scales; yellow on their fins. extraordinary elongation of second dorsal and anal fins in fish more than 3 feet long distinguishes yel- The following descriptions and drawings will lowfin from all tunas; in 5-feet fish these fins may aid in the identification of the various species of tuna be half as long as body or longer; pectoral fins and bonito that are lik ely to be caught in quantity longer than in bluefin but shorter than in bigeye and Northwest However, difficulties in the Atlantic. if albacore; vent oval or tear-shaped. are still encountered and especially if juveniles are caught, the staff of the Fisheries Research Board Distribution. Distributed around the world in of Canada Biological Station at St. Andrews, N.B., waters above 65 ° F (warmer than for bluefin, big- will gladly assist in the identification. eye or albacore); c omm on in Gulf Stream, North Equatorial current, western Sargasso Sea, Carib- BLUEFIN (Thannus thynnus) bean and s o u the rn Gulf of Mexico; in late spring yellowfin a dv an ce s into Northwest Atlantic and Other common names: Bluefin tuna , tuna, tunny, occurs there (offshore) shore ) from June until early horse , great albacore. October.

Description (see Figure 1) B1GEYE (Thunnus obesus)

Size. Largest of all tuna s ; reaches 14 feet Other common names: None. (2000 lb); most common sizes off the Maritimes are Description (see Figure 3) "giants" (400-600 lb) in early summer and "jumper s" (50-100 lb) in late summer and autumn. Size. Smaller than bluefin; r e ache s 6 feet Colour. Back, dark metallic blue with green- (400 lb). ish sheen; sides greyish, belly silvery white; finlets yellow with dark edges. Colour. Back, dark ashy blue; sides and belly dull greyish blue; tail and pectoral fins reddish Distinguishing features. Robust body, com- black; first has tinge of yellow; finlets yel- pletely covered with scales; hind edge of first dorsal low with black edges as in bluefin. fin slightly concave; second dorsal deeply concave Distinguishing features. Robust b com- and sharply pointed; short pectoral fin extends back- ody pletely covered with small scales; shaped like blue- ward only to near hind part of first dorsal; pectoral fin, weight fin shorter than in other tunas; round vent separates but and depth carried nearly as far back similar bluefin from yellowfin and bigeye in which vents are as second dorsal fin; dorsal fins in size and oval. shape to bluefin but pectoral fins longer and more pointed; eye larger than in bluefin; vent oval as in Distribution. Apparently migrates nor th in yellowfin. spring from West Indies; most common in warmer waters; found in Newfoundland, southern Gulf of St. Distribution. A deep-swimming tuna found Lawrence, outer coast of Nova Scotia, Bay of Fundy chiefly in waters be y ond the continental shelves; and southward from June to mid October; areas of common in the Caribbean Sea f r om Venezuela to concentraton vary unpredictably from year to year; Florida; a few trolled at the surface off Maryland; "giants" frequently angle d in southwestern Nova some taken off the Nova S c otia coast in 1963 by Scotia and in Newfoundland; "giants" and "jumpers" s wor dfish longline r s . taken in traps in St. Margaret's Bay, N.S. ALBACORE (Thunnus alalunga) YELLOWFIN (Thunn.us albacares) Other common names: Long-finned tuna. Other common name s: Yellowfin tuna, Allison's Description (see Figure 4) tunny, autumn albacore. Size. A small fish, reaching 75-80 lb (31 ft) Description (see Figure 2) but generally less than 50 lb; fish in eastern parts of North Atlantic smaller than those in the west. Size. A large tuna; in No r th we st Atlantic reaches 6 feet (300 lb); up to 8 feet (450 lb) in other Colour. Sides and belly have a dull brownish areas. cast and a na.rrow, bluish band lengthwise along the

- 8 - Bluefin Blackfin Thunnus thynnus Thunnus atlanticus

Ftrdel5 1?

Fig. I f Lefef01 line Pectorol fin

Yellow fin Euthynnus pelarnis Thunnus

Fig. 6

Bigeye Common Bonito Thunnus obesus Sarda

Fig. 3 Fig. 7

Albacore False Albacore Thunnus alalunga Euthynnus alleteratus

Fig. 8 side; finlets generally darker than in bluefin or big- stripes from pectoral fin to tail. eye but with some yellow, e spe cially the dorsal finlets; tail fin distinctly edged with white along rear Distinguishing features. Body weight carried margin. both farther forward and farther back than in any of • the true tunas; no scales exce pt for narrow band Distinguishing features. A robust fish com- along and in corselet around pectoral pletely covered with scales; body w e ight carried region; first dorsal fin sickle-shaped along its trail- even farther back than in bigeye, tapering abruptly ing edge; lateral line curved s ha rp ly downward beyond second dorsal fin; gr eat elongation of pec- opposite space between dorsal fins. toral fin, reaching well beyond rear margin of sec- ond dorsal, distinguishes albacore from all other Distribution. Abundant in most warm and tunas; dorsal and anal fins similar in size and shape temperate oceans; taken in purse seines as far north to bluefin and bigeye; vent round. as Long Island, New York; occasionally around Cape Cod; rare farther north. Distribution. Found in all tropical and tem- perate seas; tolerant of low temperatures, some- COMMON BONITO (Sarda sarda) times found in waters less than 60 ° F; adults occur around West Indies, Bahamas and Bermuda in late Other common name s: Atlantic bonito, skipjack, winter and spring, and as far north as Nova Scotia horse mackerel. banks in summer; a thinly distributed, deep-swim- Description (see Figure 7) ming resident of oceanic waters caught almost ex- clusively by longlines. Size. A small species; reaches 3 feet (10-12 lb). BLACKFIN (Thunnus atlanticus)

Colour. Back blue-black; upper sides with Other common names: Bermuda tuna, bigeye tuna, dark bluish stripes sloping backward and upward; Atlantic blackein tuna, blackfin bonito. lower sides and belly silvery; young fish have dark- blue vertical stripes on sides. Description (see Figure 5) Distinguishing features. Body more slender Size. Smallest of all tunas; reaches 3 feet and mackerel-like than in skipjack; completely cov- (35 lb). ered with scales; mouth large, extending back to Colour. Bright golden band along sides; belly rear of eye; trailing edge of first dorsal fin almost white s ofnetime s with small iridescent patches; straight, not sickle-shaped as in skipjack. dorsal finlets du sky bronze; ventral finlets steely grey; lack of yellow on finlets of li v e fish usually Distribution. F ound in all warm and tem- • distinguishes the blackfin; golden bands fade at death perate oceans; found in western Atlantic from but a yellowish cast may then appear on finlets. Argentina to southern Gulf of St. Lawrence; taken by sports fishermen and occasionally in trap-nets in Distinguishing features. Body very thickset; Cape Cod area; usually travels in schools, but no- scales over whole body and large s c ale s form a where abundant enough to support a regular fishery. corselet in pectoral region; eyes large; dorsal and anal fins normal size but pectoral fin longer than in FALSE ALBACORE (Euthynnus alleteratus) bluefin and extends backwards to the front of second Other common names: Little tuna, bonito. dorsal. Description (see Figure 8) Distribution. Rare north of Cape Hatteras and Bermuda; most northerly record i s Lat. 40 0 04N; Size. A medium-size fish; reaches 3 feet (30 most common in water shoaler than 100 fathoms and lb). warmer than 68 ° F; caught mainly by sport fisher- men in Caribbean, Gulf of Mexico and off Florida Colour. Back steel-blue; dark wavy horizontal coast; range expands somewhat in summer. streaks along sides above lateral line; lower sides and belly white e xce pt for a few dark spots just SKIPJACK (Euthynnus pelamis) behind head.

Other common names: , ocean bonito, Distinguishing features. Shape re se mb le s . skipjack; body without scales except for a corselet in pectoral region and a band along lateral line; Description (see Figure 6) lateral line almost straight; hind edge of first dorsal fin sickle-shaped; mouth larger than in skipjack and Size. A medium-size f i sh; reaches 3 feet extends back to about middle of eye. (50 lb); most common commercial size 2 feet (10 lb). Distribution. Widely distributed in tropical Colour. Back steel blue; sides and belly white; and temperate o ce an s ; travels in schools; occas- lovver sides haveve dark, bluish-brown lengthwise ionally taken in traps around Cape Cod.

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