Whales, dolphins, and porpoises of the western North Atlantic

by Stephen Leatherwood; David K. Caldwell; Howard Elliott Winn

Fin whales may be confused with blue whales, sei whales, and, in the southernmost portion of their range, with Bryde's whales. They may be distinguished from the blue whales by differences in overall coloration, coloration and shape of the head, and the size, position, and time of appearance of the dorsal fin at the surface (see p. [19]). After close examination they may be distinguished from Bryde's whales by the presence of three ridges along the head (of the Bryde's whale) and by the smaller, more sharply pointed falcate dorsal fin of the Bryde's whale (see [Fig. 31]). They may be distinguished from sei whales in the following similar ways:

Fin Whale	Sei Whale
DORSAL FIN
Slightly falcate, forms angleof less than 40° with backslightly more than one-thirdforward from tail.	Sharply pointed and falcate:forms angle of greater than40° with back well more thanone-third forward from tail.
SURFACING BEHAVIOR
Usually rise obliquely so topof head breaks surface first;after blowing, animal archesits back and rolls forwardexposing the dorsal fin on thelong dive; on sounding, themaximum amount of back inthe area of the dorsal finwhich is exposed is approximately2 times the height ofdorsal fin.	Primarily skimmer feeders;usually rise to surface atshallow angle so that dorsalfin and head are visiblealmost simultaneously; whenstarting the long dive doesnot usually arch the back asmuch as the fin whale; onwsounding, the maximumamount of back in the area ofthe dorsal fin which isexposed is approximately 1times the height of the dorsalfin.
BLOW
Tall (to 20 feet [6.1 m]);inverted cone (point down)or elongated ellipse.	Similar shape but smaller—rarelytaller than 10-15 feet(3.1-4.6 m).
DIVING
Dive for 5-15 (usually 6-7)min; blow 3-7 times or moreat intervals of up to severalminutes, then dive again.	Dive for 3-10 min; usuallyblow at even intervals overlong periods of time; oftenvisible just below the surface,even on longer dives.
COLOR OF UNDERSIDES
White higher up on rightthan on left side.	Mostly gray; irregular whitisharea on belly.
COLOR OF LOWER LIP
White on right, gray on left.	Gray.
BALEEN PLATES
Right one-fifth to one-thirdin front white; all othersalternate bands of yellowishwhite and bluish gray; bristlesgrayish white.	Ash black with a blue tingeand fine grayish bristles.

Distribution

Fin whales are probably the most numerous and widely distributed large whale species in the western North Atlantic.

Fin whales summer from below the latitude of Cape Cod, Mass., north to the Arctic Circle. (They are frequently seen between New York and Bermuda this time of year.) Within this zone they may sometimes be seen very close to shore and appear to be concentrated between shore and the 1,000-fathom curve from at least lat. 41°20' to 57°00' N. In recent years they have been reported in relatively large numbers in the Gulf of Maine from March through June, off Newfoundland as early as June but increasing to August, and entering Davis Straits and beyond in substantial numbers in midsummer to late summer. There is some evidence that the animals venturing farthest north are the largest individuals of the species. Movements of the population(s) southward have usually begun by October, though some fin whales sometimes remain in the northern seas sufficiently long to become trapped in the ice and killed.

During winter the range of fin whales spreads out from the advancing ice southward, reaching at least to the coast of Florida, into the Gulf of Mexico, and to the Greater Antilles, though fin whales are not at all common in tropical waters. During the winter many fin whales move into offshore waters. Northward migrations probably begin in midspring.

Fin whales may be found in Cape Cod waters all year long.

There may be two or possibly three separate stocks of fin whales in the western North Atlantic, one more northern cold-adapted stock and another more southern stock. The ranges of the two stocks appear to overlap, such that the winter range of the northern stock probably becomes the spring and summer range of the more southern stock. The third stock may consist of an isolated population in the northern Gulf of Mexico.

Stranded Specimens

Stranded fin whales may be most readily identified by 1) the yellowish-white coloration of the right front baleen and the right white lower lip; 2) the numerous baleen plates (262-473 in number); 3) the numerous ventral grooves (56-100 in number) extending to the navel and beyond ([Table 2]); and 4) the broad, flat sharply pointed head with only a single head ridge.