MIGRATION OP COMMANDER ISLANDS SEALS. 263 



furnish us with material for the discussion of various other questions to be touched 

 upon further on. 



In a general way the migration of the Commander Islands seals and the consequent 

 movements of the pelagic sealers off the coast of Japan has been pointed out by 

 Mr. Ghas. H. Townsend (see my Russian Fur Seal Islands, p. 62, and maps accom- 

 panying the report on the fur seal fishery for 1895, Senate Document 137, Part II, 

 54th Congress). The question will bear some elaboration, however, and may be stated 

 as follows : 



A glance at the accompanying map (pi. 113), which shows the density of the 

 catches off the coast of Japan of no less than 39 schooners, will convince us that the 

 seals are not scattered evenly over the vast area of approximately 125,000 square 

 miles, but that there are centers around which they appear to be massed more closely 

 together. There are thus apparently two such centers between 36° 30' and 37° 30' north 

 latitude, one about CO miles from shore, the other more than 200 miles. In latitude 40° 

 there are two, or even three, such patches, respectively about 50, 150, and 270 miles from 

 laud. In 41° there are again two smaller centers, while between 41° and 42°, practically 

 in the Gulf of Mororan (or, as it is called by the sealers, "Volcano Bay, a name, however 

 correctly, referred only to the inner bay of this gulf, in which seals are but scantily 

 taken), the seals seem to congregate in great numbers. To the northeastward along 

 the coast of Yezo, averaging 20 to 30 miles offshore there are several centers of less 

 magnitude off the island of Iturup. 



It will be noticed that practically no seals are taken south of latitude 36° or north 

 of latitude 46°. 



This distribution is pretty well understood by the sealers, a fact of which I became 

 cognizant in plotting the logs in question, and Captain Suow has given the following 

 explanation : 



Uncertain and conflicting currents, often running from two to three knots in opposite directions, 

 prevail on the sealing grounds (off Japan). These currents vary in temperature in places as much as 

 30° F. The sea hereabouts appears to he split up into alternate helts of warm and cold water of variable 

 ■widths. To pass from one streak of current of a temperature of 60° or 65° to another of 35° or 40° is 

 common during the spring months. The edges of these currents are clearly defined, the waters being 

 of different colors, with always more or less of a rip along the margins. The seals keep mostly in the 

 cold streams, few being found in water where the temperature exceeds 54°. 



It seems that these centers of density of the seal catch to some extent denote the 

 feeding and resting stations of the Asiatic seal herd on its travels northward. The 

 movement itself could not be shown on the map in question (pi. 113), but it is well 

 indicated on Townsend's maps quoted above. It appears, then, that in normal years 

 up to the latter part of April the seals are chiefly found south of the fortieth parallel. 

 At the beginning of May the seals commence to crowd the Gulf of Mororan, between 

 Hondo and Yezo, and for nearly three weeks they are assembled here, during which 

 time the heaviest damage is done to the herd. Toward the end of May the seals move 

 northeastward along the coast of Yezo, comparatively near land, making a last stand 

 to the east of Iturup about the middle of June. Prom that neighborhood they 

 suddenly disappear and do not seem to stop in their rapid northeastward course until 

 they reach the breeding grounds on the Commander Islands. 



Such is the movement in normal years. Occasionally, however, unknown causes, 

 but probably of meteorologic or hydrographic origin, may accelerate or retard it, as, 



