To what extent this fish is amenable to the influences of temperature is an unsolved problem. We are met at the outset by the fact that they are frequently taken on trawl lines which are set at the depth of one hundred fathoms or more, on the offshore banks. We know that the temperature of the water in these localities and at that depth is sure to be less than 40° Fahr. How is this fact to be reconciled with the known habits of the fish, that it prefers the warmest weather of summer and swims at the surface in water of temperature ranging from 55° to 70°, sinking when cool winds blow below? The case seemed clear enough until the inconvenient discovery was made that swordfish are taken on bottom trawl lines. In other respects their habits agree closely with those of the mackerel tribe, all the members of which seem sensitive to slight changes in temperature, and which, as a rule, prefer temperature in the neighborhood of 50° or more.
SHINING IN THE SUNLIGHT
THROWING WHITE WATER LIKE THE EXPLOSION OF A TORPEDO
The appearance of the fish at the surface depends largely upon the temperature. They are seen only upon quiet summer days, in the morning before ten or eleven o’clock, and in the afternoon about four o’clock. Old fishermen say that they rise when the mackerel rise, and when the mackerel go down they go down also.
Regarding the winter abode of the swordfish, conjecture is useless. I have already discussed this question at length with reference to the menhaden and mackerel. With the swordfish the conditions are very different. The former are known to spawn in our waters, and the schools of young ones follow the old ones in toward the shores. The latter do not spawn in our waters. We cannot well believe that they hibernate, nor is the hypothesis of a sojourn in the middle strata of mid-ocean exactly tenable. Perhaps they migrate to some distant region, where they spawn. But then the spawning-time of this species in the Mediterranean, as is related in a subsequent paragraph, appears to occur in the summer months, at the very time when the swordfish are most abundant in our own waters, apparently feeling no responsibility for the perpetuation of their species.
The swordfish, when swimming at the surface, usually allows its dorsal fin and the upper lobe of its caudal fin to be visible, projecting out of the water. It is this habit which enables the fisherman to detect the presence of the fish. It swims slowly along, and the fishing-schooner with a light breeze finds no difficulty in overtaking it. When excited its motions are very rapid and nervous. Swordfish are sometimes seen to leap entirely out of the water. Early writers attributed this habit to the tormenting presence of parasites, but this theory seems hardly necessary, knowing what we do of its violent exertions at other times. The pointed head, the fins of the back and abdomen snugly fitting into grooves, the absence of ventrals, the long, lithe, muscular body, sloping slowly to the tail, fits it for the most rapid and forceful movement through the water. Prof. Richard Owen, testifying in an England court in regard to its power, said: