It must be obvious to the most ordinary reader that the cause which led to this temporary failure was the too early interception of the mackerel while on the way to their spawning ground. Why this should be, I shall explain more interestingly; for in elucidating the subject I shall have to call attention to the peculiar habits and instincts of the mackerel, which, upon the authority of early official documents, we learn were suspected, if not known, by the fishermen of the south of Ireland more than two centuries ago.
When alluding to the instinct of the mackerel I did so in a manner that might possibly lead a reader to suppose that they possess the same unreasoning prompting to action that do all animals, whether it be that that instinct warns them of danger, safety, or the presence or propinquity of food or pleasurable object. But there is one all-important factor of common instinct which is partially absent in the mackerel—viz., danger; for, although when they are interrupted on the way to their spawning ground they avoid the place where their shoals were broken—oftentimes for many years—and execute the arc of a circle around the danger spot on their succeeding journeys to the spawning ground, it is a most curious fact that when close to their haunts they swim blindly and without any apparent unreasoning prompting or instinct of danger onward, nor do they struggle to free themselves from the meshes of the net as do all other fishes.
There can be no doubt whatever about this absence, or rather partial absence, of the instinct of danger in the mackerel.
Another peculiar trait of this member of the Salmonidæ family is that mackerel do not feed upon their own young as do most other fishes; and often, in the autumn, when the "harvest mackerel" (a smaller species than the "season" mackerel, and usually, but erroneously, supposed to be all males) frequents the waters close to the shore, I have seen them rush wildly through a shoal of sprats or brit, with which young mackerel often swim, devouring them upon all sides, but studiously avoiding those of their own family. Indeed, the petite mackerelettes do not seem to be at all so alarmed as their companions, who spring out of the water in their terror and swim scatteringly in every direction. This, too, is undoubtedly instinct upon the part of both the juvenile mackerel and his larger brother. But that fact does not importantly concern the purpose of this article.
I have shown that they possess instinct of both a perfect and imperfect order, and I have proved that, because of the interception of the shoals while on their way to the spawning ground in the spring, they abandon their usual course and travel perhaps hundreds of miles in a semicircle to reach the haunts where the roe is deposited. Of course, I have given only one example, and
