358 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



spring fish usually two or three weeks earlier than boats fishing in the offing where the 

 sea may be from 49 to 80 fathoms deep. And this is the ease when the temperature is 

 still low. This seemingly points to the conelusion that mackerel when approaching the 

 shore keep deep down, not necessarily at the bottom; that by the rising of the sea-floor 

 they are forced upward along the coast line, but that otherwise they do not rise to 

 the upper waters to spawn until there is a suitable surface temperature. In May and 

 June they shed their ova, and during these months the schools are composed of fish 

 of various sizes. 



The ordinary gill nets for mackerel are fished at the surface, but in some of the 

 bays the fishermen sink a iiortion of the net and moor it in that position. In the 

 spring, on the north coast of Mayo, the fishermen sling their mackerel nets after the 

 manner of herring nets, and often find mackerel in greatest quantities when the nets 

 are slung several fathoms from the surface. 



When spawning is over, the fish scatter and the spring fishing comes to an end. 

 While the schools are on the coast they often wander to and fro, but I have met with 

 no evidence to show that in approaching the coast they travel along it, either to the 

 north or south. From Cork to Donegal, which are the extreme limits of the fishery 

 on the Irish coast, they appear at the same time. Locally, however, the schools move 

 about a good deal and come to certain localities in greater numbers in some years 

 than in others. 



In America the mackerel fleet proceeds southward to Cape Hatteras in order to 

 meet the schools of fish which apparently migrate from south to north, and although 

 Cape Hatteras is about 35° N. latitude and the coast of Ireland is 20° farther north, 

 the same isotherm reaches the two places about same date; so the American and Irish 

 spring mackerel fishery open simultaneously. 



Statistics show that on the American coast fishing advances along the coast pari 

 passu with the isotherm of 50°. 



On our side of the Atlantic we have no great stretch of coast to compare with 

 that from Cape Hatteras to Nova Scotia, but that no such migration takes place may 

 be inferred from the fact that large numbers of French boats come to the Irish coast 

 to commence the spring fishery and there find the earliest and the largest fish. The 

 Cornish mackerel fishery is the southern extension of the Irish. It is not, however, 

 earlier and the general run of fish are smaller. 



The value of this fishery to the country may be estimated when we state that the 

 value of the fish to the fishermen for the twelve weeks it lasted during last spring on 

 the Irish coast was £150,000. The amount spent on labor, freights, and management 

 was of course in proportion. 



Method of capture. — The only method employed for catching the spring mackerel 

 is by gill nets; the larger boats use trains of nets about 2 miles long and drift with 

 them. The row boats and canvas canoes, by which the inshore fishing is carried on, 

 either anchor their nets or drift with them. The spring mackerel are not to be cap- 

 tured by hook and line, and the fishermen have come to the conclusion that they are 

 blind. 



The autumn mackerel fishery. — This fishery received a great impetus in 1887 when, 

 owing to the failure of the mackerel fishery on the American coast, a supply was 

 looked for from Ireland. Since then this fishery has proven a great benefit to the 



