356 BULLETIN OF THE UIS 7 ITED STATES FISH COMMISSION. 



young of some of our shore fishes are well known to appear in great swarms during 

 certain seasons and to be unusually scarce in others. In some cases these swarms of 

 young have been observed to appear as larger and larger fish for several successive 

 years, but in other cases their very abundance has proved their destruction by attract- 

 ing schools of blnefish, which very quickly depleted their ranks. 



Besides the lemmings, locusts, army-worms, and many other species among land 

 animals, we may also mention the great swarms of jelly-fishes, salpae, etc., which 

 appear periodically on our coasts, and the oyster, which, even aside from the question 

 of the fixation of spat, differs greatly in this respect in different seasons. Some of 

 these cases can be proved to be owing to the production of eggs or young in greater 

 or less numbers, others to the greater or less destruction, through unfavorable circum- 

 stances, of eggs or young. The records of surface towings made in the neighborhood 

 of Casco Bay show that the number of mackerel eggs present varies greatly. In 

 1894 they were very plentiful, while during the summer of 1897, although the eggs of 

 other species were present in great numbers, those of the mackerel were almost 

 entirely absent. And this was in spite of the fact that schools of mature fish entered 

 the bay during that time. This result may have been due to the mackerel having 

 spawned further off the coast in 1897 than in 1894. The winds influence the distribution 

 of the eggs by moving the surface waters, but this and similar factors were eliminated 

 in the investigations of 1897. 



IV. The last theory to be considered in this connection is one deduced from the 

 well-known wandering habits of the mackerel. Besides periodic movements toward 

 and from the shore, and coastwise migrations which occur in spring and fall, this fish, 

 like many other active pelagic organisms, is in the habit of wandering far and wide over 

 the broad expanse of the North Atlantic Ocean. How extensive these more irregular 

 movements may be in the case of particular schools of fish is not known, but it is 

 supposed that during the periods when our fishermen meet with a scarcity the great 

 body offish may remain in some region hitherto unknown or inaccessible. They may 

 either be in the open sea far oft' the coast or remain submerged and hidden. 



Everyone knows that within the actual limits of the fishing-grounds the schools 

 are very sensitive to changes in conditions, and so long as many of the influences 

 which affect them remain unknown their movements seem to us to be mysterious 

 and capricious. The fishing, both with line and seine, may be exceedingly good 

 in certain localities for a few days, when suddenly, even in the midst of their 

 abundance, the fish may " strike off" almost without warning, and either totally 

 disappear, or apparently the same school reappears at some distant point. 



.Mackerel may be present in abundance, but refuse to school or to take the hook; 

 or no mackerel may be visible at the surface, yet the occasional rush of schools before 

 the onslaughts of larger predaceous fish or mammals, or other signs, may betray their 

 whereabouts, and though plenty, none will be caught. These conditions may charac 

 terize a part or the whole of a season. During particular seasons the best fares may 

 be taken in the spring; during others, in the fall or in midsummer. Sometimes the 

 great catches, which have made the total for a season large, have been taken in a 

 few weeks; sometimes the entire season has been uniform in its results, either good 

 or bad, as the case may be. 



Again, seasons may be characterized by marked differences in the distribution of 

 the fish. One time the best catches will be secured in the Gulf of St. Lawrence; at 

 another time in the Gulf of Maine, and, again, in the waters about Cape Cod. Some- 



