122 EEPOKT OF COMMISSIONER OF FISH AND FISHERIES. [32] 



" Sars has shown that this form of movement is taken by the herring 

 on the j^orwegian coast.* 



" The mackerel are pursued by cod and hake, and these fish gather 

 YThereoffalis thrown over from vessels on which the mackerel are cleaned. 

 As a natural consequence the mackerel avoid the sea areas where their 

 enemies are congregated, and fishermen attribute the desertion of the 

 mackerel-ground directly to the throwing of offal overboard. Cod, and 

 probably hake, follow up the scent of offal or food of any description car- 

 ried by currents with remarkable facility, as may be witnessed during 

 the x)rocess of jigging for cod in calm and clear waters. On looking 

 over the side of the boat, with a man engaged in jigging at the bow 

 or stern, as soon as a fish is wounded merely by the jigger and blood 

 flows from the wound, the creature may be seen to dart here and there 

 in jiain. The neighboring fish of the cod tribe are attracted by the scent 

 and follow the blood ' tracks' agaiust the current, hunting their wounded 

 comrade to the death. A fish comiug across the stream of scent, imme- 

 diately follows ifc uf), and it is thus that fish offal or bait thrown over- 

 board in the open sea, or some distance from shore, gathers the fish on 

 the course of the current. In harbors and confined or landlocked bays, 

 where there is no constant strong current to carry off the results of 

 decomposition, and where the sea-scavengers are not sufficiently numer- 

 ous to consume it, the effect cannot fail to be extremely prejudicial to 

 young fry and to fish-spawn. t 



very rapidly from Ipswicli Bay across in the direction of Cape Cod. The schools were 

 at the surface of the water, and it is not an exaggeration to say that their speed was 

 not less than three or four miles an hour. The schools of mackerel sj^read over many 

 square miles, each body of fish was separated from the others, perhaps many hundred 

 fathoms, but all seemed to be impelled by the same motive and were moving steadily 

 in the same direction. These fish would bite eagerly at the hook for a few minutes at 

 a time, but so strong was their instinct of migration that it was inij)ossible to detain 

 them longer than a few minutes at a time in their onward movement. 



J. W. COLLINS. 

 * See chart by Dr. G. O. Sars, in his report for 1874. 



t Fisheries of British North America, pp. 20, 21. It is difficult to see how the offal 

 of mackerel could injure the spawn of the young fry of this fish since the eggs are 

 known to swim at the surface of the sea, and it is presumable that the mackerel, 

 when first hatched out, also keeps near the surface. Therefore in a depth of ten or 

 twenty fathoms it seems extremely problematical that the welfare of either the eggs 

 or young fish could be interfered with by the viscera thrown over from the fishing- 

 vessels. Another thing: It is well known that the waters of the Bay of Saint 

 Lawrence swarm with small and extremely voracious Crustacea — "sea-fleas" — which 

 rapidly devour anything of this kind which is thrown into the sea. Indeed, so active 

 are these small scavengers that codfish caught on a trawl are often completely de- 

 voured by them in three or four hours. Again, there can be no doubt but what throw- 

 ing over the offal from the vessels is really beneficial to the mackerel, which feed upon 

 it. The recent diminution in the abundance of mackerel in the Bay of Saint Lawrence, 

 and the remarkable increase of this fish on our own shores, since the New England 

 fleet has ceased to visit the waters of the Gulf in such numbers as formerly, seems to 

 prove conclusively that the decrease or increase in the abundance of the mackerel is 

 due to other causes than that of throwing over the offal which is taken from those 

 which are caught. — J. W. Collins. 



