64 KEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



diametrically differeut, for the former loves cold water, the latter warm 

 water. 



Various provincial writers are now quoted ; Mr. Perley, who says 

 that " naturalists now tell us " and " it is now considered settled " that 

 the mackerel is not migratory, but draws off into deep water at the 

 approach of winter, and Mr. Knight and Mr. Fortiu, though the reason 

 for these quotations is not apparent, since no reference to the winter 

 habits of the fish can be found therein. He does not refer to the writ- 

 ings of Mr. Ambrose and Mr. Johnson, Canadian writers, who advocate 

 the migratory tht'ory. 



Yarrell and Couch are next quoted, though neither of them has ven- 

 tured to give a decided opinion. 



Finally, we have a paragraph compiled from five French encyclope- 

 dias, good and bad, no means being afforded of distinguishing the opin- 

 ions of Cuvier from those of Chenu's literary staff. 

 ■ Mr. Whitcher's conclusion is this: that " it is clearly neither necessary 

 nor accurate that mackerel should perform the migrations ascribed to 

 them by American writers." 



The migrations of the mackerel are neither proved nor disproved by 

 special pleadings of this description. The spirit of Professor Hind's 

 writings is very differeut. He writes from the stand-point of an inves- 

 tigator, and his book is an important contribution to our knowledge of 

 the habits of fishes in relation to temperature and currents. I feel 

 obliged, however, to call attention to a very serious flaw in his chief 

 argument against the annual migration of the mackerel. 



In the chapter on the " Eelation of the Supposed Migratory Move- 

 ments of Mackerel to Isothermal Lines,"* it is claimed that a migration 

 to the north in the spring " presupposes the movements of bodies of the 

 same great schools of mackerel which are alleged to pass Massachusetts 

 Bay from the waters of the coasts of Virginia and New Jersey, not only 

 through from ten to twelve degrees of latitude, but it assumes that they 

 are able to cross in the early summer, and frequently before spawning, 

 numerous isothermal lines in descending order." 



He then refers to the article upon the Gulf Stream in Petermann's 

 "Mittheilungeu " for 1870, in which the marine isothermals for the differ- 

 ent months are shown by means of a chart. A table is given showing the 

 isothermals for July. That of 08° would touch the coast at Delaware 

 Bay, that of 63o.5 at Long Island, that of 59° at Boston, that of 54^.5 

 at Cape Sable, Nova Scotia, that of 50° at Cape Eace, and that of 45^.5 

 at the Straits of Belle Isle. 



From this he concludes that a " a school of fish, moving rapidly from 

 Delaware Bay to the Straits of Belle Isle, would pass in July from a 

 mean tenfperature of 68° to a mean temperature of 45°, a difference of 

 more than 22° Fahrenheit. 



This theory would be very satisfactory if it could be admitted that the 

 *Hilid, 0]). dr., part ii, i>p. 15-17. 



