232 



NATURE 



{June 27, 1878 



branch of the fauna of Venezuela that appears to 

 have been pretty thoroughly worked at, Herr Anton 

 Goering — the German naturalist, whose name has 

 been already mentioned in connection with the ascent 

 of the Silla of Caracas — sent all his collections of 

 birds to this country, where they were examined and 

 reported upon by two competent naturalists, who have 

 devoted special attention to the neotropical avifauna. 

 The results are given in the series of papers read before 

 the Zoological Society of London, of which the titles 

 stand last in our list of the subjects of this notice. 



Mr. Goering' s principal discoveries in the class of 

 birds were made in the Andes of Merida, where some 

 splendid novelties were obtained. And in this part of 

 Venezuela, if we mistake not, there remains most to be 

 done as regards both the fauna and the flora of the 

 republic. 



THE FISHERIES OF BRITISH NORTH 



AMERICA 1 



11. 



THE careful inquiries that have been recently carried 

 on by various able investigators in regard to the 

 habits of our chief food-fishes — the Cod, the Herring, and 

 the Mackerel — have now finally disposed of a large accu- 

 mulation of popular fallacies on the subject of their 

 migrations. On the European side Dr. G. O. Sars has 

 added most to our scientific knowledge of the subject ; 

 and on the American, the United States Fisheries' Com- 

 missioner, Prof. Spencer Baird, and Mr. Hind, of the 

 Halifax Fishery Commission, whose reports furnish a 

 most valuable body of information as to the New England 

 and Dominion fisheries. 



It may now be affirmed with certainty that the notion 

 of the long and distant migrations of these food-fishes is 

 a complete mistake : the real facts being that they never 

 range to any great distance from their ordinary habitats; 

 that their migrations, which have reference to food on 

 the one hand and to the deposit of spawn on the other, 

 are simply from deep to coastal waters, and back again ; 

 and that these migrations are chiefly dominated by tem- 

 perature. 



Commencing with the Cod, we are informed by Mr. 

 Hind that the total average weight caught in North 

 American waters is about 185,000 tons, representing 

 from 150 to 175 millions of fish, or between three and 

 four times the produce of the whole Norwegian cod- 

 fishery. Of this, the portion caught in the waters of the 

 United States is only about one-fifth. "Winter cod" 

 are taken on the southern coast of Newfoundland through 

 the whole winter, while " summer cod " are captured 

 through the summer months on the north-east shores of 

 Newfoundland, the entire shore of the Gulf of St. 

 Lawrence, and along the Labrador coast as far north as 

 the Moravian missionary stations, Nain and Okak (57^° 

 N. lat.). 



It seems now well established that the great body of 

 cod-fish inhabiting the waters of the long North American 

 seaboard is divided into numerous separate " schools," 

 which vary in their habits according to the localities 

 they respectively frequent, each keeping (for the most 

 part, at least) within its own limited range. There is no 

 specific or even varietal difference between the "winter" 

 and "summer" cod; their movements towards the coast 

 from the neighbouring deeps, in which they spend the 

 remainder of the year, being determined by the climatic 

 changes which make the northern shores afford the tem- 

 perature most congenial to the species in the summer 

 months and the southern in the winter. 



The food which lures the cod towards the shore at 

 stated periods varies with the locality and season, being 



' Continued from p. 172. - ■ 



for the most part the capelin in the colder seas and the 

 herring in the warmer ; and hence the movements of 

 these fish exert an important influence over those of the 

 cod. At other times the chief food of the cod consists 

 of the Invertebrates of the sea-bottom ; and according to 

 the predominance of any particular species will be its 

 share in their maintenance. Thus in some places the cod 

 feeds chiefly (as is shown by examination of the contents 

 of the stomach) upon bivalve or univalve Mollusks ; in 

 others upon crabs, shrimps, and yet smaller Crustaceans ; 

 in others upon sand-stars, brittle-stars, holothurians, and 

 other Echinoderms. The resort of cod to " banks " 

 seems essentially determined by the food they find there; 

 this, again, being dominated by temperature, — for, as 

 already pointed out, the water on these banks is colder 

 than water at the same depths elsewhere : many sub- 

 arctic species of shell-fish, &c., which serve as food to 

 the cod, thrive there far south of their ordinary habitats 

 (as has been observed by Dr. J. Gwyn Jeffreys on the 

 Dogger Bank); and thus, as Mr. Hind remarks, these 

 banks bear the same relation to the surrounding sea area 

 with regard to certain forms of marine life, as do the 

 oases in the desert to various species of land animals. 



An impression haS prevailed among fishermen, and 

 even among naturalists, that the Shore cod, or cod gene- 

 rally caught in coastal waters, is specifically different 

 from the Bank cod, which is taken on reefs and banks in 

 comparatively deep water, and often at a considerable 

 distance from land. But it has been conclusively estab- 

 lished by the careful observations of the two Profs. Sars 

 (father and son) that no such specific distinction exists, 

 the difference being one partly of age and partly of 

 habitat. The two and three-year old cod remain on the 

 Norwegian coast all the year round, and it is usually not 

 until they attain their fourth year that their reproductive 

 organs are sufficiently developed for multiplication. The 

 adult Norvregian cod, according to Sars, retire far from 

 the coast when the spawning season (January to March) 

 is over ; and are found during the summer on the slopes 

 of the Polar Deeps. So the cod which frequent the 

 coasts of Labrador through a great part of the year, 

 seem to be immature (though sometimes having their 

 reproductive organs developed) ; and when they attain 

 their full growth, which occurs in their fourth year, they 

 change their habits, frequenting the outside banks, and 

 only a portion of them visiting the coast during the capelin 

 season. 



According to G. O. Sars, the Norwegian cod has no 

 regular spawning ground, but drops its spawn free in the 

 sea at a considerable distance above the bottom. The spe- 

 cific gravity of the ova is slightly below that of sea- water, so 

 that the spawn rises to the surface and floats there, unless 

 the salinity of the surface-layer be lowered either by rain- 

 or by river-water, in which case the ova sink until they 

 reach more saline water. The same is the case with the 

 milt of the male, which seems to be shed at a greater 

 depth than the roe of the female, which is thus impreg- 

 nated from beneath, the micropyle of the ovum being 

 located at its lowest point. The time required for hatch- 

 ing is about sixteen days, but a further period of fourteen 

 days is required for the absorption of the yolk-bag, up to 

 the completion of which process the young fish has little 

 swimming power. 



On the North American coast the spawning of the cod 

 is not confined to a particular season, the process taking 

 place in one locality or another through nearly, if not 

 quite, every month in the year, and being obviously 

 dominated by temperature, for it appears that cod ova 

 find the coldest surface-water, provided it be free from 

 ice, the most congenial to their development. Hence, 

 as Mr. Hind justly remarks, the zone of cold water of 

 from twenty-five to thirty miles broad, which extends 

 for hundreds of miles along the Labrador coast, within 

 the line of banks on which icebergs ground, is a most 



