20 DEPARTMENT OF THE NAVAL SERVICE 



6 GEORGE V, A. 1916 

 ANNUAL SPAWNING PERIOD. 



The spawning period of the halibut in the North sea appears to extend over 

 many months. Dr. Williamson obtained some fully ripe eggs at the end of January, 

 the parent fish -having been taken about 145 miles out ENE. of Aberdeen, Scotland, 

 the depth of vpater being 65 fathoms. Others have been noticed in March on the 

 west coast of Scotland. Again, in the month of May, Dr. Williamson secured a 

 quantity of ripe eggs from Viking bank, between Shetland and Norway, while Pro- 

 fessor Mcintosh studied ripe ova of halibut in April and May. The spawning period 

 seems to range from January to August in different areas, for Dr. Brown Goods 

 speaks of July, August, and even September as the spawning months on the Atlantic 

 coast of North America; but Dr. J. B. Gilpin, a very diligent early observer, stated 

 that it was in June he observed spawn running from ripe halibut of the Nova Scotia 

 coast.^ On the Pacific coast it would appear that the eggs are ripe in winter or early 

 spring, as Professor Willey has pointed out in his paper, and the British Columbia 

 Fisheries Commission, 1905-07, in their report, based on the evidence of British 

 •Columbia fishermen and others, recommended a close season from December 1 to 

 March 31 each year, as appropriate. "A close season of four months in each year 



.will rapidly restore the threatened halibut supply, and, enforced in the limits 



named, it will include all the ' banks ' or spawning resorts in Hecate strait, etc., on 

 to which the halibut move from the open ocean outside." 



WHY FERTILIZED HALIBUT OVA NOT OBTAINED. 



While the characteristics of the ripe unfertilized halibut egg have been fully 

 described, and its recognition rendered an easy matter by the naturalist, no one has 

 yet seen the fertilized or developing egg in the open sea, or has succeeded in obtain- 

 ing ripe male and female halibut and artificially fertilizing and incubating the ova. 

 In the pioneer investigations into the life-history of marine food-fishes, in which I 

 was privileged to take a considerable part twenty-five years ago, two methods were 

 adopted for the discovery and diagnosis of fish eggs and young. Eggs naturally 

 spawned and fertilized were obtained by fine-meshed tow-nets floated near the surface 

 of the sea, and these were studied and detailed drawings made, and the species deter- 

 mined by a comparative method, or the specialist obtained living fishes of both sexes 

 from the fishing grounds, extruded the ripe eggs and fertilized them by the usual 

 methods of fish-culturists, and hatched out the young fry in the tanks of a marine 

 laboratory. In this way a body of knowledge was accumulated by the early investiga- 

 tors which has been invaluable for succeeding workers. In the case of the halibut 

 the floating eggs have not yet been secured by tow-nettings, and Professor Willey, 

 in the preceding paper, has ventured the suggestion that the eggs float at some depth, 

 not near the surface, as do the eggs of the Argentine (Argentina silus Asc.) of the 

 North Atlantic, which are of large size, 3 mm. to 3-5 mm. in diameter, and occurring 

 in oceanic strata far from the surface, according to Dr. Schmidt. The fact that the 

 eggs of the halibut must be very abundant in northern Atlantic and Pacific waters 

 and yet none have been obtained in a developing condition in the sea, strongly 

 supports Professor Willey's important suggestion. 



DIAGNOSTIC FEATURES OF TWO SPECIES OF HALIBUT. 



The earliest larval stages of the halibut are not yet known, and cannot be accur- 

 ately made known until fertilized eggs are studied and the young fish hatched out 

 and reared, as has been done in the case of such a great variety of marine food-fishes. 

 At various times, small larval fishes have been captured in the sea, which were pro- 

 nounced as most probably young halibut. In most of these cases later research has 



1 Food Fishes of Nova Scotia, Art. II, p. 23, Trans. N.S. Inst, of Sci., 1S68. A. United 

 States expert recently stated tliat an Oregon halibut on September 1, 1914, contained large 

 loose eggs and more nearly approaching ripeness than any female specimen obtained pre- 

 viously, hence the spawning period could not be far off. 



