FISHES OF THE GULF OF MAINE 



393 



Although silver hake appear as early as April or May in the Gulf of Maine 

 we have no evidence that they commence to spawn before June north of Cape Cod, 

 our earliest egg record being for the 11th of that month. Spawning, as evidenced 

 by captures of the eggs in tow nettings, is at its height in July and August and 

 continues through September, though less freely, with October 22 as our latest 

 date. Similarly, the Canadian Fisheries Expedition found no silver hake eggs in 

 Nova Scotian waters east of Cape Sable in May, but many in July, while Kuntz 

 and Radcliffe describe the silver hake as spawning in July and August about Woods 

 Hole 



According to their observations 80 only part of the eggs mature at a time, 

 hence the silver hake, like the mackerel, belongs to the rather numerous category 

 of fishes, individuals of which spawn over a considerable period. 



The temperatures and salinities in which silver hake spawn in the Gulf of 

 Maine vary widely, consequent on the considerable area serving as spawning 

 grounds and on the prolonged spawning season. Owing to the sharp temperature 

 gradient prevailing in most parts of the Gulf at the height of the breeding season 

 it is impossible to establish the exact temperature at which silver hake are spawn- 

 ing at any particular station without knowing at what level in the water the ripe 

 fish are — which may be anywhere between the surface and the bottom with this 

 species. It may be definitely stated, however, that they never spawn in as cold 

 water as cod and haddock usually do in the western Atlantic. In 1915, for example 

 (a representative season), it was not until the entire column of water was slightly 

 warmer than 41° at the locality in question that we found the first silver hake eggs. 

 If the parent fish were in the upper water layers, which the general habit of this 

 species suggests, all the rich spawnings we encountered in the Gulf during that and 

 the following year took place in temperatures considerably higher. 



Station 



10300. 

 10302. 

 10303. 

 10305. 

 10344. 

 10345. 

 10355. 



Date 



July?, 1915.. 

 July 19, 1915.. 

 Aug. 4, 1915.. 

 Aug. 18, 1915. 

 July 22, 1916.. 



do 



July 25, 1916.. 



Depth, 

 fathoms 



Surface 

 temper- 

 ature 



62 



52.9 



52.9 



51.5 



60.5 



50 



53.5 



Bottom 

 temper- 

 ature 



44.1 



45 



42.7 



47.8 



39.5 



39.2 



51.7 



Similarly the silver hake eggs taken off Halifax by the Canadian Fisheries 

 Expedition in July, 1915, and off Shelburne, Nova Scotia, by the Grampus on 

 September 6 of that year, may have been spawned in water warmer than 50°, and 

 probably were in temperatures higher than 41°, there being no necessity for assum- 

 ing that the parent fish were lying in the colder bottom stratum. As the spawn- 

 ing season draws to its close in September and October the minimum temperatures 

 for most of our egg stations have been higher than 46°, with one (our latest record 

 for the season) as warm as 57°. These data point to 41° to 45° as about the lower 

 temperature limit to the spawning of the silver hake, with 45° to 55° as the range 

 of temperature within which most of the eggs are produced. 



£0 Kuntz and RadclilTe (191S, p. 109) describe the spawning and early development. 



