BIOLOGY OF THE ATLANTIC MACKEREL 161 



place occasionally on the western coast of Newfoundland, but probably only in bays 

 in which the water warms up to 10° C. (50° F.) ; perhaps it is of irregular occurrence 

 and it is certainly of minor importance.' 



Season. — In the southern half of the Gulf of St. Lawrence, eggs were present as 

 early as May 29 and as late as August 12. The maximum catches were taken on 

 June 30, July 7, and July 8, and it may be presumed that the height of the season was 

 in the latter part of June and early part of July. 



Relative Importance of the Several Spawning Regions 



Because it is important to know which grounds are mainly responsible for recruit- 

 ment of the mackerel population, an appraisal of the relative amounts of spawning 

 in the four regions will be attempted, even though the available information is not 

 adequate for precise treatment. Since these four regions are roughly equal in size 

 and each is sufficiently large to constitute a major spawning area, it will suffice to 

 examine only average concentration of eggs in each region. The pertinent data, in 

 terms of average or usual number of eggs taken per positive surface tow with a meter 

 net are as follows: 



Continental shelf between Cape Cod and Cape Hatteras 3,000 to 5,000 



Gulf of St. Lawrence About 300. 



Gulf of Maine (exclusive of Cape Cod Bay) Less than 100. 



Coast of Nova Scotia About 14. 



Of course, these numbers cannot be taken at their face values for there are many 

 factors affecting their comparability. However, the last two items in the list are so 

 low that it may be concluded that the coast of Nova Scotia and the Gulf of Maine are 

 of negligible importance as mackerel spawning areas. 



On the other hand, the Gulf of St. Lawrence and the continental shell' between 

 Cape Cod and Cape Hatteras are both grounds of evidently some importance, and 

 their comparison with each other deserves more careful consideration. The two 

 things that might affect most obviously the comparability of the data on them are: 

 (1) the technique of towing, including the distribution of stations, (2) the fact that. 

 the Gulf of St. Lawrence survey took place more than a decade earlier than the tow- 

 netting over the continental shelf between Cape Cod and Cape Hatteras. 



The techniques employed in the Gulf of St. Lawrence by the Canadian Fisheries 

 Expedition obviously were not intended for quantitative purposes. According to 

 Dannevig (1919, p. 3) "The duration of the surface hauls varied somewhat, as a rule 

 between ten and fifteen minutes; * * *" and Huntsman (1919, p. 407) states, 

 "The tow hauls (as distinguished from the vertical hauls) are the most unreliable, 

 owing to lack of information in the records as to the manner in which they were taken 

 * * *. The tow hauls were taken in a great variety of ways." Further, Hunts- 

 man's table (loc. cit., p. 419) of hauls by the C. G. S. No. S3, which contributed most 

 of the mackerel eggs, shows that some of these hauls in reality were oblique and that 

 towing periods varied between 5 and 20 minutes, with the time not given for certain 

 of the hauls containing important numbers of mackerel eggs. 



Furthermore, the stations were closely spaced in some portions of the Gulf and 

 widely spaced in others. They may have chanced to be concentrated where the eggs 

 were thickest or the contrary. Similarly, the distribution with respect to time may 

 have been favorable to the taking of abnormally large numbers of eggs, or the contrary. 

 On the other hand, the coverage, both as to space and time, was far from haphazard. 

 The Princess occupied stations in the Gulf of St. Lawrence during June 9 to June 15 



