122 Part III. — Ticentieth Annual Report 



ratio of the width between the boards to the length of tlie headhne to 

 be as 1 to 1 "9. If the same ratio were appHed to the large otter- 

 trawls used for commercial purposes, then the distance between the 

 boards when fishmg would for the five sizes previously mentioned 

 range about 74 feet, 681 feet, 63 feet, 58 feet, and 47| feet. That 

 this ratio does apply is, however, uncertain, since the spread of the 

 net depends upon the size of the boards in relation to the resistance 

 offered by the net. The boards used by the steam trawlers usually 

 measure from 10 to 10| feet in length by 4 to 4^ feet high. 



Observations were also made to determine the speed at which the 

 trawl is towed during ordinary fishing. The patent logs on board 

 were, as a rule, unable to indicate this owing to the slow movement of 

 the vessel, and the old-fashioned log with a reel and time-glass was 

 employed. The mean of six observations on one vessel was 3'46 knots 

 per hour ; the mean of eight observations on another vessel was 2*62 

 knots, and the mean of three observations on a third 2 "21 knots, the 

 mean of the seventeen observations being 2*64 knots, or about 2|- knots 

 per hour. At this rate the extent of bottom trawled over in an 

 ordinary five hours' drag would be a little over thirteen (13i) nautical 

 miles, and if the results of the experiments on the spread of the otter- 

 net of the " Garland " are applied, the largest nets would in that 

 time sweep an area of about 661,540 square yards, or 136'7 acres. 

 Under ordinary circumstances four such drags are made in the twenty- 

 four hours, and in an ordinary weekly trip to the north-eastern 

 grounds fishing operations are carried on for about five-and-a-half 

 days. During this time, therefore, the extent of liottom fished over 

 with the otter-trawl would be approximately 4| (4-7) square (statute) 

 miles ; but as trawling is carried on in circles or sweeps, and sometimes 

 around an anchored " Dan '' (a buoy with a flag and lamp) the same 

 ground may be repeatedly trawled over and the real extent is less. 



The bearing of the conclusions as to the width of the otter-trawl 

 when fishing on the nature of 1 he catch is evident. If the distance 

 between the boards, or the -extent of bottom over which the ground- 

 rope moves, is but little greater than the width of one of the lai'gest 

 beam-trawls, then the quantity of flatfishes taken ought not to be 

 much greater, since the otter-trawl has no other special advantages 

 so far as concerns flatfishes. With large round fishes it is difierent. 

 They are active in their movements and not so strictly confined to the 

 bottom, and the thick, conspicuous beam of the beam-trawl, moving- 

 Si or 4 feet above the bottom, must disturb a proportion of them and 

 enable them to escape capture. The small headline which replaces the 

 beam is mvich less visible and will disturb them to a less extent. It is 

 probable, moreover, that the arc formed by the headline does not lie in 

 a horizontal plane, but slopes obliquely upwards as well as backwards, 

 and that tlie otter-net fishes higher above the bottom than does the 

 beam-trawl. 



The statistical evidence in regard to the i-elative efficiency of the 

 beam-trawl and the otter-trawl is derived from the particulars given in 

 Table II., which shows the detailed catches of a number of steam- 

 trawlers for a series o^ years. I have been able to ascertain the dates 

 on which the otter-trawl was substituted foi- the beam-trawl on five of 

 these vessels, and, omitting the month in which their substitution 

 took place, I have tabulated the catches for the preceding and succeed- 

 ing three months and twelve months, in the first of which the beam- 

 trawl was used, and in the last the otter-trawl. The results are as 

 follow. In the three months during which the otter-trawl was used 

 four vessels showed an increased gross catch, and one a slight decrease, 

 compared with the preceding three months in which the beam-trawl 



