of the Fishery Board for Scotland. 



133 



III.— THE CAPTURE AND DESTRUCTION OF IMMATURE 

 FISH. PART IV. THE RELATION BETWEEN THE SIZE 

 OE HOOKS AND THE FISH CAPTURED. By Dr T. 

 Wemyss Fulton, F.R.S.E., Superintendent of Scientific 

 Investigations. 



In continuation of the inquiries into the capture and destruction of 

 immature fish by various modes of fishing, a number of experiments have 

 been made concerning the relation between different sizes of hooks used 

 in line fishing and the sizes of the fishes captured by them. In last 

 year's report* the results of corresponding observations on the influence 

 of variation in the sizes of the mesh of trawl-nets on the fish captured 

 are described. It has been shown in various previous reports that 

 considerable numbers of immature fishes, and especially round fishes, are 

 caught by hooks in line-fishing ; and it has beeu frequently proposed 

 that the capture of such forms, which are commercially of little or no 

 value, might be to a large extent avoided by the use of a different hook. 

 These experiments were accordingly devised to determine this point. 

 They have been carried on by means of the ' Garland,' and principally 

 in the Firth of Forth, during autumn and spring for two years. Six 

 varieties of hooks were employed, technically known as numbers 7, 8, 10, 

 18, 19 and 20, and they were disposed in twelve alternate series of 

 200 hooks, or 2400 in all; the total length of the line being 1200 

 fathoms ; and the hooks were baited with mussels in the ordinary way. 



The number of shots made in the course of the experiments was twenty- 

 one, and the total number of fish caught was 2480, comprising chiefly 

 haddocks, whitings, cod and common dabs. A special form was prepared, 

 in which the size of the various fishes caught on each series of hooks 

 was entered by Mr T. Scott, and also particulars showing the manner 

 in which the individual fishes were caught, i.e. whether the hook had beeu 

 swallowed and become fixed in the throat or gullet, or had merely 

 penetrated the lip or other superficial part. The details in regard to the 

 precise manner of capture are of importance as indicating the proportion 

 of line-caught immature fish that would survive on being returned to the 

 sea. It was shown that those caught by the gullet are fatally injured in 

 the ordinary process of taking them from the hook, while those caught by 

 a superficial part would, as a rule, survive. 



Of the six kinds of hooks which were employed in the experiments, 

 numbers 18, 19 and 20 are commonly used in the inshore haddock 

 fishing; the other numbers are larger in size. As might have been 

 anticipated, the smaller hooks caught a greater number of fish than 

 the larger ones did. Thus, of 2532 haddocks, whitings, cod and 

 common dabs captured, 715 were taken by number 20, 540 by 

 number 19, 500 by number 18, 474 by number 10, 191 by number 8, 

 and 112 by number 7. One of the principal points to be determined 

 was the relative proportions of mature and immature individuals 

 of the various species caught by the different sizes of hooks ; 

 information similar to that already obtained respecting variation in the 

 sizes of the mesh in trawl nets. For this purpose the fishes captured 

 by each kind of hook have been divided into two groups, one comprising 

 the mature forms and the other the immature forms. Haddocks which 

 measured 10 inches or more in extreme length have been regarded as 

 mature ; whitings of 8 inches or more, cod of 20 inches or above it, and 

 common dabs of 6 inches or more, have also been included as mature ; 



* Twelfth Annual Report, Part III. p. 302. 



K 



