256 transactions liverpool biological society. 



Intensity of Fishing. 



The Summary Table shews that about 19 per cent, of 

 the plaice and 19 per cent, of all the fishes liberated 

 during the year have been recovered. Of course, several 

 of the experiments were made late in the season, and 

 many more recaptures will doubtless be made. A 

 considerable number of dabs were also marked and 

 liberated, and these have given poor results. The 

 individual experiments vary greatly in their numerical 

 results. Experiment 10, for instance, gives 50 per cent, of 

 returns for six months' fishing only, while Experiment 7 

 for nine months' fishing gives only 9 per cent, of 

 recaptures. Many factors influence the numerical result 

 of these fish-marking experiments. In Experiment 10 

 the fish had not apparently become widely dispersed, and 

 were, moreover, liberated at a place which is situated near 

 the widely-frequented fishing ground lying between 

 Liverpool North-West and Morecambe Bay Lightships. 

 Experiment 7 failed probably because the fish marked 

 were in poor condition, and had not been able to survive 

 the transference from tank to tank and the subsequent 

 marking operation. Again, Experiments 11 and 16 were 

 apparently unsuccessful because, for some reason or other, 

 the fish marked have probably become widely dispersed, 

 possibly into areas where there is at present little or no 

 plaice fishing being carried on. 



Premising, then, that by " Intensity of fishing " is 

 meant only a very rough approximation to the extent to 

 which the plaice population of the West English seaboard 

 is being exploited, and that for even an approximate 

 estimate of this value much more extensive marking 

 experiments than we have made would be required, I 

 give the figures in the last column of the Summary as 

 representing these approximations. 





