SEA-FISHERIES LABORATORY. 125 



two-thirds of these are from 2 to 3| inches in 

 length. 



(2) The 6-inch trawl-mesh catche s — 

 Rock Channel. — Except for the end of the year, 

 when the catches were rather small, plaice being scarce 

 in Rock Channel, the figures recorded in the tables afford 

 reliable pictures of the kind of fish inhabiting this part 

 of the district. It will be seen that we have to deal here 

 with a typical " small-fish " population. The modal sizes 

 vary between 16^ and 19 centimetres, differences which 

 do not appear to me to be of significance. At the middle 

 of the year (June) the modal size is least and the 

 frequency curve shows two maxima. This bi-modal 

 distribution is due to the growth of the plaice ; about 

 this time vast quantities of the smaller fish previously 

 less than about 10 cms. in length have grown to be large 

 enough to be caught in numbers in the 6-inch mesh trawl 

 net. These little fish decrease the modal size and swamp 

 the large plaice, producing the bi-modal curve. Before 

 this time the predominant fish population represented in 

 the catches were those of both of the two previous years' 

 spawning; after June the predominant part of the catch 

 consists of fish of the previous year's spawning. 



Considering the plaice which are 8 inches long and 

 less than 8 inches long, we find that from March to July 

 the proportion of the whole catch consisting of fish below 

 this length varied from 80 per cent, to 87 per cent. In 

 June there are about 93 per cent, of plaice less than 

 8 inches long in the catch. After the end of June the 

 percentage falls. In September 69 per cent, were less 

 than 8 inches in length, in October 78 per cent., in 

 November 50 per cent., and in December 40 per cent. 

 But the catches during the latter two months were small 

 ones. When these figures come to be compared with 



