SEA-FISHERIES LABORATORY. 247 
4. GROWTH-RATE OF PLAICE IN THE IRISH SEA 
AND ST. GEORGE’S CHANNEL. 
We may deduce two things from the data obtained 
by comparing the lengths of the marked plaice when 
liberated with the lengths of the same fishes when 
recaptured: (1) the growth from month to month 
throughout the year, and (2) the growth per year. These 
observations relate to plaice of the range of lengths 
dealt with in the experiments, and this was about 8 to 
11 inches. It is very unlikely that the growth rate of a 
plaice of 8 inches during the next three years of life will 
differ greatly from that of a fish of 11 inches. At any 
rate, what we are concerned with here is to obtain a 
mean expression of the growth rate of the plaice usually 
caught in the course of commercial trawling in West 
coast in-shore waters. 
It is very much easier to find defects in the methods 
employed in this investigation than to devise experiments 
which will be free from error; and one may remark in 
passing that’ it is usually those who have not personally 
made marked fish experiments that are most ready to 
criticise such results as are here presented. Various 
sources of error are obvious enough :— 
(1) The fish were initially measured to the nearest 
+ inch, but when recaptured they were measured to the 
nearest + inch. If the method of measurement adopted 
in the International Fishery Investigations had been 
originally adopted, the initial mean length would have 
been xi, v3, etc., inches, with an error of + } inch; as 
it is, the initial mean lengths are 2}, x4, etc., with an 
error of + } inch. The general result is that, in 
comparing these results with those obtained by 
investigators employing the International system of fish 
measurements, + inch for its metric equivalent) must be 
