18 
GROWTH OF PLAICE IN A TANK. 
On October 8th, 1908, just after the opening of the Laboratory, 
and only two days after the sea water was introduced, 81 plaice got 
at the trawling experiment of that date in Blyth Bay were put into 
one of the aquarium tanks. It will be seen by reference to the 
report for 1908 that 119 plaice were caught, and as all the small 
ones were kept alive for this purpose they were approximately of 
the size given in the first column of the accompanying table. 
Some of the fish were a little the worse for the voyage round to 
Cullercoats, but they all recovered. 
They were measured thereafter at intervals as shown in the 
succeeding columns of the table. Losses occurred due to various 
causes, but the majority have been preserved and are still living. 
One measuring 24 cm. was lost on July 26th, 1909. Three were 
missing on October 23rd. On April 25tli, thirteen were found to 
have died at a time when some alterations led to the supply of 
water being stopped for several days. In the table these have been 
specially noted so that the plaice now living may be exactly 
specified. The large females at this period proved to be mature, 
and the ova were shed in the tank, and in the case of the dead fish, 
the females were just on the eve of spawning. These mature fish 
measured 28 to 31 cm. 
On August 4th, 1909, I added four small one-year old plaice 
obtained in a sandy pool at Cullercoats, measuring 1£, If, If and 
Us in. These have all disappeared except one, which measured on 
April 25th, 1910, 9 cm. This plaice, then, in a period of some 
nine months has about doubled its size, that is to say, in its second 
year. 
The youngest of those originally introduced into the tank were 
for the most part 2^ years old, and in a year they have grown 
about 9 - 10 cm. This is almost exactly the rate of increase 
previously deduced from the trawling and marking experiments, v. 
Report for 1905, page 61. The plaice now alive in the tanks are 
therefore in their fourth and fifth years, and the large five-year old 
females have become mature. None has grown beyond 31 cm., 
and at first sight it would appear that this was connected with the 
confinement in the tank, and while there is doubtless some truth 
in this, the fact is that at approaching maturity there is apparently 
a temporary lull in the rate of growth. 
