OF THE GRIMSBY TRAWL FISHERY. 415 
Dutch, German, and Danish coast comprised 4623 turbot, of which 
786 or 18 per cent. measured 17 inches or more, and 3837 or 82 per 
cent. were less than 17 inches. The highest proportion of immature 
reached in individual voyages was 100 per cent. and the lowest 28 
per cent., but in only two instances did it fall short of 50 per cent. 
In the following month of the same year eighteen voyages com- 
prised 2435 fish, of which 69 per cent. were less than 17 inches. This 
slight diminution in the proportion of the immature seemed to be 
related to a slight movement offshore of the bulk of the small plaice 
on which the Eastern trawl fishery is mainly dependent. The 
smallest turbot apparently lived closest inshore. 
With regard to brill I have not much evidence of any very exten- 
sive destruction of immature members; it appears rather variable. 
As a rule, not very many are brought in from the Hastern grounds, 
but sometimes the proportion is quite considerable. I cannot 
attempt to formulate a percentage, but can at least say that it is 
much less than in the case of turbot. A lot of immature brill are 
sometimes landed from our own coast near Mablethorpe. Very few 
brill of less than 10 inches are landed by deep-sea men from any 
ground, and I think very few are caught. I have hardly ever seen 
an 8-inch brill in the market. 
The proportion of immature lemon soles landed from any ground 
is not very considerable. A good many are sometimes brought in 
from grounds near our own coast, and a number of very small ones 
are said to be caught sometimes about the Inner Dowsing, but on 
the whole I do not think the destruction that takes place is of great 
moment. 
Though a flat fish of the hardier kinds has, under the most 
favourable circumstances, some small chance of surviving its capture 
in a deep-sea trawl, it may be taken that a round fish has none. 
This is partly due to structural differences of the gill-cover, which, 
adapted to the burrowing habit in flat fishes, proves also efficacious 
in keeping the gills closed, and therefore moist, when out of water ; 
but the chief difficulty with which a round fish has to contend is its 
air-bladder. All the trawl round-fish usually met with in the North 
Sea are provided with a closed air-bladder, by the contraction or 
expansion of which the fish is enabled to maintain itself at any 
depth which it desires; but it is only able to adapt this apparatus 
to gradual changes of depth. Consequently, when it is suddenly 
drawn up from comparatively deep water, the diminution of external 
pressure is not sufficiently gradual to allow of the muscular 
apparatus keeping due control of the gases within the bladder. The 
latter expands, and the fish, though it arrive at the top otherwise 
uninjured, cannot get down again. Thus when the trawl warp is. 
