PHYSICAL FEATURES OF THE IRISH SEA, 



__ 



MAN 



..Erir 



FIG. 2. 



is probably an area of about 1,298 

 square miles of over 50 fathoms 

 in the Irish Sea. On the western 

 side the sea-bottom rises com- 

 paratively steeply from the deep 

 channel to the Irish coast, but on 

 the eastern side there is a great 

 plateau between the Isle of Man 

 and England (see Fig. 2). Water 

 of over 30 fathoms in depth ex- 

 tends in from the west both to 

 the north and, especially, to the 

 south of the Isle of Man, forming 

 depressions in an otherwise shal- 

 low area that are important 

 spawning grounds for fishes. 

 These separate the Isle of Man, 

 by moderately deep water, from 

 Scotland to the north, and from 

 Anglesey to the south, leaving it 

 united to the northern part of Lancashire by a broad area of shallow water, which is scarcely 

 in any part deeper than 20 fathoms. If, then, the floor of the Irish Sea were to be raised by 

 that amount, 20 fathoms, the Isle of Man would be united by continuous land with England, 

 and would still be separated by a 



wide and deep channel from Ire- a*^** 



^L.nev? ?:,;... 

 land. The section shown in Fig. 



3, where, to save space, the *mwr!>o F*th S 



vertical scale is much greater 76 /Cfrt/lJ 



than the horizontal, brings out I<IC " 3- 



clearly this contrast between the depths in the eastern and western parts of our area. 



The region in which most of our work, 

 both in the way of zoological investigation 

 and in taking fisheries statistics, has been 

 done is the shallow water off the Lancashire 

 and Cheshire coasts, extending as far as 

 Anglesey in one direction, and the Isle of Man 

 in another (see Fig. 4). This area has along 

 its eastern and southern sandy shores a belt 

 of shallow water which is probably quite 

 exceptional in the amount of Shrimps (Cran- 

 gon vulgaris], of immature food fishes (mostly 

 Pleuronectidae), and of Cockles (Card i urn 

 edule} which it contains. The lo-fathom 

 line is on the average about 10 miles from 

 land, and the area of shallow water within 

 that line is about 2,091 square miles, while 

 from the ro-fathom to the 2o-fathom line 

 encloses an area of about 2,885 square miles, FlG> 4< 



LANCASHIRE 



