IO FISHES AND FISHERIES OF THE IRISH SEA. 



the weather records, and we think that the large number of bottles we have made use of 

 ought to enable us to come to some definite results. Our conclusions so far then are : 



(i) A large number (over 42 per cent.) have been stranded and found and returned; 

 (2) only a small proportion (13 per cent.) have been carried out of our part of the Irish 

 Sea; (3) nearly 12 per cent, have crossed the ''head of the tide" showing the influence 

 of wind in carrying floating bodies over from one tidal system into another ; (4) most of 

 the bottles set free to the west of the Isle of Man have been carried across to Ireland, 

 only a small number (3*8 per cent.) of them have got round to the eastern side of the 

 Island and been carried ashore on the English coasts ; (5) the majority of the bottles set free 

 off Dalby have gone to the Co. Down coast ; (6) a considerable number of bottles have 

 been set free over the deep water to the east of the Isle of Man, where our more valuable 

 flat fish spawn, and of those that have been returned, the majority had been carried to 

 the Lancashire, Cheshire and Cumberland coasts. So we may reasonably conclude that 

 the embryos of fish spawning off Dalby would tend to be carried across to the Irish 

 Coast, while those of fish spawning in the deep water to the South and the South East 

 of the Isle of Man would go to supply the nurseries in the shallow Lancashire and 

 Cheshire bays, and possibly further north, and very few would be carried 'altogether out 

 of the district. These nurseries, again, on the Eastern Coasts, it must be remembered, feed 

 the offshore grounds and so benefit the Manx and the Irish and Welsh fisheries, and in 

 fact the whole of the Irish Sea. 



7. THE BOTTOM DEPOSITS 



1. The most extensive shallow-water deposit is sand. In most localities along 

 the coasts of Lancashire, Cheshire, and North Wales, from the sea-shore out to the 

 lo-fathom contour, the bottom is formed of more or less pure quartz sand. Occasion- 

 ally in spots there are local patches of stones, of shells, or of mud ; but these can 

 generally be accounted for by tidal or estuarine currents, by the entrance of fresh-water 

 streams carrying down alluvium, or by the presence of littoral or sub-littoral boulder clay. 

 These spots are all, however, of small area, and the great extent of the bottom down to 

 10 fathoms is sand. 



2. Further out, however, between 10 and 20 fathoms, the sand becomes greatly 

 mixed with mud, and much diversified by large tracts of shelly deposits or by patches of 

 gravel, and the fauna on the bottom also becomes much more abundant. In some spots, 

 at about 20 fathoms, it is made up over considerable areas almost entirely of Ophiuroids 

 (Ophiocoma nigra and Ophiothrix fragilis), which fill the dredge haul after haul. At two 

 localities off the Isle of Man, viz., along the east coast from Clay Head to St. Ann's 

 Head, and off the west coast between Contrary Head and Niarbyl, at depths between 10 

 and 20 fathoms, are great nullipore deposits formed of Melobesia and Lithothamnion, which 

 have a most characteristic appearance, smell, and fauna. 



This area of the sea-bottom, from 10 to 20 fathoms, extends across from the north 



of Lancashire to the Isle of Man, so that opposite Barrow, for example, there is a wide 



extent of about 50 miles in length of sea-floor at depths of not more than 15 or 16 



fathoms. The Isle of Man is connected with England by this plateau, and is separated 

 from Ireland by deep water (see Fig. 3 above). 



