Holt — Survey of Fishing Grounds, West Coast of Ireland. 451 



of the latter, and, examined under tlie microscope, it proved to consist of fragments of 

 Copepods. During the time we were in the neighbourhood of Boffin, Copepods (prin- 

 cipally Calanus) Avere enormously abundant at and near the surface, and even when 

 living were distinctly reddish (bright red when a number were close together in a small 

 vessel) : as is well known, when dead, these Copepods give off a large amount of bright 

 red oily matter. On the 16th of May, 1890, a great number of bright-green Copepods 

 were taken in the tow-nets, and I would suggest the possibility of such organisms 

 having affected the colouration of the stomach-contents of Pennant's specimen. This 

 j-ear we found minute green algoids (Halosphoera) enormously abundant both near the 

 shore and 45 miles from it. Statistics as to the relative abundance of all such pelagic 

 organisms, whether animal or vegetable, during the different months of the year, might 

 prove of great use in helping us to understand the migrations of such larger forms as 

 are known to prey on them. The algas, I imagine, are only indirectly the food of 

 fish, by serving as food for the minute crustaceans (to which perhaps they impart their 

 own colour). 



In northern latitudes we know that minute organisms are extremely abundant in 

 the Summer months, and are preyed on by the Eight "Whale, to whose huge gape the 

 "whale-bone" fringe is the exact analogue of the gill rakers in our shark. It may be 

 remarked that these structures, present to some extent in all bony fishes, are much 

 more developed (forming a finer sieve) in such forms (as the Herring) as prey on minute 

 organisms. 



Having left the Boffin neighbourhood, the sharks appear to move northwards. 

 They have been counted in shoals of 60 to 1 00 off Tory Island in June. One has been 

 observed in Lough Foyle in the same month (Day). In the same month, according to 

 Pennant, they make their appearance off the Firth of Clyde and the Hebrides, and 

 continue there until the end of July. Off the Orkneys they were formerly common, 

 but appear to be rarer in recent years. This may be due to the fact that little 

 or no fishing is done on the "West and North-west coast of the Islands after the 

 spring, so that the sharks might occur off those coasts without anyone seeing them 

 (Mr. W. Irvine Fortescue, in litt.). They are said to appear off the Norway coast 

 at the end of the dog-days (August). "Whilst there is, and can be no absolute 

 evidence that the same fish are seen at these different places, against the hypo- 

 thesis that it is the same fish that are seen at these different places at different 

 times of the year, it may be urged that since if a given number of fish were to start 

 eastward from some part of the Atlantic, those that steered the more southerly course 

 would, of course, strike land sooner than the rest, and each detachment would arrive at 

 its proper spot a little later, according to the degree of north in its direction ; or that, 

 since the warmth of summer is later in making itself felt as the latitude rises, it is 

 natural to expect the fish to be later in arriving at each place the further north it be. 

 There is, however, no such appreciable difference either of distance or temperature, 

 between the Aran Islands and the more northern points of the "West Coast, at which 

 these observations have been made ; and granting the migration northward as proved 

 for this coast, it is reasonable to suppose it extends along the rest. On the South Coast 

 of Ireland a specimen has been taken at Courtmacsherry in August (Day). They are 

 said to be not uncommon in the summer on the Cornish coast (Couch), and have been 

 occasionally taken on the East Coast of England. In the Irish Channel, Pennant speaks 

 of vast shoals having entered the Bays of Carnarvonshire and Anglesey in the summer 

 of 1756. They remained only during the hot months, leaving the coast about Michaelmas 

 (end of September), as if intolerant of cold. Possibly an increase of traffic in more 

 recent years may have induced them to pursue a more northerly course. 



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