of the Fishery Board for Scotland. 



259 



IV. ON THE PELAGIC FAUNA OF THE BAY OF ST ANDREWS 

 DURING THE MONTHS OF 1888. By W. C. M'Intosh, 

 M.D., LL.D., F.R.S., Professor in the University of St Andrews.* 

 (Plates III. -IV.) 



I. GENERAL REMARKS. 



The following remarks on the pelagic fauna can only be considered as 

 preliminary, since a series of observers would require to be apportioned 

 amongst the various groups so as to work them up thoroughly. More- 

 over, in regard to certain departments, e.g., post-larval fishes, it has not 

 been possible to compare the exact condition of the offshore with the 

 inshore at all seasons of the year, since only a small sailing boat manned 

 by a single fisherman was at my command. So far as the work goes, 

 however, it will form a basis for future observations • and though much 

 greater elaboration would have been possible, the limited time as well as 

 the exigencies of the public service rendered such impossible. 



The prevalence of many pelagic forms of animals has often interested the 

 marine observer: thus the numerous medusae, siphonophores, crustaceans, 

 salpae, pteropods, and other forms have in foreign waters received much 

 attention, especially as surface-fauna in fine weather. No systematic 

 examination of such animals in British seas, however, has hitherto been 

 made, though isolated observations on particular types are numerous — 

 such types having as a rule occurred as surface-fauna, or have been 

 stranded on the beach. 



In 1884, during the expeditions connected with H.M. Trawling Com- 

 mission, the importance of this subject in connection with the food of 

 post-larval, young, and adult food-fishes was fully brought out. Thus it 

 was shown that, besides the persistent pelagic types, a vast number of 

 sedentary or bottom-forms have pelagic larvse, which mount to the upper 

 regions of the water, and again descend as they approach the adult con- 

 dition. The young fishes thus have a double chance, first as the larval 

 forms ascend, and secondly as they descend in the other stages ; and it 

 need hardly be pointed out that the smaller fishes would chiefly affect 

 the former, the larger young fishes the latter. The pelagic fauna thus 

 may be grouped into two great divisions, viz., the Temporarily Pelagic 

 and the Permanently Pelagic fauna, as indeed was done in a lecture on 

 the subject delivered in November 1886.f 



In the treatment of the question a different method has been adopted 

 from that of the German observers, especially Dr Hensen,J who sunk 

 nets of a special construction, and calculated the amount of water passing 

 through them in a given time, then having counted the various eggs and 

 animals, he (Dr Hensen) apportioned them to the cubic foot of water. 



The method followed at St Andrews consisted of the steady use of 

 tow-nets at the surface and bottom, as well as in mid-water, the latter 

 being a large net — 24 feet in length, and attached to a triangle of wood 

 or bamboo — 10 feet each way. 



* I desire to record the very great assistance rendered me during this inquiry hy 

 Mr J. Pentland Smith, M.A., a distinguished student in Natural History in the 

 University. Without his aid the limited time at my disposal would greatly have 

 prolonged the investigations. I have also to thank Prof. G. S. Brady for kind 

 assistance with the Copepoda, and Dr Merle Norman for help with the same group 

 (Crustacea). 



t Abstract in Ann. Nat. Hist, Feb. 1887. 



% Vide Fiinfter Bericht der Kommission z. w. &c. der deutschen Meere. Berlin, 

 1887. 



