128 Part III. —Seventeenth Annual Report 



Gobies, were captured at the surface. All the other stations during 

 the seven months from February to August only contributed 23 

 individuals to the surface net. Leaving out the special collection 

 made at Station V., it is seen that the number of fishes increases 

 regularly with the depth, to a maximum at 4-6 fathoms, deeper than 

 which level it steadily decreases. The cod which appear in the collection 

 are all very small, and had been newly hatched, which fact seems to 

 indicate that the post-larval stages are not passed in water of less depth 

 than 15 fathoms in Loch Fyne. Of course it is necessary at present to 

 except the shallow shore waters. It is possibly simply a withdrawal from 

 the surface waters where it has been hatched to the bottom, at whatever 

 depth that may be. On the stations the bottom lay usually at a depth 

 considerably over 15 fathoms. The post-larval youug of the coarse fishes 

 then appear to be found mainly at a depth of 4-6 fathoms below the 

 surface. The cod larvae were found in every net, except the surface. 

 The plaice were found at the surface, 1, 4, and 6 fathoms. The inference 

 then seems to be warranted that most of the food-fishes on hatching leave 

 the region in which the eggs are floating, and their place is occupied by 

 fishes hatched from demersal eggs. MTntosh and Masterman say that the 

 young cod, shortly after reaching a length of '33 inches, retire from 

 the upper waters and seek the lower regions of the sea. "It is 

 " instructive to compare the change of habitat of the growing plaice and 

 " that of the sand-eel. In the former, life is commenced in the surface 

 " water, and as the embryo advances in its development it is drifted 

 " towards the shore. Here the little larva, set free from its prison, 

 " migrates gradually but surely to the bottom in shallow water. In the 

 " other case the embryo embarks on its existence (in the winter-spawning) 

 " in fairly deep water, and embedded in the dark still sand. From this 

 " secure retreat the larval form emerges, and with increased size it works 

 " it way upwards to the light and warmth, and eventually disports itself 

 " in the surface water, a prey to many a foe.'r" Petersen t found in Faeno 

 Sound " that the fry of almost all fishes with pelagic eggs which occur 

 " there, except Motella, are much rarer than the fry of those which deposit 

 " their eggs on the bottom." He discusses the fact very fully from the 

 points of view of the salinity of the water, and the currents which 

 running in the neighbourhood may affect their distribution. The Table 

 recording the larvae obtained by Holt $ at Plymouth does not afford 

 corroborative evidence. The larvae of fishes having pelagic eggs were 

 more numerous than those hatched from demersal eggs. 



The position in the water in which the young forms are floating will 

 have an important bearing on their distribution. A portion of them at 

 least will be subjected to surface currents, and ere they pass through their 

 post-larval stage may be transported long distances. Thus, while the 

 distribution of fishes having pelagic eggs is effected in the egg stage, the 

 young hatched from demersal eggs are carried away by currents during 

 the post-larval stage. An interesting mode of distribution is noted in 

 connection with the specimens of Cydopterus licmpus captured. They 

 were found at the surface on drifting pieces of Fucus. Holt § found young 

 Liparis among drift weed at the surface. 



PHYSICAL OBSERVATIONS. 



Table XVI. gives the temperature and salinity observations made 

 during the first eight months of 1898 on the stations where the other work 



* M'Intosh and Masterman. op. tiU 

 f Petersen, op. tit. 

 % Holt, op. tit. 



§Holt, Tram. Dublin Royal Soc\ 1891. 



