46 



Appendices to Fourth Annual Beport 



towards Ardrishaig. The difference of 4*7'' during the eight days which 

 the eggs were deposited delayed hatching for about five da3's. 



This experiment clearly shows that the only difference between the 

 hatching of herring ova in deep and shallow water is one of time, hence 

 we are safe in concluding that if herring deposit their eggs on suitable 

 ground, in any depth of water not exceeding 100 fathoms, they will 

 undergo development. It is conceivable, however, that the depth of the 

 water in which the eggs are deposited may have some influence on the 

 time of spawning — in other words, on the fishing season ; and the im- 

 matui'e condition of the fish caught in August during recent years may to 

 some extent be accounted for in this way. If the herring which formerly 

 spawned on the inshore banks of the Moray Firth in from 10 to 20 

 fathoms water now spawn offshore in from 40 to 60 fathoms water, the 

 hatching wiU be delayed for several days, and maturity will not be 

 reached as early as formerly. This is an argument in favour of beginning 

 the herring fishing later in the season than at present. 



But although it has been proved that herring ova are capable of 

 hatching in deep water, it may be said that the fry would never succeed 

 in finding their way to the surface ; and further, that having reached the 

 surface, the food so necessary for the early stages of their existence may 

 not be found forty to sixty miles from shore. First, as to their power of 

 reaching the surface. 



In a paper published in the Fishery Board Report for 1S83, I mentioned 

 that, ' as soon as the fry escaped, they began to ascend by a vrriggling 

 motion towards the surface of the water, rising at first only a few inches 

 at a time, to turn and slowly sinli head downwards towards the bottom. 

 During the first day they seldom succeeded in rising more than two or 

 three feet from the bottom, and this they only succeeded in accompHshing 

 after many attempts ; but on the second day they readily, almost without 

 a single rest, rose three feet at a time ; and on the fourth day they 

 succeeded in swimming freely on the surface of the water.' 



There can be little doubt as to the purpose of this strong instinct to 

 reach the sui'face ; it is to bring them to the strata of water in which 

 there is the largest supply of food. When hatched, the fry have in their 

 yolk-sac sufficient nourishment for several days — the number of days 

 depending on the time required for hatching. Those who have seen the 

 small, almost in^^isible, newly-hatched herring fry wiU naturally think 

 100 fathoms is a long way for them to travel before they reach their food 

 supplies. If, however, the fry are kept under observation, it is found 

 that, after the first day, they can ascend at the rate of a fathom per minute. 

 At this rate they could ascend 100 fathoms in 1 hour -tO min. If we 

 allow for a rest of 30 sec. every three feet for the ascent, we have another 

 hour and 40 min. to add. Again, if we suppose they sink 30 inches during 

 each rest, we increase the distance to be covered to 150 fathoms ; in other 

 words, we add 1 hour 40 min. to the time required, which gives a total 

 of about 5 hours for the 100 fathoms. This being the case, we cannot 

 suppose that the fry would have any difficulty in ascending 200 fathoms 

 before the nourishment in the yolk-sac was exhausted. 



We are not well acquainted yet with the food of the fry, but there is 

 no doubt about the richness of the surface fauna beyond even the fifty- 

 mile line. The surface fauna of the Moray Firth is extremely rich, and, 

 as I have again and again proved, surface forms are nearly as abundant 

 in the Moray Firth forty miles at sea as they are inshore. 



My thanks are especially due to Mr Brook for undertaking the work in 

 Loch Fyne, and to the master of the fish carrier ' Talisman,' the property 

 of !Mr Maclachlan, of the Glasgow fish market. 



