of the Fishery Board for Scotland. 



11 



winter-spawners, and it is thus possible to arrange for each locality 

 and over a period the main characters connected with the reproduction 

 of the shoals. It has been shown that about six months elapse 

 between the formation of yolk in the ovarian eggs and the period of 

 spawning, but it has not yet been determined how long a time may 

 elapse after a herring arrives at the " full " condition, that is, with a 

 large roe or milt, as is found in the large herrings in the upper part 

 of Loch Eyne towards the end of the year, and the actual shedding of 

 the eggs. The rate of growth of the herring and the spawning- 

 seasons are discussed. Each locality has very definite spawning- 

 seasons, a fact pointing to the fishes themselves being localised 

 and dependent on the local conditions of food, temperature, and 

 salinity ; but taking these samples from various parts of the coast 

 as a whole, spawning may be regarded as starting in July and 

 continuing to the following July, with two great periods, in August 

 and September and in February and March. 



The Influence of Temperature on the Development of 

 the Eggs of the Herring. 



At the request of the Government of New Zealand, a series of 

 experiments were made at the Marine Laboratory on the retardation 

 of the development of the ova of the herring. Information was 

 desired as to whether it was possible to prolong the period of 

 incubation 50 days, an interval which would admit of the eggs being 

 conveyed from this country to New Zealand before they hatched. 

 The New Zealand Government wish to introduce, if possible, certain 

 of the more valuable and useful of the European fishes to the waters 

 of the Dominion, and among them the herring. The experiments 

 referred to are described in the present Report by Dr. H. C. 

 Williamson, the eggs being obtained at Anstruther in the spring, and 

 they were kept in various forms of apparatus, and at various 

 temperatures, until hatching took place. The general result of the 

 experiments was to show that it would be possible to keep a 

 proportion of the eggs for a period of fifty days before hatching — a 

 few were indeed kept some days longer, but by far the greater 

 number succumbed at an earlier period. The experiments may be 

 regarded as of a preliminary kind, and from the experience gained it 

 is hoped that in the further trials now being made at the request of 

 the New Zealand Government, a much larger proportion may survive 

 the prolonged exposure to low temperatures. Experiments were also 

 made, at the request of the New Zealand authorities, with the eggs 

 of the haddock and of the plaice, as well as with small turbots, with 

 the view of determining whether the period of development of the 

 former could be satisfactorily delayed, and whether the latter were 

 able to resist low temperatures. The temperatures in the experiments 

 with the eggs varied from 06° C. to 5-6° C, and it was found that 

 the plaice eggs hatched after a period of from 27 to 43 days, while 

 the haddock eggs were partly unhatched after the lapse of 30 days. 

 T^e small turbot, measuring 6£ and 9 J inches, were placed in separate 

 apparatus. One of them, subjected to temperatures going down to 

 0*6° C, survived for over three days and then died; the other, 

 subjected to temperatures between 3*4° C. and 1*7° C. for over two 

 days, survived and recovered. 



