FISHERY BOARD FOR SCOTLAND. 



REPORT ON THE RETARDATION OF THE DEVELOPxMENT 

 OF THE OVA OF THE HERRING. 



H. CHAS. WILLIAMSON, M.A., D.Sc, F.R.S.E., 

 Makixe Laboratory, Aberdeen. 



(Plate I.) 



CONTENTS. 



The Methods Employed, 



The Rate of Movement of the Apjjaratus, 



Table of Temperatures, etc., 



Results. — The Uncooled Spawn on Gravel, 



The Spawn Incubated in a Galvanized Tin, 



Cooled Spawn, .... 



Gravel and Glass, 



Exposure to Light : Growth of Diatoms, 



The Current of Water, 



The Filter-Barrel, 



Experiments with Spawn from Live and Dead Herrings 



On Galvanized Wire Gauze and Glass Plates, 



Milt and Spawn, . . . . . 



The Crystals in the Eggs, . . . . 



Recommendations, , . . . . 



4 

 5 



fi 

 6 



7 

 8 

 8 

 9 

 9 



9 



10 

 10 

 11 



The experiments on the retardation of the herring, which have been 

 carried on at the request of the Government of New Zealand, were 

 continued during the spring of 1911. 



The eggs were fertiHzed on board a fishing boat on the evening of 

 27th February and the morning of the 29th February. The spawn 

 was obtained from live herrings caught in a drift net. It was 

 attached to glass plates and also to coarse gravel, as it was desired to 

 see how the two methods compared in respect to the well-being of 

 the ova. The method adopted in the case of the glass plates was 

 similar to that described in vcij previous paper.* For the second 

 method a layer of gravel was put on the bottom of a barrel partly 

 filled with sea-water. Some milt was pressed out into the water, and 

 then some spawn was pressed out and allowed to fall on to the gravel. 

 The gravel was left undisturbed for some hours. Twelve hours or 

 more later, the batrel, on arrival at Aberdeen, was tipped up and the 

 gravel turned out into a tub. A considerable quantity of the ova 



* "Experiments to show the Influence of Cold in retarding the Development 

 of the Eggs of the Herring {Clupea harengu.t, L.), I'laice {Pleitronedes 

 platessa, L.), and Haddock {Gadus (eglejinus, L.)." Twenty-seventh Annual 

 Report of the Fishery Board for Scotland, Part III., 1910, p. 100. 



(4189.) Wt. 10769'2.31— 500— 9/1911. 



