28 SALMONID.E OF BRITAIN. 



in Tasmania occurred on July 3rd, 186C ; by the 7tli of August fourteen females 

 Lad been stripped, and shortly afterwards five pair of trout were observed 

 constructing redds in the River Plenty. During June, July and August, 18G7, 

 the ti'out were again stripped of their ova artifici;illy. In this country, trout 

 spawn at different periods in diflerent rivers, from about September to February. 

 The very first Tasmanian bred trout hatched from English trout eggs have 

 not selected for spawning the months adopted by their ancestors in this hemisphere, 

 but have chosen others which are better suited for their purpose, clearly demon- 

 strating the possibility of trout being capable under changed conditions of varying 

 the period of the breeding season.* 



The ova having been extruded by the female in a suitable spot, are subsequently 

 fertilized by the milt of the male brought into contact with them in the water 

 when the sperraatozoids effect an entrance into the egg at the micropyle. But it 

 must be very apparent that numerous causes may be in existence either to prevent 

 fertilization, or, should such have taken place, to subsequently destroy the ova. 

 Among these deleterious agencies are the character or polluted state of the water, 

 or that when the eggs are being deposited in running streams they escape the 

 influence of the milt, or even be carried away by the current, or overwhelmed by 

 mud. Or the water may subside to that extent that they are left uncovered, 

 and perish by drought or frost, or else consumed by fish in the vicinity, who will 

 even root them \ip for this purpose. When safely deposited in redds they still 

 have enemies to contend with ; floods may sweep them away, or, should such a 

 state of the rivers continue for any length of time, the fish may not be able to 

 av.ail themselves of their usual breeding grounds, they being too deep in the 

 water. This may compel them to drop tbeir eggs in the swollen stream, when 

 they would become smothered by mud or othermse lost, or the fish might push 

 up higher to smaller water courses, which would render the chances considerable 

 of the eggs being left uncovered upon a subsidence taking place. Irrespective of 

 the seasons, the eggs have numerous enemies, as fish, the larvos of the Dragon- 

 flies Lihellulida', the May and stone-flies, Ephcwieridwf and the caddis-flies, Phry- 

 ganenlw ; some birds, as the dabchick, or little grebe, Podiceps minor, the water 

 ouzel, Ginchis aquaiicus,X ducks and swans, while the honse-rat, mice, also the 

 vole or water-rat, Arvicola ampliihia, join in their destruction. § Besides the 

 enemies to fish ova which have been enumerated, they have many more in our 

 streams, and so enormous is the loss which occurs among the eggs and young 

 that in such a river as the Severn the annual produce of salmon and grilse at 

 the present time consists of about 20,000 fish. Or were all the ova of one female 

 salmon of about 20 lb. weight to be hatched and attain maturity they would 

 suffice for keeping up the stock to its present condition. 



As the moi-tality among the eggs left to hatch in rivers and streams is so 

 enormous, while it is impossible to destroy their enemies which exist there, it has 

 become obvious that great gain might accrue were the ova to be collected and 

 artificially incubated || and thus placed out of reach of many causes of destruction, 



* The Black Swan, introduced from Australia, breeds here in our spring. 



f Brown (Stortnontfield Experiments, page 33) remarked that in the spring of 1854 Mr. Buist 

 took some eyed sahnon ova, and placed a dozen of the grubs of tlie JIay-tly (Ephemera) taken 

 from the same locality along •nith them in a vessel which was supplied with water by a syphon 

 of thread. In a tew days the grubs had devoured one of the eggs, and in a few days more the 

 whole were devoured. They were carefully watched when feeding, and five or six grubs were 

 found firmly fixed to an oviun which they never left until totally eaten up. Messrs. Asliworth, 

 of Galway, one year deposited 70,000 salmon ova in a small pure stream adjoining a plantation 

 of fir-trees, and they were entirely destroyed by the larva of the May-fly. — (Buokland, Fiah 

 Hatehina, 1863, page .51.) 



{ I gave an account in Land and Water of February 28th, 1885, how, on one of these biixls 

 being shot near Howietoun, five or six trout eggs were found in its stomach. 



§ At the Great International Fisheries Exhibition of 1883 the vole eat the eggs of the 

 Sahnonidffi placed in their cage : and since then they have been observed taking them from the 

 redds. (Field, January 5th and I'Jth, 18S4.) 



Ji It would be obviously impossible in a work of the present scope to enter fully into the 

 various modes of artificially propagating these fishes. Snch information may be obtained in 

 the Ilistori/ nf Houietoun, by .Sir .James Maitland, now in course of publication ; also in 

 Domestieated Trout, by Livingston-Stone; Fish Hutching, by Frank Buokland, 18G8 ; Fish- 



