58 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



seasons. Fish may also be kept all winter in troughs in the open air 

 by occasionally spreading blankets* over them in exceptionally cold 

 weather, and keeping the conduits carefully covered. 



The iish surviving the summer season are generally counted and 

 weighed in October, in the following manner: A large number of them 

 are dipped up from a trough in a small dip net made of cheese-cloth, 

 and from this, while it is hanging in the water in such a manner that 

 the fish can not escape, they are dipped out a few at a time, in a small 

 dipper or cup, counted, and placed in another bag net until a sufiicieut 

 number (generally 200) are counted, when they are lifted out of the 

 water, held a moment in the air to drain, and all turned quickly into 

 a pail of water which has previously been weighed. With care no 

 appreciable amount of water goes with the fish, and the increase in the 

 reading indicates their weight with a fair approach to accuracy, and 

 with care and celerity of action it is quite safe for the fish. 



The size attained by the fish varies greatly, being aifected by the 

 water, the space allowed, the feed, and perhaps by hereditary influences; 

 but when seven months old a trough-reared salmon is generally from 

 2^ to 3 inches long and weighs from 35 to 100 grains, the maximum being 

 about 130 grains and the minimum as low as 7 grains, the general 

 mean for 189G being 45i8 grains. Salmon reared in ponds have been far 

 more thrifty, their general average in 1896 being 101 grains.* The 

 losses in ponds from July to October were rather heavy, being 11.7 per 

 cent, owing to depredations of frogs, birds, and cannibal fish. The 

 losses in the troughs during the entire season were 0.1 per cent, but 

 most of these were in the early stages of fryhood. After July losses in 

 troughs are always very light. 



MATERIALS FOR FISH FOOD. 



At Craig Brook station there have been used butchers' offal, flesh of 

 horses and other domestic animals, fresh fish, and maggots. Experi- 

 ments have also been made with pickled fish, blood, fresh-water 

 mussels, mosquito larvae, miscellaneous aquatic animals of minute size, 



*A very interesting comparison between the results of rearing in troujibs and 

 ponds is afforded by the record of two lots of steelhead tront during the season of 

 1896. All the fry of this species that were devoted to rearing were fed in troughs 

 nutil July 22, when some of them were transferred to a pond which has an area of 

 about 1,100 square feet and another lot was kept in a trough. The two lots were fed 

 exactly alike, about one-sixth of their nutriment being liv maggots, and live-sixths 

 chopped meat, liver, and other butchers' oft'al. November 7, the lot in the trough 

 was overhauled, and the 762 survivors found to weigh 10 pounds 4 ounces, or an 

 average of 94 grains. Three days later the pond fish were seined out and the 7,398 

 survivors found to weigh 235 pounds 10 ounces, an average of 223 grains. It is not 

 believed that natural food occurring in the pond contributed much to this result, and 

 it would appear that the controlling factor in the case was the space afforded the 

 fish. Leaving out of the account the difference in depth, in the pond there were less 

 than 7 fish to each square foot of area, while in the trough, which had an area of 

 about 11 square feet, there were to each square foot 69 fish. A similar illustration 

 was furnished by 41 rainbow trout of the hatching of 1896 that got astray in one of 

 the ponds and 'were taken out November 11, weighing 480 grains each. Those 

 of fhe same age, reared in troughs, attained during the season only a weight of 136^ 

 grains each. 



