MANUAL OF FISH-CULTURE. 95 



THE FIELD STATION. 



For tlie egg-collecting station a point was selected on a tributary of 

 the Au Sable, llowiug about 3,000 gallons per minute, near where it 

 empties into the river. A dam was thrown across the stream and 100 

 feet above a screen was built to j)revent the fish from escaping in that 

 direction. The dam is simply constructed by banking up mud, sand, 

 and turf, and has a frame sluiceway 3 feet long, 2 feet wide, and 2 feet 

 deep. In the sluiceway is inserted a double screen of J-inch mesh wire 

 netting, two screens being necessary to keep the overflow clear and 

 reduce as low as possible any loss of fish through this outlet. The 

 inclosure accommodates about 10,000 fish. For holding the eggs two 

 pairs of troughs are placed on standards driven into the bed of the 

 stream, with a passage between them wide enough to admit a man. 

 Fish are obtained with rod and line, until they begin to run from the 

 deep pools upon the spawning- grounds, when much better results are 

 obtained with nets. With an ordinary seine at the approach of the 

 spawning season, the fish can be taken in large numbers from their 

 spawning beds. As the season advances and too many fish are caught 

 that have already spawned, operations are suspended. 



The water is received through two 1-iuch orifices in a bulkhead about 

 9 feet long, situated at the head of these troughs and fed by a roughly- 

 constructed raceway leading from a small spring about G rods distant 

 on the hillside. The water from each of the openings feeds two 

 troughs, so placed that the lower end of the upper one rests upon the 

 head of the other, thus creating a fall of nearly the height of the 

 troughs. Each trough is 11 feet long, 5 inches deep, and consists of a 

 double row of boxes, each box 17 inches long, 15 inches broad, and 2 

 inches deep, giving a capacity of from 8,000 to 10,000 eggs. 



As soon as ripe fish are found among those caught on the spawning- 

 beds, the pond is hauled with a seine and the fish are looked over twice 

 a week until all the eggs are taken. When the season is fairly opened 

 the spawn may be taken from most of the fish immediately after they 

 are caught, tlius obviating the difficulty of transferring them from the 

 point of capture to the pond, in some cases a distance of 3 or 4 miles. 



TAKING THE SPAWN — DRY PROCESS. 



A good spawn-taker can tell at a glance if a female is ripe, and only 

 in such condition should an attempt be made to take her eggs. After 

 the ripe males and females are placed in separate tubs or buckets, the 

 spawn-taker is ready to take the eggs, the implements necessary being 

 a feather and an ordinary milk-pan coated with asphaltum paint on the 

 inside to prevent rust. The pan is first dipped in water and allowed 

 to drain, leaving only the water that clings to the inside. Taking a 

 female from the tub she is held as quietly as possible till all struggles 

 cease, and then pressing gently with the thumb and forefinger a little 

 above the ventral fins, the hand is passed down the belly to the oviduct, 



