132 FISH HATCHERY MANAGEMENT 



Acquisition of Broodstock 



Stock for a hatchery's egg supply may be wild stock, hatchery stock, a hy- 

 brid of two wild stocks, a hybrid of two hatchery stocks, a hybrid of wild 

 and hatchery stock, or purchased from a commercial source. Currently, 

 broodstocks of most trout and warmwater species are raised and main- 

 tained at the hatchery, whereas Pacific and Atlantic salmon, steelhead, and 

 striped bass broodfish are captured as they ascend streams to spawn. Cap- 

 ture and handling of wild fish populations should utilize methods that min- 

 imize stress. The installation of fishways or traps has proved successful in 

 capturing mature salmon and steelhead as they complete their migratory 

 run. 



Broodfish of coolwater species, such as northern pike, muskellunge, and 

 walleye, usually are wild stock captured for egg- taking purposes. Wild 

 muskellunge broodstock have been captured in trap nets set in shallow 

 bays. As the nets are checked, the fish are removed and tested for ripe- 

 ness. Some hatcheries sort the fish and take the eggs at the net site, while 

 others transport the fish to the hatchery and hold the fish in tanks or race- 

 ways until they are ripe. 



Walleye and sauger broodfish are collected in the wild with Fyke nets, 

 gill nets with 1.5 or 2.0- inch bar mesh, and electrical shockers. Most suc- 

 cessful collections are made at dusk or at night when the water tempera- 

 ture is about 36°F. Gill nets fished at night should be checked every two or 

 three hours to prevent fish loss and undue stress before spawning. Mature 

 sauger and walleye females can be identified by their distended abdomens 

 and swollen reddish vents which change to purple as they ripen. In trans- 

 porting broodfish to the hatchery, at least 2 gallons of water should be pro- 

 vided per fish. 



Wild northern pike broodstocks can be caught in trap nets, pound nets 

 or Fyke nets (Figure 43). When pike are trapped, they become unusually 

 active and are highly prone to injury. The use of knotless nylon nets will 

 reduce abrasion and loss of scales. 



Catfish, largemouth and smallmouth bass, and sunfish broodstock may 

 be captured in the wild by netting, electroshocking, or trapping. However, 

 spawning of wild broodstock is often unreliable during the first year. Con- 

 sequently, most warmwater species are reared and held as broodstock in a 

 manner similar to that used for salmonids. 



Spawning information and temperature requirements for various species 

 of fish are presented in Table 17. 



Care and Feeding of Broodfish 



Proper care of domestic broodstock is very important for assuring good 

 production of eggs, fry, and fingerlings. Methods differ with species, but 



