SOME IMPORTANT BAIT FISHES 



number of breeders removed from 

 the pond each fall for the 4-year 

 period, it was calculated that at 

 least 30 percent of the males and 15 

 percent of the females die each year. 



Stripping creek chubs 



In regions where natural ponds 

 are used for minnow culture, creek- 

 chub raceways are not practical be- 

 cause of the lack of running water. 

 Fry for these ponds can be obtained 

 more easily by stripping the adults 

 of their eggs, fertilizing the eggs, 

 and hatching them in jars. Until 

 recently, ripe creek chubs were diffi- 

 cult to obtain and the green fish 

 would not ripen in the ponds that 

 were available. 



Michigan workers (Ball and 

 Bacon, 1954) have been successful 

 in injecting creek chubs with carp 

 pituitary to ripen them. The fish 

 then are stripped of their eggs, 

 which are hatched in Meehan jars. 



The pituitary Avas obtained from 

 6- to 8-pound carp by the following 

 procedure : 



The head of the carp was removed, and 

 the brain was exposed by removal of the 

 dorsal surface of the brain case. The 

 broad white ophthalmic nerve, attached 

 to the fore of the brain, was picked up 

 with a pair of tweezers and the entire 

 brain lifted up and laid back. The pitu- 

 itary gland, a small organ resembling an 

 acorn, is located underneath the largest, 

 rounded portion of the brain. Occasion- 

 ally the gland will remain on the floor 

 of the brain case. 



The glands were either imme<liately 

 frozen or dehydrated and defatted in cold 

 acetone for .'i6 hours. The acetone- 

 treated ^'l;inds were dried on filter paper 



and stored under refrigeration until 

 needed. 



Whole glands were used in all experi- 

 nients, no attempt to separate the lobes 

 being made. Just before use, dried 

 glands were i)ulverized in a mortar and 

 mixed with distilled water ; frozen 

 glands were macerated to form a thick 

 suspension in distilled water. No dif- 

 ference between the effects of frozen 

 and dried pituitaries on fish was noted 

 in any experiments. 



Each ripe female received one- 

 fourth of a pituitary from a 2- 

 milliliter glass hypodermic syringe 

 supplied with a No. 19 needle. The 

 tip of the needle was placed under 

 a scale, pushed through the belly 

 wall into the body cavity, and di- 

 rected parallel to the ventral sur- 

 face. Two men were required for 

 the job : one to hold the fish ajid the 

 other to handle the needle. After 

 injection, the chubs were held in 

 tanks in which water varied from 

 46° to 64° F. At the end of 48 

 hours, the fish were stripped and 

 nearly all gave up their eggs. Fer- 

 tilization of the eggs by the usual 

 hatchery method produced nearly 

 a 100 -percent hatch. 



Growing-pond operation 



As soon as the fry concentrating 

 in the base pool become conspicuous 

 and are grouped in schools along 

 the shore, they can be collected with 

 a bobbinet seine and transferred to 

 rearing ponds. The removal of the 

 fry from the brood pond is a simple 

 task. The creek-chub fry tend to 

 school in large numbers near the 

 surface along the shore of the brood 

 pond. By using a small nylon hand 



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