LEONG: MATURATION AND SPAWNING OF SCOMBER JAPONICUS 



environment is used to ripen and maintain 

 spawnable stocks of fish in the laboratory and 

 hormone injections are used to induce spawning. I 

 use 1 mg SP + 12.5 IU HCG for the first injection 

 followed by 1 mg SP + 12.5 IU HCG + 200 IU PMS 

 24 h later to spawn females and a 5-mg SP injec- 

 tion for spawning males. I inject two males to 

 insure an adequate supply of milt. The procedure 

 is essentially the same as described in the Methods 

 section. The egg strainer is checked regularly 

 beginning at 12 h after the second injection to the 

 female and the female is examined whenever eggs 

 are detected. The female is stripped if she releases 

 eggs easily and the eggs are extruded into a dry 

 finger bowl for fertilization. The male is stripped 

 and the milt collected with a spoon held below the 

 genital pore. The milt is washed into the finger 

 bowl with a little seawater and the contents 

 swirled gently for 3 min. The eggs are then placed 

 in an incubation tank for further development and 

 hatching. To date, induction of spawning has been 

 successful 26 times in 36 attempts, each spawning 

 producing 6,000 or more viable eggs, and success- 

 ful spawning has been induced during every 

 month of the year. 



ACKNOWLEDGMENT 



I thank John Hunter, Southwest Fisheries 

 Center, National Marine Fisheries Service, 

 NOAA, for his many useful suggestions in the 

 preparation of this paper. 



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