FISHERY BULLETIN; VOL. 69, NO. I 



tained except for special studies ox- for short 

 maintenance periods. An artificial photoperiod 

 of 16 hr light: 8 hr dark (16L:8D) was main- 

 tained by time clocks (Tork, Model 7100') in a 

 light-tight room with 400 w, white mercury 

 lamps (Sylvania, H33-1-GL/C'), suspended 1.5 

 m above the water surface at the center of each 

 tank. Deviations from this water temperature 

 and light schedule are reported where appro- 

 priate. 



Young fish, less than 13 cm in length, were 

 fed 0.238 cm Oregon Moist Pellets' from Allen 

 automatic trout feeders' activated with time 

 clocks (Paragon Model 4001-0"). As fish grew 

 larger their consumption of pellets diminished 

 until they were fed exclusively on squid which 

 was ground semifrozen into pieces ranging 

 from 0..5 to 2.5 cm^. All fish were fed squid 

 ad libitum twice daily during the week and once 

 a day on weekends. I consider adequate feeding 

 to be an important factor in gonad maturation, 

 but it was not a variable in this study. In the 

 laboratory, young fish doubled their weight in 

 2 months and, later, added about 10 g each 

 month, reaching 80 to 100 g by the end of the 

 first year. Salton Sea fish weigh 40 to 50 g 

 at the end of 1 year; the largest gulf croaker 

 caught during this study weighed 420 g. 



Initially, and for later studies of the effects 

 of a series of hormone injections, fish were 

 never disturbed without first draining the tanks 

 to within 10 to 15 cm of the bottom and then 

 adding anaesthetic until the fish could be touched 

 without causing a sudden reaction. Fish to be 

 injected were then removed and completely an- 

 aesthetized for 1 to 3 min in MS-222 (Tricaine 

 Methanesulfonate)" at 0.6 g/3.8 liters. Treated 

 fish were replaced in fresh seawater; if neces- 

 sary, fish were held with gloved hands and 

 moved rapidly back and forth at the surface to 

 aerate the gills and assist their recovery. There 

 is little danger of fish mortality when the an- 

 aesthetic is properly used, and no adverse effects 



on fish reproduction were found. Later, exper- 

 ience enabled us to net unanaesthetized fish rap- 

 idly and place them directly into buckets with 

 MS-222 until they were unconscious. This was 

 done routinely when spawning techniques were 

 thoroughly known. 



Fish were individually marked with subcuta- 

 neous injections of a 65 mg/ml stock solution of 

 Bismark Brown or Fast Turquoise PT.'° Hor- 

 mone, antibiotic and other injections wei'e car- 

 ried out with 0.5- to 1.0-cc disposable syringes 

 fitted with 25- to 26-gauge, 1.27- to 1.90-cm 

 ('/2-%inch) needles. Needles 0.95 cm (% inch) 

 long proved useful for intraperitoneal (ip) in- 

 jection where internal damage was possible, but 

 these allowed too much fluid to escape when in- 

 tramuscular (im) injections were used. Inmost 

 cases the needle was carefully slipped into the 

 skin between scales, and carrier fluid (oil and sa- 

 line) was slowly injected into the deep muscles of 

 the back adjacent to the dorsal fin. Slow with- 

 drawal and pressure over the wound site helped 

 to retain most of the fluid. Sesame oil was used 

 in most cases as a carrier, but no essential dif- 

 ferences were noted between oil and Holtfreter's 

 saline injections. 



LIST OF HORMONES AND 

 THEIR PREPARATION 



1. Oxytocin (Pitocin, Pituitary grade I)." In- 

 jectable solution, 20 lU/ml, used as obtained 

 and stored at 4° C. 



2. Deoxycorticosterone Acetate (DOCA, grade 

 II)." Injected as a slurry in sesame oil.'- 



3. Human Chorionic Gonadotropin (HCG, 

 stock No. CG-2)." Anhydrous powder was 

 made to volume with Holtfreter's saline just 

 prior to injection. 



4. Gonadotropin from Pregnant Mare's Serum 

 (PMS)." Powder dissolved in distilled 

 water and stored at —10° C. 



5. Carp Pituitary (freeze-dried powder)." 



' Pacific Wholesale Electric Company, San Diego, 

 Calif. 



* R. V. Moore Company, La Conner, Wash. 

 ' G-Z Company, Sacramento, Calif. 

 ' J. F. Zwiener Company, San Diego, Calif. 

 ' Crescent Research Chemicals, Scottsdale, Ariz. 



'° Allied Chemical Company, San Francisco, Calif. 



" Sigma Chemical Co., St. Louis, Mo. 



" A. Sahadi Co., Moonachie, N.J. 



" Stoller Fisheries, Spirit Lake, Iowa. 



160 



