HAYDOCK: GONAD MATURATION OF GULF CROAKER 



Powder was homogenized wt/vol in sesame 

 oil or Holtfreter's saline. 



6. King Salmon, Oncorhynchus tshaivytscha, 

 Pituitary." Glands removed and placed in 

 acetone for extraction within 15 min of 

 spawning. Whole glands were homogenized 

 wt/vol in sesame oil or Holtfreter's saline. 



Multiple intramuscular (im) or intraperi- 

 toneal (ip) injections were accompanied with 

 200 lU Potassium Penicillin G and 0.025 mg ac- 

 tive Streptomycin Sulfate. Fish that were 

 handled several times, with disposable plastic 

 gloves, were routinely treated with Furacin 

 water-mix antibiotic (Vet. grade), at an initial 

 concentration of 250 mg/3.8 liters. 



PREPARATION OF SALMON PITUITARIES 



Early in the project my attention was directed 

 to the possible usefulness of fish pituitaries for 

 inducing spawning (Pickford and Atz, 1957; 

 Clemens and Sneed, 1962; Atz and Pickford, 

 1964) . Carp pituitaries are commercially avail- 

 able, but there is no assurance that these are 

 removed from spawning fish, a time at which the 

 glands are assumed to have high titers of spawn- 

 ing hormones. Glands from Bairdiella, taken 

 during the spawning season, would be ideal, but 

 the bony nature of the brain case makes their 

 removal difficult and their small size makes the 

 effort relatively unrewarding. Spawning grun- 

 ion, Leuresthes tenuis, are seasonally abundant 

 locally but, again, collecting a large number of 

 glands would require great effort. Salmon pro- 

 vide a convenient source of fish pituitaries, since 

 they are available in large numbers at fixed lo- 

 cations (fish hatcheries) . Each gland is of con- 

 siderable size (about 13 mg dry weight), and 

 the bony brain case is reduced to a soft cartilage 

 by decalcification near the time of spawning. 

 Each fish is graded at the hatchery so that 

 spawning females are only sacrificed when at 

 the peak of running ripeness. Fish return to 

 spawn at different times at various hatcheries 

 which allows some flexibility in the timing of 

 collecting operations. All these advantages, plus 



'* Nimbus Fish Hatchery, Rancho Cordova, Calif. 



the fact that the glands proved useful in spawn- 

 ing croakers, justify a detailed discussion of the 

 method developed by Nimbus Hatchery person- 

 nel for removing the pituitary from king salmon. 

 I thank W. H. Jochimsen and D. R. Von Allmen 

 for originally demonstrating this technique to me. 

 A technique for removing pituitary glands 

 from salmon with a special tool exists (Tsuyuki, 

 Schmidt, and Smith, 1964), and similar equip- 

 ment was available at the Nimbus Hatchery. 

 However, hatchery personnel have developed a 

 simple and rapid technique which allows one 

 person, with a little practice, to directly remove 

 100 to 200 pituitary glands during the course 

 of a morning's spawning activities at the hatch- 

 ery. The number of fish spawned limits the 

 number of glands obtained; several hundred fish 

 are spawned each week during November, the 

 peak season at Nimbus Hatchery. The largest 

 numbers of fish enter the hatchery ponds from 

 the river on overcast days or during winter rains. 

 Female and male pituitary glands were re- 

 moved from spawned fish within 15 min of death 

 (unfortunately, following death, a severing of 

 the head artery which bleeds the fish often 

 destroys the pituitary in the process) . The fish 

 to be used for pituitary extraction are held up- 

 right with the gill cover slipped over a sharp 

 stake clamped to a table. A large, sharp butcher 

 knife is used to slice through the cartilaginous 

 tissue of the brain case, parallel to the jaw and 

 just above the level of the eye (a metal glove, 

 as worn by fish-market personnel, would be use- 

 ful for this step, which is carried out while the 

 neuromuscular system of the large fish is still 

 active). A rubber coat and rubber boots are 

 also necessary accouterments at this gross stage 

 of dissection. The cut exposes the brain, or, if 

 at the appropriate depth, the pituitary stalk 

 (sometimes the gland itself) is severed and the 

 gland can be removed from its cavity with a 

 pair of forceps or a narrow scoop. Some cuts, 

 at odd angles, sever nerve cords as well as the 

 pituitary stalk and expose three cavities. Once 

 learned, the location, consistency, and color of 

 the pituitary differentiate it from nervous or 

 other fatty tissues with which it might be con- 

 fused. At first, shallow cuts can be made to 



161 



