LEONG: INDUCED SPAWNING OF ANCHOVY 



Table 1. — Female anchovies after various hormone in- 

 jections having eggs larger than 1.0 mm in diameter. 

 The occurrence of females with eggs larger than 1.0 mm 

 is considered to be an indication of induced egg matur- 

 ation. Of more than 500 captive uninjected fish sampled 

 during the previous 16 months none had eggs larger than 

 1.0 mm. The average injected fish weighed about 25.0 g 

 and measured 125 mm in length. 



Type of injection 



Dose/fish 



No. females 

 injected 



No. females 

 with eggs 

 >I.O mm 



cases because most of the injected fish were 

 males or had died through handling. Of the 

 more than 500 females examined during the 

 previous 16 months, none had eggs larger than 

 1.0 mm. The occurrence of females, Table 1, 

 with eggs larger than 1.0 mm indicates that 

 salmon pituitary, carp pituitary, and HCG are 

 capable of promoting overnight growth of eggs. 

 Salmon pituitary appeared to be the most po- 

 tent for producing growth. The largest eggs 

 observed were over 1.3 mm in diameter and 

 within the size range, 1.23 to 1.5 mm, of na- 

 turally spawned eggs (Bolin, 1936). DOCA 

 and PLH at the dosages tested were not effec- 

 tive in stimulating egg growth- The prepon- 

 derance of fish with smaller eggs may be due to 

 a low state of ovarian development at the time 

 of injection. 



In the second series of trials, HCG followed by 

 DOCA, PLH, or PMS did not induce spawning 

 and subsequent stripping produced only unovu- 

 lated eggs which were not successfully fertilized. 

 The combinations of HCG followed by salmon 

 pituitary and HCG followed by carp pituitary 

 induced spawning within 18 hr after the second 

 injection. The fish spawned and fertilized the 

 eggs themselves and large numbers of eggs were 



caught in the nets at the outflows of the tanks. 

 Spawning was repeated several times with each 

 of these two combinations of injections. The 

 spawnings produced from 6,000 to 16,000 eggs 

 with the percentage hatching varying from 25 

 to 80 '^r. The larvae from the.se induced spawn- 

 ings appeared morphologically normal and many 

 were reared past 25 days by the methods of 

 Lasker et al. (1970). The differences in the 

 hatching percentage mqy be attributed to var- 

 iation in the state of gonad development of 

 parent fish at the time of injections. 



The number of eggs collected suggests that 

 only one or two females from any of the spawn- 

 ing groups contributed eggs. According to es- 

 timates by MacGregor (1968) female anchovies 

 spawn almost 600 eggs per gram of fish. The 

 average female in these trials weighed approx- 

 imately 25 g and should have produced nearly 

 15,000 eggs. Only one or two females from any 

 of the twice-injected groups extruded ovulated 

 eggs upon stripping. Although the eggs were 

 translucent and measured about 1.5 mm in di- 

 ameter less than 10 Cr hatched after being mixed 

 with motile sperm. 



In the final series of trials, three injections 

 of salmon pituitary or three injections of HCG 

 over a 3-day period failed to induce spawning. 

 The stripped eggs were opaque and fertilization 

 was not successful. These limited results sug- 

 gest that the combination of HCG followed by 

 salmon pituitary is more eflfective for induction 

 of spawning than when these hormones are 

 administered alone. 



The results of these injection trials demon- 

 strate that the northern anchovy can be induced 

 to spawn in captivity and two eff'ective treat- 

 ments are HCG followed by salmon pituitary or 

 HCG followed by carp pituitary after gonads 

 are matured by a specific light-dark treatment 

 of the fish. The induction of spawning of an- 

 chovies in the laboratory provides a practical 

 way for supplying viable eggs for studies on 

 larvae. In this study the time of spawning 

 was controlled and eggs can probably be pro- 

 duced the year around if a large stock of fish 

 is maintained. This was emphasized by the 

 fact that the fish in this study were induced to 



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