NOTES 



SEASONAL SPAWNING CYCLE OF THE 



BLACK CROAKER, CHEILOTREMA SATURNUM 



(SCIAENIDAE) 



Detailed information is lacking on the spawning 

 cycle of the black croaker, Cheilotrema saturnum. 

 Previous works (Eigenmann 1892; Skogsberg 

 1939; Limbaugh 1961; Fitch and Lavenberg 1975) 

 have indicated spawning occurs in spring and 

 summer. This report describes the histological 

 changes occurring in the spawning cycle. Com- 

 parisons are made with the spawning cycles of two 

 other sciaenid fishes (Genyonemus lineatus and 

 Seriphus politus ) which were studied by Goldberg 

 (1976). Cheilotrema saturnum ranges from Mag- 

 dalena Bay, Baja California, to Point Conception, 

 Calif. (Miller and Lea 1976). 



Methods 



A total of 154 mature female C saturnum were 

 examined from collections made in January, 

 March, July, September 1977 and 1978. Specimens 

 were collected during heat treatment processes at 

 the Scattergood Steam Plant (City of Los Angeles, 

 Department of Water and Power, LADWP), El 

 Segundo (lat. 33°50' N, long. 118°30' W), Los 

 Angeles County, Calif. Steam generating plants 

 periodically reverse the flow of cooling water 

 in their intake and discharge pipes and raise 

 the temperature to a level that will kill off 

 entrapped organisms. Immediately after collec- 

 tion, fish were slit along the abdomen and placed 

 in lQ9c Formalin.^ Ovaries were embedded in 

 paraffin; sections were cut at 8 )u,m and stained 

 with iron hematoxylin. Body and ovary weights 

 were measured on a torsion balance to the nearest 

 0.01 g. Standard lengths (SL) were measured to 

 the nearest millimeter. Gonosomatic indices (GSI 

 = ovary weight/fish weight x 100) were calculated 

 from measurements made after preservation. 



Results and Discussion 



Ovaries were classified histologically into four 

 stages (Table 1). Stage 1 (regressed or regressing 



ovary): the nonspawning condition consists prin- 

 cipally of primary oocytes ( <100 /im in diameter). 

 Stage 2 (previtellogenic): slightly enlarged vacuo- 

 lated oocytes (100-200 ixm m diameter) predom- 

 inate prior to onset of yolk deposition. Stage 3 

 (vitellogenic): yolk deposition in progress. Stage 4 

 (spawning): mature (ripe) oocytes O300 /j.m) 

 predominate. 



Ovaries were regressed (Stage 1) during autumn 

 and winter (Table 1, Figure 1). GSI values began to 

 increase during winter and Stage 2 oocytes be- 

 came common. In late spring enlarging follicles 

 undergoing yolk deposition (vitellogenesis) were 



Table l. Monthly distribution of standard lengths and 

 stages in Cheilotrema saturnum spawning cycle, January 1977- 

 November 1978. 



13.0- 



11.0- 



9.0- 



8 7.0- 



DD 



5 5.0- 



>- 

 tr 



% 3.0- 

 o 



LO- 



IS 



6 16 



u 



-1 1 1 



14 



'Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



JAN MAR MAY JUL SEP NOV JAN MAR MAY JUL SEP NOV 

 1977 I 1978 



Figure l. — Seasonal gonosomatic indices for Cheilotrema 

 saturnum. Vertical line = range; horizontal line = mean; 

 rectangle = 959c confidence interval and sample size above 

 each month. 



FISHERY BULLETIN: VOL. 79, NO. 3, 1981. 



561 



