Fecundity, Multiple Spawning, and Description of the 

 Gonads in Sebastodes 



By 



JOHN S. MacGREGOR, Fishery Biologist 



Bureau of Commercial Fisheries Fishery-Oceanography Center 

 La Jolla, California 92037 



ABSTRACT 



More than 50 species of Sebastodes , an ovoviviparous genus of scorpaenid 

 fishes, occur off the California coast. In the ovaries of nine species examined, 

 evidence of two spawnings per spawning season was found in three (S^. ovalis , S. 

 constellatus , S. paucispinis ) but not in the other six (S. carnatus , S, rosaceus , 

 ^, serriceps , S. serranoides , S. atrovirens , S. ruberrimus ). Two spawnings were 

 indicated by either (1) small numbers of advanced larvae entrapped in the ovaries 

 and associated with full complements of developing eggs or early ennbryos or 

 (2) a secondary group of developing eggs along with about equal numbers of ad. 

 vanced embryos. The relative number of eggs or embryos was lower in the three 

 species that gave evidence of two spawnings (162 eggs or embryos per gram of 

 fish) than in the other six species (280 eggs or embryos per gram of fish). 



INTRODUCTION 



The rockfishes of the genus Sebastodes 

 (family Scorpaenidae) support an important 

 commercial and sport fishery along the coast 

 of California, where more than 50 species 

 occur (Phillips, 1964). These fishes are of 

 special biological interest because they are 

 ovoviviparous. Together with 18 species of 

 viviparous Embiotocidae they contribute to a 

 marine fauna that probably contains a higher 

 proportion of species of live-bearing fishes 

 than that in any other similar area in the 

 world. 



Estimating the seasonal fecundity of a fish 

 species presents two prinnary problenns. The 

 first and easier problem is to determine the 

 numbers and size distribution of yolked eggs 

 in the ovary. The second and more difficult is 

 to determine how many times the fish spawns 

 during the spawning season. 



Seasonal spawning in relation to the size 

 distribution of yolked eggs within the ovaries 

 may follow one of four patterns: (1) a bimodal 

 (or multimodal) distribution of eggs in which 

 spawning of the nnore advanced group is fol- 

 lowed by development and spawning of one or 

 more additional groups derived from the sec- 

 ondary group; (2) a bimodal distribution of 

 eggs in which the most advanced group is 

 spawned and resorption of the secondary 

 group follows; (3) a unimodal distribution of 

 eggs constituting the only spawning for that 



season; (4) a unimodal group of eggs which is 

 spawned either shortly before or shortly after 

 a secondary group is developed from the 

 reserve of nonyolked egg cells. In this last 

 situation, if a bimodal condition is present, 

 it is present only when the advanced eggs 

 are ripe or nearly ripe-- unlike the more 

 usual bimodal condition that is present from 

 the earliest differentiation by size of the ad- 

 vanced group. In addition to the above four 

 patterns, fish may develop eggs that are 

 resorbed without spawning if the necessary 

 environment or other spawning stimuli are 

 absent. 



Often where multiple spawning is sus- 

 pected, evidence of previous spawning seems 

 to disappear within a relatively short time. 

 Fishes of the genus Sebastodes offer a unique 

 opportunity to investigate some aspects of 

 multiple spawning because they are live-bear- 

 ers that have eggs of a type similar to the pe- 

 lagic, nonadhesive eggs of many marine fishes. 



MATERIALS AND METHODS 



The rockfish examined for this paper were 

 taken by the BCF (Bureau of Commer- 

 cial Fisheries) research vessel. Black 

 Douglas , on: January 20, 1961, at Forty- 

 mile Bank, about 40 nautical miles west of San 

 Diego, Calif.; March 3, 1961, at the Rockpile, 

 about 20 nautical miles south of San Diego; 

 and on April 11, 1961, at Tanner and Cortes 



