Abstract. — Callorhynchus cal- 

 lorhynchus Linnaeus ("cockfish" or 

 "pez gallo"), the only holocephalan 

 fish species found in the coastal 

 waters of the southwestern Atlan- 

 tic Ocean, has been caught off Ar- 

 gentina as bycatch of the hake, 

 Merluccius hubbsi, fishery since 

 1920. Here we describe the mor- 

 phology of its reproductive system 

 and report on several aspects of its 

 reproductive biology. This study is 

 based on survey data and sampling 

 of commercial landings from San 

 Matias Gulf (41-42°S; 64-65°W), 

 conducted from 1984 to 1986. 



The data suggest that reproduc- 

 tive activities extend nearly 

 throughout the year; mating and 

 spawning occur in spring and early 

 summer, followed by a short period 

 (ca. one month I of gonadal recov- 

 ery. Average size at sexual matu- 

 rity (standard length, measured 

 from the tip of the mouth to the 

 origin of the superior caudal lobe) 

 is 40 cm for males and 49 cm for 

 females. Male gonadal and green 

 gland indices peak asynchronously. 

 During the mating season the 

 green gland forms spermatophores 

 that are transferred to the female 

 at the time of copulation. The 

 cloaca of adult females has a semi- 

 nal receptacle where the mass of 

 spermatophores is stored after 

 copulation. Female gonadal and 

 nidamental gland indices peak syn- 

 chronously. After fertilization the 

 oocytes are encapsulated before 

 spawning. Oocyte diameter in- 

 creases with the size of females up 

 to a maximum of 48 mm. 



Reproductive biology of the 



cockfish, Callorhynchus 



callorhynchus (Holocephali: 



Callorhynchidae), 



in Patagonian waters (Argentina) 



Edgardo E. Di Giacomo 

 Maria Raquel Perier 



Institute) de Biologia Manna y Pesquera "Alte Storm" 

 CC 1 04, 8520 San Antonio Oeste, Rio Negro, Argentina 



Manuscript accepted 26 January 1994. 

 Fishery Bulletin 92: 531-539 ( 1994). 



The cockfish, Callorhynchus callor- 

 hynchus Linnaeus, 1758, is the only 

 holocephalan fish species found in 

 the coastal waters of the southwest- 

 ern Atlantic Ocean (Norman, 1937; 

 Hart, 1946; Menni and Gostonyi, 

 1982 ). Adults are caught as bycatch 

 of the hake, Merluccius hubbsi, fish- 

 ery that operates off Argentina (Di 

 Giacomo and Perier, 1991). Al- 

 though there is considerable con- 

 cern with regard to harvesting fish 

 species with comparatively low re- 

 productive potential ( such as many 

 elasmobranch and holocephalan 

 species), the reproductive biology 

 and life history of the cockfish are 

 poorly known. In this study we de- 

 scribe the morphology of the repro- 

 ductive system of C. callorhynchus 

 and present information on its re- 

 productive biology. 



Materials and methods 



Bottom trawl surveys 



A survey off the north coast of San 

 Matias Gulf (northern Patagonia; 

 41-42°S, 64-65°W; Fig. 1) was con- 

 ducted from 15 to 19 October, 1986, 

 aboard the FRV C. Cdnepa. Thirty 

 three 30-minute hauls were made at 

 depths ranging from 20 m to 130 m, 

 by using a 96-foot commercial otter 



trawl with rectangular doors (Di 

 Giacomo and Perier, 1991). All 

 specimens of C. callorhynchus were 

 processed following laboratory pro- 

 cedures described below. 



Sampling of the commercial 

 landings 



The commercial catch of the bottom 

 trawl fishery landed in San Anto- 

 nio Oeste (40°43'04"S, 64°56W) was 

 sampled monthly between Febru- 

 ary 1984 and July 1986. On each 

 sampling date three boxes (N=2Q 

 fish per box) weighing 37 kg each 

 were randomly selected. Samples of 

 the commercial catch were not 

 available during April, September, 

 June, and December because either 

 the fishery was inactive or no 

 cockfish were landed. 



Laboratory procedures 



Standard length (SL, distance from 

 the tip of the snout to the origin of 

 the upper caudal lobe, Fig. 2A), to- 

 tal weight and liver weight were 

 obtained from each fish sampled. 

 Specimens were dissected to expose 

 the reproductive system; testes and 

 green glands of males, and ovaries 

 and nidamental glands of females 

 were individually weighed. The 

 number of mature yolk oocytes and 

 immature oocytes, maximum diam- 



531 



