Abstract. - The school shark 

 Galeorhinus galeus was sampled by 

 otter trawl on the continental shelf 

 of southern Brazil from 1980 to 1986 

 between latitudes 32°S and 34°40'S, 

 at depths between 10 and 500 m. The 

 species is a winter migrant, present 

 in the study area from April to Nov- 

 ember. A total of 1548 specimens 

 were examined. Sexual maturity oc- 

 curred at total length of 107-1 17 cm 

 in males, and 118-128cm in females. 

 The reproductive cycle was annual in 

 the male and three years in the 

 female, with uterine rest and slow 

 vitellogenesis during the first year, 

 maturation of oocytes and copulation 

 during the second year, and gesta- 

 tion during the third year. In Novem- 

 ber, the diameter of mature follicle 

 was 4. 6-5. 5cm, ovulation occurred, 

 and full-term embryos occurred with 

 average total length of 30.3 cm. 

 Uterine fecundity varied between 4 

 and 4 1 with a mean of 23.1, of which 

 94.2% were normal embryos, 5.2% 

 were non-developing eggs, and 0.6% 

 were abnormal embryos. Copulation 

 took place up to 5 months before 

 ovulation, with passive transport of 

 spermatophores through the uterus. 

 Liver weight as a percent of gutted 

 body weight averaged 8% in imma- 

 ture animals of both sexes, 7% in 

 gravid females, 11% in adult males 

 and nongravid females in the first 

 year of the reproductive cycle, and 

 17% in non-gravid females in the sec- 

 ond year of the cycle, and it de- 

 creased during winter. 



Sexual Development, 

 Reproductive Cycle, and 

 Fecundity of the School Shark 

 Galeorhinus galeus off Southern Brazil 



Monica Brick Peres 



Carolus Maria Vooren 



Fundacao Universidade do Rio Grande, Depto. de Oceanografia 

 Caixa Postal 474, 96200 Rio Grande, RS, Brazil 



Manuscript accepted 10 July 1991. 

 Fishery Bulletin, U.S. 89:655-667 (1991). 



Annual landings of demersal sharks 

 at the port of Rio Grande, Brazil, in- 

 creased from 1414 tons in 1973 to 

 3217 tons in 1986 and then decreased 

 to 2023 tons in 1989 (SUDEPE 

 1990). This raises the question of the 

 impact of increasing fishing effort on 

 the stocks. The school shark Galeo- 

 rhinus galeus comprises the major 

 part of the landings (Wahrlich and 

 Peres 1990). Accounts of fisheries for 

 this species in other areas are classic 

 examples of the rule that sharks are 

 unable to maintain their abundance 

 under heavy fishing. This is due to 

 their live-bearing mode of reproduc- 

 tion, which implies that fecundity is 

 low and recruitment is proportional 

 to the abundance of the adults (Hol- 

 den 1977). Management of the fish- 

 ery requires estimates of reproduc- 

 tive parameters. 



The reproductive cycle of female G. 

 galeus has been described as annual 

 off California and Tunisia, and bian- 

 nual off Australia (Ripley 1946, Olsen 

 1984, Capape and Mellinger 1988). 

 However, the simultaneous occur- 

 rence of three distinct reproductive 

 stages of adult females off southern 

 Brazil led to the hypothesis of a tri- 

 annual reproductive cycle (Vooren 

 and Guzenski 1982). This hypothesis 

 was tested in the present study. 



This paper describes sexual matur- 

 ation and the reproductive cycle for 

 both sexes, and uterine and ovarian 

 fecundity of female school shark off 

 southern Brazil. 



Materials and methods 



The study area was the continental 

 shelf of Rio Grande do Sul, between 

 Cape Santa Marta Grande (lat. 

 28°40'S) and Chui (lat. 33°44'S), 

 Brazil. From June 1980 to Septem- 

 ber 1986, the area was surveyed dur- 

 ing 12 cruises by the RV Atlantico 

 Sul, at depths between 10 and 500 m, 

 using an otter trawl with groundrope 

 of 50 m and codend mesh of 45 mm 

 between opposed knots (see Fig. 1 for 

 location of stations). Tows lasted 60 

 minutes, and towing speed was 5.5 

 km/hour. Samples were also obtained 

 with similar nets during five commer- 

 cial trawling trips. The data series in- 

 cludes all months of the year except 

 December and March. One specimen 

 found on 13 December 1985 on the 

 beach near Rio Grande, and nine 

 specimens obtained on 24 June 1986 

 from commercial landings at Monte- 

 video, were also examined. 



In each haul, the weight of the 

 catch (in g) and the body length (in 

 cm) and sex of all specimens were 

 recorded. Total length (TL) was mea- 

 sured with the tail aligned with the 

 long axis of the body. Biological data 

 were taken from random samples of 

 the catches, totaling 904 females of 

 43.0-154.5 cm TL and 644 males of 

 43.5-148.0 cm TL. Weights (in g) of 

 the whole body, liver, and gonads 

 were recorded. Total body weight 

 was measured until November 1983. 

 Thereafter, the eviscerated body 



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