143 



Reproduction of the blacknose shark 

 (Corcharhinus acronotus) in coastal waters 

 off northeastern Brazil 



Fabio H. V. Hazin 



Paulo G. Oliveira 



Matt K. Broadhurst 



Depaitamento de Pesca, Laboratorio de Oceanografia Pesqueira 



Universidade Federal Rural de Pernambuco 



Av Dom Manuel de Medeiros, s/n 



Dois Irmaos, Recife PE, Brasil, CEP: 52.171-900 



E mail address (for F Hazin) fhvhazin gelogica com br 



The blacknose shark, Carcharhiin/s 

 acronotus, is a relatively small car- 

 charinid, typically inhabiting continen- 

 tal shelf areas in the western Atlantic 

 Ocean, from North Carolina through- 

 out the Gulf of Mexico (Bigelow and 

 Schroeder. 1948) and along the South 

 American coast to Rio de Janeiro (Com- 

 pagno, 1984). The abundance of this 

 shark in nearshore areas throughout 

 its distribution makes it accessible to 

 commercial fishing, mainly from in- 

 shore hook-and-line and gill-net fish- 

 eries (Trent et al.. 1997; Mattes and 

 HazinM. 



Aspects of the biology of C. aci-ono- 

 tus have been reported by Springer 

 11938); Bigelow and Schroeder (1948); 

 Clark and von Schmidt ( 1965); Dodrill 

 (1977); Branstetter (1981); Schwartz 

 ( 1984 ); Castro ( 1993 ); and Carlson et al. 

 (1999). Schwartz (1984) provided the 

 most comprehensive synopsis, includ- 

 ing information on their reproduction 

 and life cycle off North Carolina. Many 

 of the other studies were based on rel- 

 atively few specimens collected off the 

 southeastern United States and cor- 

 roborate much of Schwartz's (1984) 

 work, including patterns in spatial and 

 temporal abundances, size at maturi- 

 ty, fecundity, and time of parturition. 

 However, some inconsistencies exist 

 with respect to the duration of the 

 ovarian, gestation, and breeding cycles: 

 i.e. Dodrill (1977) proposed a biennial 

 breeding cycle with gestation taking 

 between 10 and 11 months, Schwartz 

 (1984) suggested a gestation of ap- 

 proximately 9 months, and Branstet- 

 ter ( 1981) observed two gravid females 



with large ovarian eggs (having con- 

 current ovarian and gestation cycles, 

 copulation having occurred shortly af- 

 ter parturition). 



Because C. acronotus are represent- 

 ed in catches from various inshore fish- 

 eries and carcharhinids typically are 

 characterized by low rates of popu- 

 lation increase, adequate information 

 about their reproductive cycle is re- 

 quired to facilitate management of 

 stocks. Given the uncertainty of knowl- 

 edge about reproduction in C. acrono- 

 tus and the lack of information for the 

 southern part of their range, our aims 

 in the present study were to provide 

 a preliminary overview of the repro- 

 ductive biologv' and life cycle of the 

 blacknose shark in coastal waters off 

 northeastern Brazil, using available 

 fishery-dependent data. 



Material and methods 



Fishing gear used and 

 data collected 



Carcharhinus acronotus (79 females 

 and 45 males) were collected from the 

 catches of commercial gillnetters and 

 vessels using bottom longlines off the 

 coast of northeastern Brazil (approx. 

 7°30' to 9°30'S — near Recife) between 

 August 1994 and January 1999. The 

 configuration of fishing gears used 

 remained similar over this period. Gill 

 nets were monofilament, 900 m in 

 length, and had a stretched mesh size 

 of 17 cm and a depth of 70 meshes. Nets 

 were set perpendicular to the beach at 



depths between 5 and 10 m. Bottom 

 longlines consisted of a multifilament 

 mainline (6 mm in diameter) with up to 

 100 secondary lines, each approx. 5 m 

 in length and constructed from 3-mm 

 diameter monofilament attached to a 

 wire snood ( 1 m in length). Types of 

 hooks varied among brands, but rela- 

 tive sizes (i.e. 9/0 ) remained similar The 

 main baits were sardine (SardineUa 

 hrasiliensis) and mackerel (Scomber 

 spp. ), although some other species, 

 including sting ray (Aetobarus nari- 

 nari) and skipjack tuna iKatsuwonus 

 pelamis) were occasionally used. Long- 

 lines were set on the continental shelf 

 at depths between 10 and 60 m, but 

 most sets were shallower than 40 m. 

 All fishing gears were set at dusk and 

 hauled the following morning at dawn. 



All specimens were measured (total 

 length ITLj in the natural position ) and 

 dissected. Reproductive organs were 

 removed and stored in a solution of 

 lO^-'f formalin in seawater prior to be- 

 ing transported to the laboratory. Data 

 collected from females included weight 

 and width of the oviducal gland and the 

 functional right ovary, maximum ovar- 

 ian follicle diameter (MOFD), width of 

 the largest uterus, and, if present, the 

 TL, sex, and number of embryos. Using 

 the methods described by Pratt ( 1993), 

 we examined the oviducal glands of 

 10 mature females for the presence of 

 spermatozoa. Length and calcification 

 stage of claspers, width of epididymi- 

 des, and the presence of seminal fluid 

 in the ampullae of the ductus deferens 

 were recorded from males. Reproduc- 

 tive organs were measured to the near- 

 est 0.1 mm with vernier calipers. 



Inferences on stages of reproduction 

 were made according to definitions pro- 

 vided in previous studies on carcha- 

 rinids (e.g. Pratt, 1979; Hazin et al., 

 2000). Females were categorized into 

 six stages, mainly based on develop- 



' Mattos, S. M. G. and F. H. V. Hazin. 1997. 

 Analise dc viabilidade economica da pesca 

 de tubaroes no litoral do estado de Per- 

 nambuco. Boletim Tecnico-cientifico do 

 Cepene. 5: 89-114. IBAMA (Instituto 

 Brasiliero de Meio Ambiente e dos Recur- 

 sos Naturals Renovaveis), Rua Samuel 

 Hardman, s/n Tamandare - PE, Brazil. 



Manuscript accepted .5 July 2001| 

 Fish. Bull. 100:143-148(2002). 



