156 



Abstract— Age and growth of the night 

 shark (Carcharhinus signatus) from 

 areas off northeastern Brazil were 

 determined from 317 unstained ver- 

 tebral sections of 182 males (113-215 

 cm total length [TLI>, 132 females 

 (111.5-234.9 cm! and three individuals 

 of unknown sex ( 169-242 cm ). Although 

 marginal increment (MI) analysis sug- 

 gests that band formation occurs in the 

 third and fourth trimesters in juve- 

 niles, it was inconclusive for adults. 

 Thus, it was assumed that one band 

 is formed annually. Births that occur 

 over a protracted period may be the 

 most important source of bias in MI 

 analysis. An estimated average percent 

 error of 2.4'S was found in readings for 

 individuals between two and seventeen 

 years. The von Bertalanffy growth 

 function (VBGF) showed no significant 

 differences between sexes, and the 

 model derived from back-calculated 

 mean length at age best represented 

 growth for the species (1^=270 cm, K= 

 0.11/yr, t =-2.71 yr) when compared to 

 the observed mean lengths at age and 

 the Fabens' method. Length-frequency 

 analysis on 1055 specimens (93-260 

 cm) was used to verify age determina- 

 tion. Back-calculated size at birth was 

 66.8 cm and maturity was reached 

 at 180-190 cm (age 8) for males and 

 200-205 cm (age ten) for females. Age 

 composition, estimated from an age- 

 length key, indicated that juveniles 

 predominate in commercial catches, 

 representing 74.3% of the catch. A 

 growth rate of 25.4 cm/yr was esti- 

 mated from birth to the first band (i.e. 

 juveniles grow 38?< of their birth length 

 during the first year), and a growth rate 

 of 8.55 cm/yr was estimated for eight- to 

 ten-year-old adults. 



Age determination and growth of the 

 night shark (Carcharhinus signatus) 

 off the northeastern Brazilian coast 



Francisco M. Santana 



Rosangela Lessa 



Universidade Federal Rural de Pernambuco (UFRPE) 



Departamento de Pesca, Laboratory de Dinamica de Populacoes Mannhas - DIMAR 



Dois Irmaos, Recile-PE, Brazil, CEP 52171-900 



E-mail address (for R. Lessa. contact author) rplessaigig.com br 



Manuscipt approved for publication 

 26 June 2003 by Scientific Editor. 



Manuscript received 20 October 2003 

 at NMFS Scientific Publications Office. 



Fish. Bull. 102:156-167 (2004). 



The night shark (Carcharhinus sig- 

 natus) is a deepwater coastal or semi- 

 oceanic carcharhinid that is found in 

 the western Atlantic Ocean along the 

 outer continental or insular tropical 

 and warm temperate shelves, at depths 

 exceeding 100 meters (Bigelow and 

 Schroeder, 1948). The species has been 

 recorded from Delaware to Florida, the 

 Caribbean sea (Cuba), and northern 

 South America (Guayana) (Compagno, 

 1984). It has also been recorded in 

 southern Brazil, Uruguay, and Argen- 

 tina (Krefft, 1968; Compagno, 1984; 

 Marin et al., 1998), and on the sea- 

 mounts off northeastern Brazil (02°16' 

 to 04°05'S and 033°43' to 037°30'W. 

 Menni et al., 1995) where it is called 

 "toninha." 



Since 1991, tuna longline vessels have 

 targeted the night shark in northeast- 

 ern Brazil (Hazin et al., 1998) because 

 of its highly prized fins, the increasing 

 value of shark meat in the local market, 

 and their relatively large abundance 

 and accessability on seamounts (Menni 

 et al., 1995). This species is most im- 

 portant in the area, making up 909; 

 of catches over shallow banks (CPUE, 

 in number, is 2.94/100 hook), and only 

 15% of catches on the surrounding deep 

 area, yielding 0.04/100 hook (Amorim 

 etal., 1998). 



Information on this species is re- 

 stricted to taxonomic descriptions 

 (Bigelow and Schroeder 1948; Cadenat 

 and Blache, 1981; Compagno, 1984, 

 1988), and some biological aspects 

 (Guitart Manday, 1975; Hazin et al., 

 2000). Night sharks reach >270-280 cm 

 maximum total length (TL) (Compagno, 

 1984; Branstetter, 1990). Off northeast- 

 ern Brazil, females mature at 200-205 



cm TL, males at 185-190 cm. Litter sizes 

 range from 10 to 15 pups and the gesta- 

 tion period may last one year ( Hazin et 

 al., 2000). The assumed size-at-birth off 

 the United States is 60-65 cm TL (Com- 

 pagno, 1984; Branstetter, 1990). Age and 

 growth have not been estimated. 



The aim of this study is to present 

 the first growth curve for Carcharhinus 

 signatus from vertebral and length-fre- 

 quency analyses. This information will 

 permit the use of age-based stock as- 

 sessment methods for the management 

 of the species in the Exclusive Economic 

 Zone (EEZ) off Brazil. 



Materials and methods 



Sampling data and vertebrae were col- 

 lected from November 1995 to Novem- 

 ber 1999 from commercial landings 

 (Natal, Brazil) caught in deep (Aracati, 

 Dois Irmaos, Fundo, Sirius) and shallow 

 (Pequeno, Leste, and Sueste) seamounts 

 with depths between 38 to 370 m at the 

 summits (Fig. 1 ). 



Commercial vessels were equipped 

 with -30 km Japanese-style multifila- 

 ment longline gear (Suzuki et al., 1977). 

 On average, each vessel used 970-980 

 hook per day; mainline sets began at 

 -02:00 h and ended at -06:00 h. The 

 retrieval of gear began at noon and fin- 

 ished by dusk. The Brazilian sardinella 

 (Sardinella brasiliensis), margined fly- 

 ingfish (Cypselurus cyanopterus), and 

 squid [Loligo sp. ) were used as bait 

 (Hazin etal, 1998). 



A total of 1055 individuals, landed 

 whole, eviscerated, or as carcasses 

 (headless and finless). were sampled. 

 The interdorsal space (posterior dorsal 



