Age determination and growth of the smalltail shark, Carcharhinus porosus,from northern Brazil

Age and growth of C. porosus was;estimated from seasonally formed marks in vertebrae of 504 specimens (30.0-101.0 cm total length), and from length-fr equency data from 1128 individuals (29.4-120.5 cm). Estimated von Bertalanf fy growth parameters were: from observed length-at-age, L-infinity 125.1 cm , K 0.101 year(-1) and t(0) -2.89 year; from back-calculated lengths, L-inf inity 136.4 cm, K 0.077 year(-1), t(0) -3.27 year; and from length-frequenc y analysis, L-infinity 131.0, K 0.080 and t(0) -3.40. Growth did not differ significantly between sexes. Males and females were mature at 71.0 and 70. 0 cm, respectively, corresponding to 6 years old. The largest shark aged fr om vertebrae was a 12-year-old female (101.0 cm). Growth rates calculated f rom mean observed lengths were 7.0 cm year(-1) for the first four years and 4.0 cm year(-1) after maturity. Lee's phenomenon was not apparent. The ann ulus forms from September to January. Parameters derived from back-calculat ed lengths were considered to best describe growth. Like most carcharhinids , C. porosus follows he general pattern of K-selected species, exhibiting s low growth, late maturity and low fecundity.