Reproductive biology of the Brazilian sharpnose shark (Rhizoprionodon lalandii) from southeastern Brazil

Abstract

Motta, F. S., Namora, R. C., Gadig, O. B. F., and Braga, F. M. S. 2007. Reproductive biology of the Brazilian sharpnose shark (Rhizoprionodon lalandii) from southeastern Brazil. – ICES Journal of Marine Science, 64: 1829–1835. The reproductive biology of the Brazilian sharpnose shark, Rhizoprionodon lalandii, off southeastern Brazil was investigated using data from gillnet landings. The size-at-maturity for males and females was estimated to be 59 and 62 cm total length (LT), respectively. Ovarian fecundity ranged from 3 to 7 follicles (mean = 4.54), and uterine fecundity from 1 to 5 embryos (mean = 3.3). There was a slight positive relationship between female LT and the number of ovarian follicles, but uterine fecundity was not related to female LT. Embryonic growth is fast following fertilization during summer and autumn. Gestation requires 11–12 months, and peak parturition is between August and September. A comparison of size-at-maturity between animals from northeastern and southeastern Brazil suggests the existence of at least two stocks of R. lalandii along the Brazilian coast.

Reproductive biology and diet of the grey sharpnose shark Rhizoprionodon oligolinx Springer, 1964 (Chondrichthyes: Carcharhinidae) from the north-eastern Arabian Sea

“…Interestingly, in the same genus, Motta et al (2007) reported size-at-first maturity of Rhizoprionodon lalandii as 62 cm TL for females, 59 cm TL for males in south-eastern Brazil, which were quite similar to our estimates of the same genus; where as Lessa (1988) reported 56 cm TL for females and 52 cm TL for males for same species in Maranhao (north), Brazil. In this study, the females and males were found to be mature at a larger size, compared to previous studies and it is possible that differences could have resulted from distinctive oceanographic conditions in the region, or fisheries influence, regional differences, or sampling difference which could cause differences in biological parameters between populations, such as maximum size, growth rate, size-at-maturity and fecundity (Parsons, 1993;Lombardi-Carlson et al, 2003;Motta, et al, 2007).…”

“…In this study, the females and males were found to be mature at a larger size, compared to previous studies and it is possible that differences could have resulted from distinctive oceanographic conditions in the region, or fisheries influence, regional differences, or sampling difference which could cause differences in biological parameters between populations, such as maximum size, growth rate, size-at-maturity and fecundity (Parsons, 1993;Lombardi-Carlson et al, 2003;Motta, et al, 2007). Size at birth estimated in the study was 25-30 cm TL which was larger than those reported (as 21-26 cm TL) earlier by Appukuttan and Nair (1988).…”

“…Estimates from northern Brazil ranged from 2 to 6 follicles and from 2 to 5 embryos (Lessa, 1988). Motta et al (2007) reported ovarian and uterine fecundity ranging from 3 to 7 follicles and from 1 to 5 embryos respectively off south-eastern Brazil. Simpfendorfer (1992) reported 1 to 10 embryos for Rhizoprionodon taylori off Cleveland Bay, Northern Queensland.…”

“…In general, a significant functional relationship between number of embryos and body size/total length of females has been recorded for other Rhizoprionodon species (Parsons, 1983;Stevens and Mcloughlin, 1991;Simpfendorfer, 1992;Castillo-Geniz et al, 1998;Mattos et al, 2001;Motta et al, 2007). According to Stevens and Mcloughlin (1991) and Motta et al (2007), the relationship between embryo size and female size should not be considered as a rule for Carcharhinids. An equal sex ratio in the embryo would be expected if the 1:1 adult population sex ratio, often observed in many elasmobranch species was maintained (Jennings et al, 2001;Henderson et al, 2006).…”

DNA barcoding reveals the diversity of sharks in Guyana coastal markets

“…However, despite generally high fecundity, these small sharks are under some pressure from overfishing in Brazil, where R. lalandii is listed as locally 'Vulnerable' due to intense harvest of all size and age classes in artisanal gillnet fisheries (Rosa et al, 2004;Motta et al, 2005Motta et al, , 2007. Rhizoprionodon lalandii made up 83% of the samples from Guyanese fish markets.…”