Reproductive biology and population variables of the Brazilian sharpnose shark Rhizoprionodon lalandii (Müller & Henle, 1839) captured in coastal waters of south‐eastern Brazil

Abstract

visits to the landing site of a small urban fishery (APREBAN) in Rio de Janeiro city were conducted and 816 specimens of Rhizoprionodon lalandii were analysed. The sample, mostly females, was composed of two cohorts: young-of-the-year were abundant in spring and summer and adults predominated in autumn and winter. Gravid females were most abundant from April to June, whereas postpartum females composed most of the catch in August to September. Adult males were present all year although were more abundant between February and July. No neonates were captured during the study and most embryos collected measured slightly below the reported total length (L T ) at time of birth (L 0 ) for the species, suggesting that parturition may occur slightly outside the main fishing grounds or that neonates were not captured in commercial gillnets set at this time of the year. The mean L T at maturity (L T50 ) for males was 578 mm and females matured between 620 and 660 mm, although a precise estimate of L T50 for females could not be determined. The total length (L T ) and total mass (M T ) relationship ðM T ¼ 7E À L 3Á2597 T Þ was calculated for both sexes and showed no significant differences. The mean condition factor increased steadily from February to July followed by a steep decrease in values relative to females in August and September, suggesting a pupping season. The present study area can be classified as a coastal juvenile habitat and a probable mating ground for R. lalandii.

Feeding ecology of elasmobranch species in southeastern Brazil

“…The study of feeding ecology of elasmobranchs is essential because in general they occupy intermediate or high trophic levels (Vianna et al, 2000;Ebert, Bizzarro, 2007); because of the intensifying fishery exploitation that is reducing populations of these organisms (Vooren, Klippel, 2005;Andrade et al, 2008), the scarcity of biological data that hinders knowledge of the species (Vianna et al, 2000;Chiaramonte et al, 2004;Massa et al, 2006;Rosa et al, 2004;Andrade et al, 2008;Silva Junior et al, 2011;Viana, Vianna, 2014;Bornatowski et al, 2014c) and the possibility that elasmobranchs may become contaminated by persistent organic pollutants, with consequences for the entire food web (Rosenfelder et al, 2012).…”

“…From 1979 to 1997, the shark 2 e160176 [2] catch rates increased, during a period with low fishing effort; then from 1998 to 2008 the catch rates decreased and the fishing effort increased; and from 2008 to 2011 shark catches remained stable or increased and the fishing effort was again low (Barreto et al, 2016). Consequently, devising strategies for fishery management and biodiversity conservation is a complex matter (Vooren, Klippel, 2005;Andrade et al, 2008;Dulvy et al, 2014;Davidson et al, 2015), principally in developing countries such as Brazil (Bornatowski et al, 2014b), where the fauna is highly endemic in the southeastern region, with high species richness (Lucifora et al, 2011;Davidson, Dulvy, 2017).…”

“…Since 1980, because of the high value of their fins and other byproducts, and also because of the depletion of traditional fishery resources such as teleosts, fishing for sharks and rays has intensified (Vooren, Klippel, 2005;Andrade et al, 2008;Bornatowski et al, 2014b;Dulvy et al, 2014;Davidson et al, 2015), in addition to the already large numbers taken in bycatch (Costa, Chaves, 2006;Bornatowski et al, 2014b). Currently, the price per kilogram of shark fins is about $1,697 and the price per individual for marine species ranges from $11,121 for dwarf sawfish to $341,139 for the whale shark (McClenachan et al, 2016).…”

New data on the distribution and size composition of the North Pacific spiny dogfish <i>Squalus suckleyi</i> (Girard, 1854)

“…The tope shark, Galeorhinus galeus, on the shelf of northern Patagonia shows an increase in condition factor between January and April (no samples were collected later in the year) (Elias et al 2004). In the Brazilian sharpnose shark, Rhizoprionodon lalandii, off the southern coast of Brazil the condition factor of males remains virtually unchanged throughout the year, but in females it increases gradually from December and peaks in June-July (Andrade et al 2008). Juveniles of the scalloped hammerhead shark, Sphyrna lewini, in Hawaiian waters exhibit a minimum condition factor in autumn and winter and a maximum value in spring and summer (Duncan and Holland 2006).…”

Biology of Rhizoprionodon lalandii (Elasmobranchii: Carcharhinidae) captured by the artisanal fishery of Margarita Island, Venezuela

“…Existen diversos estudios sobre la especie en Brasil que incluyen aspectos sobre su biología reproductiva (Ferreira, 1988;Lessa, 1988;Menni & Lessa, 1998;Motta, Namora, Gadig, & Braga, 2007;Andrade, Silva-Junior, & Vianna, 2008;Macedo, Sousa, & Batista, 2012;Martínez, Álvarez, & Acero, 2012), genética (Mendonça, Oliveira, Gadig, & Foresti, 2009;2013), proporción sexual, frecuencia de longitudes, relación longitud-peso (Motta, Gadig, Namora, & Braga, 2005), edad y crecimiento (Lessa, Santana, & Almeida, 2009) y aspectos alimentarios (Lima, Daros, Mazzoleni, & Hostim-Silva, 2000;Bornatowsky, Heithaus, Albilhoa, & Corrêa, 2012). En contraste, en Venezuela a pesar de que hace más de 50 años que se reconocen sus capturas en las pesquerías (Méndez-Arocha 1963;Ginés et al1972), la información disponible sólo abarca una descripción general de la especie realizada por Cervigón & Alcalá (1999) y la relación longitud-peso para ejemplares capturados en Isla Margarita (Tagliafico, Rago, & Rangel, 2014).…”