Reproductive cycle of the blacknose shark Carcharhinus acronotus in the Gulf of Mexico

Abstract

The reproductive periodicity of blacknose sharks Carcharhinus acronotus in the northern Gulf of Mexico was determined by examining reproductive tissues from specimens collected monthly from 2002 to 2005. Monthly changes in shell gland mass, right ovary mass and ovarian follicle diameter were assessed for 74 mature females. Temporal changes in testes mass, testes width and proportion of mature spermatocysts were examined for 64 mature males. Trends in female reproductive tissues suggested an annual peak in reproductive activity during June and July, while trends in male variables suggested an annual reproductive peak during May and June. Although male and female reproductive activity peaked in different months, a strong synchronicity existed between the proportion of mature spermatocysts and the diameter of the largest ovarian follicle. Based on these results, the mating season of blacknose sharks lasts from mid‐May to July in the Gulf of Mexico. Maximum embryo sizes were observed in May, which suggested that partition occurs during late May or early June. Results indicate that blacknose sharks have a clearly defined annual cycle in the Gulf of Mexico. This conclusion is further supported by the complete absence of gravid females without vitellogenic ovarian follicles among all mature females examined.

Biological aspects of sharks caught off the Coast of Pernambuco, Northeast Brazil

“…cit. ) and in the Gulf of Mexico (Sulikowski et al, 2007). The progressive increase in embryos TL over the months suggests a 9 month gestation period, which is similar to that described by Hazin et al (2002) and Schwartz (1984), respectively, 8 and 9 months, and lower to values presented by Dodrill (1977) and Driggers et al (2004), which were between 11 and 12 months (both studies were carried out off Florida, USA).…”

Variability in the Reproductive Biology of the Atlantic Sharpnose Shark in the Gulf of Mexico

“…Researchers have speculated that this short opportunistic window evolved to maximize the reproductive success of these species by increasing the survival of the young (Castro 2009). Despite the general acceptance of this view of carcharhinid reproductive strategy, the information on which it is based has been obtained from only a few species, largely ones from the temperate waters of the western North Atlantic Ocean, including the Atlantic Sharpnose Shark (Parsons 1983;Loefer and Sedberry 2003), Blacktip Shark Carcharhinus limbatus (Castro 1996), Finetooth Shark (Castro 1993), Blacknose Shark (Driggers et al 2004;Sulikowski et al 2007), Sandbar Shark C. plumbeus (Baremore and Hale 2012), and Bonnethead Sphyrna tiburo (Parsons 1993). In addition, several of these studies have lacked sample sizes and intervals adequate to fully assess the potential reproductive patterns and/or anomalies that could exist within a population.…”

Age and growth of the blacknose shark, Carcharhinus acronotus (Poey, 1860) off the northeastern Brazilian Coast

“…The life history of the blacknose shark in the northern hemisphere has been extensively investigated, focusing on age and growth estimates, estimation of size at maturity and the length of reproductive cycles (Springer, 1938(Springer, , 1960Clark and von Schmidt, 1965;Branstetter, 1981;Schwartz, 1984;Carlson et al, 1999Carlson et al, , 2007Driggers et al, 2004a,b;Sulikowski et al, 2007). With exception of reproductive aspects (Hazin et al, 2002), information on the species in the southwestern Atlantic is scarce.…”