Thesis (MSc)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: The soupfin shark, Galeorhinus galeus, is a circum-global shark species of great economical importance. Their reproductive biology is reasonably well understood, but intraspecific differences between global populations necessitate the study o f populations separately. For this study, 70 male and 74 female specimens were collected along the southwestern coast of South Africa between 34°8'S; 18°27'E and 34°24S; 21°25'E. Morphological changes were described and serum steroid hormone concentrations evaluated by enzyme-linked immunosorbent assay (ELISA) over an almost-complete reproductive cycle. Males display an annual spermatogenic cycle that starts with a significant peak in testosterone concentrations coinciding with the start o f spermatogenesis around April-May. Testosterone levels decrease to reach a minimum in late-winter after which spermiogenesis commences. The prevalence of spermiogenic cysts in the testis increase to reach a peak between February and April, after which mating occurs until about July. Females (aplacentally viviparous) are suggested to have a triennial cycle, similar to the Brazilian & Australian populations, but different from the Californian & Mediterranean populations. During the first year after parturition there is not much reproductive development. The following year sees increased vitellogenic activity in ovarian follicles and development of the oviducal glands and uteri. Ovulation then occurs towards the end of that year. Mating is suggested to precede ovulation by two to three months necessitating sperm storage by the females in their oviducal glands. A 12-15 month gestation ensues and ends in parturition the following summer. Testosterone and estradiol levels fluctuate together and are involved in the preparation for ovulation and oviducal gland development. Progesterone levels show two distinct peaks during the year, in both immature and mature females, and could not yet be functionally linked to any reproductive activity or condition. This cycle is not very tightly synchronised among the South African females. / AFRIKAANSE OPSOMMING: Die vaalhaai, Galeorhinus galeus, kom wereld-wyd voor en is van groot ekonomiese belang in baie lande. Die spesie se voorplantings biologie is reeds redelik deeglik ondersoek maar intraspesifieke verskille tussen verskillende wereld populasies noodsaak die bestudering van populasies afsondelik. Daar is 70 mannetjies en 74 wyfies versamel vir hierdie studie langs die Suid Afrikaanse suid-wes kus tussen 34°8'S; 18°27'E and 34°24S; 21°25'E. Morfologiese veranderinge is beskryf en serum hormoon konsentrasies is ge-evalueer deur middel van die ELISA tegniek vir 'n amper-volledige voortplanting siklus. Mannetjies vertoon 'n jaarlikse spermatogeniese siklus met 'n piek in testosteroon konsentrasies aan die begin van spermatogenese in April-Mei. Hiema daal testosteroon vlakke tot minimum vlakke in die laat-winter, waama spermiogenese begin. Die proporsie spermiogeniese siste in die testis vermeerder tot maksimum waardes bereik word tussen Februarie en April. Paring vind hiema plaas tot omtrent Julie. Wyfies (aplasentaal vivipaar) het 'n voorgestelde driejaarlikse siklus, soortgelyk aan die Brasiliaanse & Australiese populasies maar anders as die Kalifomiese & Mediterreense populasies. Tydens die eerste jaar na bevalling vind daar nie veel voortplantings ontwikkeling plaas nie. Die daaropvolgende jaar verhoog vitellogeniese aktiwiteit in die ovarium follikels en ontwikkeling van die dopkliere en uteri. Ovulasie vind nader aan die einde van hierdie jaar plaas. Paring vind heel moontlik twee tot drie maande voor ovulasie plaas, wat noodsaak dat die wyfies sperm moet stoor in hulle dopkliere. 'n 12- 15 maande dratyd begin na ovulasie en eindig in geboorte teen die volgende somer. Testosteroon en estradiol konsentrasies fluktueer saam en speel 'n rol tydens voorbereidings vir ovulasie en dopklier ontwikkeling. Progesteroon vlakke piek twee maal gedurende die jaar, in beide onvolwasse en volwasse wyfies, maar dit kon nog nie funksioneel geassosieer word met enige voortplantings aktiwiteit of toestand nie. Die siklus is nie baie nou gesinkroniseer onder die Suid Afrikaanse wyfies nie.

published_or_final_version / Biological Sciences / Master / Master of Philosophy

The blacknose shark (Carcharhinus acronotus) is a common small coastal shark species found in nearshore waters along the southeast coast of the United States, from North Carolina into the Gulf of Mexico and extending further south into the Bahamas. There has been some debate in recent years over the reproductive periodicity of C. acronotus in waters off the U.S. coast. Earlier studies have suggested that Gulf C. acronotus reproduce on an annual basis whereas the Atlantic populations of this species may reproduce biennially. Additionally, there have been no known studies on the diet of C. acronotus. The goal of the present study was to re-evaluate the reproductive biology of the Atlantic populations of C. acronotus with the intent on clarifying discrepancies in reproduction as well as provide information on dietary trends. This was accomplished by examining male and female reproductive tracts and gut contents in animals caught throughout the Atlantic range of C. acronotus. Based on these data, spermatogenesis occurs between late May to early July with peak sperm production occurring in June and July. In females, follicular development is complete by late June-early July with ovulation occurring shortly afterwards. Mating occurs between mid-June and early July based on the presence of fresh mating scars on females captured during this time. Current data suggests that gestation begins late July with parturition occurring late May to early June the following year. As observed in earlier studies, reproductive periodicity appears to be largely biennial. However, evidence for concurrent follicular development and pregnancy was observed in several females, suggesting that at least a portion of the Atlantic population may reproduce on an annual basis. Dietary data shows a dominance of teleost prey items in the diets of C. acronotus with scianids making up the majority of the identifiable teleosts.