The dusky shark (Carcharhinus obscurus) is listed 'vulnerable' on the IUCN red list. Here, archived data sets and the application of modern biogeochemical tags are combined to advance the ecological knowledge base of this species off Southern Africa. Tag-recapture data identified that juveniles undertake small scale movements (<100 km) throughout the year within a core nursery region in KwaZulu-Natal (KZN) and defined a seasonal migration between KZN and the Cape region. Calculated growth rates of small dusky sharks ranged from 10.3 - 11.5 cmyr¯¹ . A comparative analysis of condition indices [hepatosomatic (HSI), condition factor, relative condition and residual condition] identified that HSI was a more rapid and sensitive measure of condition. Accurate inferences on condition, however, require the careful division of data by size, sex, reproductive state and the isolation of neonatal and juvenile sharks. The first empirical evidence for maternal investment in newborn sharks in the form of an enlarged liver, constituting ∼20% of body mass, is presented. Additionally, through a
quantitative modelling approach, it was found that the reproductive output of the dusky and spinner shark (C. brevipinna) increased with maternal size with evidence for a moderate decline in the largest mothers. Near-term pup mass increased with month identifying either variable parturition strategies and/or regulation of the length of the gestation period. Through a semi-controlled experiment, diet-tissue discrimination factors for shark muscle tissue of
2.29 º/∞± 0.22 (δ15N) and 0.90º/∞ ± 0.33 (δ¹³C) were derived. The application of these values to wild sampled animals found that stables isotopes do provide a reasonable estimate of trophic position (TP) when compared to standardised stomach content data (SC). Ontogenetic δ¹³C data provided reasonable coarse resolution movement profiles. Data presented provide new techniques to study sharks and will assist regional management plans.