South Africa has two commercial fishing sectors that target tuna – the Large Pelagic Longline and the Tuna Pole-Line (baitboat) sectors. The latter sector mainly targets (Thunnus alalunga) and to a lesser degree yellowfin tuna (Thunnus albacares) and rarely operates in the IOTC Area of Competence. The Large Pelagic Longline sector comprises two fleets with different histories: the South African-flagged Large Pelagic Longline vessels that traditionally used swordfish (Xiphias gladius) targeting methods, and the Japanese-flagged vessels that operate under joint-ventures and fish for South African Rights Holders. The Japanese-flagged vessels typically target tropical tunas and southern bluefin tuna (Thunnus maccoyii) with their effort focused in the Indian Ocean. In 2017, 16 longline vessels were active in the IOTC Area of Competence, which is less than that in 2016. However, effort has remained constant and the number of hooks set in 2017 (1 284 160) is remarkably similar to that in 2016 (1 284 756). Despite constant effort, catches increased from 2016 for southern bluefin tuna (163%), albacore (33%) and bigeye tuna (29%). The substantial increase in southern bluefin tuna catch is a result of South Africa’s longline fleet actively targeting this species due to the increased nominal TAC from 40 tons in 2015 to 150 tons in 2016/2017. For the same period, decreases in catch were observed in swordfish (39%), blue shark (39%), yellowfin tuna (25%) and shortfin mako shark (23%). The high inter-annual variability in catches for species can largely be attributed to a high proportion of longline vessels fishing across the IOTC/ICCAT boundary line. Observer coverage exceeded all RFMO requirements and 73% (939 835) of hooks set in the IOTC Area of Competence were set while an observer was onboard, of which approximately 42% of hooks set were actively observed. In 2017, only a single Tuna Pole-Line vessel fished in the Indian Ocean for 12 hours – this vessel was likely searching for tuna and crossed the ICCAT/IOTC boundary temporarily. Negligible catches of yellowtail (Seriola lalandi) were made by this vessel.