Masters Thesis Follows Shark Trail

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Four testing months at sea on commercial fishing vessels was all part and parcel of Mr Gareth Jordaan’s research which earned him an MSc in Biology from UKZN.

His interest was sharks, in particular, shark bycatch and discarding practices by pelagic longline fishing fleets.

Jordaan – a passionate environmentalist who is a research assistant based at the Oceanographic Research Institute (ORI) in Durban under the supervision of senior Scientist, Professor Johan Groeneveld –  accumulated a unique dataset of information on sharks during investigations which tested his personal tenacity and logistical resourcefulness at sea.

‘Global shark landings have increased over the last few decades, with many being caught as bycatch from fisheries targeting tuna and swordfish,’ said Jordaan. ‘Some of the captured sharks are retained and prepared for export, whereas others are discarded overboard.

‘The species, numbers and fate (alive, injured, or dead) of discarded sharks are not recorded. This omission gives rise to hidden shark mortalities and ultimately inaccurate shark population assessments,’ he said.

Sharks are apex predators which play a vital role in balancing the marine ecosystem and several species are listed as being vulnerable or threatened on the International Union for Conservation of Nature (IUCN) red list.

As part of his research, Jordaan was provided with landings data – collected when fishing vessels off-loaded their catch in port – by the Department of Agriculture, Forestry and Fisheries (DAFF). He also went out to sea on eight pelagic longline fishing vessel trips to get information on species composition of catches, discard practices and the fate of the discarded sharks.

Jordaan said foreign longliners fished seasonally along the east coast where they caught mostly tuna and sharks. Local longliners fished year-round, mainly along the west, south-west and south coasts and caught the bulk of sharks. Mainly blue sharks and shortfin makos were caught.

Larger blue sharks and a higher diversity of shark species (but lower numbers) were caught in the Indian Ocean compared to the Atlantic where juvenile blue sharks were abundant. More sharks were caught during the warm season and more tunas during the cool season. Discarded blue sharks outnumbered those retained and more than half of those discarded were dead.

‘Blue shark mortality is therefore much higher than reflected in DAFF landings data,’ said Jordaan. ‘Nearly all makos were retained, irrespective of size or fleet, suggesting that mako mortality is similar to landed numbers.’

Jordaan’s study is the first to investigate shark discards in pelagic longline fisheries in the south-east Atlantic Ocean and south-west Indian Ocean regions, and provides evidence that shark landings records grossly underestimate shark mortalities as a result of fishing.

‘Discard practices are complex, vary between vessels and also over time on individual vessels,’ he said.

Jordaan’s research is significant because in estimating the number of sharks discarded (alive and dead) by pelagic longline vessels, it provides important information to fisheries managers on the total shark mortalities that occur at sea, that may not be accounted for in the landings numbers.

This ultimately leads to more accurate population assessments of those shark species where discards are significant and for those that are more vulnerable than others to over fishing.

Jordaan said he has always had an interest in sharks from high school where he started scuba diving with them. Through his research he hopes to find a way to curb the shark bycatch problem in longline fishing vessels.

Jordaan thanked his supervisors, family and God for the support and opportunities he had received during his research.

A keen sportsman, scuba diver and lover of the outdoors who is passionate about living sustainably, he plans to develop his skills in fisheries assessments going forward in order to make sure fisheries are operating sustainably.

‘I also want to make people aware of the importance of sharks and help them to realise that sharks are not the enemy.

‘I want to help sustain these incredible, vulnerable animals,’ he said.

 Words by: Sally Frost

Photograph by: Abhi Indrarajan