Everything you need to know about shark nets and drumlines
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Durban - For a week, beaches along the KwaZulu-Natal coast went unprotected to possible shark attacks.
This after the KZN Sharks board removed the shark nets from 37 beaches stretching from Richards Bay in the north to Port Edward in the south after workers aligned to the South African Liberating Public Sector Workers Union went on strike.
The board removed the nets to ensure "zero environmental impact" as many sealife including fish and dolphins is caught between the nets.
As the shark nets were re-installed on Friday after a wage agreement was settled between the board and the workers, many are questioning the need for shark nets and drumlines.
How effective are they to preventing shark attacks and how do they work?
According to the KZN Sharks Board, most of the shark nets deployed along the KZN coast are 214m long and 6m deep and are secured at each end by two 35kg anchors; all have a stretched mesh of 51cm. The nets are laid in two parallel rows approximately 400m offshore and in water depths of 10-14m.
What are drumlines?
The KZN Shark Board says that a drumline consists of a large, anchored float (which was originally a drum) from which a single baited hook is suspended. Most beaches are protected either by two nets or by one net and four drumlines, but the quantity of gear varies from beach to beach. A total of 76 drumlines were introduced at 17 beaches along the Hibiscus Coast in February 2007. The drumlines replaced almost 50% (a total of 4km) of the nets, which were in place. The idea of introducing drumlines is to reduce the bycatch of harmless non-shark species such as whales, dolphins and turtles, which are accidently caught in the nets. The capture of non-target species has been reduced by 47,5% with the installation of these drumlines. Drumlines have also been installed at Richards Bay and were introduced to all protected beaches in the KwaDukuza Municipality in November 2015. A total of 107 drumlines are currently in off the KZN coastline.
How do shark nets and drumlines work?
The KZN Shark Board says that shark nets do not form a complete barrier and sharks can swim over, under or around the ends of the nets. Neither, of course, do drumlines form a physical barrier. Both types of equipment function by reducing shark numbers in the vicinity of protected beaches, thereby lowering the probability of encounters between sharks and people at those beaches. The nets may have a limited barrier effect as well, but the fact that about one-third of the catch is caught on the shoreward side of the nets is evidence that such an effect is only partial. Drumlines are a recent introduction on the KwaZulu-Natal coast but their successful use in Queensland, Australia, indicates that the fishing effect of the protective equipment is of primary importance.
The KZNSB boat crews service the nets and drumlines, every Monday through Friday, weather permitting.
Only four of the 15 skiboats operate from harbours, with three boats based at Durban harbour and the forth at Richards Bay.
All the other craft have to launch though the often heavy surf to reach the shark safety gear.