View single post by Pylstert
 Posted: Mon Mar 11th, 2019 02:22 pm
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Pylstert

 

Joined: Fri May 4th, 2007
Location: Wagina Island
Posts: 1948
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Mana: 
And here is the abstract from a study done on catches in the shark nets:


Population status of 14 shark species caught in the protective gillnets off KwaZulu–Natal beaches, South Africa, 1978–2003 Sheldon F. J. Dudley A C and Colin A. Simpfendorfer B + Author Affiliations Marine and Freshwater Research 57(2) 225-240 https://doi.org/10.1071/MF05156
Submitted: 22 August 2005  Accepted: 17 January 2006   Published: 10 March 2006
Shark nets have been set off the beaches of KwaZulu–Natal, South Africa, since 1952 to reduce the risk of shark attack. The nets fish in fixed localities 400 m from shore and both directly affect local shark populations and act as fisheries-independent monitoring devices. Reliable catch information at the species level was available for the period 1978–2003. Trends in catch rate and size were used to assess the population status of 14 commonly caught shark species. In addition, a demographic modelling approach was used in conjunction with the catch information to assess the potential effect of the nets on populations. Catch rates of four species (Carcharhinus leucas, C. limbatus, Sphyrna lewini and S. mokarran) showed a significant decline, as did the mean or median length of three species (Carcharhinus amboinensis, C. limbatus and female Carcharodon carcharias). For three species that showed declining catch rates or length the potential effect of the shark nets was assessed to be low, suggesting that other sources of catch were responsible for the declining status. The potential effect of the shark nets was assessed to be high for two species (Carcharhinus obscurus and Carcharias taurus, neither of which showed declines in catch rate or length), because of very low intrinsic rates of population increase.

Last edited on Mon Mar 11th, 2019 02:24 pm by Pylstert