Treknets this Summer
Posted on Thursday, 6 March 2014
Spending time down at the treknets along Muizenberg and Strandfontein has always been a part of our summers, and many of you who have been following our activities through the years will know that we have released thousands of sharks and rays with the help of the fishermen who work the nets. I can’t stress enough how involved the fishing crew are with releasing the sharks. After many years of education they realise the importance of sharks in the eco system, and even though they are allowed to keep and sell the shark carcasses, they choose to release them.
The shark species most commonly caught are bronze whaler sharks and small smooth hound sharks. Less often ragged tooth sharks, spotted gully sharks and thresher sharks are caught and on extremely rare occasions a great white shark is caught. Many species of rays are also caught including Duckbill rays, Diamond rays, blue stingrays, biscuit skates, one fin electric rays and sometimes huge short tailed devil rays.
From the spring months of September and October until around March our summer wind, the south easter, blows strongly in False Bay which causes very churned up water and upwelling. This water movement is the catalyst for an algal bloom, Anaulus australis, which baitfish such as southern mullet (haarders) feed on. This algal bloom stands out very clearly as it turns the water varying shades of brown. Chris had the privilege of joining a friend on a 2.5 hour helicopter ride this week and his photographs very clearly show the algal bloom and the extent of it after a windy few days.
The most common misconception amongst the public is that this is polluted or sewage water. In fact it indicates a very healthy situation and is vital to the wellbeing of the False Bay eco system. The baitfish in turn attract summer gamefish such as elf, yellow tail, kobbeljou and a variety of other fish species, and of course along with this, larger predators such as sharks and rays. The fishing practise has a huge amount of bycatch and although it’s the summer fish species and mullet that are targeted everything that the net is dragged through is caught.
Our involvement is purely on a volunteer basis to release all the elasmobranchs and protected and undersize fish species. It is an amazing feeling to release all these animals and it also plays an important role in educating the public. Over the summer hundreds of people from the public come to watch the nets and seeing the fishing crew and ourselves actively releasing certain animals goes along to highlighting shark conservation and understanding that sharks have a place in our fragile ecosystems.
Over the years we have sadly seen a massive decrease in the numbers of bronze whaler sharks due to their commercial exploitation further up the coast. In fact if we saw 30 individual sharks over a whole summer, this would be the norm.
Of particular concern is the dramatic decline of smooth hound shark numbers and average size. This species has also been commercially targeted and the population has plummeted. This shark species is an important part of the Great white shark’s summer diet and we strongly believe that the decline of its prey source is causing the Great white sharks to go into areas that they historically had no need of venturing into, as they now have to search harder for their food. This ultimately increases the interaction between sharks and people.
We have continued to see less smooth hounds this summer but the good news is that we have seen far more bronze whaler sharks, and we estimate that close to 100 bronze whalers were released.
We had a number of occasions of “perfect shark conditions” and we had 2-3 day periods of 10 or more sharks in a net, along with high numbers of rays. When this happens, it is manic and complete chaos. The fishermen are trying to pull the net up the beach, the public are all pushing and shoving to get a closer view and we are trying to get to the sharks to release them. Miraculously though, it all works out and the crew help us to get the sharks quickly, and they themselves make it a priority to release sharks.