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Our 2015/2016 survey season finished at the end of April 2016 when Peter and Frances followed the swallows back to England.
By the end of April we had completed 2 full assessments on all 14 sites with the help of our willing volunteers – who are now nicknamed the mud larks after getting stuck in a couple of really muddy sites which didn’t dampen their enthusiasm one bit. We have continued to refine assessment methods as we gain more experience. We now take a quarter meter square quadrat for each of the different biota at each site in order to obtain detailed information on population numbers. We have found and identified over 200 species which shows the huge amount of life living in the Estuary and is great indicator of its health. We can now compare the results of two assessments at each site and Frances is spending much of her time in England sorting out the mass of data into some sort of order.
Interesting observations included an explosion in the numbers of shaggy sea hares (Buraetella leachi) in March many of which were found washed up on the shores all round the Estuary. The cause is not known but many were seen to be mating so this may have been one of the reasons for such large numbers. We accessed water data from the KEMP data recorders and found that oxygen levels had been lower than normal at that time and this could also have been a factor. Those who assessed the rock stack at Featherbed Bay were fascinated to watch a large octopus hunting for food along the water’s edge.
The most striking feature of the last year has been the effects of the sheets of sea lettuce (Ulva lactuca) which now cover large areas of the shores especially in the Ashmead Channel and its approaches. This is smothering the eelgrass and mud and affecting the species that normally live there – for example in some areas the mud prawns have almost disappeared. This is turn will reduce their value as nurseries for young fish. However we will have to learn to live with this as the recent paper by Dr Allanson et al, ‘Insights into the cause of an Ulva lactuca Linnaeus bloom in the Knysna Estuary’, suggests that the sea lettuce is unlikely to go away. We have also been dismayed to see the damage to the eelgrass beds in Kingfisher Creek caused by extensive digging by baiters. This is a major threat to Knysna’s environmentally important eelgrass beds which account for half of the eelgrass in South Africa.
Part of the routine of ShoreSearches now is to take plastic sacks with us and collect litter on the walk back from the assessment site which is particularly valuable in the more remote areas where official litter pickers do not reach. Sadly we usually find just as much litter when go back a few weeks later.
ShoreSearchers are fully involved in Knysna Basin Project’s education programme with local and visiting schools, public groups and visiting organisations such as WESSA. We have been particularly involved with Knysna Primary’s Eco Club and Riverwood Primary, and we spent a very worthwhile morning in April introducing new SANParks staff to the life of the Estuary. Our interaction with schools covers the shore and saltmarshes and includes classroom presentations and guided beach and shore walks where pupils are shown the many species living around the estuary and how important it is to treat the estuary and its inhabitants with care and respect. For many it is the first time they have seen how beautiful shaggy seahares are, the casings where moonshine worms live and the many other wonders of the Knysna Estuary.
We start assessments again in early October 2016 and we look forward to renewing contact with our volunteers and another successful ShoreSearch season. The good news is that SANParks have extended our research permit until 2019 which will enable us to further increase our data base of species diversity and frequency and to develop how best to present the data for the authorities and public.