Gastropods, namely snails and sea slugs, are the largest class of molluscs, with at least 2,500 species occurring only in Eastern Africa. Inside this group, we can find Nudibranchs, a particularly intersting and often beautiful kind of sea slug.
Nudibranchs are the largest order in the subclass Opisthobranchia. This group is special due to the fact that most of them lack of a protective shell, and therefore have unprotected and exposed gills. There are approximately 4,000 species worldwide, most of them being marine and ranging in size from 2mm to 30cm. Their amazing shapes, striking colors and intricate patterns have made them very popular among photographers and scientists. They are easily seen by snorkelers and divers due to their bright and beautiful coloration and that they are attracted to coral and shallow rocks.
All gastropods have a toothed radula used when scraping algae off rocks or rasping at tissue of shells of invertebrates or other dead animals on which they feed. Nudibranchs are carnivorous and feed on all groups of invertebrates from hydroids and barnacles to polychaetes and other gastropods.
In the Kisite Marine Park include we can find the species Phyllidia varicose from the suborder doridacea. This nudibranch is oval shaped and black in color with white/blue tubercles showing bright orange tips. These are found among shallow coral reefs. Phyllidia zeylanica has also been seen in South Kenyan waters, with its oval shape, bands of low pink tubercles and alternate smooth black bands. These are also found among shallow coral reefs.
Yesterday dawned, dark and drizzly, the rainy season is also the windy season, and the waters were rough! Somewhat unsurprisingly we saw no dolphins; if they had been there a doubt we would have spotted them over the white caps. When we reached the transect, it was bright and sunny, the water was warm and there were no waves in this sheltered bay.
The colourful courtship displays of a male cuttlefish
Today, in addition to the countless colourful little damselfish, there were larger angelfish and butterfly fish and a lone pufferfish. At the end of the transect we suddenly spotted something in the deeper water – a flash of colour and a fluttering fin – it was a large cuttlefish! With another one next to it… We watched intently as their colour changes flashed across their bodies, from pure white to mottled brown to grey and black. As we watched them swim around each other, rippling their tentacles, we realised it was a courtship dance! The male did most of the colour changing and the female stayed mostly sandy coloured. It was like watching a cryptic form of sign language; the colours clearly having a meaning but we couldn’t comprehend them. It was something unique I have never experienced before and won’t be forgetting anytime soon!
In a blog earlier this year we discussed our plans for developing and improving reef fish surveys in Kisite Mpunguti Marine Protected Area. We thought it was time for an update…
We have been busy doing surveys 1 and 2 on almost all of our survey transects through this and the previous expedition, with volunteers and staff both learning to identify and estimate the sizes of different families and species of important reef fish. Survey 1 assesses coral health by using bio-indicator species so in this survey we look at butterfly and angelfish and Survey 2 assesses the relationship between trigger fish, sea urchins and herbivorous fish including surgeon and parrot fish. Both these surveys give a good indication of the health and stability of the different reefs and the levels of biodiversity. This study will also help to determine the impact of fishing on the coral reef communities. Even in these initial stages it is possible to identify some key trends and differences between the transects and reefs surveyed.
Lethrinidae lethrinus nebulosus - caught for consumption - the number and size of Emperor fish are recorded for Survey 3
Survey 3, which focuses on commercially important fish including the following families; Emperors (lethrinids), Snappers (lutjanids), Groupers (serranidae) and Rabbitfish (siganidae), indicates the impacts of fishing by recording differences in abundance and size on transects within and around the Marine Park. This week we have had 4 people pass the required identification test and are ready to start surveying! We have 4 weeks left of this expedition and we aim to cover each transects at least once for each survey. It’s going to involve a lot of snorkeling and although challenging, it’ll also be really interesting.
Last week the marine team were fortunate enough to go on a mini road trip and visit the Watamu Marine Association early on Friday morning. Watamu is a small village on the Kenyan coast which has pristine beaches and reef protected lagoons.
The Watamu Marine Association (WMA) was formed in 2007 with the vision of protecting Watamu as a natural asset and encouraging economic prosperity by promoting quality tourism primarily to benefit the local community. It is a non-profit and voluntary organisation and its members include the local community, environmental sectors as well as tourism sectors.
Recently the International Fund for Animal Welfare (IFAW) started funding a dolphin conservation programme in Watamu, enabling the WMA to focus its attention on the welfare of the dolphins in the area. This programme will focus on community education and enforcing responsible dolphin watching protocols locally. Research will also be an important element of the project, the number of dolphins and the population distribution in the marine park and reserve will be studied.
The main purpose of our visit was to share information, skills and learn from each other and it was a great success… As GVI has been studying dolphins in Kenya since 2006 WMA can learn a lot from the challenges and initiative successes we have had in our dolphin research. In return, they have been working on a waste management programme and making crafts from recycled materials, such ideas are a great addition to the waste management improvements we have been implementing in Shimoni and are setting up in Mkwiro too.
Through collaboration, hopefully a national conservation plan for resident and migratory cetaceans in Kenya can be developed in the future. All of us thoroughly enjoyed the trip and spending some time with the fantastic team at WMA. They are in an exiting stage of the process and it will be interesting to see where they take it!
To find out more about Watamu and the marine association and some of their projects or to get involved visit their website or check them out on facebook.
Crown of thorns (Acanthaster) are a vicious looking ‘starfish’ with a spiny circular body and more than 20 short arms covered in short spines. They tend to have red or green colouration and are unmistakable. Juveniles feed on coralline algae but adults feed voraciously on living coral. For this reason they are considered a pest and threat to coral reef health. Sudden increases in populations can be responsible for large areas of coral death; such population outbreaks are possible when natural predators such as triggerfish, wrasses and the giant triton shell are removed from an area. With the reduction in coral cover, biodiversity and abundance of fish species is impacted heavily, with families such as Butterfly fish who feed directly on live coral tissues disappearing from these areas.
Crown of thorns (Acanthaster) in high densities can destroy areas of coral
Recently, on GVI Kenya’s snorkel surveys we have spotted three Crown of Thorns; two were found on transect 13 which is an area reef near Sii Island, still under pressure from fishing methods such as seine and ring nets which are dragged along the sea floor, and one on Transect 3, a reef inside the Mpunguti Marine Reserve where only traditional line and trap fishing is permitted. Corresponding closely with this was the number of sea urchins also located on these particular transects with 350 and 480 respectively.
Sea urchins are a fascinating class of species from the Echinodermata or ‘spiny skinned’ animal group – they evolved 600 million years ago and today approximately 800 species exist worldwide, and around 60 species have been found in the shallow waters of the Western Indian Ocean. On our snorkel surveys, we have been recording the abundance of sea urchins and so far have found key species present to include the Needle Spined Urchin (Diadema setosum and D. savignyi) with long thin black spines up to 30m in length, Echinometra mathaei with short thick black spines, and Astropyga radiata with densely packed needles, vivid pink bordered with iridescent blue spots.
Astropyga radiata with densely packed needles, vivid pink bordered with iridescent blue spots
Sea urchins have five teeth in their mouth on their underside and mainly feed on sea grasses or algae living inside dead coral; in times of high population numbers they can also attack living coral. Population outbreaks can occur on dead reef patches caused by an environmental disturbance, such as an El Nino event or over-fishing of predatory fish such as Triggerfish and Wrasse. This can lead to bio-erosion of large areas of limestone rocks and reefs, toppling erect coral structures, which reduces the topographic complexity of the reef. This removes certain niche habitats and can limit overall biodiversity of reef areas.
Populations of the Needle Spined Urchin (Diadema setosum) can increase dramatically when predatory fish species are removed
We are noticing through our surveys a trend common in many similar studies, that protected (non-fished) areas have higher abundance of predators such as Triggerfish, but they are rarer in unprotected reefs allowing sea urchins to exploit the area. It has been determined that the removal of top, invertebrate-eating, fish carnivores can have cascading effects on coral reef community structure and function (McClanahan and Shafir, 1990). It is also true that sea urchins themselves have an important role to play in the nutrient cycle and regeneration of reef habitats.
Following on from our last blog, talking about the problem of spear fishing, recently some positive action to address such problems has been taken by local Beach Management Units (BMUs) alongside the Fisheries Department, East African Wildlife Society (EAWLS) and Kenyan Wildlife Service. Facilitated and funded by Flora and Fauna International, last week Shimoni held a big event to get local stakeholders together to discuss the possibility of establishing Community Conserved Areas (CCAs).
Representatives from all seven districts put forward their ideas for areas managed locally by the people who have the most invested in that area, and also put forward the problems and support they foresee being needed from other organisations. It was a progressive day with communities working together, sharing thoughts and moving forwards in conserving their natural resources. The aim of the CCAs would be to reduce destructive and illegal fishing methods by patrolling the areas and enforcing agreed regulations, and to charge small entry fees to tourists wanting to snorkel or dive on the reefs.
A healthy reef off Sii Island - one proposed CCA
This project will no doubt grow and develop over the next few weeks with so many enthusiastic people coming together to get invovled, both from the scientific and local communities, so we will keep you updated!
During the past 3 months, GVIs marine team have noticed an increased number of sightings of spear fishermen; that is fishermen snorkelling carrying illegal spear guns off the shallow reefs around Wasini Island.
Spear fishing is illegal in Kenya due to the damage it causes to coral reefs when the spear is shot and misses its target and breaks pieces of coral – this can be irreparable or slow to recover, and destroys both refuges and food sources for many fish and larger vertebrate species. Unfortunately, enforcing this regulation proves difficult and it does still happen up and down the coast. Last week, we saw a particularly successful catch for one fisherman just off the Eastern tip of Wasini Island. On his line we saw Parrotfish, Snappers and Octopus.
A spear fisherman's catch off Wasini Island
We have speculated a few possible reasons for the apparent increase, at least in the times we are witnessing spear fishing. The first is simply that there is a movement towards this fishing method as a more lucrative and efficient way of catching fish, despite the risks. The second is that it may be because our search effort has been focused on areas outside the KMMPA … The third is perhaps the kaskazi monsoon season is making fishing out in traditional canoes impossible in the rough waters, so alternatives have had to be sought. Whatever the reason, we have been seeing action from Beach Management Units, the Fisheries Department and KWS hoping to stop this trend and eliminate spear fishing from the local waters.
Over the last few months, GVI had been working hard to assess different coral reef fish communities within and around the Kisite Mpunguti Marine Protected Area (KMMPA). We particularlywant to assess the impact of fishing on specific commercially important species by looking at the presence and individual size of fish on different transect sites within the survey area.
One of the commercially important families we are surveying - Grouper or Serranidae
In recent years, fish stocks in this area seem to have been declining due to increased population pressure on the coast resources and increased tourism demands alongside the global problem of overfishing. GVI has found out that local fishermen have witnessed a decrease in individual fish size and in the amount of fish they are catching through interviews and measuring fish catches, so it is integral that we investigate this concern for future sustainability and conservation. A decreasing population of certain fish species can threaten both the biodiversity of important marine habitats and the livelihoods of the local communities.
By conducting surveys on transect sites that lie within the Kisite marine park, where fishing is prohibited, and the marine reserve where fishing is limited and comparing it with data collected from unprotected areas, we hope to gain a better understanding of how the KMMPAis affecting the presence and size of Snappers (lutjanids), Groupers (serranidae), Emperors (serranidae) and Rabbitfish (siganidae). We hope the data collected will signify the necessity of marine reserves and encourage local people to support them and the positive impact such recruitment grounds can have on fish stocks.
Recently, GVI has been collating information so that we can assess the ecologically important reef fish within and around Kisite MpungutiMarine Protected Area (KMMPA) and in the wider area. We have been collecting this data from our snorkel transects for a few months now, and now want to refine it to isolate key species of interest to assess the presence, absence and abundance of certain fish. This provides an insight into the well being of coral reef communities and will highlight any ecological differences between coral reefs inside and outside of the protected areas.
Firstly we focus on assessing coral health by recording the occurrence of butterflyfish. A healthy reef is considered to be one which has a high abundance and biodiversity of coral speciesand Butterflyfish are well known to be bio-indicators of reef health because many feed specifically on coral polyps. Thus, a more productive feeding ground allows the butterflyfish to flourish.
The presence of key species of Butterflyfish indicates a healthy coral reef
Secondly we focus on a key relationship between Triggerfish, herbivorous fish and echinoderms on the reef. As well as being commercially important, Triggerfish are a keystone species within the community. They prey on echinoderms and when triggerfish populations are exploited, sea urchin numbers increase significantly. Echinoderms primarily feed on alga; however they also feed on other reef organisms such as coral. Typically, this means that there are higher densities of sea urchins on more degraded reefs where alga is more abundant. Conversely, if algal cover reduces or the competition for food increases, sea urchins become more generalised feeders which can significantly reduce coral cover when present in high abundance. In addition they compete for food with other herbivorous fish such as Surgeonfish (acanthurids) and Parrotfish (scarids).
Surgeon fish are herbivourous feeding on algae
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