We had a very exciting sighting a couple of weeks ago on marine – as you may have read – our sighting of a tiger shark, and in remarkable circumstances. This was the first GVI recorded tiger shark in our south coast study area and caused quite a stir amongst the team!
There are around 50 species of shark in the western Indian Ocean region from 13 different families – one of those families is named the ‘true shark’ or Carcharinidae family containing 20 species of powerful predatory shark. The tiger shark or Galeocerdo cuvier falls into this family and is distinguished by its pattern of darker spots and stripes on its grey dorsal surface; it has a large blunt head and mouth and a long slender tail with a pointed tip. The most unique feature of the tiger shark is its teeth (!) which are serrated. They reach up to 5.5m (18ft) and are quite robust, heavily built specimens.
The two individuals we spotted exhibited the distinctive patterning and were around 4m in length; they also had with them a young individual. Sharks are normally solitary, and tiger sharks feed on turtles seabirds and other more opportunistic items, but may have gathered here at the opportunity of this food source (see previous blog on the stranded humpback whale body).
Tiger sharks are listed as the most dangerous to humans seen in this area; but I for one hope we see them again.
Some weeks ago, as you may have read, GVI Kenya attended the 7th Western Indian Ocean Marine Science Association (WIOMSA) scientific symposium in Mombasa. It brought together a diverse array of organisations, fields and nations to discuss current and future issues facing the conservation of our marine resources and species, focused on the Western Indian Ocean.
GVI presented 5 posters detailing the research and community development initiatives going on with our different programmes – see previous blogs for full details. We were also able to attend a series of talks and presentations on other research projects both in Kenya and the surrounding countries, discuss potential collaborations and partnerships and take part in 3 workshops developing conservation of sea birds, sea turtles and the incorporation of health and education in local communities.
It was overall a huge success, with a better appreciation of the need for good scientific and integrated research within this region, to promote conservation and resilience of our marine resources.
One of the most amazing creatures we see in Kenya is the migrating humpback whale. The humpback whale migrates along the Kenyan coast from late June through to December. In the past three months we have had 6 sightings of humpback whales with an average group size of 2.16, ranging from 1 to 4.
Some of these groups have been mothers and calves plus another adult whale. It is reported that “escort males” can accompany mothers and calves during their migration. It is thought that the male travels with the mother and calf with the intention of mating if the mother comes into post partrum oestrus. Occasionally another male humpback whale will join the group (becoming a secondary escort), challenging the principle escort for access to the female mother (termed the nuclear animal). The escort will defend the nuclear animal from other intruding males with behaviours including shoving, breaching and blowing bubble screens. This also acts as protection for the humpback whale calf.
It has also been known for escorts to be female, the reason for a female escort is currently unknown, though the escort may be related to the mother. This links to the sightings we have been having and might explain why a group of 3 adults and one calf have passed through the south of Kenya.
Humpback whale escort
Although smaller and possibly less exciting than some of the ‘mega’fauna found off the Kenyan coast, the intertidal species we have recently been recording has including some very unique and special species. The Tridacna maxima is also known as the elongate giant clam, with a shell up to 35cm long and 6-12 broad radial ribs with strongly developed concentric scales. Examples of this clam can be found fossilised dotted around the local landscape, some large enough to step inside! Live examples are found embedded in coral or rock during our snorkel surveys, when disturbed by snorkelers they snap shut.
The Tridacna maxima or Giant Clam
A number of shells from different molluscs are also present on our shoreline, for example the Conus ebraeus with its whitish colour and pattern of black squares, it also has a short round spire. Sea Hares are similar to sea slugs, very well camouflaged molluscs with a small internal shell. One species we identified today was the Dolabella auricularia – a large and bulky species, up to 20cm long with a flat, sloping posterior with a green to brown body, covered in papillae, making it appear prickly. Sea hares are unique in their size, they can reach up to 2kg and 60cm and the fact that some can secrete a purple ‘smokescreen’ when disturbed.
- Distinctively patterned Conus ebraeus
It is important to understand and appreciate the variety and diversity of marine species, and their integral role to the health and growth of each small niche habitat. these surveys will help us develop a list of all local species, their habitats and abundance.
As part of developing our intertidal surveys today, we went down to the beach at low tide to discover what creatures are living in rock pools and the caves in the cliff at Mkwiro beach. We photographed and then identified everything we found, and discovered numerous species from crabs and sea stars to sea slugs and even very small fish. Some of the more interesting species of crab were the Calappa hepatica – also known as the box or shy crab, who has a mottled greenish carapace covered with tubercles and is about 45mm in length and the Menaethius monoceros; a small crab (length 22mm) with a triangular yellow carapace with an elongated rostrum. This species often covers itself with weeds and sponges allowing the crab to effectively camouflage.
The cleverly camouflaged Menaethius monoceros
We were joined by some local interested children who helped us spot a number of different Sea Stars including the Leiaster coriaceus, a cream/ greenish brown colour with red patches and distinctive long, narrow cylindrical and skin covered arms and Brittlestars such as the Ophiocoma scolopendrina with a variable colour and irregularly banded arms. This species is usually found under rocks and boulders with arms extending outwards in order to collect food particles from the water surface. See our next blog for the other interesting discoveries right on our doorstep.
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.
The next item GVI Kenya will be presenting on at the WIOMSA scientific symposium in Mombasa in October is the seasonal occurance and distribution of sea turtle sightings in and around the Kisite Mpunguti Marine Protected Area (KMMPA). We most commonly see Green and Hawksbill turtles both from the vessel and in-water while snorkelling, during our research days; with 41% and 53% of sightings prospectively.
Sea turtles are often seen surfacing from the research boat
Sea turtles were most commonly seen in two focal areas; the KMMPA and the Wasini Channel. We also conducted interviews with 75 fishermen whose responses corresponded with this, indicating that they encounter sea turtles most frequently (61%) in the Mpunguti Marine Reserve, and in the kaskazi season (January to March) with 29.5% of responses. We will be discussing the importance of the KMMPA and surrounding waters as critical habitats for Hawksbill and Green turtles, and how community education and awareness programmes will play an important role in conserving local populations.
The first poster GVI Kenya will present at the WIOMSA scientific symposium focuses on the Humpback dolphin population present around the Shimoni area, using sightings data and photographs taken since 2006 to estimate population size, location and possible threat from anthropogenic activities.
- Identification Number 016 – this dolphin has evidence of a fishing line injury
We have identified a population of 32 dolphins, who inhabit mainly shallow coastal areas between Sii Island and Funzi Bay, through the Wasini Channel. Four individuals have evidence of injuries from fishing equipment or boat interactions. In addition, the core range of their distribution does not fall within the boundaries of the KMMPA, meaning no restrictions on fishing levels and methods are in place.
The Western Indian Ocean Marine Science Assocation (WIOMSA), alongside the Kenyan Marine Fisheries Research Institute (KMFFRI) have organised a scientific symposium in Mombasa this October, focusing on the issues around Coping with Global Change.
In April, GVI Kenya’s marine team submitted abstracts on a series of topics and findings from our research programme on the south coast under themes of global change and the marine environment, biodiversity and ecological processes and overexploitation of resources and. We had three abstracts accepted for poster presentations at the symposium in a couple of months. The next three blogs will describe the focus of the presentations GVI will make and the significance of the data being collected.
Since our first sighting of the Humpback Whales on the 21st July, we have had three more sightings, with possibly up to 11 individuals seen. On the 29th July we encountered four whales in a group together, moving slowly, surfacing often and performing lob tailing behaviour. Previous years we have only seen groups of up to three whales together, so this was particularly exciting!
Three Humpback Whales were spotted in the shallows off Nyuli Reef
Our third sighting occured at Upper Mpunguti, just outside the Marine Reserve, with one smaller individual coming into very shallow waters and one Humpback Whale spotted both by our research vessel and the passing tourist boats, much deeper breaching over 10 times before disappearing from sight. And just this week we had our fourth and fifth sightings, one whale being spotted travelling between the two islands of the Marine Reserve and another heading west just behind Wasini island. We managed to also observe this individual from land with our telescope – and find that it was actually part of a group of 3 whales again breaching and travelling slowly past the coast.
Extended periods of lob-tailing was observed in 2 individuals