Category Archives: Marine Debris

Turtle strandings

Going out on the boat to survey marine life, we’ve encountered Green and Hawksbill turtles, Bottlenose and Humpback dolphins, and even a black tip reef shark while snorkelling out at Kisite. It has been fantastic to see so many pods of dolphins foraging nearby with calves and juveniles.

This week was, however, also marked by tragedy. While on dedicated search a volunteer spotted something bobbing in the distance, so we went to take a closer look. As we got nearer we saw that it was a turtle but it wasn’t acting at all normally. Usually turtles will swim just below the surface and will only pop their head out to take a breath before lowering back into the water. This one was limp, just floating along. Our captain confirmed it had died. Very recently.

After inspection, we were able to identify it as a Hawksbill Turtle with a 1m shell length. This species is critically endangered and it was heartbreaking to see that the cause of death was that it had tried to digest a plastic bag. Probably confusing a floating plastic bag for its usual choice of jellyfish was a deadly mistake for this unsuspecting turtle.

1m Green Turtle found stranded

1m Green Turtle found stranded

It really brings home the detrimental effect of pollution and littering on the environment, and if we were all to reduce our waste and pick up rubbish each day we could prevent tragedies like this. Since this sighting we have now seen another four dead turtles, both being mature green turtles – cause of death unknown. Dicussion amongst the group and with KESCOM have brought us to one possible conclusion – that the current season of Kaskazi, bringing rough seas is causing eratic boat movements and may be throwing turtles off course and increasing boat strikes.

The Elusive Humpback

I was sitting outside the cottage discussing the different types of hornbills found in Kenya, as a Trumpeter Hornbill had just flown over head, when Sergi (the marine officer of expedition 094) pulled me aside to talk about my independent project. I was secretly chuffed that I got given the one I did, as there was a choice of three. The title of my project was “Data Analysis of Indo-Pacific Humpback Dolphins (Sousa chinesis) collected by GVI Kenya Marine Team from 2006-2009.”
 HBD sightings

These animals are very shy animals and are not as well known as the bottlenose dolphins. Maybe because they are shy or perhaps because of their habitat distribution, there is very little data available. So this was a great opportunity to be able to provide some information. The GVI Marine Team has been collecting data on them since 2006. Whilst out on the boat on a survey day, if we have a spotting we follow them around, taking photos and also monitor their behaviour. Using a GPS (Global Positioning System) we are able to plot the route taken by the dolphins that day.  This allows us to see the areas where the humpbacks dolphins feed, rest, socialise, breed etc. As well as being able to gain data on group sizes and composition.

 So I went forth and did some research on our friends the humpbacks and also plotted the information on our study area (see picture) which is the Kisite-Mpunguti Marine Park and Reserve and the surrounding area.
 Humpback dolphins occur in small groups (3-7) and are distributed throughout Indian and Western Pacific oceans as well as the coast of south east Africa. Inhabiting tropical and subtropical waters (15oC – 20oC), they prefer coasts with mangroves, rocky reefs, estuaries and lagoons. Typically found in waters less than 20m depth, they only venture a few miles from the shore line (as shown on the map), and occasionally they swim up rivers. The distinctive hump on their dorsal fin gives rise to their name; and they are medium sized 2.5m – 2.8m.
 

boat trWasini channel and the surrounding waters are prone to quite a lot of boat traffic and fishing. Humpbacks tend to avoid boats, although marks caused by propellers have been observed. This is a concern not only because of the damaged caused to the dolphin but also because of the resultant change in their behaviour, e.g. leaving the area. Another concern is that being situated on the coast; the communities living here depend upon fishing as a resource. Recent efforts have been made to educate some of the local community as to the importance and implications of over-fishing and pollutants.

 HBD spyhopping

It is my aim to develop a catalogue of the humpback dolphins, as this will allow us to determine population numbers and residency rates in this region. This is a technique called mark-recapture, and it uses the dorsal fins to identify each individual, mostly from the notches made by other dolphin or boats, but also by the shape, colour and size of the fins. Plus, on the cheeky side I will get to name some of them!

Sarah Watson was a conservation intern on 094 Expedition, and is currently doing her work placement with GVI, as staff member on the Marine and Terrestrial Programmes

Litter-Picking In The Mangroves

Low tide amongst the mangroves revealed hundreds of tiny male and female fiddler crabs scuttling between little holes in the sand. The aim of our day though was to attempt to clean up some of the mountains of rubbish that travel the Indian Ocean currents from as far as south east Asia, to wash up on the East African coastline, trapped amongst the mangroves here on the southern shore of Wasini Island having floated through the Kisite Marine Park. Seeing all the cool little creatures that make the mangroves their home was an added bonus!

the-mangroves-along-the-southern-shore-of-wasini-island.jpg

The open beach, exposed by the receding water, was so covered in small gastropods (and occasionally hermit crabs in shells they had commandeered from the gastropods) that we could not set foot on it for fear of crushing a delicate little home, and had to content ourselves with watching a group of yellow-billed storks through the trees. The male fiddler crabs put on a bit of a show for us and performed a strange sort of Mexican wave display with their one large claw; whether this was to try and attract the ladies or warn off others we weren’t quite sure.

All along the tide line seaweed intermingled with broken pieces of plastic, glass bottles, plastic bags and bottles, toothbrushes and flip flops. A five by ten meter path along the beach yielded five bin liners of rubbish and a bucket of glass, which was all we could carry back with us. It would take an army to clean all the debris that collects here from other parts of the world, and even then you’d be left with the feeling that just as much would be deposited after the next high tide. Walking back to base under the strain of our rubbish bags did, however, leave us with a small sense of achievement and as they say ‘every little bit helps’!