Thursday, 25 February 2010

Hydrophone deployed at Sandwich Harbour!

We’ve been wanting to do some work down in Sandwich Harbour for a while now and eventually managed to get there today by boat. Sandwich Harbour is a similar, but shallower embayment ~50km south of Walvis Bay. Although it used to be deep enough for ships to sail into it and refill their water supplies, the movement of the dunes and erosion by the sea has made the whole bay much shallower, the mouth narrower and dug considerably into the dunes which lie alongside the sea. To illustrate how dynamic an environment these sandy coastlines are here – the GPS map was WAY off down there and indicated us being on land on several occasions.

The attraction of this area from our point of view is that there is almost NO human activity in the area (barring a bit of light fishing and the occasional weekend boat), which makes it a very interesting comparative site to Walvis Bay with its harbour, tourism and aquaculture – are the animals using the area differently down there? We hope that a month of a hydrophone logging the presence and absence of the dolphins in the area will gives us some indication of their habitat use patterns in the absence of human activity.

We looked at various options to get down there including towing the boat down the beach, borrowing a smaller boat to tow or using a bigger boat which we could stay on. I briefly flirted with the idea of buying our own catamaran, but then remembered I’m a scientist not an internet millionaire. So in the end, the quickest and easiest way was to drive down the coast with Nanuuq and back. It’s a very long way (the GPS track showed 84nm total for the day – I won’t tell you how much fuel we used, it makes me feel a little bit sick) along a very exposed and lonely section of coastline. We had really hoped to stay over there and send fuel down by car and then be able to work for two days in the area to allow us to do some more exploring and photo-ID work, before heading back up and thus make the most of the fuel use. Unfortunately the Ministry of Environment (MET) wouldn’t give us a permit to stay over, merely to enter the area (it is part of the Namib Naukluft National Park).

So with the wind picking up quite strongly every afternoon here, we were on a pretty tight time schedule and had to leave Walvis at 6am and head straight down there only recording dolphins as we passed. But the good news is that the weather held out all day, we got the hydrophone in the water (red star on map) and back home safely before the wind picked up! Not many dolphins to report unfortunately, a few small groups of Heaviside’s in the mid-section of the trip (the blue dots on the map) but a good day all round. The white bar on the map indicates 50km

Moving house tomorrow and then back on the water on the weekend.

Saturday, 13 February 2010

While out yesterday on a fairly average misty, windy day, we encountered a Heaviside’s dolphin with clear propeller wounds down the length of its body. As you can see from the photos below, it was quite a horrific looking injury. However, the animal was remarkably unafraid of the boat and would still occasionally bow ride our boat and we hope it will make a full recovery over time.

Why dolphins bow ride is not fully understood, but simple ‘play’ behaviour is the most likely reason. It's occurrence is clearly affected by the behavioural state (or mood) of the animal, as well fed or socializing animals bow ride far more keenly than those which are busy hunting or resting. Dolphins ride swell in the open ocean and surf near beaches and they will even ride the bow wave of large whales. The behaviour may be related to the practice of swimming in their mothers slipstream as calves. Heaviside’s dolphins, when in the mood, are particularly avid bowriders. Heaviside’s dolphins will even ride a boat going in reverse, when they swim very, very close to the engines. The keenness with which some species and individuals bow ride can be likened to dogs chasing cars. And it is the role of the boat skipper to bear in mind that just because an animal will react in a certain way to a boat, it is not necessarily a good practice to do it (would you throw stones at elephants to make them charge you?).

The high amount of boat traffic at Pelican Point has always been a concern to local conservation organizations and understanding the potential impact of this traffic was one of the motivating factors behind the development of the Namibian Dolphin Project. Sightings like this re-enforce the need for protocol compliance and the application of common sense and environmental responsibility while interacting with these fantastic animals.

Thursday, 11 February 2010

Beach survey to Cape Cross

by Michelle Wcisel

“There is a sufficiency in the world for man's need but not for man's greed.” ~Mohandas K. Gandhi (Warning: Some readers may find the pictures in this blog post disturbing).

Yesterday, we took a shore-side drive to Cape Cross to scope out potential launch sites with the hope of expanding our coverage of the coast to the north. However the tone of the trip quickly changed to a beach scavenging expedition as we learned the truth behind the “Skeleton Coast.” We found countless Cape fur seal skeletons, a few leatherback turtle carapaces that had been bleached in the sun, dozens of stranded shore birds, and four spotted gully sharks. The majority of the carcases were there due to natural causes, but every shark we found had been hooked and carelessly cut from the line.

When your career is in a biological science, especially one that is based in field research, you are exposed to life and death daily. You come to understand that cycle as an integral piece of a healthy ecosystem, and seeing a natural death of an animal changes from a mournful moment to solemn recognition of a bigger process in action. But, when you come upon an animal that has had its life taken by a hook, or a piece of line that cuts through its body, or a plastic bag lodged in its throat, you never stop feeling infuriated.

The first spotted gully shark had been killed within the hour we found it. It was a female, her gills were bright red and her body was still cold to the touch (cold because she had just been in the cool water, if she had been on the beach for awhile, her skin would have been hot from the sun – like the other three sharks we found). The line had cut through the corner of her jaw and it was obvious she had given the fishermen a “lekker fight” since the tension of the line had worked a massive wound into the side of her face. Out of curiosity, we collected her to do a full autopsy to further determine her cause of death, but were not expecting to find that the majority of this 1.55m shark’s body cavity was uterus. She was carrying 8 pups, 4 female and 4 male, all around 33cm in length. We eventually found the hook, which had punctured through her oesophagus, worked into her pericardial cavity, and pierced the left side of her heart. It is impossible to tell which of these injuries killed her first.

A mass loss of life like this feels overwhelming when you extrapolate it to all the world’s beaches, especially when you consider how this pales in significance to some of the horrors happening in the offshore fishing fleets. It is legal in Namibia to catch spotted gully sharks and they are classified on one of the lowest ranks by the IUCN Red data list as “near threatened”. However, it is important to recognize this type of blatant waste in order to inspire more research, more students, and further grasp the sense of urgency our oceans are silently suffering. If nothing else, the death of those sharks inspired a blog, maybe a few conversations, and perhaps some of you readers got to see images that are unfortunately all too commonplace to us in marine biology.

Sunday, 7 February 2010

Welcome to summer season 2010! After a long drive/bus trip from our starting points of Johannesburg and Cape Town, we started the season off in Lüderitz to pick up and dust off Nanuuq. After 2 days of howling wind we took advantage of a lull in the weather to get in one good sea day. Lüderitz is after all, the “Heaviside’s capital of the world”. The dolphins in Guano Bay started the day being somewhat evasive, preferring the company of the kelp to that of the boat. However, they became a lot more amenable as the day wore on and we had many boat friendly groups, including a mother calf pair (will try to put up a video link when we get a better internet connection). This was out first ‘photo ID’ day in Lüderitz and it was great to see so many well marked animals – we’ll begin developing a catalogue for the area in the near future, which will start to feed into future abundance estimates for the region. Alas, high winds and a dropping tide put an early end to our day, although we did get a chance to check on the C-POD in Shearwater Bay and it hasn’t moved an inch since it was deployed by Ruth in December!

Two days of tar road driving later (we didn’t want to chance the boat and trailer on the dirt roads in this rainy summer season) we arrived back in Walvis Bay. During our first day out at sea we didn’t get too many good photos with the dolphins being evasive and the weather cloudy. However, we were excited to discover that two of the marked animals we photographed were Heaviside’s known from the 2008 catalogue! This was a great way to kick off the season and our first confirmed evidence on long term residency of Heaviside's dolphins in Namibia (the general behaviour of the animals at Walvis Bay is so different to those in South Africa that there was no certainty of this characteristic either). Later in the week, “Dave” the bottlenose joined us with three of his friends for a romp around the shipping channels. “Dave” is probably the most boat friendly and photogenic of the bottlenose dolphins in Walvis Bay and does his best to hog the limelight during encounters with him.

Neels Dreyer informed us of a stranded Heaviside’s dolphin in Donkey Bay (on the outside of the Point) and we were able to collect it the next day. It was a small, juvenile male only just over a metre long – the plates in the skull weren’t even fused yet. It was unfortunately too desiccated after a few days on the beach in the Namibian sun to allow for the collection of many samples, but we kept the skull which will be passed on to the museum in due course and got a few basic measurements.

The days have been characteristically cool with bright sunshine on the dunes but clouds over the sea. With any luck, we’ll run into the rumored humpback whale sometime soon…