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Protocol For Marine Mammal Monitoring

1. AIMS

  • To provide long term extensive and comprehensive data set on cetacean siting areas, behaviour, ecology within the Kisite-Mpunguti MPA & Kilifi local areas.
    • A sub-aim would be to monitor population abundances year round and link any changes with anthropogenic or natural pressures
  • To create a sound library of marine mammal sounds to accompany cetacean siting data for use in monitoring of cetacean species.

2. METHODOLOGY

2.1. Sample Site

The Kisite-Mpunguti Marine National Park (coordinates) lies off Kenya’s south coast just south of Wasini Island, bordering Tanzania. The MPA covers approximately 11km2 while the Mpunguti marine reserve covers approximately 28km2. The area contains exceedingly high levels of biodiversity including approximately 64 genera of coral, 10 species of mangrove and 12 species of seagrass. Additionally the area is highly abundant with marine mammal activity and is regarded as one of the ‘hot spots’ for cetacean spotting on the coast of East Africa.

2.2. Cetacean Siting

There are a number of potential ways in which to conduct this research however for the sake of volunteer level monitoring the two main ones are as follows:

2.2.1. Shipboard random stratified

Pre-planned GPS routes should be methodically spaced (i.e. at set distances away from each other), but randomly placed along a range of different depth contours in order to cover different habitat types. When cetacean activity is spotted, the boat deviates away from the track towards the cetaceans where data can be collected.

With the use of high powered binoculars, observers will use the research vessel as a platform in order to spot and record type of species and numbers of individuals. At the same time, those not observing (they can take turns) will record the GPS location, date & time of day, and if possible direction of travel & behaviour (i.e. feeding, mating, travelling etc). This can be done with a bit of experience and training. At the same time observers should take photo-graphs for ID purposes and permanent record. As majority of marine mammals are highly energetic and therefore difficult to photo-graph, a good suggestion is to set cameras to high shutter speed or sport picture mode (most modern cameras will have this setting) which allows the observer/photographer to hold down the shutter and take a sequence of pictures and then select the most favourable.

The photos will then be analysed back at the lab along with the collected data where using the mark-recapture technique, abundances, behaviour and migratory routes can be calculated.

2.2.2. Distance Sampling from line transect surveys

This method is similar to the previous method, however is much more intensive in terms of effort required. Consequently the data collected is far more valuable.

As before pre-defined tracks should be methodically spaced and randomly placed encompassing a range of habitats and depth contours. In theory it is often best to cross depth contours as perpendicularly as possible. Transects can also have a zigzag pattern which will cover more parts of the MPA and may vary in length.

During the searching effort the boat will not deviate from the transect lines while observers, using high powered binoculars, will spot cetacean activity. On the occasion when cetaceans are spotted, searching effort will be terminated and the vessel will turn its direction towards the cetacean group. Photos should be taken, again for mark-recapture data.

This time, in addition to GPS location, time of day etc from the previous section (section 2.2.1.); distance to transect; angle of cetaceans to transect; and any human activities within the area (e.g. fishing) should be recorded. Additionally boat speed, visibility, wind speed and direction, water temperature, and sea state (Beaufort scale) should also be recorded.

In order to properly estimate abundances, correction factors must be applied in order to account for missed sightings of individuals close to the transect, environmental conditions, and boat type.

2.3. Underwater Acoustic Recording

Underwater hydrophones will be placed underwater once cetaceans have been spotted. The hydrophones must be placed on the same side and position of the vessel each time data is recorded. The recording device should be set to record continuously and be placed into the water column so as it completely covers the recording part for sufficient time to record (this may vary, but 5 minutes can be a bench mark although testing in the field will give a better idea). The sound data will be analysed back at the lab onshore.

The sound data collected will accompany the siting and photo-ID data whereby individuals may be distinguished from the sounds and matched to the corresponding photograph. This is especially useful for certain species of marine mammal that do not break the surface of the water very often (e.g. humpback & Risso’s dolphin), and subsequently are difficult to spot/photograph on a regular basis. Instead the sound data can be used to ID them on that occasion.

As the computer software program is able to display sound in a spectrogram time series, the sound data should also be able to provide information on behaviour and so linking behavioural activity to certain pitches and sound activity within a pod should be looked into.

Additionally the software can also provide distance and bearing of cetaceans to the device/boat, therefore accurate estimates of distances of cetaceans to transect lines as well as bearing angle to transect lines can be calculated if the distance sampling from line transect surveys (section 2.2.2) wish to be conducted. This data should be recorded regardless.

3. MANAGEMENT

DPSIR Framework

In order to make management decisions as a result from potential detectable change, protocol should follow the DPSIR framework approach to conservation. DPSIR stands for: Driver; Pressure; State; Impact; Response. See Fig. 2 for examples and explanation.

The DPSIR framework approach for conservation
Fig. 2 The DPSIR framework approach for conservation

The DPSIR framework allows for an easy way to identify where problems/threats lie within
an ecosystem. Therefore allowing for easier ways to present findings to people in authority.

For example government officials, game departments etc so as to make informed decisions
and policies based on good scientific data.