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There is an urgent need to monitor and protect the marine environment in the Greater Dyer Island area. Specifically, to date, no fine-scale long-term study has been carried out in the area concerning the distribution and behavioural patterns of cetaceans (marine mammals). The area is facing potential development and is already under impact from various forms of marine tourism. Cetacean species known to use the area include the endangered Indo-Pacific humpback dolphins (Sousa chinensis), southern right whales (Eubalaena australis), humpback whales (Megaptera novaeangliae), Bryde’s whales (Balaenoptera edeni), Indo-Pacific bottlenose dolphins (Tursiops aduncus) and common dolphins (Delphinus capensis). Many of these species are listed as either Data Deficient or Vulnerable on the IUCN list.

The area is exposed to a variety of potentially detrimental human impacts. Collecting data now is therefore important as the area is already impacted by the shark cage diving industry, boat-based whale watching, and leisure boats, as well as a potential site for an aquaculture and a nuclear power station.

Aquaculture
The effects of aquaculture on cetaceans are not well studied. Some threats such as animals becoming entangled in anti-predator nets are clear. Many others are quite subtle and difficult to measure. Habitat loss may be one of the largest impacts of aquaculture on near-shore dolphin populations. Observations of dolphins around shellfish farms show clear patterns of avoidance and reduced usage of the farm. Loss of these key habitats could have important population level impacts for cetaceans.

Nuclear Power Station
Potential impacts of a nuclear power station include:
(1) Increased water temperature (estimated up to 12° C around outlet pipes).
(2) Increased background noise (unknown).
(3) Up to 10.07 million m³ of sediment discharged into the water column.
(4) Water intake and output (risk of animals being sucked in).
(5) Contamination (chlorine, sewer discharge during pipe cleaning and flushing).

It is not known how these impacts will affect the cetaceans in the area.

Tourism and leisure boats
The area is highly important as a recreational and tourism location. Depending on weather, the eight shark cage diving boats and two whale watching boats use the area on a daily basis. There is strong evidence showing clear behavioural changes in many species of cetacean caused by boat traffic, including horizontal avoidance, longer dives, increased speed and changes in vocalisation. More recently, longer term studies have shown that these short-term behavioural changes may accumulate into larger population-scale effects including temporary and permanent emigration of some individuals from key habitats.

Objectives
This study will address the following questions:
• What is the seasonality of cetacean species using the area?
• How long do the different species of cetaceans stay in the area?
• Do different cetacean species use the area differently?
• Do certain individuals use the area more frequently than others?
• What types of behaviours are observed in the area?
• What is the seasonal pattern of the different types of behaviour?
• How vocal are the cetaceans in the area?
• What are the seasonal and diurnal patterns of vocalisation?
• Can we use these vocalisations to monitor cetacean habitat use?

The result of this study will allow us to address conservation issues relating to the development of the area including identifying key areas and times that are of maximum conservation priority. Knowledge provided by this study can be utilised in future decisions concerning the protection of the marine environment and will contribute directly to the protection of the cetacean species located in this area.

This study is the first of its kind in South Africa. The project implements the combined methods of passive acoustic monitoring, theodolite tracking and the creation of an archived long term (11 years) database of opportunistic observation data from the Dyer Island Cruises whale watching vessel.

Methodology
This study will use three main methods:
• Passive Acoustic Monitoring (PAM) using four bottom mounted DSG-Oceans (Loggerhead Systems).
• Land-based tracking of cetaceans using a surveyor’s theodolite (a precision instrument for measuring angles in the horizontal and vertical planes).
• Unique dataset of 11 years of observations from a commercial whale watching boat.

Passive Acoustic Monitoring
Cetaceans are highly vocal animals, relying on sound for orientation and communication. PAM enables the researchers to monitor an area acoustically. Cetaceans spend the majority of their time submerged. Thus, passive acoustic techniques have the advantage over visual methods in being able to detect animals with substantial dive times, at night, and in poor weather.

Detection rates of cetaceans using acoustic methods can be five to eight times higher than visual techniques. When combined, visual and acoustic survey methods maximise the detection probability of marine mammals.

Four specialised acoustics recorders will be mounted on the sea floor recording vocalisations and background noise in the study area to indicate the presence/absence of animals. The acoustic recorders are being deployed on the sea floor from June 2011 to June 2012, recording for one to two months at a time. Two are in two bay areas, Pearly Beach and Franskraal, which enables the comparison of the two areas.

The maximum frequency of the acoustics recorder is up to 80 kHz, which is ideal for baleen whales as well as dolphins. Even if the dolphins can produce sounds which are well above 40 kHz (echolocation sounds) they also produce whistles and pulsed calls that are below or contain frequencies below 40 kHz.

Baleen whales use low-frequency sounds well below 1 kHz. The sound production of the southern right whales off the South African coast has not yet been intensively studied. However studies from Argentina show that the sounds of the southern right whales are concentrated in the frequency range from 50 to 500Hz.

Theodolite tracking
A theodolite is being used in combination with the four recorders, as not all individual cetaceans vocalise. The theodolite is land based and is used to track the whales and dolphins. Data is collected during daylight hours from two main observation stations: Pearly Beach and the Franskraal Mountain, on an alternate schedule. Each shift consists of three observers: one skilled observer and volunteers from the Dyer Island Conservation Trust volunteer programme, as well as local students. Binoculars and the naked eye will be used during all daylight hours between 30 minutes after sunrise to 30 minutes before sunset. Once seen, groups of animals will be tracked spatially using a surveyor’s theodolite and their behaviour observed with a 30X magnification spotting telescope.