Fine-Scale Habitat Use and Movement of Humpback Whale, Megaptera Novaeangliae, in Urbanised

Fine-scale habitat use and movement of humpback whale, Megaptera novaeangliae, in urbanised near-shore waters

Background

About 50 000 people enjoyed whale watching at the Gold Coast in 2009 alone. This generated an income for the city of approximately 4.4 mio AUD not including the indirect economic stimulation for the tourism industry. In fact, the stretch of coastline ranging from the very south end of the Gold Coast to the tip of Moreton Island experiences the worlds largest Humpback Whale (Megaptera novaeangliae) migration every year with 8 000 individuals in 2006 (DEWR, 2007) and an estimated 14 000 Humpback Whales in 2010. The IUCN – the World Conservation Union (Hilton-Taylor, 2000) and the Queensland Nature Conservation (Wildlife) Regulation 1994 both classify Southern Humpback Whales as ‘‘vulnerable’’. Humpback Whales annually migrate between their summer feeding grounds in Antarctica to their tropical breeding grounds in winter. The exact timing of the migration period can vary from year-to-year (DEWR, 2007). In general, Humpback Whales are sighted in southern Australian waters in May and migrate slowly up the east coasts. By October the majority of whales have started their southward migration and sightings are rare after November. The Gold Coast area functions similar to a bay in which the current reverses and calm waters become present in particular in October each year (Tomlinson and Foster, 1987). This makes the Gold Coast a unique area as documented by anecdotal reports from fishermen who have seen resting whales on the ocean floor. In addition upwelling occurs along the continental shelf (Tomlinson pers. comment).

The south-east coastline of Queensland is one of the most populated areas in Australia with more than 2 million people - increasing yearly by 10-13% with resultant impacts upon the adjoining marine environment (ABS, 2008). It is one of the most rapidly growing regions in the world (Skinner et al., 1998). Coastal development and tourism activities have the potential to affect the behavior of Humpback Whales. Because of their presence in shallower coastal waters in the South-west Marine Region, they may be susceptible to disturbance from tourism operations and impairment of near-shore waters from coastal development and vulnerable to climate change induced changes in the marine environment. At peak times up to 40 vessels following the Humpback Whales have been reported (Gold Coast Bulletin, 2008). For example, high levels of boating traffic have been found to cause lactating female Humpback Whales and calves to leave traditional inshore areas in favor of offshore waters (DEW, 2007). An investigation on boats in Hawaii and their effects on humpback whale behavior demonstrated the ‘strongest reaction’ in response to the loudest boat (e.g. abrupt course changes, abnormally long dives) (Au and Green, 2000). Ocean currents such as the East Australian Current are likely to shift or even weaken with increased ocean temperatures with unforeseen consequences for migrating marine life such as Humpback Whales. On a smaller scale, interactions between Humpback Whales and boats as well as human construction such as desalination plants and shark nets (Gribble et al., 1998) will increase with predicted development in southern Queensland waters.

While it has been demonstrated that significant populations of marine mammals can coexist with highly developed coastal environments (Chilvers et al., 2005), impacts of and interactions with coastal development on M. novaeangliae are poorly known and the environmental pressure on marine megafauna is increasing. Interpreting the rapidly increasing numbers of Humpback Whales as an indicator of a healthy population is a false judgment. Humpback whales continue to recover from their 90% population decline in the late 1960s caused by decades of whaling. Given the predicted development in southern Queensland waters we expect incidents with gillnets (shark control program) and boats to double or triple as seen in recent years. Even more concerning is an expected increase of death of individual whales due to higher population density in combination with high stress levels caused by depleted krill in Antarctica, temperature and current changes and direct incidents with humans.

To avoid unpopular and costly incidents and improve management of humpback whales in nearshore coastal waters around Australia, information on movement patterns and core activities of humpback whales in relation to physical parameters such as currents and behavioural activity are required in combination with previously collected long term point observations at the east coast of Australia.

Objectives

The main objectives are to collect data on humpback whale abundance, distribution and movement patterns together with physical water properties and to establish community involvement in urbanised coastal areas. This will allow building up knowledge for prolonged and intense studies of humpback whales in the Gold Coast region in the near future. The following elements have been identified as objectives:

û  provide more scientific data on the pathways and behaviours of migrating humpback whales integrating existing information with new techniques

û  establish their long and short term movement tracks over interannual migration

û  repeat measurements and compare between a disturbed and undisturbed region and two different population in terms of fine scale habitat use (based on dive patterns, swimming speed, social behaviour) with a focus on mother/calve and young bulls

û  investigate the value of the Gold Coast region as a migration, resting and opportunistic feeding ground and define percentage of migrating whales utilising the Gold Coast bay

û  involve whale watching community and industry for additional movement and behaviour information

û  measure spatial distribution of currents, temperature, bathymetry, salinity, turbidity during whale migration within 10 km of the Gold Coast shore

û  understand the relationship between movement of Humpback Whales and physical water properties in particular flow

û  potential impacts of urbanisation on the behavioural response of Humpback Whales (shark nets, boats, constructions)

û  observe individual life histories, social role, habitat use, reproductive status and mating systems

û  undertake whale skin biopsy sampling for health status identification (stress indicator) to supplement the track information

û  explore noise levels

û  explore skin biopsy to determine sex and food sources

The gathered information on Humpback Whale distribution and behaviour in the Gold Coast region are the base for recommendations for whale conservation and management strategies that are developed for relevant management bodies in the Gold Coast region to maintain the conservation value of this unique habitat for the whales.

To accommodate the large amount of information required to undertake a holistic and system based approach rather than a collection of unrelated data sets, the project is divided into three stages. Each stage is estimated with a 2-3 year timeframe and includes a number of campaigns to collect project related data. .

Methods

Surveys

Visual surveys are established through land, boat and aerial based observation along the Gold Coast recording abundance, distribution and behaviour of Humpback Whales in particular within the 3nm zone. During the three types of surveys, data will be collected through specifically designed sheets and photographs of flukes and scars. The survey includes the counting number and type of boats (engines), recording boat strike marks, attempted predation (shark bites) or direct recreational diver/boat interactions. Photographs of flukes and scars allow identifying of individuals and determination of individual life histories, social role, migration, habitat use, distribution, and reproductive status. Boat based surveys are undertaken daily for up to 5 hours during whale migration. The location of each sighted whale is determined within a range of 10 m and entered into a GIS based spatial data system. Photographs of flukes are compared using the software “Fluke Matcher” with other available data collections from the east-coast of Australia (Byron Bay, Point Lookout, Hervey Bay). Videos taken during the boat and air based surveys are used to assist in determining behaviour, sex and individuals. Air based surveys are undertaken using a low flying aircraft, high resolution photography and video to count whales and boats throughout a grid system at randomly allocated time intervals.

Land based surveys are undertaken using survey sheets and Theodolites in conjunction with Software for tracking whales. Workshops and presentations at the Gold Coast are used to engage with members of the community. 3-5 people at key location (high buildings along the coast) are trained using Theodolites and up to 50 people are trained to use a simple handheld device for estimating travel speed. Simple survey sheets are also given to people who randomly use the coastal area for recreational purposes. Data sheets are collected at the end of each whale season and entered into the data base.

The information gathered during the surveys are analysed for abundance and distribution of whales, relationship to physical parameters and behaviour.

Behavioural responses are for instance a demonstrable change in the activity of an animal in response to a sound or visual contact. These effects can be difficult to detect due to the cryptic and variable nature of cetacean behaviour, but they can indeed be demonstrated with careful data collection. Examples of behavioural effects include the abandonment of an important activity (e.g. resting) or location (Nowacek et al., 2007). Other more obvious behavioural activities can be related to the mating system. Previous observations at Hawaii wintering grounds have shown that males swim along with preferable large females in different groups. A primary escort spends most of the time close to the female and a secondary escort associates from time to time and experiences strong competitive behaviour (Pack et al., 2009). Such activities are likely to be identified during the migration as well.

Underwater video recording

National Geographic’s Crittercam, a video recording system, documents on the behaviour of individuals and allows establishing of short term tracks by collecting speed, depth, temperature and direction. National Geographic’s Crittercam is used as a data collector to investigate short term behavioural changes. Crittercam has been applied successfully on Humpback Whales in Hawaii and Canada using a suction cup to attach the unit. The system records video and audio data and information on depth, temperature, salinity, direction and flow and can help to define certain water quality preferences. Crittercam combines data with imagery and makes the observation of short term behavioral changes possible. This includes the observation of resting, nursing, competitive behaviour and potential predator. In addition, the gained data will be compared with previous results from Hawaii and Canada to confirm and add to current knowledge.

Crittercam is deployed using a small and mobile vessel and trained operators. During the deployment trials, under water video is taken to determine size and possible sex of individual whales. After successful deployment of Crittercam the recording system remains with the animals for up to two hours and is collected using a VH frequency. The research vessel stays within 500m of the emitted signal to avoid interference.

The tracks of individuals are combined with collected water property information such as currents, temperature, depth and sound and analysed for relationships and behaviour.

Satellite tagging

Satellite tagging techniques have improved over the past years and can reveal movement behaviour previously unknown and over significantly longer time periods than suction cup tags. A small numner of humpback whales are to be satellite tagged to provide longer term information on the movement pattern of humpback whales in particular during southern migration. Currently no data is available for the east coast of Australia ranging from their breedings grounds to southern New South Wales. Satellite tags are the only available methods to allow weeks or month of movement observations in particular in regards to current and temperature changes.

A new, non-invasive technique is being developed for this purpose with a U.S. partner.

Acoustics

Certain frequencies of sound will be recorded by hydrophones strategically located alongside Gold Coast beaches and used for boat noise level determination during the second project stage and at a third stage for potential abundance and distribution measurements of vocalising humpback whales. Continuous acoustic data can be collected using EAR hydrophones (Lammers et al., 2008) deployed on drumlins along the coast. Sound is also collected using Crittercam during deployments and will be recorded for the main frequencies of the most common engines.

Skin biopsy

During boat based surveys whale flakes are collected to allow for skin biopsy. To supplement the track information whale skin biopsy samples for health status identification (stress indicator) are send to our partner at Woods Hole Oceanographic Institute for analyses.

Sex and age determination as well as individual identification can be undertaken using genetics to supplement the Crittercam and survey information. The length of telemores in chromosomes are analysed to determine age and the chromosomes to determine sex (Gillett et al., 2008; Jayasankar et al., 2008). Stable isotopes are sampled to investigate food sources and possible links with size, age and sex.

Water properties

A fine-scale model or spatial resolution of water column profile data including current velocity and direction, depth, temperature, salinity, turbidity, chlorophyll and turbulence is developed. The physical parameters to be measured include water column profile data (current velocity and direction), to be collected by stationary, bottom mounted ADCPs (Acoustic Doppler Current Profilers) and ADCP transect lines from a moving vessel if possible (environment dependant). Furthermore we plan to undertake spot downcasts of CTD (conductivity, temperature, depth), salinity, light penetration, turbidity, chlorophyll and turbulence throughout the water column from a vessel.

The surveys will be undertaken during the south (May-June) and northward migration (September-October). In addition GPS fitted drifter or dissolvable drifters are released during the deployment of Crittercam and water profile measurements are taken to measure surface currents.

EonFusion, a software package for 4 D tracking may be used for modelling and to combine the collected data and run analyses.