Acoustic surveys of Humpback Whales in Southern Mozambique

Mozambique is endowed with a diverse suite of tourism assets. Many of which are focussed around their biological riches both on land and in the water. In 2005, an estimated 130 million USD was earned through the tourism sector and is growing at a rate of 15% per annum (Tourism in OECD Countries 2008: Trends and Policies). Yet, Mozambique is also rich in resource assets and, given its 2500km coastline, also offers a wealth of opportunity to provide import/export infrastructure for land locked African countries such as Zimbabwe, Botswana and Zambia. Given this, a recent memorandum of understanding between Zimbabwe, Botswana, and Mozambique was signed to develop a port primarily for coal export in southern Mozambique, south of Maputo in the Ponta Do Ouro Partial Marine Reserve (PPMR). While existing port infrastructure exists in Maputo, the shallow water, and need for continual dredging has encouraged the Mozambique government to re-investigate its options south of Maputo within the PPMR. This region was initially earmarked for development in the 90's and plans were abandoned on environmental grounds. However, although the specifics on timing and beginning of development are clouded in secrecy, the port development has been recognised by the PPMR management plan as a major threat to the future of the region.

In 1995, the U.S. National Marine Fisheries Service (NMFS) set underwater “do not exceed” criteria for exposure of marine mammals to underwater pulses from seismic airguns to prevent injury. These criteria included sound pressure levels (SPL) of 180 dB re 1 μPa for mysticetes (including humpback whales). However, behavioural disturbance criteria for pulsed sounds have typically been set at an SPL value of 160 dB re 1 μPa, (Southall et al., 2007), and behavioural disturbance has been observed with received levels as low as 140 dB re 1 μPa (McCauley, 1998). These levels are typically over a bandwidth of 1 Hz to 10 kHz. However, recent data indicated that humpback whales produce some signals with harmonics extending above 24 kHz (Au et al., 2006), extending the upper limit of the hearing previously thought to be around 10 kHz. Anecdotal evidence suggests that in the PPMR the humpback whales can be less than a hundred metres from the shoreline. Indeed, in this area many whale surveys are shore-based (Findlay and Best, 1996). This implies that the humpbacks could be well as close as a few hundred metres from the port construction zone, if work is conducted during times of migration. Simple models of transmission loss would estimate construction noise SPLs could exceed the behavioural disturbance criteria levels of 160 dB re 1 μPa at receiver (humpback) ranges likely to occur around the port. Therefore it is feasible that if construction occurred during whale migration, without noise management many humpbacks could be exposed to SELs of sufficient level in induce behavioural disturbance, possibly the levels thought to induce physical injury in this taxa.

Legislation around environmental impacts exists and requires all sectors to adhere to internationally accepted processes (screening, scoping, consultation, assessment of impact, review, and monitoring and evaluation), yet in practice, numerous problems limit the effectiveness of the process. Among many communication issues across governmental ministries and offices other more difficult to overcome problems limit the effectiveness of Mozambique’s EIA Act (Decree 45/2004). These relevant to the current project include - A shortage of technical expertise for evaluating environmental impact in Mozambique; Absence of legislated environmental standards against which impact can be measured; And, a lack of clarity and overlap of environmental management roles and responsibilities among government sectors (Mozambique Biodiversity and Tropical Forests 118/119 Assessment, USAID, September 2008) this last point is exemplified in the current plans to develop a port in a protected area. In general there is a requirement under the EIA Act that all developments which will effect coral reefs, mangroves, zones of conservation or protection, and zones containing endangered species of animal or vegetation, habitats and ecosystem; require an EIA assessment (Walmsley, B and Tshipala, K.E 2007). To our knowledge however, there has been no EIA work in the region related to the proposed development. Therefore, the study proposed here will be an important contribution to the EIA process and evaluation of the suitability of the site.

While globally humpback whales have been changed from their 'vulnerable' status in 1998 to 'least concern' in 2008 on the IUCN red list this is largely due to the global range of the species combined with the data collected in developed countries and the change in the 'vulnerable' threshold criterion between the two assessments from 20% of population to 50% (IUCN, 2012). Studies of humpback whales in Australia have shown a population increase rate of around 10% per annum since the cessation of whaling (Findlay et al., 2011; Salgado Kent et al. 2012). This has been expected for the coast of Mozambique, however, preliminary results were drawn from shore based surveys. There is limited data on the overall population along the east coast of Africa and any detrimental effects of the port development could have a significant unknown impact on the migrating stream. Three migratory streams have been hypothesised for the southwestern Indian Ocean to breeding grounds for C1, C2 and C3 populations of humpbacks. It is anticipated that whales passing the proposed port location would be of the C1 and possibly C2 breeding stocks. The last survey in the region was conducted in 2003 by Findlay et al (2011) using vessel line transects to provide a snapshot of the winter breeding stock distribution. This survey was conducted at a time to record the maximum number of whales, but does not show the temporal distribution of whales passing the port site. 'Snapshot' surveys are also confounded by temporal variations in migration trends which have ben shown to vary by up to five weeks between years. Additionally, since that study, little data has been available to provide a basis for the current state of the stock from which management decisions can be drawn and any impacts of the port construction can be compared. The need to provide estimates of temporal distribution of the migrating whale population prior to development is therefore paramount if we are to accurately assess any impacts of port construction and subsequent use.

Globally, the CMST has been a leading research group in underwater acoustics for over two decades and on humpback whales over the last decade. The group boasts a number of internationally renowned experts on marine bioacoustics, anthropogenic noise, the effects of underwater noise on marine fauna, marine mammal survey and underwater acoustic propagation, each of which is required to accurately conduct this study. Additionally, the CMST is also one of the lead organisations in a current international study on the impacts of seismic survey on the great whales and routinely conducts acoustic and visual surveys of vocal marine fauna.

This work will build on other initiatives that have been established and are ongoing within the PPMR for the last three years by Dr. Caine Delacy. Since the inception of the PPMR, Dr. Delacy’s research group has been monitoring the status of reef fish and coral communities. The goals of these studies are to monitor the increase in abundance and biomass of target fish species, health of coral populations and changes over time due to climate change. The latter is particularly important given the these high latitude coral reefs are most likely to be the first to show impacts from increase water temperatures and tropicalisation of the fauna. In concert with these research projects Dr. Delacy has also developed relationships with the local marine park managers, decisions makers and local business owners. These community members are critical in maintaining efficient operation of any research program in the region and these relationships are not trivial to gain. He has witnessed first hand the whale migrations and knows the value of the whales to local and national economies through ecotourism, but also recognizes the importance for one of the world’s poorest countries to gain economic prosperity through port developments and the fiscal rewards that a port will bring to a struggling national economy.

Firstly, these data will provide the baseline and framework for management decisions regarding the timing of construction phases of the port development. Knowing when the whales arrive, the proportion of the population around at a given time, and how long for, can help implement strategies to minimize acoustic noise from construction and hence stress on the animals.

Secondly, the effects of anthropogenic noise on marine fauna are becoming increasingly understood and globally guidelines on acceptable levels of sound production during construction and seismic study are being enforced. Data from the deployed array of hydrophones offers the ability to localise individual callers and anthropogenic noise sources. The result is to estimate the sound exposure levels whales are likely to experience as they pass by the site and subsequent the impacts of the sound on them. This will help determine whether measures are required to limit the noise generated as per Resolution 10.24, Points 3 and 5 and the extent of measures to match global standards of sound exposure levels which impact the behaviour and health of cetaceans. This knowledge of construction noise source level and its propagation can also be applied to other local mega fauna. For example, modelling the propagation of construction noise to areas inhabited by dugongs and turtles to estimates the sound exposure levels any animal present is likely to experience during construction

Thirdly, the expansion of Mozambique's port infrastructure and the continual increase in eco-tourism that rely on marine megafauna for income cannot go without balancing the needs of both of these important income sectors of the economy. Therefore these data will ensure that both sectors can move forward without significant impacts to economic growth as Mozambique emerges from its poor economic state.

Finally, this study will develop infrastructure and research capacity for an on-going monitoring plan. Engaging local research teams and communities promotes education and provides avenues to ensure long-term monitoring can be carried out involving those it will affect most. If successful this project can be expanded to examine whether humpbacks merely avoid the port or change migration patterns on a larger scale.

Providing marine management with accurate information on anthropogenic noise levels and their transmission is the first and most vital step to ensuring the whales are not subjected to excessive and detrimental levels of noise during their routine behaviour. On-going monitoring of their numbers and broadscale behaviour ensures that any possible impacts are observed and future steps may be taken to limit their effects.   

Within this project training of Mozambique researchers and students will also be a planned in order to build capacity within Mozambqiue, relevant to underwater acoustic techniques. This training and subsequent skills will allow Mozambican researchers to continue the planned study, but also apply these techniques towards other marine mammals that are important to Mozambique such as Dugongs.  

Acquire acoustic data on humpbacks and construction noise; Local researchers/management engagement; Final report including comments to address UNEP/CMS/Resolutions 9.19 and 10.24

Description:Deploy/retrieve noise loggers
Fecha de inicio:01 August 2012
End date:01 August 2013
Output:Acoustic data acquired and quality assurance conducted culminating in interim report.
Description:Workshop on passive acoustics to involve members of the PPMR and Mozambique researchers and students to train them in the deployment of the acoustic equipment, their use, and how to use them for monitoring marine mammals
Fecha de inicio:01 December 2012
End date:
Output:Rangers trained in the basics of marine bioacoustics and the deployment of acoustic equipment. Students and researchers will learn about these techniques to build capacity within Mozambique
Description:Data analysis/report writing
Fecha de inicio:
End date:01 August 2013
Output:End of year Report including abundance estimate and temporal pattern of migration.

No hay fotos para Acoustic surveys of Humpback Whales in Southern Mozambique

Implementing AgencyCentre for Marine Science and Technology
Collaborating agenciesDr. Caine Delacy, Adjunct Lecturer, University of Western Australia [email protected] +61409317615 The Ponta do Ouro Partial Marine Reserve, as the National agency to co-implement the project. Contact- Miguel Gonçalves- [email protected]

Activity start dateAugust 2012
Activity end dateAugust 2013
CMS AppendixAppendix I
Taxonomic groupMarine mammals
Target regionAfrica
Target countryMozambique
Final technical reportNo

Habitat loss and degradation
Infrastructure and service corridors
Residential and commercial development
Human Disturbance


Hechos e información sobre la enfermedad del coronavirus (COVID-19) y la vida silvestre migratoria. Aprende más