Tag Archives: Swan River

New Paper: A Tale of Two Soundscapes

I am a little bit behind in posting about my various PhD publications.  But a pretty cool one that came out in the August edition of Acoustics Australia focused on comparing the acoustic characteristics of urban versus pristine coastal dolphin habitats.

I’ve previously spoken about the need to define the soundscape of dolphin habitats and examine patterns of when and where noise occurs.  But whilst we can monitor dolphin acoustic habitats and describe how they are now, in many cases it is hard to say how they were in the past.  We simply don’t have enough long-term datasets that capture the expansion of human activities into the marine environments – i.e. datasets that go far enough back in time to capture when the habitat was pristine and free of human influence.  Understandably, this can also make it hard to decide how we best manage man-made noise in these habitats into the future.  It’s hard to determine what noise mitigation measures are necessary when you don’t know how quiet an area is ‘supposed’ to be.

A potential solution to this conundrum for managing ‘urban’ areas is to find comparable ‘pristine’ areas which are also used by the study species, and see what differences exist.  Of course, this is reliant upon pristine areas still existing in the first place.  However, in Western Australia we are fortunate enough to have some areas up in the remote north of the state.

The Kimberley region in north-western Australia is one of the most remote, pristine wildernesses in the world.  The largest town in the region is Broome, which has a permanent population of only 16,000 people (although the temporary population can increase to 45,000 in the tourism season).  Broome is located on the shores of Roebuck Bay, with a relatively large population of snubfin dolphins and is also regularly used by bottlenose dolphins and humpback dolphins.  This area offers a nice contrast with the busy, urban environment of the Swan River, which flows through the Western Australian state capital of Perth.  This river is also used by bottlenose dolphins.  To create successful noise mitigation strategies for coastal dolphins, there is a need to compare ‘quiet’ and ‘noisy’ acoustic habitats.  Roebuck Bay and the Swan River offer the perfect opportunity to do just this.

Prepping the Roebuck Bay acoustic gear

I chose to compare the pristine soundscape of Roebuck Bay with the Swan River’s anthropogenically-noisiest site, the Fremantle Inner Harbour.  I used autonomous underwater acoustic recorders to monitor the soundscape at these sites, and assessed these using a combination of weekly spectrograms, power spectrum density percentile plots and probability densities, octave-band levels, broadband noise levels, and generalised estimating equations – i.e. a shedload of nifty acoustic analyses.

What these essentially showed were that these two sites are very different in their acoustic characteristics.  In Roebuck Bay, biological sounds (such as crustaceans and fish) were the most prevalent sound sources, with very few instances of vessel noise.  However, in the Fremantle Inner Harbour, man-made noise dominated.  This worked out to a 20 dB difference between sites on average, and the frequencies used by dolphins for communication were more likely to be masked in Fremantle Inner Harbour based on elevated noise levels.

In this study, I was also lucky enough to get some acoustic recordings of sounds produced by snubfin and bottlenose dolphins in Roebuck, and could use these for a comparison with the sounds produced by bottlenose dolphins in Fremantle.  This helped me to discuss the potential consequences on Roebuck Bay dolphins if noise levels were to increase at that site.  Such information is going to be useful going into the future, as several coastal developments are currently planned for Roebuck Bay.

To find out more, check the paper out online or contact me!

Snubbies are happy little dolphins – hopefully they stay that way! (Photo: Sarah Marley)

 

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New paper: Behavioural and acoustical responses of dolphins to vessel traffic and noise

Last night, my sixth (and final) PhD paper was published in the journal Scientific Reports!

In earlier papers, I established that the Swan River is a pretty noisy place.  One of the noisiest sites from an anthropogenic perspective is the Fremantle Inner Harbour, which experiences high levels of vessel traffic.  However, during my initial visual observations I discovered that dolphins continued using the harbour, even though it was a busy noisy environment.  So in this latest paper, I searched for evidence of dolphins responding to boats and noise at a subtler scale.

To do this, I used a combination of visual and acoustic monitoring techniques.  I found that dolphins significantly increased their movement speeds when vessel traffic occurred at high levels.  Similarly, dolphins also changed their behavioural budgets at high vessel densities, spending more time travelling and less time resting or socialising.

I monitored dolphin movement speeds and behaviours, to see how these changed as vessel traffic increased

I also looked for acoustic responses, by measuring nine characteristics to describe the shape and frequencies of dolphin whistles in different noise scenarios.  I found that all nine of these characteristics varied with increasing levels of broadband noise, and that the response was particularly strong for low-frequency noise.

I used nine characteristics to describe dolphin whistles

I’ve spoken before about the importance of scientific publishing, in terms of career brownie points for researchers.  So I’m pretty chuffed to have completed publishing my PhD!  To view the full list of papers from this and other projects, check out my Publications page.  Now to deal with all the ‘leftover’ PhD data that I collected, but didn’t get around to including!

New Paper: Spatial and temporal variation in dolphin acoustic habitats

There is a growing awareness of underwater noise in our oceans and the potential impacts of such noise on marine life, an issue which was the major theme of my PhD thesis.  This is particularly relevant for “acoustically-specialised” species, such as dolphins.  However, before we can start investigating the effects of noise on these animals, we first need to define the soundscape of dolphin habitats and examine patterns of when and where noise occurs.

We get a glimpse of them at the surface – but what about their acoustic habitat beneath the surface? (Photo: Sarah Marley)

This description of noise in dolphin habitats formed my third PhD chapter, which has now been published online in the scientific journal Frontiers in Marine Science.  In this paper, I examine spatial and temporal variability in the soundscape of the Swan River using over 11,600 hours of acoustic data collected from five sites within the river system across eight years.  Multiple sound sources were recorded at these sites, but the prevalence of these sounds at each site differed, giving each location a characteristic soundscape.  Consequently, some sites were ‘noisier’ than others.

Deploying acoustic recording equipment with help from Fremantle Ports. Spot the dolphins in the background! (Photo: Jeanette Murray)

Want to know more?  The full paper is available online! I’d love to hear your thoughts 🙂

Marley et al. (2017) Spatial and temporal variation in the acoustic habitat of bottlenose dolphins (Tursiops aduncus) within a highly urbanised estuary.  Frontiers in Marine Science, 4: 197.

And watch this space, as the remaining three PhD papers should be going up online in the next few months!

 

 

First PhD Chapter Published!

After months of graft, I’m extremely chuffed to announce that my first PhD chapter has now been published online!

Chapter 1 - Marley et al 2016

To view the full article, please visit the Springer website.  If you have any issues, please contact me.

One down, one draft on supervisor’s desk, and three more to go!

Is it a plane? A duck? A police car? No, it’s a fish…

For the last few weeks I have been working on the first chapter of my PhD describing the underwater soundscape of the Swan River.  Overall, this has been a really good way of becoming more familiar with identifying underwater sounds.  By far the most baffling of which have come from fish.

Hard-core headphones are becoming my default fashion accessory at the moment...

All about that bass: Hard-core headphones are becoming my default fashion accessory at the moment…

It turns out that many fish species produce a whole variety of ridiculous sounds, including quacks, knocks, grunts, sirens, trumpets and even Rolf Harris impersonations (sounds like his infamous wobble-board).  These sounds are all produced in different ways:  some are made using sonic muscles located on or near the swim bladder; others sounds are the result of the fish rubbing together or striking its skeletal components; and sometimes even changes in swim speed or direction can result in noise production.

But, like many animal sounds, the purpose of many fish noises is still to be determined.  Sound production might be intentional, in the form of vocalisations or calls, in which case noises are most likely signals to other animals (e.g. to attract mates, warn off competitors, co-ordinate with conspecifics, or raise the alarm about predators).  However, sounds can also be produced unintentionally as the result of feeding or swimming.  And when your subjects are mostly occurring in the cold, dark oceanic depths it can be pretty tricky to figure out the behavioural context of recorded sounds!

The majority of sounds produced by fishes are of low frequency, typically less than 1000 Hz.  By themselves they can be pretty hard to pull out of a large dataset, thus requiring a systematic search through potentially months of data.  But a really cool characteristic of some fishes is that they call in choruses.  This is when multiple (dozens or even hundreds) of individual fish within the same area produce the same call.

These choruses occur all over the Australian continental shelf, in both tropical and temperate waters and were first discovered in the late 1960s.  Many show significant seasonal trends in chorus levels and differences between years, potentially indicating that chorus activity reflects secondary productivity (see “Continental shelf fish choruses in Australian Waters” by Robert McCauley and Douglas Cato).  Others are reliably produced at specific times of year, and are believed to be associated with reproduction (see “Fish choruses from the Kimberley, seasonal and lunar links as determined by long term sea noise monitoring” by Robert McCauley), although the nature and intensity of some reproductive choruses can change in association with physical and environmental cues (see “An investigation into active and passive acoustic techniques to study aggregating fish species” by Miles Parsons).  Thus, these calls can play significant roles in the life function of many species.

Great to know that, in all these long hours you spend sitting at the computer, you are probably listening to fish sex!

Listening to the Sound of Success!

Two different projects came to fruition last week, neatly coming in time for my birthday!  Not so sure about the ageing part, but it was definitely good timing on the research outcomes!

From listening for dolphins…

Earlier this month I spent a morning out on the river with the ‘Destination WA‘ TV crew, filming a short segment about the Swan River dolphins.  We spent a lovely few hours out on the Swan River Trust boat Kwilana (Noongar for ‘dolphin’) whilst the team did interviews with myself, Delphine Chabanne (Murdoch University), Marnie Giroud (SRT), and Jennie Hunt (Dolphin Watch).

It was really interesting to see ‘behind the scenes’ for the filming process, especially given the great camaraderie of the TV crew!

… to interpreting blue whales!

Non-song vocalisations of pygmy blue whalesAnother project success last week was finding out that our paper “Non-song vocalizations of pygmy blue whales in Geographe Bay, Western Australia ” had been published online by the Journal of the Acoustical Society of America!  This study used simultaneous land-based visual observations and underwater acoustic recordings to examine the communication of pygmy blue whales.

These animals are famed for their songs, made up of repeated patterns of notes.  But in this study, we focused on the non-song sounds produced by pygmy blue whales and found six different vocalisations – five of which had never been described for this population before!  Hopefully this will help inform passive-acoustic monitoring for the species.

And as for ‘Older and Wiser’?

Well, that remains to be seen!  But entering 28 as a PhD Student, TV Star, and three-times Published Scientific Author isn’t a bad way to start 😉

Strength in Numbers – citizen science project outnumbers dolphins 28 to 1

Last week I was invited to talk at the latest Dolphin Watch training event.  Not that I need much of an excuse to talk about dolphins in general, but the chance to help introduce 180 new recruits to the Swan River dolphins was definitely not to be missed!

Background:  the Dolphin Watch project

The newest recruits of Dolphin Watch

The newest recruits of Dolphin Watch!

I’ve discussed the Dolphin Watch project in previous posts – but for those of you not in the know, Dolphin Watch is a citizen science project monitoring the dolphins inhabiting the Swan-Canning Riverpark.  It is a partnership between the Swan River Trust (SRT), Curtin University and Murdoch University which was instigated in 2009 to learn more about the bottlenose dolphins residing in the Swan and Canning Rivers.  Since this river system stretches for over 60km, it would be pretty tricky for the researchers to survey alone.  But by creating a network of citizen scientists, we now have eyes throughout the river park!

Dolphin Watch volunteers are generally people who are regular river users – whether they are kayaking up the Canning, sailing through the Swan, or just walking along the river trails!  And if they’re out by the river, then why not report the presence of dolphins?  Of course, it is just as important to know which areas the dolphins are not being sighted in.  This helps us to create a presence / absence map of dolphin sightings, and get a feel for what areas might be particularly important to this population.

Training Time!

Dr Chandra Salgado Kent explains the online monitoring form at Dolphin Watch training

Dr Chandra Salgado Kent explains the online monitoring form at Dolphin Watch training

Twice a year, Dolphin Watch runs training nights for new volunteers.  They get to hear about the purpose of the project, monitoring river health, some background to the dolphins, and how to collect sightings information.  Plus they pick up a pretty snazzy shirt and hat combo, not to mention a tote bag full of Swan River Trust goodies!

Wednesday 26th March was the first training session of 2014 down at Scitech.  Speakers included Marnie Giroud (Program Manager of the SRT’s “River Guardians” program), Dr Kerry Trayler (Principle Scientists at SRT), my supervisor Dr Chandra Salgado Kent, and Piers Higgs (Director of Gaia Resources who developed the Dolphin Watch app).  An amazing 180 new volunteers attending, bringing the total number of Dolphin Watchers to over 700 people!  With only around 25 dolphins in the riverpark, we’ve got a pretty good chance of spotting them!

And now introducing…

My role was to discuss Dolphin Ecology.  So, after a few minutes fighting with the tempremental microphone, I gave a run-down on some bottlenose dolphin life history, previous research, distribution and habitat-use, foraging ecology, and dolphin conservation.  Half an hour just flew by!  The question-time was pretty fun, with lots of good questions about dolphin behaviour 🙂

It was pretty strange being back in Scitech.  Especially doing a presentation there that didn’t involve slime, liquid nitrogen, or a single explosion!  I had quite a bit of nostalgia for the good old days of being an Outreach Science Presenter…  But at the same time, it felt fantastic to stand up and talk about something that I really cared about.  As much as I love setting myself on fire in the name of science, nothing beats talking about your own research!  Although if you have any suggestions on how I can work a fireball into a talk on dolphin ecology, please email them through! 😉

Interested in Joining?

Our next training day will be in August 2014.  If you’re keen on coming along, check out the Dolphin Watch website or shoot me an email for more information!