Eavesdropping on Whales: Describing Fin Whale Presence using Passive Acoustic Monitoring

Tal Koubi-Bahar & Jemma McKinnon

age 15 | Halifax, NS

Shambhala School Science Fair Best in Biology Award | Halifax Sci-Tech Expo: Best Biology Project and Medal of Excellence

Edited by Vanessa Poirier

Worldwide, whales are endangered due to various threats, such as illegal whaling, unstable climate, and commercial fishing, to name a few. In order to mitigate these threats, we first need to know where and when whales are present, and one way to do that is to track them using their calls. Our goal was to determine if there was a correlation between the duration of fin whale presence and season. We analyzed recordings of fin whale mating calls collected in 2016-2017 in Emerald Basin, Nova Scotia for hourly presence by month. A chi-square test showed a significant difference in hourly presence by month, where presence was up to 100% in colder months, and down to 0% in warmer months (May and June). This suggests that Emerald Basin is an important habitat for fin whale mating. We suggest that by engaging conservationists and encouraging them to consider our information on fin whale presence, conscientious decisions related to human activity in Emerald Basin could be made to reduce harm.

INTRODUCTION

Many species of whales are endangered because of pollution, overfishing, commercial boating, and illegal whaling (Thomas et al, 2016). To best protect them against these threats, we first need information on their occurrence. One way researchers find this information is by tracking their movements and presence using their calls (Zimmer, 2011).

Whales call to each other to communicate, and when recorded, these calls indicate their presence, and sometimes behaviour, in a particular location at a particular time. Researchers use passive acoustic monitoring, using technology to passively listen and record ocean sounds in a particular area over a determined amount of time (Zimmer, 2011). This can determine the presence of whales, and even threats they may encounter. Passive acoustic monitoring works best for species that have distinct and frequent calls (Zimmer, 2011). Luckily for researchers, fin whales are one such species, which allows researchers to track them easily.

Fin whales’ most common call off Nova Scotia is referred to as the 20Hz call, which is a burst of sound at the 20Hz frequency (Watkins et al, 1987); (Figure 1). Fin whales will repeat this call as frequently as 15 seconds between calls, and though it is believed to be primarily used in mating, it can be heard year-round (Watkins et al, 1987). As this call is both specific to fin whales and frequently emitted, the 20Hz call is the perfect candidate call for passive acoustic monitoring, and we can use it to track their presence through space and time.

The purpose of this study was to use the hourly presence of the fin whale 20Hz call to determine the seasonal preference of fin whales for a particular location off Nova Scotia, known as Emerald Basin. We used fin whale calls to see if there is a correlation between their duration of stay and seasons. We were interested in the duration of fin whales by season in Emerald Basin to determine if this is a significant location for the whales at any time. Emerald Basin is site to a significant amount of fishing, as well as Halifax-bound shipping routes.. The more we know about fin whales and how areas such as Emerald Basin are important to their life cycles, the more we can work towards conserving them.

**Figure 1:** A spectrogram showing fin whale 20Hz pulses. Pulses appear as small orange blips at the bottom of a purple screen. Spectrogram made in PAMlab (JASCO Applied Sciences Ltd.)

MATERIALS & METHODS

We used underwater recordings of fin whale calls collected in 2016-2017 by Fisheries and Oceans Canada in Emerald Basin, an area of ocean off Nova Scotia (Figure 2). These recordings previously were analyzed by a researcher from Fisheries and Oceans Canada for daily fin whale presence. We used a program called PAMlab (JASCO Applied Sciences, Ltd.) to look for fin whale calls in recording files (see Figure 1 for example). Fin whale 20Hz pulses appear as a small orange blip of sound that consistently appears on the lower half of the computer screen multiple times. We checked every hour of 24 consecutive hours of one day per month between October 2016-September 2017. To keep the recording day consistent, we analyzed the data from the 15th day of each month. Every hour with a fin whale call was marked with a “1,” indicating presence, while a lack of fin whale calls was marked with a “0” in a Google Spreadsheet.

Once we collected all the hours with fin whale presence per month, we calculated the mean and standard deviation of how many hours per day a fin whale was present in Emerald Basin. A bar graph shows the percentage of hours with fin whale calls in a day, per month (Figure 3). We used a chi-square test to test whether the whale’s calling behavior and presence had changed significantly between months.

**Figure 2**: Screencap showing Google Earth map of Emerald Basin, Nova Scotia, and relative locations.

RESULTS

Fin whales were heard an average of 13.92 hours (± 8.22 standard deviation) per day across the year. Using a chi-square test, we compared the number of hours within a day per month that fin whales were present at Emerald Basin (Figure 3). The difference in hours with calls between months were statistically significant (χ 2 11=53.38, p < 0.001). In months May and June, there was a complete absence of fin whales where in comparison to October, the whales were there 100% of the time (Figure 3).

**Figure 3**: A blue and white bar graph showing the percent of hours with fin whale presence in a day per month in a year long period (October 2015 - September 2016) recorded at Emerald Basin, Nova Scotia.

DISCUSSION

Our objective was to determine if there was any correlation between seasons & duration of fin whale stay in Emerald Basin, and our results show that there is. Fin whales produce fewer 20Hz calls in the summer at Emerald Basin, and their peak calling is in colder months. We were specifically analyzing a known mating call, so this pattern is likely due to fin whales primarily breeding during colder seasons, therefore leading to higher presence of their mating call during that time. This means that Emerald Basin is likely a crucial place for the purpose of fin whale mating. Being aware that fin whales search for mates during colder seasons means that this time period is very important in order to sustain and grow fin whale population numbers. This means that during the fall and winter months of September-November, threats to fin whales endanger current, and future, generations. Therefore, it would be ideal to lower the amount of threats around Emerald Basin during mating seasons such as ship traffic & other dangerous fishing materials. The research we conducted gives a partial picture of fin whale presence, as we only analyzed one of the three known fin whale calls, and studied only one location. Expanding this project further could include analyzing all known fin whale calls in Emerald Basin, or to other locations in Nova Scotia. In addition, we could include visual observations of the whales alongside their calls. Practical applications of our work would be engaging conservationists and encouraging them to consider our information on fin whale presence when making decisions around human activity such as commercial fishing and shipping routes that could harm the whales in Emerald Basin.

CONCLUSION

We discovered that fin whale presence in Emerald Basin is higher during the winter and fall. Using this information, we can make plans to protect the fin whales from further harm during these months.

acknowledgements

We would like to thank Dr. Hilary Moors-Murphy at Fisheries and Oceans Canada for access to the acoustic recordings. Without these recordings, we would not have had any data on fin whales and so would not have been able to begin our project in the first place. Thank you JASCO Applied Sciences, Ltd. for access to PAMlab to analyze these recordings. Most importantly, we had a significant amount of guidance in each step of our project from our supervisor, Gabrielle Macklin (M.Sc.). We would also like to thank Inbal Bahar for initially suggesting we reach out to Gabrielle, JD McKinnon for driving us to every science fair meeting, and our science fair teacher Mr. Fletcher for his assistance and guidance through the science fair process. We have Gabrielle and everyone else who assisted us along our way to acknowledge, as this project would not be possible without them.

BIBLIOGRAPHY

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