Music of the ocean: The importance of fin whale vocalizations

By Adrianna Davis, SRC intern

The fin whale (Balaenoptera physalus) is the second-largest baleen whale (Figure 1). They can grow to be up to 85 feet in length and 80 tons. Their large size made the fin whales a target for commercial whalers in the mid-nineteenth century, ultimately reducing their population (NOAA Fisheries). Currently, fin whales are an endangered species with a population of approximately 100,000 individuals (Duna & Nábelek 2021). 

Figure 1: Lateral illustration of a fin whale (Balaenoptera physalus) (Source: NOAA Fisheries)


Fin whales, like other cetaceans, have a unique vocalization pattern. They produce primarily 20-Hz and 40-Hz frequency downswept calls (Wiggins & Hildebrand 2020) that are short (<1 s) and repeat every 7 to 40 seconds for up to ten hours. These vocalizations are strong and can reach up to 189 dB (Duna & Nábelek 2021). The calls serve to establish and maintain contact with other whales and attract a mating partner (Wiggins & Hildebrand 2020).  

Over the last several decades, the amount of noise in the ocean has increased. This increase is due to more frequent anthropogenic activity in the ocean, including ship traffic and ocean bottom studies. Seismic airgun array is one example of an ocean-bottom survey. These arrays are primarily used to find oil and gas in the subsea strata but are also used for research. The sound pulses produced from airguns are fired every 8-15 seconds for periods lasting longer than 24 hours. Many arrays last for months and are conducted over thousands of square kilometers (Dunlop et al. 2017).  

Although the impact of anthropogenic sound sources on marine animals has been studied for more than 30 years, little is known about the severity at which it impacts them (Dunlop et al. 2017). The low-frequency bands utilized by marine mammals for communication, navigation, and foraging are dominated in many areas by the noise from traffic and ocean-bottom surveys (Castellote et al. 2012), so it is possible that they are negatively affected by the background noise in the ocean. Concerns arise about the repercussions for the conservation of the populations being impacted (Dunlop et al. 2017), especially if they are endangered, like the fin whale. One study was done in the Mediterranean Sea, which has the highest background noise levels of the ocean basins, as well as the Northeast Atlantic Ocean. The researchers found that fin whales were displaced and their singing behavior altered by anthropogenic noise sources. Although these effects were non-lethal, they are still concerning, as they increase the energetic costs of living for the whales (Castellote et al. 2012).  

Fin whale songs may be used to complement seismic studies, such as airgun arrays. Fin whale vocalizations are strong and detectable over long distances; their source levels are comparable to noise from large ships. Ocean-bottom seismometer stations, used for monitoring earthquakes, often pick up fin whales’ vocalizations, as part of the energy from fin whale calls can transmit into the ground as a seismic wave (Figure 2) (Duna & Nábelek 2021).  

Figure 2: (A) Spectrogram of an unfiltered fin whale song (B) Song section (C) Single whale call magnified from the song section (E) Travel path used to estimate the whale distance from the OBS (Source: Duna & Nábelek 2021)

In a study done by Duna and Nábelek, fin whale recordings were analyzed from three OBS network stations. Six songs, two from each station, were analyzed (Figure 3). The three sites’ results were consistent with observations made from previous seismic surveys, indicating that fin whale calls can potentially be used for seismic imaging; however, the fin whale results gave a lower resolution than the airgun surveys. This could be due to the narrower frequency band and lower dominant frequency of the calls. Other whales, such as sperm whales, may provide higher resolution results, as their vocalizations are higher-pitched (Duna & Nábelek 2021).  

Figure 3: (A) Travel paths of whales in relation to the OBS network and seafloor bathymetry
(Source: Duna & Nábelek 2021)

There are many ways that anthropogenic activity has changed the oceanic ecosystem. The impacts of background noise due to ship traffic and seismic studies are poorly understood; however, they are likely to have a negative impact on marine species, especially those who rely on using vocalization methods, such as whales and other marine mammals. Using whale frequencies as a complement to ocean-bottom studies could decrease the demand for other more invasive techniques. They would also emphasize the importance of having those species in the ocean and could foster conservation efforts.  


Works Cited 

Castellote M., Clark C.W., & Lammers M.O. (2012). Acoustic and behavioural changes by fin  whales (Balaenoptera physalus) in response to shipping and airgun noise. Biological Conservation, 147(1), 115-122. doi:10.1016/j.biocon.2011.12.021 

Dunlop R.A., Noad M.J., McCauley R.D., Kniest E., Slade R., Paton D., & Cato D.H. (2017). The  behavioural response of migrating humpback whales to a full seismic airgun array. Proceedings of the Royal Society B: Biological Sciences, 284(1869). doi:10.1098/rspb.2017.1901 

Duna V.M., & Nábelek J.L. (2021). Seismic crustal imaging using fin whale songs. Science,  371(6530), 731-735. doi:10.1126/science.abf3962 

NOAA Fisheries (n.d.) Fin whale (Balaenoptera physalus). Retrieved from 

Wiggins S.M., & Hildebrand J.A. (2020). Fin whale 40-Hz calling behavior studied with an  acoustic tracking array. Marine Mammal Science, 36(3), 964-971, doi:10.1111/mms.12680  

The transfer of energy within a food chain: Why do large whales feed on small plankton?

By Meagan Ando, SRC intern

The ten-percent rule toward energy transfer among levels of a trophic system is one that has been used to study ecosystems’ energy dynamics for a long time. But, in order to understand it, one must have a basic understanding of a food chain (Figure 1). Food chains describe the transfer of energy from its source in plants, through herbivores, up to carnivores and onto higher order predators (Sinclair et al. 2003). These different “levels” are known as trophic levels, which is properly defined as the position within the food chain or energy pyramid that an organism can be found. But how much energy is passed along through each level? This is where the ten-percent rule comes in.

Figure 1: An example of a food chain. The first trophic level consists of primary producers gathering energy from the sun, which will be passed up to herbivores, then multiple levels of carnivores (source:

Food webs are often pretty short, which confused many scientists for a long time. Ever wonder why such a large whale feeds on such small planktonic organisms, such as krill? The evidence for the evolutionary advantage of this strategy lies within the definition of the ten-percent rule. When energy is passed along throughout an ecosystem from one trophic level to the next, only 10% of the energy that the first organism receives will actually be passed along. The way in which to study this phenomenon has certainly presented it’s difficulties, as it is clearly impossible to actually visualize the transfer of energy. However, the primary means for determining what marine organisms eat is to study their stomach contents, which is exactly what Reilly et al. 2004 did.

It was known that the International Whaling Commission (IWC) along with the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) shared a common curiosity in the idea of the feeding ecology of Baleen whales. This was significantly due to their interests in efforts to place management decisions within an ecosystem context (Reilly et al. 2004). The most efficient way for them to determine their prey sources was to estimate krill consumption by various species of Baleen whales in the Southern Atlantic region during the summer feeding season in the year 2000. In order to successfully draw these estimates, inferences had to be made pertaining to how frequently the whales actually filled their stomachs. This included diurnal change in the forestomach content mass, which ended up producing estimates of 3.2-3.5% of body weight per day (Figure 2) (Reilly et al. 2004). To follow through with the energy tests, four ships participated in the survey to weigh the stomach contents of whales that were unfortunately killed for commercial or research whaling.

Figure 2: Daily consumption rates determined by the four models pertaining to various baleen whales (Humpback, Fin, Right, Sei, and Blue) (Reilly et al. 2004).

In total, 730 cetacean sightings were recorded which included 1,753 separate individuals. It was determined that 83% of the annual energy intake for the whales in this region occurred during this
120-day feeding span in the summer season. The range of total consumption was 4-6% of the standing
krill stock (Reilly et al. 2004). This percentage was derived from the fact that the initial stock included approximately 44 million tons of krill, of which the whales consumed somewhere between 1.6 million and 2.7 million tons (Reilly et al. 2004). These numbers allowed the scientists to make connections between food consumed and the total amount of energy a whale needs to carry out daily bodily functions to survive. It also allowed them to draw conclusions based on where they feed to better protect threatened animals as well as to tweak quotes set for the commercial exploitation of krill, as it is their main food source.

With all of this in mind, it still may not make sense as to why such a large animal would feed on some of the smallest organisms in the ocean. Blue whales, which can be 20-30 meters long, feed on shrimp-like krill that are a mere 2-3 centimeters long. As stated above only ten percent of the energy obtained from one trophic level gets passed along to the next trophic level. For this reason, ecosystems with longer food chains are proven to be, on occasion, less stable than those whose food chains are shorter (Sinclair et al. 2003). Therefore, it is more advantageous for the whale to eat animals on a trophic level in which there is more energy available to be taken in. Hill et al. 2018’s textbook Animal Physiology describes this concept in more depth. In it, they contrast two different possible mechanisms by which a whale can obtain food. One is for the whale to eat fish that are somewhat smaller than themselves. These fish can potentially eat fish that are slightly smaller than themselves, and so on. In this case, there are many trophic levels that the energy will have to pass through before reaching the whale. To apply the ten percent rule directly, we can say that the primary producer produces 10,000 units of energy obtained from the sun. The crustaceans that feed on the producer will generate 1,000 units of energy, from which the small fish that feeds on them will produce only 100 units of energy. The larger fish that feeds on this fish will produce only 1 unit of energy, which may not be enough to sustain the large whale. This is why Baleen whales have evolutionarily evolved into suspension feeders, using Baleen plates to take in large amounts of water and sift through to find small krill. The Baleen whales can eat organisms much smaller than themselves, which can cut down the trophic levels between primary producer and the whale itself, making the energy available to the whale population 1,000 units, as opposed to only 1. In summation, shortening the food chain will in turn increase the food energy available to the whales by a factor of 1,000 (Figure 3) (Hill et al. 2018).

Figure 3: Shorter food chains deplete the energy available to whales less that longer food chains. (Hill et al. 2018).

By better understanding the way in which whales, or any animal for that matter, obtains energy through food, we can further implement new methodologies to better protect them. For example, now that it is known that krill play an extremely important role in the survival of the Blue Whale, agencies can implement new ecological management strategies to be sure that krill populations are not significantly affected by anthropogenic impacts. They may seem like invisible creatures floating in the ocean, but to Baleen whales, they mean a whole lot more.

Works cited

Hill, Richard W., et al. 2018. Animal Physiology. Sinauer Associates/Oxford University Press. “Life on the Food Chain.” The Food Chain.

Reilly, S., Hedley, S., Borberg, J., Hewitt, R., Thiele, D., Watkins, J. and Naganobu, M., 2004. Biomass and energy transfer to baleen whales in the South Atlantic sector of the Southern Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 51(12-13): 1397-1409.

Sinclair, Michael, and G. Valdimarsson. 2003. Responsible Fisheries in the Marine Ecosystem. Food and Agriculture Organization of the United Nations 8: 125-131.

Whale Conservation in the Mediterranean

By Jessica Wingar, RJD Intern

Conservation of threatened species is very critical in order to maintain the state of our oceans. There is a wide range of reasons for why the species needs to be conserved from threat of boat strikes to disease outbreak. However, humans cause many of these threats. In an effort to protect these threatened species from humans, marine protected areas, or MPAs, can be established. In this study, researchers were looking at whether it would be more effective to establish a series of MPAs or to restrict shipping through the International Maritime Organization, IMO, in order to protect the Mediterranean fin whale. The researchers looked at the advantages and disadvantages to all of the options available to determine what would be the best method of protection for a wide-ranging cetacean such as this species of fin whale.


Current distribution of the Mediterranean fin whale in the Mediterranean Sea.

Researchers from University College London and Stockholm University looked at the current state of the Mediterranean fin whale and the causes of its need for conservation to devise the most effective course of action to protect this species. This species of fin whale is on the IUCN’s red list as Vulnerable. The main threat facing this species is collisions with ships. One of the issues facing the protect of Mediterranean fin whales is that a lot of the Sea is not governed by any particular country. However, some of the countries bordering the Mediterranean are currently trying to create a collection of MPAs to protect these waters.


Current protected areas in the Mediterranean

In the study, the researchers concluded that including IMO in the conservation of whales would lead to increased protection of these animals. One of these reasons is that this organization has the tools to monitor the area in order to decrease factors that lead to whale and boat collisions. One of these ways would be to order a reduction in boat speed. If IMO puts this law into place, it becomes mandatory for all of the member nations of IMO to follow this. IMO is also respected in the shipping industry, so by them recognizing the threat of ships to whales, other vessels will follow creating a cascading effect. In addition, changes can occur quickly under IMO  and ships are more likely to feel inclined to follow the rules of IMO than if the area was a MPA.

Studies of this nature are very important because they discuss an alternative plan for protection and start a discussion about the pros and cons of each plan. IMO and the governments of the countries involved will, hopefully implement the plan for conservation that the researchers devised. Thus causing greater plans for the protection of the Mediterranean fin whale.



Geijer, C. K.A., and Peter J.S. Jones. “A network approach to migratory whale conservation: Are MPAs the way forward or do all roads lead to the IMO?” Marine Policy 51 (2014): 1-12.