Octopus Farming –– Is It Ethical?

By Hope Jackson, Paige Bernstein, Lydia Sellers, and Natalie Turner


Octopus are cephalopods and members of the order Octopoda. Cephalopods have the largest brain per unit body weight of any invertebrate, and octopus are among the most highly intelligent and neurologically advanced of all invertebrates. Octopus have been known to escape complex enclosures, use extreme camouflage techniques to escape their predators, use tools, pick locks, raid lobster traps, solve problems, and more. They can recognize human faces, have been shown to have long-term and short-term memory, and some evidence even suggests that they can experience pain and suffering. They are carnivores who eat clams, shrimp, lobsters, fish, sharks, and even sometimes birds. They can be found in oceans all over the world, but mostly being found in pelagic habitats near the water’s surface. 

Octopus demand has exponentially increased over the past decade. Over 100 species of octopus are currently caught in the wild. It is estimated that over 350,000 metric tons of octopus are caught from the ocean every year, with the highest demand coming from Korea, Japan, Spain, Portugal, Greece, and Italy. 2/3 of the annual catch comes from Asia, and at least half of that is from China. Since the 1980s, consumer demand has grown so much that octopus populations have decreased significantly as a result of overfishing. Their mild, chewy, and delicate meat is popular in a variety of dishes like poke, sushi, and tapas. It is also high in vitamins, minerals, and healthy fats. In Korea, octopus is sometimes even eaten live. The demand for octopus meat is continuing to grow quickly across the world and to meet this growing demand, many countries are experimenting with raising octopus in captivity.


Aquaculture is defined as the breeding and harvesting of animals or plants in water environments. On a global scale, marine aquaculture provides over 50 percent of all human consumed seafood and is used to restore habitats, replenish wild stocks, and rebuild populations. Marine fish farming usually begins with hatcheries and then moves to net pens in water or in tanks on land. For octopus, males and females are caught using nets, lines and traps. Then, they mate and the female’s eggs are placed in an “incubator” which is dark and cool. Once hatched, the juveniles are moved into larger tanks or pools and usually hand fed using a paste of squid and crab. Once they reach a mature weight, they can be sold. However, some octopus hatch into a paralarval stage in which they have stubby arms and float through the water column like plankton, eating whatever microscopic food that comes their way. They eventually settle at the bottom of the sea and for scientists, recreating these environments is a major difficulty. Some of the key variables that must be monitored and maintained diligently in a tank or pen, which is a difficult task, include temperature, dissolved oxygen levels, space, and salinity. 

Ethical and Ecological Concerns:

Although at first thought aquaculture may seem like a viable solution to the growing consumer demand for octopus, farming octopus through aquaculture actually has an overwhelming amount of ethical and ecological concerns. The main ethical concern is the welfare of an octopus in factory-farming or domesticated environments. Octopus are highly intelligent and complex animals that require stimulating and dynamic environments for maximum success, something that would be very difficult to replicate in aquaculture, which relies on controlled and monotonous environments. Not only would overcrowding be an issue, but octopus can also experience frustration and boredom without proper mental stimulation. Additionally, intense farming systems have been shown to be linked to increased mortality rates, increased aggression and more frequent infection.

The main ecological concern surrounding the farming of octopus is the additional pressure that would be placed on other fish and invertebrates in the wild. Because octopus are carnivores, they rely on fish protein and oil for nutrition, and this live food must come from somewhere. Increasing the population size of octopus through methods of factory farming puts extra pressure on wild fish populations that must be used for fishmeal. Currently, about one-third of the global fish catch is used to feed other animals, with about one half of that going to aquaculture. Because octopus eat about three-times their body weight over their lifetime, keeping octopus fed in captivity would put even more strain on already over-taxed fisheries, and would likely contribute to declining food security for humans as well. Aquaculture has many additional negative environmental impacts as well including pollution and contamination caused by feces, food waste and fertilizers, and the loss of natural habitats used for farms.

Looking to the Future:

When looking to the future, cephalopod farming should not be a part of it. Conscious diets that avoid high ecological footprints and primary education that encourages community investment for the protection of these animals are part of the solution to this pending problem. Alternative protein markets could also respond to this demand. Companies like Beyond Meats and Toona already impact traditional seafood markets and clearly demonstrate a market response to alternative meat solutions. Consumers have the direct power to end the demand for octopus cuisine now!  

Original Article: http://www.digitaljournal.com/news/environment/marine-researchers-we-must-absolutely-not-farm-raise-octopuses/article/564399

Works Cited:

Fail, Robin. (2020, February 12). Lecture on Cephalopods. Duke University, Durham NC.

Graham, K. (2019, December 30). Marine researchers – We must absolutely not farm-raise octopuses. Retrieved April 12, 2020, from http://www.digitaljournal.com/news/environment/marine-researchers-we-must-absolutely-not-farm-raise-octopuses/article/564399 

Knowles, D. (2019, May 13). Millions of people eat octopus- here’s why we shouldn’t. Retrieved April 16, 2020, from https://www.weforum.org/agenda/2019/05/millions-of-people-eat-octopus-heres-why-we-probably-shouldnt/ 

Root, T. (2019, August 21). The Race to Produce the World’s First Farm-Raised Octopus. Retrieved from https://time.com/5657927/farm-raised-octopus/

Simke, A. (2019, December 13). The World Is Hungry For Octopus, What’s Wrong With Farming Them? Retrieved April 16, 2020, from https://www.forbes.com/sites/ariellasimke/2019/12/13/the-world-is-hungry-for-octopus-whats-wrong-with-farming-them/#632166c02302 

US Department of Commerce, & National Oceanic and Atmospheric Administration. (2019, April 2). What is aquaculture? Retrieved fromhttps://oceanservice.noaa.gov/facts/aquaculture.html

Zimmer, C. (2018, November 30). Yes, the Octopus Is Smart as Heck. But Why? Retrieved April 14, 2020, from https://www.nytimes.com/2018/11/30/science/animal-intelligence-octopus-cephalopods.html







Whales and Marine Gigantism

Ashley Marko, Hannah Folks, Dana Adcock, Madison Ding, Mara Turkieltaub Paredes

Overall Summary:

In a recent news article by Inside Science, Joshua Learn discusses the advantages and evolutionary history of gigantism as it relates to the largest of all cetaceans–whales. Whales have evolved a long way from the dog-sized organisms they were millions of years ago, he notes, and the limitations to marine gigantism were for many years obscure and unknown. In an effort to identify what limits the body size of these massive marine mammals, Learn introduces a critical research study by marine biologists J.A. Goldbogen and others at the Goldbogen Lab in Stanford. In this study, data was taken from multisensor devices, acoustic devices, and the stomach contents of beached whales in order to determine energy expenditure and intake during feeding. Through such collection and analysis, it was found that while the gigantism and overall body size of toothed whales were limited mainly by the body size of their prey, baleen whales were limited by the availability and temporality of their prey. That being said, Learn does conclude the article by discussing the possibility of seeing even larger whales in the far future. 


   From avoiding predation by smaller organisms to allowing for a more efficient metabolism, gigantism—very large body size—serves as an incredibly useful adaptation in most marine environments. However, the utility and advantage of gigantism become more nuanced and multi-faceted when it comes to whales. In fact, a recent news article by Inside Science shows that the evolutionary pathway for gigantism is split for rorqual and toothed whales—each group’s unique foraging strategies (filter-feeding, bio sonar-guided hunting on individual prey) spurred a propensity towards a large body size in order to better adapt to the spatial, temporal, and physiological characteristics of their prey and environment.


   During the Oligocene, specialized foraging mechanisms likely led to the diversification of cetaceans. Odontocetes used biosonar-guided foraging to capture individual prey, while mysticetes used engulfment and lunge-propelled filter feeding. These differences in evolved behavior enabled separate pathways to gigantism, which had also evolved in order to promote greater metabolic and locomotion efficiency. For toothed whales, a bigger body size allows them to dive deeper, granting them the ability to catch a greater abundance of fish at lower water levels, rather than having to depend on populations that thrive on the near surface. The body size of baleen whales has evolved to improve their efficiency in catching abundant, yet patchily distributed small prey. These advantages are a direct result of the relationship between body size and respiratory functions. As body size increases, mass-specific oxygen storage is constant, while mass-specific oxygen usage decreases. Therefore, larger deep divers spend less energy while feeding for prey, making them more efficient predators than their smaller counterparts. Despite this, the energy toothed whales obtain from successful hunting does not outweigh the costs associated with a larger body size and the effort needed for deeper diving. Baleen whales, on the other hand, are relatively more efficient. Thanks to their filter-feeding foraging strategies and massive size, larger baleen whales perform fewer feeding events per dive and are able to engulf a greater biomass of prey, all at lower trophic levels than their deep diving counterparts. As such, rorquals are on average able to gain higher amounts of energy per feeding event.


    Learn highlights that the researchers studied foraging performance using multisensor tags. The data from these tags showed the largest odontocetes exhibited high feeding rates during long, deep dives. The energetic efficiency of the dive was determined mostly by the number of feeding events and the amount of energy obtained during each feeding event. The amount of energy obtained per feeding event was calculated from prey type and size distributions historically found in the stomachs of odontocetes and the acoustically measured biomass, density, and distribution of krill at rorqual foraging hotspots.


   The results of the study demonstrate that larger odontocetes (toothed whales) appear to feed on larger prey relative to the size of the prey of its smaller counterparts. However, these prey were not disproportionately larger, and smaller toothed whales fed more frequently. Therefore, the energy obtained from prey didn’t quite outweigh the increased costs of having a larger body size or undergoing deeper dives, which means there is actually a decrease in energetic efficiency observed with increasing body size in odontocetes. 

    However, in the case of rorquals (largest group of baleen whales), the measured distribution and density of krill biomass suggest that larger rorquals are not limited by the size of their prey on individual dives. In fact, baleens experience more rapid increases in energy from their prey along with increasing body size, as larger rorquals have larger capacities for engulfment. Rorquals also have the ability to maneuver more than their toothed counterparts, and increase feeding rates per dive when krill density is higher, indicating that their energy efficiency would increase in conjunction with their body size. These results were robust to assumptions about trait similarity from shared ancestry as well as the scaling of each group’s metabolic rates. This implies that it is evolutionarily advantageous for rorqual whales to increase in body size. Because of this, provided the availability of its prey can keep up, these whales could get bigger.


    Gigantism in cetaceans has many benefits, including energy storage for more efficient and prolonged migration as well as granting the ability to better retain heat, making these animals incredibly productive predators. Whales are perhaps some of the most recognizable marine megafauna and vary widely in size across species, leading scientists to question the differing limitations between groups. Goldbogen et al. found that prey availability is the primary restriction on marine gigantism in whales. For toothed whales, a higher abundance of larger prey could make them even more massive, and the same goes for baleen whales, whose prey consists of small krill with variable availability and concentration throughout the year. In the past 50 million years, whales have nearly grown 10,000 times larger, and depending on the future availability and temporality of their prey, Goldbogen believes they could get even larger.

Significance and Future Studies:

  Gigantism is a particularly interesting adaptation in an ecological and environmental context given our current battle against climate change. Although their large body size allows for these massive creatures to act as the efficient and successful predators they are, the issue of commercial overfishing is utterly devastating to cetacean populations. Historically, the overall body size of many whale species has been decreasing, and now that we know how prey abundance and body size affects the body size of whales, a direct correlation between these events is clear. This news article and study give us further insight on the ecosystem dynamics and evolutionary history behind gigantism and how both top-down and bottom-up interactions yield a balanced yet fragile food web. Future research should focus on how physical changes in an ecosystem (such as temperature, oxygen availability, and turbidity) can affect prey populations and marine gigantism, which inherently impact predator-prey dynamics. Furthermore, future studies could focus upon marine gigantism in other endothermic and exothermic species, relating the similarities and differences in limitations on body size against cetaceans.

News Article:


Scientific Study/Article:



Arnold, Carrie. 2018. “Why Do Whales Get So Big? Science May Have an Answer.” National 

Geographic, 26 Mar. 2018, nationalgeographic.com/news/2018/03/whales-size-animals- ocean-marine-mammals/.


Goldbogen, J. A. et al. (2019). Why whales are big but not bigger: Physiological drivers and 

ecological limits in the age of ocean giants. Science, 366(6471), 1367–1372. doi: 10.1126/science.aax9044


Learn, Joshua. 2019. “How Whales Got So Large — And Why They Aren’t Even Bigger.” Inside

Science, 12 Dec. 2019, insidescience.org/news/how-whales-got-so-large-and-why-they-  

aren%E2%80%99t -even-bigger.


Williams, T. M. (2019). The Biology of Big. Science, 366(6471), 1316–1317. doi:



Yong, Ed. 2018. “Why Whales Got So Big” The Atlantic, 4 Apr. 2018,


Cuttlefish 3D Vision

Chumba Koech, Gus Dodd, Maria Zurita Ontiveros, Flo Cordova, Maya Suzuki


Scientists know that the human brain is far different from that of a cuttlefish, but what they aren’t so sure is how cuttlefish use depth perception in the same way humans do. For this study, scientists focus on the common European cuttlefish, Sepia officinalis. They are in the subclass Coleoidea, “soft-bodied”, with octopus and squid, live one to two years, and have eight arms and two tentacles. This species of cuttlefish preys on fish and small crustaceans, including crabs, shrimp, and prawns. They forage in 4 stages: detection, positioning, strike start, and prey seizure. Cuttlefish must obtain a distance close enough to grasp the prey with its tentacles, but far enough away to not startle the prey. An example of a foraging strategy includes hypnosis, where cuttlefish use their color-changing abilities to stun their prey and eat them while they are distracted. This particular study focuses on the use of stereopsis for depth perception as they forage.


Stereopsis can be defined as “3D vision”, or how eyes perceive depth.  It is documented in many mammals such as primates (including us), birds, cats, horses, and praying mantises.  However, there have been no previous studies conducted on marine megafauna, thus this study gathered a fair amount of scientific attention.  There had been previous evidence suggesting that cuttlefish may have depth perception. First, the cuttlefish’s camouflage ability is thought to be influenced by depth perception.  Experiments on checkerboard and pebble backgrounds suggested that cuttlefish produced more effective disruptive patterns when a light object was placed in front of a dark object, and when backgrounds had edges and contrast.  Regarding cuttlefish’s hunting, prey attacks were confirmed to be initiated purely by visual cues. Other studies concluded that cuttlefish use pictorial cues and directional illumination, but it was not clear whether cuttlefish could calculate attack distance.  The design of this experiment allowed for isolation and testing of cuttlefish’s stereoscopic vision.


The study used 11 adult cuttlefish. The researchers created a fish tank that had two cameras and a monitor used to display the moving shrimp images. The cuttlefish were trained to attack the screen image of the two differently colored shrimp while wearing the 3D glasses. The “attack” was defined by the cuttlefish deploying their tentacles. The researchers offset the images of the shrimp to test the disparity. Stereopsis was tested by isolating the use of one eye through various disparity distances.


When faced with the visual stimulus of the shrimp with disparity (a shift between left and right eye visuals), the cuttlefish would adjust its position relative to the screen, and the larger the disparity, the further away the cuttlefish would position itself before striking. When faced with only one eye (quasi-monocular) stimulus, the cuttlefish took longer to strike, travelled farther, and struck at prey from a closer distance than when faced with two eye (binocular) stimulus. This shows that cuttlefish do use stereopsis when hunting, since they compare visual images from both eyes. Cuttlefish also struck at the TV shrimp when both eyes received the exact same stimulus (correlated) and when each eye received the same stimulus but with reversed luminosity (anticorrelated), but not when the stimulus was completely different for both eyes (uncorrelated), which requires different cognitive abilities than those in mammalian and praying mantis stereopsis. Finally, the study found that cuttlefish eyes can move independently and the eyes don’t need perfect convergence in position in order to use stereopsis, another marked difference with humans.


As we have seen, stereopsis was originally considered undiscovered among marine megafauna. The fact that the cuttlefish has evolved to be able to use stereopsis has significant implications for the way that it has evolved. The ability to perceive depth grants enormous benefit to the cuttlefish, particularly in relation to the way that it hunts; namely, stereopsis allows them to detect prey faster and strike from a further distance and with greater accuracy than other cephalopods. Despite increasing fishing levels, cuttlefish are not an endangered species. Thus, there exists an opportunity to conduct more tests on them in order to understand the origins of stereopsis, particular in relation to marine life. Why this diversification amongst cephalopods has taken place is not obvious but it paves the way for greater research into why certain marine species have this ability and others do not.


Feord, R. C., Sumner, M. E., Pusdekar, S., Kalra, L., Gonzalez-Bellido, P. T., & Wardill, T. J. (2020). Cuttlefish use stereopsis to strike at prey. Science Advances, 6(2), eaay6036.

Kelman, E. J., Osorio, D., & Baddeley, R. J. (2008). A review of cuttlefish camouflage and object recognition and evidence for depth perception. Journal of Experimental Biology, 211(11), 1757-1763.

Messenger, J. B. (1968). The visual attack of the cuttlefish, Sepia officinalis. Animal Behaviour, 16(2-3), 342-357.

Nityananda, V., & Read, J. C. A. (2017). Stereopsis in animals: evolution, function and mechanisms. Journal of Experimental Biology, 220, 2502–2512. doi: 10.1242/jeb.143883

Zylinski, S., Osorio, D., & Johnsen, S. (2016). Cuttlefish see shape from shading, fine-tuning coloration in response to pictorial depth cues and directional illumination. Proceedings of the Royal Society B: Biological Sciences, 283(1826), 20160062.


The Effect of Heatwaves on Whale Entanglements 

Ansley Arnow, Caleb Stevens, Giselle Wang, Nathan Cho, Rahul Sengottuvelu


As human civilization grows ever greater, we are placing more and more impact on nature, especially the ocean. One specific conservation issue that emerges from humans’ extensive use of the ocean is managing shared space between marine animals and fisheries. It is estimated that each year, over 300,000 marine mammals die from entanglement with fishing gear. This problem is exacerbated on the west coast of the United States where people have observed an increasing number of entangled humpback whales that are coming to the coast more often, where there is a high density of crab-fishing operations. The whales seem to be coming to the coast because an increased number of marine heatwaves caused by climate change are compressing their habitats and pushing them to the coast to feed. It is a stark reminder that the ocean is a vast and extremely interconnected system. This particular issue raises awareness for the location-specific and indirect impact of climate change and calls for a better approach to managing the co-existence of humans and marine animals.


When the temperature of the ocean is significantly higher than the expected value at a certain time of year for an extended period of time, it is defined as a marine heatwave. Its causes can be simply the movement of marine currents and an increase in atmospheric temperature. Climate change has induced more frequent marine heatwaves, which greatly affects biodiversity. Some organisms benefit from it and some are suppressed, leaving a significant imbalance in the ecosystem. 

Humpback whales are filter feeders, eating krill, plankton, and small fish. Marine heatwaves narrow the range of ocean zones that benefit from coastal upwelling to areas that are more inshore, so whales come to these areas to feed on the great abundance of food brought to inshore waters from the deep sea or surface currents. 


Santora (2020) evaluated the relationship between the extent of habitat compression and the number of whales that share space with crab-fishing activities and found a positive relationship. They took into account factors such as normal ecosystem biodiversity, whale occurrence, entanglement records, habitat compression, and fishing operation locations.

The study also interviewed fishermen and provided management solutions to reduce harm for marine bycatch species.


The study found that the behavior of coming further inshore to feed is indeed a probable cause for higher entanglement rates, as their feeding area now overlaps with crab-fishing operations. This area manifests unusually high biodiversity from marine heatwaves and upwelling, making it an attraction for both predators and fishermen, which can be problematic.

Therefore, the study provides a few policy solutions, including a more dynamic management approach that adjusts according to seasonal changes in the ecosystem, especially in the face of MHW. It would also be helpful if ecologists provide fishermen with easily caught indicators of ecosystem health, so they can act quickly and effectively. 

Conclusion & Future Studies

Apart from bycatch, the decrease in prey species also causes other problems for humpback whales, including a lack of nutrition and thus a decrease in reproductive success and increased calf mortality. We might observe a sharp decrease in the overall humpback whale population if marine heatwaves become a frequent phenomenon. 

A study in Alaska shows that when the region was affected by a prolonged marine heatwave from 2014 to 2016, sand lance, a key prey fish, decreased in abundance and size, causing a shortage of food for various marine mammals, seabirds and large fish. This shows how marine heatwaves can affect the whole marine ecosystem in a bottom-up fashion, and further studies on this phenomenon are crucial to understanding its impact.

More research into indicators of a potential marine heatwave is also highly recommended. Such indicators could include changes in the diet of certain predators, lack of abundance of prey fish or change in thermohaline movement. If we can predict and map marine heatwaves, we can set up policies in advance to minimize anthropogenic damage when new animals move into a habitat. It is also recommended that further studies be done on what triggers marine heatwaves and provide projections for how frequent they will be in the future. 

A new wave of the marine heatwave we call “the blob” is coming back as of 2019, and if we learn from past experiences in dealing with them, maybe we can protect the lives of more animals and fishing businesses this time.

This is the original research paper mentioned in the article


Santora, J.A., Mantua, N.J., Schroeder, I.D. et al. Habitat compression and ecosystem shifts as potential links between marine heatwave and record whale entanglements. Nat Commun 11, 536 (2020). https://doi.org/10.1038/s41467-019-14215-w

Related Articles:


Marine heatwaves become more frequent under global warming


Marine heatwaves threaten global biodiversity and the provision of ecosystem services


Bycatch number


Multiyear Marine Heatwaves


Decline in prey species due to MHW

Synchronized Swimming: Or How “Fear of Killer Whales Drives Extreme Synchrony in Deep Diving Beaked Whales”


Beaked whales are a unique species for various reasons—one of these is their diving mechanisms. Most deep-diving mammals will spend a great deal of time foraging at the bottom, employing typical biosonar-mediation techniques. Beaked whales, however, like to do the typical deep dives, but only use echolocation at the deepest depths possible for a short period of time. This deep dive is followed by several shorter ones.

While the strategy as a whole is unusual and taxing, their lack of echolocation usage is another thing altogether—researchers believe this is in order to decrease the risk of predation. One natural predator of theirs, the killer whale, employs acute hearing as one of its hunting strategies, meaning that animals such as the beaked whales will be more susceptible to being hunted if they are constantly using biosonar methods of foraging.


This study proposes that much of beaked whale behavior is strongly linked to their relationship with killer whales. Killer whales are an incredibly influential apex predator and are thought to have caused some species of toothed whales to utilize large groups as social defense, or even change the frequencies of their vocalizations. However beaked whale behavior is noticeably different from these other cetaceans. Beaked whales have developed an extreme-predator response which makes them incredibly sensitive to naval sonar and vulnerable to mass strandings. The results suggest beaked whales coordinate vocal productions and movements when returning from the safer deep waters to the surface. This study delves into the unique foraging and diving behavior of beaked whales, and the influence of predation by killer whales. 


The depth and movement patterns of 14 Blainville’s beaked whales near the Canary Islands and 12 Cuvier’s beaked whales in the Gulf of Genoa and near Azores were tracked via digital acoustic recording tags (DTAGs) attached by suction cups for up to 20 hours before the tags were released and recovered. Recordings from the hydrophones on the DTAGs were analysed using the DTAG toolbox to identify beaked whale vocalizations: clicks, buzzes, rasps, whistles. 



The team analyzed the data from literature and biologging beaked whale pairs during deep dives to tell them information about their spatial relationship and coordination efforts during their deep dives. Figure 1 shows the dive profiles of three pairs of beaked whales. The red triangles signal when each whale in the pair starts and ends making vocal noise. Since these are close together, it shows synchronization in vocalization, which results in the group being silent for approximately 80% of the dive, keeping them undetectable from predators. The blue lines at the bottom of Figure 1 are points at which the whale pair splits, and the result is the immediate loss of coordination at this point.

This deep dive coordination allows for approximately 5 hours a day of sound overlapping in foraging, resulting in groups of beaked whales being shielded from killer whale acoustic detection over 75% of the time.

Silent Ascent Swimming

The team also tested the predictability of beaked whale ascents, believing that they move horizontally in a way that makes it difficult for killer whales to track their location. The reconstruction of tracks from past ascents shows that beaked whales swim on average one kilometer from where their last sound was made to where they surface, and they do so in a way that is counter to that of predator expectations. This unpredictable ascent creates confusion for the killer whales as they now have a wide circle of possible surfacing locations to search, as well as yields a significantly lower rate of interaction between the two species when compared to more common vertical ascent behavior.

Significance/Future Impacts 

This study gives some insight on the impacts of human-generated sonar on marine mammals. These beaked whales sacrifice massive amounts of energy and foraging time for the sake of evading predators, as running and hiding are their primary means of combating predation. As a result, should they hear anything akin to the sound a predator makes (like naval sonar), they have no choice but to assume the worst. This anti-predator response may “push beaked whales beyond their physiological limits and in some cases lead to sonar induced mortalities” (Aguilar de Soto et al.). There have been efforts in past years to get the navy to decrease their use of sonar in areas with marine mammals, and some of have been successful, such as in 2015 when the navy agreed to ease their sonar testing in the ocean off the west coast of California, a popular spot for beaked whales. But now that we know exactly what the beaked whales are interpreting the sonar as, hopefully we can move towards a longer term solution than simply a ceasefire.


Beaked whales may evade killer whales by silently diving in sync


Other sources/references: 

Killer Whale Predation:


Effects of sonar on beaked whales:






Blainville’s Beaked Whales:


Image at top of post credit: https://www.fisheries.noaa.gov/species/blainvilles-beaked-whale


The Curious Case of Grey Seals and the Underwater Clap


The grey seal (Halichoerus gryphus) is a member of the Phocidae family, or “true seals”. As a member of Phocidae, they do not have ear flaps and they propel themselves with their hind flippers. Grey seals live only in the North Atlantic Ocean and are separated into three distinct populations, or “stocks.” Generally, grey seals live between 25 and 35 years, with the females living slightly longer than the males. Female grey seals reach sexual maturity when they are around 4 years old and then give birth once a year. The pups are born during the breeding season, when large groups of grey seals haul out onto land or ice. All parental care is provided by the female, but males protect the females during birth. Traditionally, seal communication has been thought to be a means of sharing information throughout the social breeding season. Their main vocalizations consist of hisses and growls, especially between males competing for a female. The seals also use physical cues such as neck darts and opening or closing their mouth. In the past, seals in human care have been prompted to clap, but this study is the first time that they have been observed clapping in the wild.


In October 2017, a camera caught footage of a male grey seal making percussive actions. This took place near the Farne Islands in the Northeast of England. In the video, a wild male grey seal approaches a female seal. The female seal communicates with a “guttural rup.” The male seal hits its front flippers together to make a loud clap, and a few seconds later a reply clap comes from another male out of frame. In response, the initial male claps twice more. The male seal outside of the frame claps back. Later, the female returns, prompting another two claps and a pursuit for the female. After the chase ends, the male then makes a final single clap and a “guttural rup.” 


This video marks the first time in which clapping behavior has been recorded among grey seals, and it is particularly interesting that the clapping elicits a response from nearby seals. While this video footage is still anecdotal and lacks more supporting examples, it strongly suggests that clapping serves an important social function among grey seals. From a scientific standpoint, claps have a greater sound frequency range than other vocal signals and also match up with optimum hearing sensitivity among phocids, so this could be an extremely effective method of communication in noisy waters. The lead author of the study compares the clapping behavior to the chest beating of a male gorilla, hypothesizing that their purpose may be to discourage competitors and simultaneously attract mates by serving as an indicator of strength. Naturally, being cognizant of this behavior and its implications for grey seals’ survival is crucial when designing future regulations around human generated sound profiles in the ocean.

Conclusion/Further Research

While scientists note that “clapping” behavior has been observed frequently in seals in zoos and aquaria for the entertainment of its guests, this is the first time researchers have recorded wild seals performing such an action underwater. Although there is currently no concrete evidence for the motivation or purpose of these behaviors, researchers believe that male grey seals use the mechanism to ward off competitors and/or attract mates. However, more behavioral studies and observations are needed to confirm this explanation or even the concrete existence of this behavior. Regardless of the reason for these percussive claps, this data acts as further evidence for the importance of auditory behaviors in marine mammals, including grey seals. Therefore, anthropogenic noise pollution from boats and other sources could possibly interfere with these mammals’ communication. Due to the grey seals’ proximity to the surface, human noise pollution could have, and possibly already has had, adverse effects on the seals’ social behaviors. More research is needed to determine if and how this noise pollution interferes with the grey seals and what could be done to prevent it. 

Main Sources:

News Article: https://phys.org/news/2020-02-grey-underwater.html

Dropulich, Silvia. “Grey Seals Discovered Clapping Underwater to Communicate.” Phys.org, Phys.org, 3 Feb. 2020, phys.org/news/2020-02-grey-underwater.html.

Research Paper: https://onlinelibrary.wiley.com/doi/full/10.1111/mms.12666

Hocking, David P., et al. “Percussive Underwater Signaling in Wild Gray Seals.” Marine Mammal Science, 31 Jan. 2020, doi:10.1111/mms.12666.

Other References: 

Bowen, D. 2016. Halichoerus grypus The IUCN Red List of Threatened Species 2016: e.T9660A45226042. https://dx.doi.org/10.2305/IUCN.UK.2016-1.RLTS.T9660A45226042.en. Downloaded on 25 February 2020.

“Gray Seal.” NOAA, www.fisheries.noaa.gov/species/gray-seal.

“Gray Seal.” Oceanwide Expeditions, oceanwide-expeditions.com/to-do/wildlife/gray-seal.

“Gray Seal.” Smithsonian’s National Zoo, Smithsonian, 26 July 2018, nationalzoo.si.edu/animals/gray-seal.

“Grey Seal.” Ecomare, Stichting Texels Museum, www.ecomare.nl/en/in-depth/reading-material/animals/seals/grey-seal/.

Killer Whale Grandmothers Boost Survival of Calves


Along with being one of the world’s most powerful predators, Killer whales are also highly intelligent and social creatures with intricate techniques of interaction. They can be found almost all around the world in highly productive areas of cold water upwelling. They are usually found in ‘pods’ which consist of various sexes and ages. It usually contains the mother and the one or two offspring. The strong associations between the pod members carry on into adulthood, therefore family associations are very strong, where each member has certain roles. This article looks at the effect post-menapausal grandmothers have on their offspring compared to breeding grandmothers. They do this by looking at salmon population data as they believe grandmothers play a large role in collecting prey. 


Besides humans, only 4 species are known to experience menopause: belugas, narwhals, killer whales and short-finned pilot whales. According to one of the authors of the study, Sam Ellis, in killer whales, the reason to stop reproducing is because both male and female offspring stay with the mother for life. If the mother keeps having young, they would have their own descendants competing for resources. Older females share their knowledge in order to help their group survive. Killer whales have “the longest post-reproductive life span of all nonhuman animals: Females stop reproducing in their 30s to 40s but can survive into their 90s.” This allows the mothers to maximize the fitness of her offspring by ensuring their survival and that the offspring achieve reproductive success.

Methods (Models and Variables)

With regard to methodology, this research was comprised of 3 interconnected methods: Study populations, Survival Model with Time-Dependent Effects, and Interbirth Interval Model. In the Study Populations, demographic records were collected manually using photographic censuses for 2 resident killer whale populations: Southern (1976-2016) and Northern (1973-2016) populations in the inshore coastal waters of Washington State and British Columbia, Canada. Individuals were identified by their unique fin shapes, saddle patches, and the presence of any nicks or scratches, and were sexed using distinctive pigmentation patterns around the genital slits and, in adults, differences in fin size. Genealogical relationships were inferred from long-term observations of social organization, and mothers were identified by their repeated association with young calves.

Overall, the Data collected for the analysis was comprised of the following variables: Year of Birth (YOB), Year of Death  (YOD), ID of Mother. The aforementioned variables were used to deduce the Age of Death, and Maternal Grandmother ID in order to provide enough variables to run the models. In the Survival Model with Time-Dependent Effects, a Cox Proportional Hazards model was created to examine the consequences of a grandmother’s death on grand offspring survival. Lastly, an Interbirth Interval Model was used. A Generalized additive model was used to examine the consequences of a grandmother’s status on her daughter’s interbirth intervals. To test whether grandmothers decrease their daughters’ interbirth intervals, the researchers regressed a number of covariates on each interbirth interval. 


Considering the above methods to compile forty years’ of data into a survival model and an interbirth interval model, numerous specific models were considered for each task. The best model for the survival model was given by the following equation which reflects a general grandmother and post-reproductive grandmother effect.


Where sMR is 1 for male, 0 for female (if mother died in past two years) GMR is 1 if grandmother died in past two years, and GMo45 = 1 if grandmother was post-reproductive, slm is salmon index.

From this we see that the loss of a grandmother within the last two years increases mortality hazard by 4.5, while the loss of a post-reproductive grandmother increases mortality by 6.7, if the salmon index is at the norm of 1. If the salmon index is lower (meaning food is scarcer), the grandmother effect becomes even more pronounced. The sex impacted the mother effect, but not the grandmother effect.

The best interbirth interval model demonstrated that living grandmother’s did not impact the interbirth interval for mothers. However, two alternative equations with low AIC relative to the best model, both included grandmother effects on interbirth interval but shockingly showed that the presence of a grandmother tended to increase the interbirth interval of a mother.


The purpose behind menopause has been an evolutionary puzzle, especially as only humans and four species of whales experience menopause. Female killer whales in particular have evolved the longest post-reproductive life span of all nonhuman animals. By demonstrating that post-reproductive grandmothers reduce grand offspring mortality more than grandmother killer whales that are still reproducing, this research reveals the measurable positive influence that menopause has on killer whales’ grand offspring. Knowing the benefits that menopause brings to the killer whales is essential to understanding why female killer whales have evolved to live long lives post-reproduction.

Chosen News Article


University of York. “Killer Whale Grandmothers Boost Survival of Calves.” ScienceDaily, ScienceDaily, 9 Dec. 2019. 


Foster, E. A., Franks, D. W., Mazzi, S., Darden, S. K., Balcomb, K. C., Ford, J. K. B., &
Croft, D.
P. (2012). Adaptive Prolonged Postreproductive Life Span in Killer Whales. Science,
337(6100), 1313. https://doi.org/10.1126/science.1224198

Imster, E. (2018, August 31). Beluga whales and narwhals go through menopause. Retrieved
February 16, 2020, from

Nattrass, Stuart, et al. “Postreproductive Killer Whale Grandmothers Improve the Survival of Their Grandoffspring.” PNAS, National Academy of Sciences, 26 Dec. 2019,   www.pnas.org/content/116/52/26669

Nationalgeographic.com. (2010). Orcas: Killer whales are the largest dolphin species. [online]
Available at: https://www.nationalgeographic.com/animals/mammals/o/orca/ [Accessed
17 Feb. 2020].

Robin W Baird and , Hal Whitehead ” Social Organization Of Mammal-Eating Killer Whales:
Group Stability And Dispersal Patterns – Canadian Journal Of Zoology “. 2020. Canadian
Journal Of Zoology.

Yong, E. (2017, January 12). Why Killer Whales (and Humans) Go Through Menopause. Retrieved February 16, 2020, from https://www.theatlantic.com/science/archive/2017/01/why-do-killer-whales-go-through-menopause/512783/

Great Barrier Reef decline over the last 90 years and how to save them!



The Great Barrier Reef, home to the largest coral reef system and thousands of species of organisms, faces threats of climate change, pollution, and fishing, bringing its health into great concern. The decline of reefs due to changes in the way they build and the species that inhabit them risk the food and livelihood of hundreds of millions of people. This study examines data collected over the past 91 years to better understand the survival of coral reefs, exploring the documented environmental conditions surrounding coral reefs, community structures of organisms there, and highly accurate mapping of the reef. 



The researchers selected a reef that had been subject to study a number of times in the past, dating back to a quadrat-based survey that ran from 1928 to 1929. They observed coral and marine species biodiversity, supplementing their work with photographs. Areas previously studied were photographed and these photographs edited into one continuous mosaic. Comparing that mosaic (and the species it featured) to reports from previous expeditions allowed the researchers to determine the nature and extent of major trends in the reef.



The barrier reef has seen the worsening of coral cover, colony size, and species diversity over the last 90 years. Coral cover and colony size have declined, with no corals in many intertidal areas named for their dominant reef-building coral. There has been a drastic fall in species richness. Revisiting 13 sites from 1954 found that many species of coral were near extinction and all the sites saw their population decline to half. Corals forms have changed from hard corals to soft corals and from branching corals to massive corals. Many invertebrates that called these intertidal coral colonies home have vanished.


 Figure 1: Dead coral reefs near Low Island



In the past, coral cover has been used as an indicator for reef health as it strongly predicts the capacity of a reef to track sea-level rise and resist drowning. However, species diversity and richness are crucial indicators of reef health. In addition to lower coral cover and size, there has also been a huge drop in species diversity and richness since 1928. This lower diversity is likely as a result of chronic stress and disturbances. These conditions select for coral species which are disturbance resistant and slow-growing, such as soft corals and massive corals. Coral now takes longer to recover following a disturbance such as a cyclone. Additionally, coral reefs which fail to reassemble a diverse community have higher vulnerability and sensitivity to future disturbances. Low Island has failed to reassemble a diverse community and is more susceptible to both drowning and cyclones than it was in the past. Reports since 2000 suggest identical effects in inshore and offshore reefs globally. Hence, the decline of reefs on low isles provides an unfortunate story for coral reefs globally. 


Potential Solutions

Solving the Coral reef problem requires pollution control, better fishing policies, reducing CO2 emissions and extreme temperatures. Better fishing practices improve reef health by preventing overfishing of keystone species crucial to the local ecosystem(Health Fisheries). One example is the decline of shark populations(keystone species) due to overfishing. It has lead to an increase in mid-level feeders, a decline in herbivores and an increase in algae, which harms the coral reefs(Earthsky). Extreme high temperatures due to climate change can potentially destroy 90% of the reefs. Scientists like Daniel Harrison believe that reducing CO2 is insufficient. Instead, they propose reducing reef water temperatures by making clouds brighter and reflecting more sunlight in a process called Marine Cloud brightening(Temple, J.).

Figure 2: Impact of overfishing and loss of species diversity on coral reefs


Figure 3: Mechanism of action of Marine Cloud brightening




  1. Fine, M., Hoegh-Guldberg, O., Meroz-Fine, E. et al. Ecological changes over 90 years at Low Isles on the Great Barrier Reef. Nat Commun 10, 4409 (2019). https://doi.org/10.1038/s41467-019-12431-y
  2. Bar-Ilan University. “Longest coral reef survey to date reveals major changes in Australia’s Great Barrier Reef.” ScienceDaily. ScienceDaily, 27 September 2019. <www.sciencedaily.com/releases/2019/09/190927074930.htm>.
  3. Chemical & Engineering News. “Climate Change Is Destroying Our Coral Reefs. Here’s 3. How Scientists Plan to Save Them.” Accessed February 11, 2020. https://cen.acs.org/environment/climate-change/Climate-change-destroying-coral-reefs/98/i6.
  4. Healthy Fisheries. (n.d.). Retrieved from https://coral.org/what-we-do/healthy-fisheries-for-reefs/
  5. Earthsky, Researchers find coral reefs at risk when sharks overfished. (n.d.). Retrieved February 12, 2020, from https://earthsky.org/earth/researchers-find-coral-reefs-at-risk-when-sharks-overfished
  6. Temple, J. (2017, April 20). Are brighter clouds the best bet for the Great Barrier Reef? Retrieved February 12, 2020, from https://www.technologyreview.com/s/604211/scientists-consider-brighter-clouds-to-preserve-the-great-barrier-reef/

Article Source


https://www.sciencedaily.com/releases/2019/09/190927074930.htm -Online article


https://www.nature.com/articles/s41467-019-12431-y Actual Study article references


Earthquakes – They Affect Marine Life, Too!


Earthquakes – They affect marine life, too!

Sperm Whale

Sperm Whale

It seems obvious that earthquakes affect land animals. However, after coming across a National Geographic article on earthquakes and sperm whales, our group became interested in how earthquakes can affect marine megafauna.


Abundant evidence exists demonstrating the effects of earthquakes on land animals. Historical evidence from 373B.C. documents that animals such as rats, snakes, and weasels had abandoned the Greek city of Helios days before an earthquake devastated the place. Anecdotal reports throughout hundreds of years detail similar strange behavior before earthquakes even strike: pet owners have long recorded reports of cats and dogs barking, whining, or showing signs of nervousness before a quake. However, it becomes less clear how these earthquakes may affect marine megafauna.



Sperm Whale Eating Squid Animation

Animation of a Sperm Whale Eating a Squid



         Sperm whales, or Physeter macrocephalus, are a species of marine mammal that can weigh 35 to 45 tons and are typically longer than the average school bus. Sperm whales received their name because they have large quantities of an oily substance called spermaceti in their heads. Although scientists are not completely sure about the purpose of this fluid, some hypothesize that it helps them change their buoyancy as they dive deep for squid and other prey. 

         In November of 2016, a 7.8 magnitude earthquake devastated Kaikoura, New Zealand. Although the number of human casualties was low, it caused complex environmental disturbances. The Kaikoura underwater canyon is one of the few places in the world where you can see sperm whales very close to the shore. The earthquake triggered a series of widespread underwater mudslides in the canyon, causing both powerful currents and changes in water depth relative to sea level. These landslides not only clouded the water, but they also killed or swept away many of the marine invertebrates living in the canyon. These invertebrates are an important source of food for squid and bottom dwelling fish, which are two key prey for male sperm whales. Therefore, scientists hypothesized that the loss and restructuring of marine invertebrates in the Kaikoura canyon would have profound effects on sperm whale feeding patterns. Marine biologist Liz Slooten happened to be studying in the Kaikoura canyon when the earthquake occurred, so she had the chance to directly study the effects of this earthquake. The article emphasizes that such an opportunity is rare in marine research.


Kaikoura Canyon

Kaikoura Canyon

 Results of the study

Using directional hydrophones, researchers tuned into sperm whale breathing sounds and found that post earthquake, male sperm whales spent roughly 25 percent longer at the surface to gather oxygen and rest their muscles. Scientists like Liz Slooten and PhD student Marta Guerra reasoned that this increase in surface breathing resulted because the earthquake swept away marine prey, causing the whales to have to dive deeper and longer to find food. According to the study, before the earthquake, sperm whales foraged in the upper parts of the canyon, but afterwards, they dove to deeper regions. Although this change seems disturbing, one positive note of resilience is that a year after the earthquake, the whales returned to their pre-earthquake breathing patterns. 

 Why are these findings significant? 

         If earthquakes are affecting the abundance and spatial variation of marine life, it is important to understand these effects so that governments can implement appropriate catch and fishing quotas to manage these areas post earthquake.

         Overall, it is clear that while these earthquakes may seem to only be affecting small invertebrates, the movement and death of these invertebrates can have profound trophic cascades. These trophic cascades will affect squid and other fish directly and the large sperm whale predators indirectly.

Additionally, while this study found that sperm whale feeding returned to normal after a year, additional studies should attempt to observe multi-year impacts to understand how earthquakes affect marine ecosystems over long periods of time. 

 Our Chosen Article:  

Rapp, J. L. (2020, January). Earthquakes can make it harder for whales to find food, first-ever study says. National Geographic. Retrieved from https://www.nationalgeographic.com/animals/2020/01/earthquakes-sperm-whales-feeding-new-zealand/

Other References

Mott, M. (2003). Can Animals Sense Earthquakes. National Geographic. Retrieved from https://www.nationalgeographic.com/animals/2003/11/animals-sense-earthquakes/

National Geographic. (n.d.). Sperm Whale. National Geographic. Retrieved from https://www.nationalgeographic.com/animals/mammals/s/sperm-whale/

Wagner, E. (2011). The Sperm Whale’s Deadly Call. Smithsonian Magazine. Retrieved from https://www.smithsonianmag.com/science-nature/the-sperm-whales-deadly-call-94653/

Melanism in Manta Rays

manta ray

After reading a New York Times article on melanism in manta rays, our group felt inspired to learn more about the species and its interesting condition. For more information, the article is linked here, as well as in the References section!

Background on Manta Rays

There are many organisms of astonishing size in the ocean, but one of the biggest and most magnificent is the manta ray. They are about 25 feet long wing to wing, and due to their extreme size, they have very few predators. There are two different species: the Mobula birostris (the pelagic type) and the Mobula alfredi (the reef type), both of which generally reside in the Indo-Pacific waters. Both species are listed as vulnerable on the IUCN Red List of Threatened Species. When viewed from below, one can observe that most manta rays have a solid white stomach; however, some have unique black spots. These black spots result from melanism—a common condition among land animals but very rare in aquatic animals.

What is Melanism?

Melanism is defined as an increased production of melanin pigments, resulting in darker colored individuals. This is very common on land and has been linked to evolutionary advantages across land animals such as pocket mice, snakes and insects. Underwater, however, melanism is highly uncommon, and out of hundreds of species of cartilaginous fish only two species—both the only known mantas—exhibit melanism. Additionally, melanism exhibited in these mantas only occur in some populations. The variation in melanism frequency in mantas from different locations has caused researchers to wonder if this phenotype provides any evolutionary advantage. 

Melanism and Natural Selection

Melanism in terrestrial animals has proven to be an advantageous result of natural selection. For example, pocket mice in contrastingly light and dark terrain have adapted to match their coat to their surroundings as a means to avoid predators. Beyond camouflage, melanism aids some species in regulating body temperature and resisting disease. Given mantas’ unique development of melanism, researchers aimed to identify which, if any, aspect(s) of fitness it could facilitate. Most manta rays have white bellies, enabling them to blend in with contrasting light from the surface and avoid being seen from below. Though manta rays have few predators, a black belly, or even a spotted one, would presumably make them more prone to predation. Given this hypothesis, marine researchers from the United States, Australia, and Indonesia recently conducted a study to determine whether melanism affects the manta ray’s survival.

Conclusion and Future Work

There is no one definitive answer as to why melanism started to show up in certain manta ray populations around the world. Current studies concluded that melanism does not give mantas survival advantage over their predators; rather, it may just be a product of genetic drift. However, it would be interesting to see a future study on their hunting habits (e.g. time of day), which can help researchers understand if melanism provides an advantage related to when mantas look for their prey. However, future research is increasingly becoming difficult with manta populations dwindling. Nevertheless, it is important to continue to better understand mantas and its important ecological role in the environment.

Ecotourism: The Value of Protecting the Manta Rays

The dwindling populations of Mobula birostris and Mobula alfredi mean their protection and conservation is more important than ever. Off the North Sudanese coast of the Red Sea, high concentrations of reef type mantas frequently congregate in and around Sanganeb Marine National Park and Dungonab Bay – Mukkawar Island Marine National Park. These two sites comprise a marine protected area (MPA) and UNESCO World Heritage Site. In fact, the only documented sighting of a Mobula birostris X Mobula alfredi hybrid ray occurred in this MPA. However, two conflicting proposals may determine the future of the area and the mantas. The Heart of the World, a Dubai-esque proposal including an airport and a huge skyscraper, would involve heavy coastal dredging, increasing turbidity and decreasing plankton abundance—two challenges for the mantas. On the other hand, there’s potential for small-scale ecotourism development based in Mohamed Qol and Dungonab, where manta-watching would promote local economic development while ensuring the MPA stays well protected. Ecotourism is rising across the world and has already shown promise in Sudan. Promoting such practices will provide the best protection for the mantas, facilitating further research into melanism and many other phenomena we’ve yet to discover.   



Augliere, B. (2020 Jan 8). For Manta Rays, Survival Isn’t Black and White. Hakai Magazine.

Kessel, S. T., Elamin, N. A., Yurkowski, D. J., Chekchak, T., Walter, R. P., Klaus, R., Hill, G., & Hussey, N. E. (2017). Conservation of reef manta rays (Manta alfredi) in a UNESCO World Heritage Site: Large-scale island development or sustainable tourism? PLOS ONE, 12(10), e0185419. doi: 10.1371/journal.pone.0185419

Klein, J. (2019 Oct 14). The Mystery of Melanistic Manta Rays. New York Times Science. 

Márquez, M. C. (2019 Dec 26). It’s Not All Black and White: Melanism in Manta Rays. Forbes

Murray, A. (2019 Sept 15). Protecting the Million-Dollar Mantas. Save our Seas.Venables, S., Marshall, A., Germanov, E., Perryman, R. & Tapilatu, R. (2019 Oct 9). It’s not all black and white: investigating color polymorphism in manta rays across Indo-Pacific populations. The Royal Society Publishing. 100(9). 5268-73. doi: 10.1073/pnas.0431157100