The Microplastic Problem

By Megan Buras, SRC intern

Figure 1: Plastic products are ubiquitous in our lives and the environment (Photo via Tanvi Sharma on Unsplash)

Today plastic is everywhere, from grocery stores to health products and even the shoes on our feet. The massive amount of plastic used daily, and its improper disposal have led to the accumulation of these plastics in the environment. Once plastic debris enters the ocean, it “breaks down into microplastics by photolytic, mechanical and biological degradation” (Alfaro-Núñez et al. 2021). These microplastics cause a wide range of issues, including ingestion by filter feeders mistaking this debris for plankton. One study reported “that 26%–52% of the fish collected in the English Channel had plastic debris in their gut” (Silva-Cavalcanti et al. 2017). The accumulation of microplastics in the environment has reached a point where it has begun to impact the species that live there. A study published in 2021 focused on the Tropical Eastern Pacific and Galápagos archipelago collected 240 samples from 16 different marine species. They found microplastic particles in 100% of the samples (Alfaro-Núñez et al. 2021). Species are now commonly encountering and ingesting microplastics. So what does this mean, and why is this an issue? In terms of the species that are primarily ingesting these microplastics, it has been found to cause intestinal issues, reduce nutrient absorption, and even impact fish metabolism and interfere with their immune system’s responses (Lu et al. 2016, Silva-Cavalcanti et al. 2017). Fish species that humans commonly consume have been found to contain microplastics, but little research has been done on how microplastic consumption affects humans.  

Fish and aquatic products make up a significant portion of the diet of many people globally. The amount of global aquatic animal food production has “increased over threefold from 40.8 million tonnes in 1970 to 128 million tonnes in 2010”(Tacon and Metian 2013). It is evident that fisheries play an important role in global food security. This demand for increased aquatic food production has led to damaging and catastrophic effects on the global fish stocks, threatening the food security of the world while trying to meet its demands. The rise of aquaculture has also been significant but comes with its own series of challenges in terms of what is used to feed the fish as well as disease management and resource usage. 

Figure 2: Commercial fishing has been found to have an important connection to microplastic pollution (Photo via Megane Delhaie on Unsplash)

On top of all that information, a study has found that commercial fishing contributes significantly to microplastic pollution. Results from the study “showed that the dominant contaminants (polypropylene fibers and polyethylene fibers) might originate from the abrasion of fishing gear and contributed to 61.6% of the total abundance of microplastics in surface sediment”(Xue et al. 2020). Overfishing and microplastic pollution are connected in more ways than previously thought. This begs the question: How can we better manage global fisheries productively and efficiently without compromising microplastic pollution?

Figure 3: Global food security depends on the stability of fish stocks and proper management (Photo via David Todd McCarty on Unsplash)

Looking to the future, what can be done to reduce microplastic accumulation in the environment? Reducing the demand for plastic-packaged products and plastic microbeads could potentially cut off the source of plastic debris. Better regulation and disposal of plastic could limit the amount entering the ocean and environment. What can be done to protect fisheries? More effective management of commercial marine fisheries to sustain the global fish stocks for future generations. And, of course, more research into the effects of microplastic ingestion in humans would be an excellent place to start too.


Works cited

Alfaro-Núñez, A., D. Astorga, L. Cáceres-Farías, L. Bastidas, C. S. Villegas, K. Macay, and J. H. Christensen. 2021. Microplastic pollution in seawater and marine organisms across the Tropical Eastern Pacific and Galápagos. Scientific reports 11:1-8.

Lu, Y., Y. Zhang, Y. Deng, W. Jiang, Y. Zhao, J. Geng, L. Ding, and H. Ren. 2016. Uptake and accumulation of polystyrene microplastics in zebrafish (Danio rerio) and toxic effects in liver. Environmental science & technology 50:4054-4060.

Silva-Cavalcanti, J. S., J. D. B. Silva, E. J. de França, M. C. B. de Araújo, and F. Gusmão. 2017. Microplastics ingestion by a common tropical freshwater fishing resource. Environmental pollution 221:218-226.

Tacon, A. G., and M. Metian. 2013. Fish matters: importance of aquatic foods in human nutrition and global food supply. Reviews in fisheries Science 21:22-38.

Xue, B., L. Zhang, R. Li, Y. Wang, J. Guo, K. Yu, and S. Wang. 2020. Underestimated microplastic pollution derived from fishery activities and “hidden” in deep sediment. Environmental science & technology 54:2210-2217.

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  

Using Light to Reduce Sea Turtle Bycatch

By Emma Schillerstrom, SRC intern

We often hear about light pollution as a threat to sea turtle nesting success and hatchling survival. Artificial light near beaches discourages females from nesting, disorients hatchlings toward landing sites where they cannot survive, and can even increase the activity of predators that target their offspring (Silva et al., 2017) (Information About Sea Turtles: Threats from Artificial Lighting, n.d.). However, light may not be all bad for sea turtles. It could help them if employed as a method of bycatch reduction.

Bycatch, or the incidental capture of non-target species when fishing, is a threat to many marine animals (Henry, n.d.). Electric and magnetic devices have been studied as potential strategies to deter sharks from fishing equipment. They work by overstimulating their ampullae of Lorenzini – a sensory organ of jelly-filled pores which detect electrical impulses. Similarly, studies suggest fishers and managers may use light to protect sea turtles from fishing efforts.

Image of a sea turtle caught in fishery netting (Doug Helton, NOAA/NOS/ORR/ERD, Public domain, via Wikimedia Commons).

Bycatch reduction efforts for sea turtles have primarily focused on longlines and bottom trawls rather than set gillnets (Virgili, Vasapollo, & Lucchetti, 2018). TEDs, or turtle excluder devices, consist of a metal grid attached to trawl nets to physically block sea turtles from being able to enter the net, and NOAA has required them since 1987 for use by shrimp fisheries in the Gulf of Mexico and South Atlantic (Southeast Fisheries Science Center, 2019). While TEDs have been modified and improved over time, a similar device does not exist for gillnets.

Image of a turtle excluder device (William B. Folsom, NMFS (US National Oceanic and Atmospheric Administration), Public domain, via Wikimedia Commons)


Drawing of a bottom set gillnet set-up (Joseph William Collins, Public domain, via Wikimedia Commons)

Using acoustic devices is not an effective strategy because sea turtle hearing is not sensitive enough for them to be selectively warded off (Virgili, Vasapollo, & Lucchetti, 2018). Visual deterrence, however, is much more promising since they rely heavily on visual cues for hunting, and bright light can be overstimulating (Virgili, Vasapollo, & Lucchetti, 2018). Chemical light sticks and LED lights have been tested in several studies and were found to be effective (Virgili, Vasapollo, & Lucchetti, 2018). Green, loggerhead, and leatherback sea turtles are sensitive to light in the ultraviolet (UV) range, whereas many commercially coveted fish are not (Wang, Barkan, Fisler, Godinez-Reyes, & Swimmer, 2013). UV-LED lamps are generally more expensive but have a longer life and greater light intensity, perhaps further lending to increased efficacy (Virgili, Vasapollo, & Lucchetti, 2018).

In a 2017 study, researchers at the CN-ISMAR Institute of Marine Sciences in Italy tested the ability of UV light to reduce loggerhead turtle bycatch in gillnets employed in the Mediterranean Sea (Virgili, Vasapollo, & Lucchetti, 2018). They modified nets by lining them with UV lamps spaced five and ten meters apart. By equipping some nets with lights and some without, they could compare the effectiveness of illumination for bycatch reduction through a measure called catch per unit effort, or CPUE. In this case, the catches were measured by weight or by the number of individuals, and the unit of fishing effort was standardized to be 1000 meters of net sitting underwater for 12 hours.

The addition of lamps led to a 100% decrease in bycatch. Sixteen loggerhead turtles were caught in control nets, while none were caught in the UV-lit nets. In this study, about 31% of the bycatch turtles were found dead, but in general, the mortality rate of sea turtles caught by gillnets may be as high as over 60% (Virgili, Vasapollo, & Lucchetti, 2018). All turtles caught were in nets at least 400 meters away from the illuminated nets. Between the control and illuminated nets, there was no significant difference in the CPUE in terms of the number or weight of animals caught once the bycaught turtles were excluded.

There was no observable effect of illumination on target catch efficiency, composition, or size of individuals (Virgili, Vasapollo, & Lucchetti, 2018). These findings suggest that the light did not affect the capture of target species, meaning fishery productivity should not be impacted by the addition of lamps to their nets. Based on optimized lamp spacing of 15 meters and an average net size of 300 meters, the cost of implementing this bycatch reduction device (BRD) would be around $6087 USD for an Italian vessel (Virgili, Vasapollo, & Lucchetti, 2018). A study in the Adriatic Sea in 2018 corroborated the effectiveness of this set-up, producing a 100% reduction in bycatch with two turtles caught in control nets among a mix of 20 illuminated and unaltered nets (Lucchetti, Bargione, Petetta, Vasapo, & Virgili, 2019).

In a 2013 study, researchers worked with volunteer commercial fisherman of a bottom-set gillnet fishery in Mexico (Wang, Barkan, Fisler, Godinez-Reyes, & Swimmer, 2013). They attached UV LEDs every five meters and turned them on in a subset of the nets. Fishery operations were carried out as usual. During the expedition, 332 green turtles were caught, with 209 caught in the control nets and 123 caught in the experimental nets, corresponding to a 39.7% reduction in the mean catch rate of the turtles. The scientists found no significant difference in target fish catch rates or the mean value per unit effort (VPUE) – bycatch profit – between the control and experimental nets (Wang, Barkan, Fisler, Godinez-Reyes, & Swimmer, 2013). The LEDs cost around $2 USD each, but a cost estimate for the whole fishery was not provided (Nuwer, 2013).

An alternate study conducted in northern Peru also tested green turtle bycatch reduction in gillnets (Ortiz et al., 2016). The CPUE of the turtles went down by 63.9% when illumination was added to the nets. Instead of UV light, they used standard LEDs, and the estimated costs for this set-up were 34 USD per turtle or 9200 USD for a whole gillnet fishery in Sechura Bay (Ortiz et al., 2016).

The current aim should be to optimize this bycatch reduction method by finding a balance between effectiveness and cost – in terms of device cost and any potential reductions in fishery catch – for realistic implementation. Currently, a great barrier to implementing light-based BRDs in fisheries appears to be their financial cost. However, TED use is nationally enforced offers hope that the regulated use of other bycatch reduction devices is possible and hopefully on the horizon.


Works Cited

Henry, L. (n.d.). What is bycatch? Understanding and Preventing Fishing Bycatch. (n.d.). Retrieved March 29, 2021, from 

Information about sea turtles: Threats from artificial lighting. (n.d.). Retrieved March 29, 2021, from 

Keledjian, A., Brogan, G., Lowell, B., Warrenchuk, J., Enticknap, B., Chester, G., . . . Cano-Stocco, D. (2014). Wasted Catch: Unsolved Problems In US Fisheries. Oceana.

Lucchetti, A., Bargione, G., Petetta, A., Vasapo, C., & Virgili, M. (2019). Reducing Sea Turtle Bycatch in the Mediterranean Mixed Demersal Fisheries. Frontiers in Marine Science.

Nuwer, R. (2013, November 1). Ultraviolet Illumination Warns Sea Turtles away from Fishing Nets. Retrieved from Scientific American.

Ortiz, N., Mangel, J. C., Wang, J., Alfaro-Shigueto, J., Pingo, S., Jimenez, A., . . . Godley, B. J. (2016). Reducing green turtle bycatch in small-scale fisheries using illuminated gillnets: the cost of saving a sea turtle. Marine Ecology Progress Series, 251-259.

Silva, E., Marcob, A., Graça, J. d., Pérez, H., Abella, E., Patino-Martinez, J., . . . Almeidaa, C. (2017). Light pollution affects the nesting behavior of loggerhead turtles and predation risk of nests and hatchlings. Journal of Photochemistry and Photobiology B: Biology, 240-249.

Southeast Fisheries Science Center. (2019, June 4). History of Turtle Excluder Devices. Retrieved from National Oceanic and Atmospheric Administration.

Virgili, M., Vasapollo, C., & Lucchetti, A. (2018). Can ultraviolet illumination reduce sea turtle bycatch in Mediterranean set net fisheries? Fisheries Research, 1-7.

Wang, J., Barkan, J., Fisler, S., Godinez-Reyes, C., & Swimmer, Y. (2013). Developing ultraviolet illumination of gillnets as a method to reduce sea turtle bycatch. Biology Letters.

Message in a bottle: Open source technology to track the movement of plastic pollution  

By Meagan Ando, SRC intern

The oceans on our planet are intricate, expansive, and provide a home for many organisms while maintaining a delicate balance that makes this environment so inhabitable. However, in recent times, many anthropogenic effects have been threatening them, one of which is the infamous plastic water bottle. Single-use plastic water bottles are all too familiar and are now so common that a majority of people would say they’ve seen one at some point while in natural areas. Based on beach clean-ups performed over 25 years, the International Coastal Cleanup listed these single-use nightmares fifth on the list of reported items of marine pollution (International Coastal Cleanup 2020). But how these pieces of trash end up in the oceans is a major topic of study for scientists worldwide. Because a large amount of debris is thought to originate from inland communities, rivers act as a critical transportation method as large quantities of garbage are dumped into the ocean and have been found to contribute to about 70-80% of all plastics present within the environment (Horton et al. 2017, Sarkar et al. 2019, Law and Thompson 2014). Previous studies have analyzed and modeled the drifting of this waste, which provided a basis for the research that Duncan et al. (2020) wanted to undertake. This group applied GPS networks and satellite technology to modified 500 mL plastic bottles deployed in the Ganges River and the Bay of Bengal. This technology was used due to its possibility to better understand movement through rivers and into marine habitats and how these quantities could potentially pollute open-ocean systems (Jambeck et al. 2015, Schmidt et al. 2017).  

To carry out this study, replicated “bottle tags” were designed and built to replicate movement patterns of a plastic bottle based on size, shape, and buoyancy (Figure 1) (Duncan et al. 2020). Custom electronics were constructed using a computer-aided design model along with O-rings and epoxy to keep the device afloat. The tools were deployed during the National Geographic Sea to Source Ganges Expedition in 2 phases. Ten Phase A bottles were released in the pre-monsoon season and configured to activate every 3 hours to acquire a GPS fix, while a total of 15 Phase B bottles (12 in the river pre-monsoon and 3 in the bay) were deployed and programmed to mobilize every 4 hours to spend up to 30 seconds acquiring a GPS position before returning to a resting state until a satellite passed over (Duncan et al. 2020). 

Figure 1: Visualization of the size, shape, and internal makeup of the deployment devices (Duncan et al. 2020).

Overall, the maximum distance tracked came out to be 2845 km over 94 days. Phase A tags were tracked for an average of 20.1 ± 5.7 days and, when plotted, showed a ‘stepwise’ movement (Figure 2 (a, b, c)). These deployments showed an issue with human interference and consequently being removed from the river due to high urbanization. The 12 Phase B bottles in the river were trailed for an average of 23.1 ± 9.3 days and also showed this ‘stepwise’ displacement (Figure 2 (d)). However, the 3 Phase B bottles deployed in the open-ocean were tracked for an average of 41.6 ± 26.7 days and ended up displaying a more continuous shift over the period of time (Figure 2 (e, f)). The biggest issue with these devices was due to high fishing pressure, in that they would constantly become entangled in fishing gear. To conclude, this proof of concept was successfully displayed in order to help understand how plastic waste such as water bottles is transported through the environment. The capacity for which this satellite technology can be used shows a significant ability to increase and gain new knowledge identifying various habitats associated with the accumulation of plastic debris, which could help conserve those under the most immediate threat of degradation.  

Figure 2: Bottle displacement versus time tracked (Duncan et al. 2020).


Works cited 

Duncan EM, Davies A, Brooks A, Chowdhury GW, Godley BJ, Jambeck J, et al. (2020) Message in a bottle: Open source technology to track the movement of plastic pollution. PLoS ONE 15(12): e0242459. 

Horton AA, Walton A, Spurgeon DJ, Lahive E, Svendsen C. Microplastics in freshwater and terrestrial environments: Evaluating the current understanding to identify the knowledge gaps and future research priorities. Sci Total Environ. 2017 May 15; 586:127–41 

International Coastal Cleanup. Tracking Trash: 25 Years of Action for the Ocean (2020) 

Jambeck JR, Geyer R, Wilcox C, Siegler TR, Perryman M, Andrady A, et al. Plastic waste inputs from land into the ocean. Science (80-). 2015 Feb 13; 347(6223):768–71. 

Law KL, Thompson RC. Microplastics in the seas. Science (80-) [Internet]. 2014 Jul 11; 345(6193):144–5. 

Sarkar DJ, Das Sarkar S, Das BK, Manna RK, Behera BK, Samanta S. Spatial distribution of meso and microplastics in the sediments of river Ganga at eastern India. Sci Total Environ. 2019 Dec 1; 694:133712. 

Schmidt C, Krauth T, Wagner S. Export of Plastic Debris by Rivers into the Sea. Environ Sci Technol. 2017 Nov 7 ; 51(21):12246–53. 

It’s complicated: Understanding non-compliance in small-scale fisheries

By Peter Aronson, SRC Intern

Following regulations can be vital for conservation, yet the world’s realities place pressure onto people, which can incentivize non-compliance. This undermines conservation work and the positive ecological outcomes achieved by it. In the ocean specifically, short bursts of illegal fishing can negate the effects of decades of protection, especially for species whose populations take a long time to recover, like many sharks (Russ and Alcala, 2010). As shark populations have declined globally, conservationists have advocated for shark sanctuaries to be established to protect sharks from exploitation (Dulvy et al., 2014; Ward-Page and Worm, 2017). By understanding the motivations and traits of those not following regulations, strategies can be developed to increase compliance (Keane et al., 2008). Nearly all fishers in the world live in lower-income countries and are engaged in small-scale fisheries, but research on the behavioral drivers of illegal fishing has traditionally focused on recreational fishers in wealthier countries (Bova et al., 2017; World Bank et al., 2012). A group of scientists set out to Myanmar to study fishers’ awareness of, compliance with, and perceptions towards shark fishing regulations.

Figure 1) Populations of some shark species, such as whale sharks, have been in decline globally due to overexploitation. (Victor Researcher (2008). 21 Ton Whale Shark. WikiCommons.)

Myanmar prohibits the capture and sale of whale sharks and has two shark reserves in which shark fishing is not permitted; however, many fishers are unaware of these regulations. The Department of Fisheries also lacks the ability to enforce them. There is additionally ambiguity as the law was declared informally, and it doesn’t address instances of bycatch. Scientists studied five coastal communities they had well-established relationships with where prohibited shark fishing was known to occur. They conducted surveys with fishers, in which fishers could voluntarily answer whether, where, and when they had caught sharks and witnessed others catching sharks. Scientists found 40% of respondents had accidentally or intentionally caught an estimated 4821 sharks in the year prior to the survey (MacKeracher et al., 2020). Of the 58 respondents, 35 reported having caught sharks themselves (MacKeracher et al., 2020). Overall, 49% of respondents were aware of shark fishing rules, with levels of awareness varying among communities (MacKeracher et al., 2020). Shark fishers tended to be younger and not to own their own boat. Most sharks being caught fell within three families: bamboo and epaulette sharks (Hemiscylliidae), requiem sharks (Carcharhinidiae), and hammerhead sharks (Sphyrnidae) (MacKeracher et al., 2020). Nearly 80% of fishers came from the large coastal city of Myeik and sold their catch there and other large coastal cities, while the remainder of fishers from the local communities sold their catch locally (MacKeracher at al., 2020). Fishers who reported catching sharks themselves most commonly said they did so for money, and also mentioned food (MacKeracher et al., 2020).

Figure 2) Boats in the Myeik Archipelago, Myanmar. (Go Myanmar. (2013). The Myeik Archipelago, Myanmar (Burma)[Photograph]. WikiCommons.)

Understanding the levels and potential drivers of illegal shark fishing puts the issue into context and allows resource managers to strategically and effectively plan how to improve compliance. In areas where poverty rates are high and options for alternative sources of income are low, there is a high incentive to fish illegally. Further, communities with limited interactions with fisheries officials are less likely to be aware of regulations, which can contribute to non-compliance. In resource-dependent communities with few options as sources of income, shark conservation efforts can benefit from strategies to reduce fishing pressure by providing incentives for alternate sustainable livelihoods. Further, as most shark fishers are young men, these can be incentives targeted for that demographic. While educational campaigns can improve awareness and compliance, long-term compliance must be achieved by addressing broader issues such as poverty and food security.


Works Cited

Bova, C.S., S.J. Halse, S. Aswani, and W.M. Potts. 2017. Assessing a social norms approach for improving recreational fisheries compliance. Fisheries Management and Ecology 24: 117–125.

Dulvy, N.K., S.L. Fowler, J.A. Musick, R.D. Cavanagh, P.M. Kyne, L.R. Harrison, J.K. Carlson, L.N. Davidson, et al. 2014. Extinction risk and conservation of the world’s sharks and rays. eLife 3: e00590.

Keane, A., J.P. Jones, G. Edwards-Jones, and E.J. Milner-Gulland.2008. The sleeping policeman: Understanding issues of enforcement and compliance in conservation. Animal Conservation 11:75–82.

MacKeracher, T., Bergseth, B., Maung, K. M. C., Khine, Z. L., Phyu, E. T., Simpfendorfer, C. A., & Diedrich, A. (2020). Understanding non-compliance in small-scale fisheries: Shark fishing in Myanmar’s Myeik Archipelago. Ambio, 1-14.

Russ, G.R., and A.C. Alcala. 2010. Decadal-scale rebuilding of predator biomass in Philippine marine reserves. Oecologia 163: 1103–1106.

Ward-Paige, C.A., and B. Worm. 2017. Global evaluation of shark sanctuaries. Global Environmental Change 47: 174–189.

World Bank, Food Agriculture Organization, and WorldFish. 2012. Hidden harvests: The global contribution of capture fisheries, economic and sector work. Report No. 66469-GLB. Washington, DC: The World Bank.

Using Local Fisher’s Knowledge in Marine Conservation

By Megan Buras, SRC Intern

To set historical baselines for conservation actions, scientists are using new tactics to involve fishers in marine management. Gaps in long-term scientific data about species abundance and diversity can lead to mismanagement of exploited ecosystems. Scientists from the University of Aberdeen interviewed 53 fishers in three different ports of northern Italy to use Fisher’s Ecological Knowledge to determine historical baselines for conservation in the Northern Adriatic Sea. These interviews collected data from three different groups, novices (fishermen with 1-20 years experience), experienced (21-40 years experience), and veteran (greater than 40 years experience) fishermen (Veneroni and Fernandes 2021). From the interviews, the scientists were able to determine trends in fish abundance and collect information about generational accounts of degradation in both species diversity and the seafloor. 

Figure 1: The study interviewed fishers across a broad span of experience to determine generational comparisons of species abundance and diversity. (Image via Egor Myznik on Unsplash)

In terms of species abundance, the study found a linear decrease in cuttlefish catch rates, a significant decline in sole populations, and no significant change in the catch rates of red mullet over 60 years (Veneroni and Fernandes 2021). The study found significant differences between old and young fishers in the generational accounts of species’ diversity. This is evidence of something called Shifting Baseline Syndrome. In this paper, Shifting Baseline Syndrome refers to an incorrect perception of the health of the ecosystem due to false information about its past conditions. This syndrome can lead to mismanagement of an ecosystem appearing to be healthier than it truly is. In the generational accounts of species’ diversity, the study found that veteran fishers listed a greater number of depleted commercial species than novice fishers. In the generational accounts of seafloor degradation, the study found that many of the veteran fishers believed that trawling equipment was the primary cause for degradation, while the novice fishers cited high fishing effort. 

Figure 2: The study interviewed fishers in 3 different ports in Northern Italy, including Cesenatico, Rimini, and Cattolica. (Source: Veneroni and Fernandes 2021)

Fisher Ecological Knowledge provided knowledge on the historical trends of species abundance and diversity in the Northern Adriatic Sea. This information was found “often exceeding national and international scientific data sets” (Veneroni and Fernandes 2021). While it is evident through generational comparisons that Shifting Baseline Syndrome is at play here, there are other examples of conservation being impeded due to similar circumstances. Dogger Bay in the North Sea is another example of how long-term human exploitation can cause marine management failure set on incorrect baselines (Plumeridge and Roberts 2017). Gaps in knowledge contributing to Shifting Baseline Syndrome are not limited to the field of marine conservation. Even ethnobotanical research has found a loss of generational knowledge to inhibit people’s perceptions of the environment (Hanazaki et al. 2013). All this information indicates that Fisher Ecological Knowledge should be implemented into local conservation efforts. This study utilized “cultural brokers” or individuals from the community to gain social entry and acceptance. This highlights the importance of cultivating relationships with local fishers and community members to better protect and understand local environments.


Works cited

Hanazaki, N., D. F. Herbst, M. S. Marques, and I. Vandebroek. 2013. Evidence of the shifting baseline syndrome in ethnobotanical research. Journal of Ethnobiology and Ethnomedicine 9:1-11.

Plumeridge, A. A., and C. M. Roberts. 2017. Conservation targets in marine protected area management suffer from shifting baseline syndrome: A case study on the Dogger Bank. Marine pollution bulletin 116:395-404.

Veneroni, B., and P. G. Fernandes. 2021. Fishers’ knowledge detects ecological decay in the Mediterranean Sea. Ambio:1-13.

How Recreational Fishing Videos are Aiding Management Efforts

By Nina Colagiovanni, SRC intern

As technology advances in today’s world, scientists are becoming more aware of the benefits of data gathered from platforms like YouTube. Research conducted by Sbragaglia et al. collected YouTube videos relating to recreational fishing of four species of grouper: dusky (Epinephelus marginatus), white (Epinephelus aeneus), goldblotch (Epinephelus costae) and dogtooth (Epinephelus caninus). Recreational fishing refers to any fishing activity that is not done for commercial purposes (Giovos et al., 2018).

Figure 1:  mA Fishing Rod and Reel Set Up [Wynand van Poortvliet via Unsplash]

This research was carried out in Italy between the years of 2011 and 2017 in order to understand the ecological patterns of groupers in the Mediterranean Sea and to demonstrate how data can aid in conservation science (Sbragaglia et al., 2020). Data was obtained from anglers and spearfishers who had uploaded videos of their catches publicly. 

Prior research examined recreational fishing videos of common dentex (Dentex dentex) which is an important species in the Mediterranean, and it was found that there was greater support as well as a greater mass of fish caught in angling videos versus spearfishing videos (Sbragaglia et al., 2019). 

This research focused on groupers which are currently listed under the International Union for Conservation of Nature (IUCN) Red List. Their hypothesis included that larger target species will search for protection from fishers in deeper waters, known as the “depth refuge” hypothesis (Sbragaglia et al., 2020). Additionally, they wanted to examine whether there was a northward expansion in the white grouper.

Figure 2: Number of Annual Videos Related to Recreational Fishing of Groupers [Sbragaglia et al. 2020]

A total of 2097 videos were identified over the years, with 1714 (82%) relating to spearfishing and 383 (18%) relating to angling (Sbragaglia et al., 2020). The videos were reported in regard to fishing method, which marked angling with red triangles and spearfishing with blue circles, as shown in Figure 2 (Sbragaglia et al., 2020). It can be seen that the trends differed depending on the species. For instance, the dusky, white and goldblotch groupers had more videos relating to spearfishing, while the dogtooth did not. This is due to the fact that dogtooth groupers inhabit deeper water where it is more difficult to spearfish.

In comparison to the common dentex, spearfishing videos were more representative in grouper species. This could infer that more spearfishing videos are being uploaded to YouTube or that spearfishing is a more popular method for grouper catches.

Figure 3: A Dusky Grouper [Pascal van de Vendel via Unsplash]

Overall, their results found that body mass and depth in angling videos were greater than in spearfishing videos for both the dusky and white groupers, and that there was a northward expansion of the white grouper (Sbragaglia et al., 2020). This supported their initial hypothesis, indicating that there were shifts in grouper distribution.

This research not only provides insights into the ecological patterns of groupers, but also displays how digital data gathered from platforms like YouTube can be utilized for research purposes and can contribute to management of marine species like the grouper or the common dentex in the future. 


Works cited

Giovos, I., Keramidas, I., Antoniou, C., Deidun, A., Font, T., Kleitou, P., . . . Moutopoulos, D. (2018, June 28). Identifying recreational fisheries in the Mediterranean Sea through social media. Retrieved March 10, 2021, from

Sbragaglia, V., Correia, R., Coco, S., & Arlinghaus, R. (2019, June 14). Data mining on YouTube reveals fisher Group-specific Harvesting patterns and social engagement in recreational anglers and spearfishers. Retrieved March 10, 2021, from

Sbragaglia, V., Coco, S., Correia, R., Coll, M., & Arlinghaus, R. (2020, October 04). Analyzing publicly available videos about recreational fishing reveals Key ecological and social insights: A case study ABOUT groupers in the Mediterranean Sea. Retrieved March 10, 2021, from

Behavior modifications in whale sharks (Rhincodon typus) suggest a need for tourism management intervention

By Adrianna Davis, SRC intern

The whale shark (Rhincodon typus) is the world’s largest extant fish species (Figure 1). Whale sharks are solitary animals; however, they aggregate where there is high availability of copepods, fish eggs, and crab larvae, which are staples of the whale shark’s broad diet (Legaspi et al. 2020). The elusiveness of the whale shark contributes to its popularity with tourists. Encounters with whale sharks began in 1980s at Ningaloo Marine Park and have since been adopted in other areas where whale sharks frequent. In 2018, approximately $10 million was input into the economy by the 500,000 tourists who visited Oslob, Philippines to see whale sharks (Legaspi et al. 2020). Despite economic benefits, concerns have arisen regarding the pressure this puts on whale sharks.  

Figure 1: Anterior view of a whale shark swimming at the surface (Source: NOAA 2019)

A recent study conducted by Legaspi et al. suggests that management intervention is necessary to mitigate the tourism pressure on whale sharks. The team conducted focal follow surveys in an interaction area off of the Philippines (Figure 2) from February 2015 to May 2017 to understand how external stimuli influences shark behavior. Researchers used photograph identification to record sharks’ behaviors in response to events that occurred in the survey period. The events and behaviors were previously outlined by the researchers (Legaspi et al. 2020). The collected data was analyzed using a binomial generalized linear mixed model (GLMM) to integrate variables.  

Figure 2: Map of the study site in the Philippines that magnifies into the interaction area (c) (Source: Legaspi et al. 2020)

From the 358 twenty-minute surveys that were conducted, there were 692 events recorded, including 38 active touches and 301 passive touches. Violations to regulations set by the local government included 75.1% of swimmers coming within 2 m of the shark and 13.4% of at least one diver coming within 2 m of the shark (Figure 3). These events made the sharks more likely to exhibit an avoidance behavior, which was recognized by the shark diving, swimming off, rolling back its eyes, or shuddering violently (Legaspi et al. 2020).  

Figure 3: Frequency of the number of people seen within 10 m of the sharks in comparison the recommended maximum of six (indicated by the red line) (Source: Legaspi et al. 2020)

 The whale sharks that were observed feeding were less likely to display avoidance behaviors. This may indicate that the whale sharks learned to associate food with the site (Legaspi et al. 2020). Although the learning abilities of sharks have not been heavily studied, an experiment on small-spotted catsharks (Scyliorhinus carnicula) found that the foraging efficiency of the catsharks significantly improved when food was used for positive reinforcement techniques (Kimber et al. 2013). It is possible that whale sharks in Oslob have begun to exploit the provisions of tourist boats. One concern that arises is how non-target species will be impacted by provisioning. Studies on bait and chum input from shark cage-diving have shown that nontarget species will forage on these provisions and alter their diet (Meyer et al. 2020).  

As wildlife tourism increases in popularity, the threats of overcrowding and noncompliance of visitors, as well as the implications from provisioning, will continue to negatively impact shark behavior if not properly monitored. One possible mitigation strategy is developing an assessment framework available to researchers, managers and policy makers (Meyer et al. 2021). The wellbeing of the whale shark population must be prioritized so that the species can thrive, allowing tourists to continue to have memorable experiences and local economies to thrive.  


Works Cited 

Kimber J.A., Sims D.W., Bellamy P.H., Gill A.B. 2013. Elasmobranch cognitive ability: using electroreceptive foraging behaviour to demonstrate learning, habituation and memory in a benthic shark. Anim. Cogn. 17:55-65. 

Legaspi C., Miranda J., Labaja J., Snow S., Ponzo A., Araujo, G. 2020. In-water observations highlight the effects of provisioning on whale shark behaviour at the world’s largest whale shark tourism destination. R. Soc. Open Sci. 7:200392.  

Meyer L., Apps K., Bryars S., Clarke T., Hayden B., Pelton G., Simes B., Vaughan L.M., Whitmarsh S.K., Huveneers C. 2021. A multidisciplinary framework to assess the sustainability and acceptability of wildlife tourism operations. Conservation Letters 

Meyer L., Whitmarsh S.K., Nichols P.D., Revill A.T., Huveneers C. 2020. The effects of wildlife tourism provisioning on non-target species. Biological Conservation 

NOAA, 2019. Whale shark viewing photographer [Photograph]. 

Corals and Seaweed: The Fight for Dominance

By Konnor Payne, SRC Intern

Coral reefs exist because the environment around them gives them the means to survive. These conditions are also the perfect environment for seaweeds, which compete with the corals for space. Worldwide, there have been recorded occurrences of transitions from coral to seaweed dominance. Researchers at the University of California Santa Barbara theorized that this was due to the overfishing of herbivores that would otherwise keep the seaweeds at bay, or nutrient enrichment, leading to an explosion of seaweed. To test this hypothesis, they traveled to the barrier reef of Moorea, French Polynesia. This reef had experienced an outbreak of coral-eating sea stars in the past few decades that reduced the coral cover to less than 5%. For unknown reasons, the fore reef (outer slope) has recovered but not the corals in the lagoon (back reef), which have been taken over by a seaweed called Turbinaria ornata. Investigating the difference in the corals’ resilience along the fore reef and lagoon could give insight into herbivory tipping points to maintain a coral-dominant environment. There was also a chance of “hysteresis,” or the idea that a slight change in one parameter produces an environment that requires a more significant change in the same parameter to return the environment to its original state. 

Figure 1. Adult Turbinaria ornata in Moorea, French Polynesia that compete with corals for space and resources (Schmitt, 2019).

The resilience test was conducted in the lagoon by mimicking storms’ varying intensities for 26 months on patch reefs and observing their recovery over 37 months. The researchers replicated a storm disturbance by removing all or parts of seaweed on the sample site. The researchers compared the abundance of coral at the beginning of the experiment to the end. The corals were highly resilient to a moderate disturbance, but not severe disturbance, from which they failed to recover and became dominated by turf algae. If the amount of herbivory is insufficient, the area will convert fully to seaweed dominance due to fishing pressure. 

Figure 2. The exclusion cage is placed on a patch reef to limit herbivorous fish’s body size that graze on it (Schmitt, 2019).

To test for hysteresis, a series of cages with various-sized holes were placed across patch reefs to limit the herbivorous fish body size, limiting their feeding capacity (Fig. 2). The researchers left these sites for as long as needed until the system naturally reached a stable state. The researchers found hysteresis at both sites by comparing the stable states of coral versus seaweed across the fore reef and lagoon. However, the standard conditions on the fore reef had herbivory action high enough to prevent seaweed dominance. In contrast, the lagoon is on the tipping point. The lagoon is at risk for completely transitioning to a seaweed-dominant environment, whereas the fore reef will likely remain coral-dominated. The researchers concluded that reversing an undesired shift on coral reefs would be difficult due to the hysteresis effect. The results suggest that proactive management strategies to prevent shifts in the first place will be more effective than management strategies targeted at restoration. 


Works Cited

Schmitt, R. J., Holbrook, S. J., Davis, S. L., Brooks, A. J., & Adam, T. C. (2019). Experimental support for alternative attractors on coral reefs. Proceedings of the National Academy of Sciences, 116(10), 4372-4381.

Crime on the High Seas: How Organized Crime Could Hinder a Sustainable Ocean Economy

By John Proefrock, SRC Intern

When you think of organized crime your mind probably drifts towards the mafia and cartel or the dramatized versions of these organizations that show up in TV shows and movies. So, it may come as a shock to some that there is a direct threat from organized crime to the future of a sustainable ocean economy. Organized crime in the fisheries industry isn’t a new issue, even Al Capone utilized the commercial fishing industry to smuggle rum during prohibition (Ensign, 2001), but there is a lack of awareness on the international stage to the danger that crime organizations can have on maritime industries. The goal of Witbooi et. al. (2020) is to provide the current state of knowledge on organized crime in the fisheries sector so that the information can be distributed and acted on by nations which have a vested interest in the growth of a safe and sustainable ocean economy. 

Organized crime on the sea is not as lighthearted as The Pirates of the Caribbean would have you believe. These organizations indiscriminately use illegal fishing practices to obtain copious amounts of sea life. The illegal catch is then sold on the market to unsuspecting consumers using fraudulent documentation, often undercutting the ethically sourced seafood and perpetuating the cycle of harmful practices. One example of such an operation is the case of The Viking, a ship that was detained in Indonesian waters by the Indonesian Navy. This ship was illegally catching and selling Patagonian Toothfish, Dissostichus eleginoides. The operators of the ship were utilizing illegal gillnets, the most discarded fishing equipment in the commercial sector, meaning that many end up entangling whales and other large sea fauna (Shester et. al, 2011). Use of nets over 2.5km long is punishable by 5 years in jail and a fine up to $150,000 US dollars. These fishermen also reported to a organizer who profited from the illegal sale.

A Patagonian Toothfish: Dissostichus eleginoides Source:

Aside from fisheries violations, organized crime on the ocean also encompasses fraud, money laundering, smuggling/drug trafficking, corruption and forced labor. The challenge associated with dealing with this wide variety of issues boils down to a couple main points. The first is a lack of national prioritization due to a lack of information and the difficulty associated with investigating claims of illegal activity. There is also the issue of unclear jurisdiction, or who can actually act on crime that has been observed and a lack of capacity and skillset of law enforcement to deal with organized crime on the high seas. 

A pelagic thresher shark, Alopias pelagicus, killed after getting caught in a gill net.

Positive developments in this field would include the strengthening of international cooperation to create a wide-sweeping net of jurisdiction so that no illegal operation flies under the radar, with a constant exchange of information and intelligence. Training the law enforcement agencies to deal with this specific breed of crime would also prove beneficial to the future of sustainable fisheries. These steps can ensure the future of our oceans and a sustainable maritime economy.


Work Cited:

Ensign, Eric S. Intelligence in the Rum War at Sea, 1920-1933. Joint Military Intelligence Coll Washington Dc, 2001. 

Shester, Geoffrey G., and Fiorenza Micheli. “Conservation Challenges for Small-Scale Fisheries: Bycatch and Habitat Impacts of Traps and Gillnets.” Biological Conservation, vol. 144, no. 5, 2011, pp. 1673–1681., doi:10.1016/j.biocon.2011.02.023. 

Witbooi, Emma, et al. “Organized Crime in the Fisheries Sector Threatens a Sustainable Ocean Economy.” Nature, vol. 588, no. 7836, 2020, pp. 48–56., doi:10.1038/s41586-020-2913-5.