Close
today i learned (til)

I love sharks, maybe you should too!

December 3, 2025

“Fish are friends, not food.” – Bruce from Finding Nemo. When I watched Disney’s Finding Nemo (2003) as a child, I was absolutely horrified by Bruce the Great White Shark. I was so afraid that when I went on family vacations to the beach, I would be wary of sharks patrolling. I would watch out for the triangular fin and didn’t want to stray too far away from the shore. Ironically, I’ve never seen the iconic Jaws (1975) movie. The director, Steven Spielberg, has said he “truly regrets” his portrayal of great white sharks and the movie’s contribution to the animal’s population decline. Even the author of the 1974 book Jaws, which inspired Spielberg’s movie, Peter Benchley, has apologized for the impact his book had on sharks and dedicated the rest of his life to shark conservation! Check out Benchley’s website–it’s awesome!

I’m not sure when I became a big fan of sharks, but I think it might’ve been because I watched a YouTube or TikTok video about them, and since then, I love sharks!

Background

Sharks belong to the class Chondrichthyes, or cartilaginous fish, meaning their skeletons are made of cartilage, rather than bone like other fish (Chapman, 2017). Fossil records have shown that members of this class have been around since 400-450 million years ago, which also means that sharks are older than trees and some dinosaurs (Chapman, 2017)! Chondrichthyans represent “one of the most species-rich lineages of predators on Earth and they continue to play important functional roles in coastal and oceanic ecosystem structure and function” (Chapman, 2017). The Chondrichthyes class has two groups: Holocephali and Elasmobranchii (“Shark Species”). The Elasmobranchii group has 8 orders of sharks, so each order classifies the “biology, physical characteristics, and behavior of sharks in that order” (“Shark Species”). Check out the Shark Research Institute’s website to learn more about sharks from different orders (you can also click on a shark to learn more about them). 

Sharks are typically found in marine habitats (although bull sharks, Carcharhinus leucas, may be found in estuaries and rivers in tropical/warm temperate regions), from shallow coastal waters and the continental shelf and slope to the deep ocean (Bennet, 2005). Sharks are highly diverse, with species ranging in size from about 20cm to over 18m (Dedman et al., 2024).

Here are some fun facts! Whale sharks are the largest fish in the sea—they can grow more than 12m long and can weigh over 21 tonnes (Chapman, 2017). You can visit Yushan, the whale shark, at the Georgia Aquarium (the only US aquarium with a whale shark). I visited the aquarium two summers ago, and whale sharks are really just gentle giants. Greenland sharks are the “longest-lived vertebrate known, with recent studies estimating a lifespan of about 390 years, give or take 120 years” (Nielson et al. 2016). Isn’t it crazy to think a species of shark could outlive three human family generations? 

Ecological Roles of Sharks

It’s actually a misconception that all sharks are apex predators (Chapman, 2017). Their exact role in the ecosystem depends on the “species, region, age/size, behavior, and/or sex” (Chapman, 2017). Chapman explains that apex predators must occupy the highest trophic level, control the ecosystem from the top down, and influence the productivity of the entire system (2015). In addition, “macropredatory and large mesopredatory sharks often induce behavioral shifts in their potential prey through predation risk and possibly competitive interactions with other predators” (Dedman et al., 2024). This means that sharks can impact how prey feed, hide, or move. Most sharks do not uphold these behaviors and would be classified as mesopredators (mid-level predators); only a select few sharks are considered apex predators, i.e., “great sharks” (Chapman, 2017). Sharks are not simply large predators: they can fill ecological roles at varying trophic levels (Dedman et al., 2024). Their diets range from filter feeding (like whale sharks) to parasites to small crustaceans to classic big predators that eat fish, turtles, seals, and other sharks (Dedman et al., 2024). However, it is challenging to create a comprehensive “understanding of ecological roles and the importance of sharks because of the inherent difficulties of studying their interactions and the mechanisms through which sharks may–or may not–affect ecosystems” (Dedman et al., 2024).

Sharks also have a bottom-up and/or facilitation role in ecosystems. Though research here is currently limited, we know that sharks move nutrients across great distances: “from pelagic environments to coral reefs, shallow to deep mesophotic coral reefs and vice versa, coastal oceans to estuarine waters, and across latitudinal gradients” (Dedman et al., 2024). These nutrients are deposited via “egestion and excretion or carcasses of sharks that die” (Dedman et al., 2024). It is worth noting that the ecological importance of this deposition needs to be further studied, as it remains unknown. 

Threats to Sharks

According to Dulvy et al.,”24% of shark, skate, and ray species are considered Threatened with extinction by the IUCN Red List’s Shark Specialist Group (2014). Targeted overfishing and bycatch (unintentional catches) contribute to the shark population decline (Shiffman and Hammerschlag, 2016). Shark fishing involves the sale of meat (for consumption), jaws (as tourist trinkets), cartilage and liver oil (as alternative medicine); the major reason for shark fishing is for shark fin soup (Shiffman and Hammerschlag, 2016). According to the Fisheries and Aquaculture Department (FAO), trade in shark parts is worth approximately US $1 billion annually worldwide (2010). Unfortunately, because of sharks’ slow growth, late maturity, and low reproductive rate, sharks are especially vulnerable to overfishing (Friedrich et al., 2014).

Conservation Efforts 

Raising awareness about shark issues and the destructive impacts human activities have on shark populations has been found to improve attitudes towards shark conservation (Friedrich et al., 2014). At a consumer level, we can consider purchasing sustainably sourced seafood or engage with campaigning for policy change (Friedrich et al., 2014). The image of sharks as fearsome predators greatly limits public engagement and support for shark conservation, which is due to cultural representations in media, such as Jaws and sensationalized media reports of shark attacks (Friedrich et al., 2014). Effective shark protection is rooted in “international strategy, changes to fisheries regulations, and tailored conservation tools (Friedrich et al., 2014). To determine effective conservation strategies, we must study ecological communities, species’ roles, and “the context of pervasive human presence in the oceans” (Dedman et al., 2024). 

Video of Yushan and Taroko from 2024 that I took! Unfortunately, Taroko died in August 2025.

Whale Sharks – Yushan and Taroko at the Georgia Aquarium’s Ocean Voyager

Sources:

Chapman, B. (2017). Shark attacks: Myths, misunderstandings and human fear. Csiro Publishing.

Bennett, M. (2005). The role of sharks in the ecosystem. St. Lucia: School of Biomedical Sciences, The University Of Queensland.

Dedman, S., Moxley, J. H., Papastamatiou, Y. P., Braccini, M., Caselle, J. E., Chapman, D. D., Cinner, J. E., Dillon, E. M., Dulvy, N. K., Dunn, R. E., Espinoza, M., Harborne, A. R., Harvey, E. S., Heupel, M. R., Huveneers, C., Graham, N. A., Ketchum, J. T., Klinard, N. V., Kock, A. A., … Heithaus, M. R. (2024). Ecological roles and importance of sharks in the Anthropocene Ocean. Science, 385(6708). https://doi.org/10.1126/science.adl2362

Dulvy, N.K., Fowler, S.L., Musick, J.A., Cavanaugh, R.D., Kyne, P.M., Harrison, L.R., Carlson, J.K., Davidson, L.N.K., Fordham, S.V., Francis, M.P., Pollock, C.M., Simpfendorfer, C.A., Burgess, G.H., Carpenter, K.E., Compagno, L.J.V., Ebert, D.A., Gibson, C., Heupel, M.R., Livingstone, S.R., Sanciangco, J.C., Stevens, J.D., Valenti, S. & White, W.T. (2014). Extinction Risk and Conservation of the world’s sharks and rays. eLife 3. (Online DOI: doi: 10.7554/eLife.00590).

FAO Fisheries and Aquaculture Department (2010). The state of world fisheries and aquaculture. Rome: Food and agriculture organization of the United States.

Friedrich, L. A., Jefferson, R., & Glegg, G. (2014). Public perceptions of sharks: Gathering support for shark conservation. Marine Policy, 47, 1–7. https://doi.org/10.1016/j.marpol.2014.02.003

Shiffman, D. S., & Hammerschlag, N. (2016). Shark conservation and management policy: A review and Primer for non‐specialists. Animal Conservation, 19(5), 401–412. https://doi.org/10.1111/acv.12265

0Likes
About Author

You May Also Like

Funny Bone, today i learned (til)
Carcinization: Evolution’s Favorite Shape is Crab
today i learned (til)
Left? Right? Left?
today i learned (til)
I Got My Brain Scanned for Science
today i learned (til)
Music Influence in Daily Life

Your journey starts here! Let’s talk!

ThemeRex © 2026. All rights reserved.
  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.