Sharks are really Some-fin Else: A closer look at fish fins

Picture credit: Open source

A curious individual could spend hours in a Google warp about fish fin diversity (warning: this may cause lack of studying for exams), and limiting that search to Chondrichthyes fin diversity would only increase time in the warp (and possibly make you forget a dentist appointment). 

The media often displays a sleek dorsal fin breaking the water’s surface to adrenaline pumping music, but the dorsal fin of many shark species (especially our jawesome deep sea sharks) never break the surface.  Some shark species, like the filled shark, don’t have the classic fins our mind visualizes at all (check it out: https://www.finsunited.co.nz/bite-blog/frilled-shark)! The dorsal fin is commonly utilized for stability and balance, but shape, size, and quantity can vary between species. Some may have an anterior and posterior dorsal fin, even topped with spines for added protection! The pectoral fins on a shark assist with lift and often work as a unit with the pelvic fins to keep the shark stable and provide support when turning. This teamwork leads scientist to refer to the pectoral and pelvic fins as the paired fins. My personal favorite, the caudal fin, is a sleek, powerful tool that propels sharks through the water. Caudal fins also differ with unique adaptations. Thresher sharks use their caudal fins to stun their food (enter whip sound effect here) (https://www.finsunited.co.nz/bite-blog/general-thresher-sharks).
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The caudal fin also displays a difference between fish and marine mammals.  Fish caudal fins run vertically, creating a side to side movement and sometimes even the appearance of a second shark.  The caudal fins of marine mammals are horizontal, creating up and down movement. One could say marine mammals swim with more of a porpoise, but sharks are more proFISHent swimmers :)

Credit: Paste Magazine

​Struggle with remembering which fin is which? Try this nifty song to the tune of “head, shoulders, knees, and toes”

Dorsal, pectoral, pelvic, caudal, pelvic, caudal
Dorsal, pectoral, pelvic, caudal, pelvic, caudal
Lateral line, gills, operculum*
Dorsal, pectoral, pelvic, caudal, pelvic, caudal
 
*this song is for fish in general, sharks actually have gill slits instead of an operculum!
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In addition to keeping sharks fast and upright, fins help scientists identify species AND individuals. Larger species have more dorsal fin surface area to observe, and individuals can have different spots, scars, and tears. Identifying species is helpful when studying population dynamics and ranges. Identifying individual sharks can help us better understand migrations, ages, and behaviors. If you’re lucky to observe sharks up close you could even help identify individuals and record their patterns!

​Sadly, the image I picture most often when thinking of shark fins is not the awesome diversity, or the majestic shark the fin is attached to, but dried out shark fins in market places. Shark fins have been harvested for multiple generations and for many uses, but unfortunately they are not collected in a sustainable way. The demand and collection is detrimental to current shark populations. Often the shark is alive when the fins are removed, and the process doesn’t immediately kill the individual. The sharks are dumped finless back into the water and sink to the bottom. The collected fins are used in food and traditional medicine. Shark fin soup is considered a delicacy, served in high end places or as a way to flaunt ones wealth and status. Many companies and celebrities have been speaking out in an attempt to make individuals realize how the fins are collected and why the process needs to change. Scientists working against shark finning have turned to DNA extraction processes to determine species that are being hit the hardest. While advances in technology and transportation are modern marvels, they’ve made it easier for the harvesting and transport of shark fins (and other wildlife) around the globe. However, these advances also make it easier for shark lovers everywhere to be involved and help save our sharks! The best place for a shark fin is on the shark, whether it is used for protection, predation, or pure visual perfection. 
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Picture credit: SHAWN HEINRICHS / BLUE SPHERE MEDIA

Want to help stop shark finning?
Here are few great organizations and awesome resources:

• Project Aware
  
• ​Oceana
  
• Stop Shark Finning

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glossary

• Diversity: a variety of species
• Chondrichthyes: cartilaginous fish, lacking bone. Includes sharks, skates, and rays
• Adaptation: a characteristic or behavior that helps an animal survive in its environment
• Dorsal: relating to the back
• Pectoral: relating to the chest, thoracic
• Pelvic: relating to the pelvis
• Paired fins: the pectoral and pelvic fins
• Caudal: at or near the tail end
• Anterior: at or near the beginning, mouth
• Posterior: at or near the end, rear
• Sustainable: capable of being supported over time

GUEST BLOGGER AND TFUI OFFICER CARISSA THIEL

Carissa Thiel graduated with a BS in marine biology and then spent a few years working in environmental education. She now works as a Guest Engagement Educator, spreading conservation messages to locals and visitors alike!

Carissa loves exploring, reading, talking to people, and awkward get to know you questions. If she could be any bird she would want to be an osprey, because they have wonderful adaptations to hunt fish and are always found by water. However, she would probably be an emu because they have long legs, make awkward faces, and only watch other birds fly.