By Jessica Schieber, M.S. Graduate Student, Nova Southeastern U & Shark Angels Intern
Scientific Study: Morphological characterization and hydrodynamic behavior of shortfin mako shark by Patricia et al, 2019.
General Biology and Ecology
Shortfin mako sharks are a member of the Lamnid family, commonly known as Mackerel Sharks, which include the great white, (Carcharodon carcharius), the porbeagle shark (Lamna nasus), the salmon shark (Lamna ditropis), and the longfin mako shark (Isurus paucus). Shortfin makos can be typically found within temperate and tropical waters between the surface and up to 600 meters deep.[12] Bony fishes, otherwise known as teleosts (tee-lee-osts), such as mackerels, tunas, and swordfish, can make up a shortfin mako’s diet.[2,12] Male and female mako sharks grow at different rates. Males generally reach sexual maturity at a faster rate and smaller size than females.[12] Mako sharks can reach up to 13 feet long and live for 30 years or more.[6,7] These sharks are a slow growing, late maturing species.[1,6] They display a form of reproduction known as aplacental viviparity, or ovoviviparity, where eggs develop inside the mother and are “hatched” or birthed when ready, which for mako sharks is roughly after 18 months[2].
The Mako Is One Of The Fastest Sharks In The Ocean. But How??
The shortfin mako shark is considered one of the fastest sharks in the ocean, reaching top speeds of 45 mph/70 kph.[9] The longfin mako can reach speeds up to 35 mph/56 kph. These sharks can reach top speeds thanks to their specially formed skin, otherwise known as dermal denticles. Dermal denticles are small tooth-like scales that are made of a crystalline mineral, known as apatite, making them extremely strong and hard.[9] Dermal denticles are designed to reduce drag, prevent abrasions and parasites, as well as protect against predators.[3,9] A study performed by Patricia et al. (2019) looked specifically into what made the dermal denticles and their relation to their location on the dorsal fin of shortfin mako sharks so unique. The dorsal fin controls the direction and movement of a shark through the water. Patricia et al. (2019) took digital images and specific measurements of 46 individually dehydrated scales and input them into a 3D modelling program to analyze the hydrodynamic efficiency of the dorsal fin. They learned that different types of dermal denticles, based on size, shape, and location are strategically placed to minimize drag for a mako shark. In addition to scale morphology (shape and size), Mako sharks also have body functions and shapes similar to that of their prey (tunas and billfish). These adaptations include similar muscle movement and structure, elevated body temperatures and similar body shapes.[4]
Threats To Mako Sharks
According to the IUCN Redlist, mako sharks are considered to be near threatened with populations continuing to decrease around the world.[5] Mako sharks are a common bycatch species for tuna/billfish long-lining vessels. In addition to commercial fishing risks, mako sharks are sometimes caught by recreational fishermen as mako’s tend to put up a good fight and have high-quality meat.[12] Annual catch rates for mako sharks in the North Atlantic reach more than 3000 tons, or over 120,000 individuals, although that is grossly underestimated.[11] Shortfin mako sharks are managed under the ‘Consolidated Atlantic Highly Migratory Species Fishery Management Plan’ which enacts gear restrictions, permit requirements, compliance guides for both commercial and recreational fishermen, and commercial quotas and limits for catches. [7]
References:
[1]Bishop, S., Francis, M., Duffy, C., & Montgomery, J. (2006). Age, growth, maturity, longevity and natural mortality of the shortfin mako shark (Isurus oxyrinchus) in New Zealand waters. Marine and Freshwater Research, 57(2), 143-154.
[2]Campana, S. E., Marks, L., & Joyce, W. (2005). The biology and fishery of shortfin mako sharks (Isurus oxyrinchus) in Atlantic Canadian waters. Fisheries Research, 73(3), 341-352.
[3]Dillon, E. M., Norris, R. D., & Dea, A. O. (2017). Dermal denticles as a tool to reconstruct shark communities. Marine Ecology Progress Series, 566, 117-134.
[4]Donley, J. M., Sepulveda, C. A., Konstantinidis, P., Gemballa, S., & Shadwick, R. E. (2004). Convergent evolution in mechanical design of lamnid sharks and tunas. Nature, 429(6987), 61-65.
[5]IUCN 2020. The IUCN Red List of Threatened Species. Version 2020-3. https://www.iucnredlist.org. Downloaded on [02 January 2021].
[6]Natanson, L. J., Kohler, N. E., Ardizzone, D., Cailliet, G. M., Wintner, S. P., & Mollet, H. F. (2006). Validated age and growth estimates for the shortfin mako, Isurus oxyrinchus, in the North Atlantic Ocean. In Special Issue: Age and Growth of Chondrichthyan Fishes: New Methods, Techniques and Analysis (pp. 367-383): Springer.
[7] NOAA Fisheries 2020. The Atlantic Shortfin Mako Shark.
https://www.fisheries.noaa.gov/species/atlantic-shortfin-mako-shark#overview. Accessed on[02 January 2021]
[8]NOAA Fisheries 2020. The Atlantic Yellowfin Tuna. https://www.fisheries.noaa.gov/species/atlantic-yellowfin-tuna. Accessed on [02 January 2021]
[9]Patricia, F.-W., Guzman, D., Iñigo, B., Urtzi, I., Maria, B. J., & Manu, S. (2019). Morphological characterization and hydrodynamic behavior of shortfin mako shark (Isurus oxyrinchus) dorsal fin denticles. Journal of Bionic Engineering, 16(4), 730-741.
[10]Shortfin Mako. (2018). Retrieved from https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/isurus-oxyrinchus/
[11]Sims, D. W., Mucientes, G., & Queiroz, N. (2018). Shortfin mako sharks threatened by inaction. Science, 359(6382), 1342.1341-1342.
[12]Stevens, J. D. (2008). The biology and ecology of the shortfin mako shark, Isurus oxyrinchus. Sharks of the open ocean: biology, fisheries and conservation, 87-94.