Shortfin mako: The peregrine falcon of the sea
The shortfin mako shark (Isurus oxyrhinchus) is a pelagic shark of the lamnidae family. It is considered the fastest shark in the world and is possibly in the top five fastest fishes, just behind the billfishes, earning it the nickname “the peregrine falcon of the sea“. Speeds of 50 km/h have been officially recorded, although there are some estimates of adult shortfin mako sharks that may have reached 70 km/h.
But how is this possible in an aquatic environment that offers so much resistance?
The answer to this question is simple. Design and power. Shortfin mako sharks are evolutionarily designed for speed. A long, pointed snout and streamlined body make them incredibly hydrodynamic. In addition, they have a powerful, half-moon-shaped tail that propels them through the water. Their skin, like that of all sharks, is covered with millions of tiny tooth-like scales called dermal denticles, which point backwards to reduce friction with the water, but in this case, the design is taken to the extreme. In areas of increased water flow, for example on the edges of the pectoral fins, shortfin makos also have “flexible scales” which, when the flow increases, become bristly, helping to push water over the body more efficiently, like the flaps of a racing car. This design allows them to reach high speeds and also perform jumps of about 9 meters out of the water. In addition, they are also great swimmers, being able to cover average distances of almost 60 km per day.
Another great adaptation, also present in other lamnids such as the white shark (Carcharodon carcharias), is what is known as endothermy, i.e. the ability to retain the heat generated by muscle activity and metabolism, which allows them to maintain a body temperature well above the water temperature (in some species up to 20ºC). This increases their muscle power, facilitates digestion and their movements can be faster and more explosive.
Despite these evolutionary advantages, like many other sharks, their biological characteristics make them highly sensitive to overfishing. Shortfin makos have a very low reproductive rate and only produce pups every 3 years. Females mature at 18 years and produce only 4-25 pups, after a gestation period of 15-18 months.
Highly valued for their meat and fins, they are targeted by fishing fleets and are also caught as bycatch. Decades of harvesting without setting fishing limits have driven the North Atlantic stock to an unprecedented level of depletion that raised alarm bells in 2017 when scientists detected serious levels of overfishing and recommended a ban on catching them. Scientists estimate that if we were to stop all catching right now, the stock would only have a 50% chance of recovering to healthy levels by 2045, and a 70% chance of recovering by 2065.
Despite the critical nature of the situation and the clarity and seriousness of the scientific advice, the EU, the Fisheries Ministries of various countries (Spain among them), the Regional Fisheries Management Organisations (RFMOs from now on) such as ICCAT, are still dragging their feet and putting obstacles in the way of banning their retention in the North Atlantic (in the Mediterranean their fishing has been banned for years).
Fortunately, in 2019, the shortfin mako shark was listed in Appendix II of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora), which means that it is necessary to demonstrate that exports and landings of this species come from legal and sustainable fisheries. The latest news suggests that the Ministry of Ecological Transition, which is responsible for the CITES authority in Spain, is not going to issue any certificates and that the commercialization quota for 2021 is going to be 0. Similar moves are also being seen in the Portuguese government, which has also recently announced the same thing. Both of these things give some hope for the future of shortfin mako shark stocks in the North Atlantic, especially as Spain and Portugal are the countries that catch the most mako shark. We will see if the trend continues and if finally, also from Fisheries, the EU and the RFMOs, it is decided to follow the advice of scientists to ban the retention on board of shortfin mako sharks and thus begin to build the road to recovery of their populations.