Longfin mako shark

The longfin mako shark (*Isurus paucus*) is a large predator in the mackerel shark family, known as Lamnidae. It is a pelagic species, meaning it lives in the open ocean rather than near the coast. While it is often confused with its faster relative, the shortfin mako, it is a distinct and much rarer animal. This shark plays a vital role in the marine ecosystems of tropical and warm-temperate waters. Because it is uncommon, scientists are still learning much about its specific life history and habits.

The longfin mako has a very specific physical build. It possesses a slim, fusiform shape, which is a torpedo-like body designed for moving through water. Its most striking features are its long, broad pectoral fins. These fins are as long as, or even longer than, its head. Scientists believe this shape makes the shark a slower, less active swimmer than the energetic shortfin mako. The shark also has a long, pointed snout and large eyes. It lacks nictitating membranes, which are protective third eyelids found in some other species.

Reproduction in the longfin mako follows a complex biological process called aplacental viviparity. In this system, embryos hatch from eggs inside the mother's uterus. Once they hatch, the young need a way to continue growing. They use a method called oophagy to survive. This means the embryos eat nonviable eggs that the mother produces. This provides the nutrition needed for the pups to develop. While most litters consist of only two pups, a female caught near Puerto Rico in 1983 was found with eight well-developed embryos.

The history of this species' classification involves several scientific discoveries. The shark was officially described in 1966 by a Cuban marine scientist named Darío Guitart-Manday. He based his work on three adult specimens from the Caribbean Sea. Its scientific name, *paucus*, comes from the Latin word for "few." This name was chosen to highlight how rare the shark is compared to the shortfin mako. Genetic studies using mitochondrial DNA have confirmed that the longfin and shortfin makos are sister species. Interestingly, their closest relative is the great white shark (*Carcharodon carcharias*).

Longfin mako sharks have a wide, though difficult to track, global distribution. In the Atlantic Ocean, they are found from the Gulf Stream near the United States to the Iberian Peninsula and Ghana. They have also been spotted in the Mozambique Channel in the Indian Ocean. In the Pacific Ocean, they inhabit waters off Japan, Taiwan, and southern California. These sharks change their depth based on the time of day. They typically stay in the upper mesopelagic zone during the day. At night, they ascend into the epipelagic zone, which is closer to the ocean surface.

The size of the longfin mako is quite impressive. It is the second-largest species in the Lamnidae family, following only the great white shark. Females are larger than males and can reach lengths of over 4 meters. Some large specimens have even been recorded scaling over 5 meters. In terms of weight, they can exceed 450 kilograms. Their diet focuses on small, schooling bony fishes and cephalopods, such as squid. They are visual hunters, which is suggested by their large eyes and their attraction to chemical lights.

Today, the longfin mako faces significant threats from human activity. The International Union for Conservation of Nature (IUCN) has listed the species as Endangered. This status is due to its natural rarity, its low reproductive rate, and high bycatch mortality. Bycatch occurs when sharks are caught unintentionally on longlines meant for tuna or swordfish. Because they produce so few offspring, their populations struggle to recover from these losses. In the United States, the retention of this species has been prohibited since 1999 to help protect their numbers.