Discovery of a Shortfin Mako Nursery
Featured Image Caption: Two shortfin mako sharks (Isurus oxyrinchus) by MarkConlin, public domain from U.S. National Oceanic and Atmospheric Administration via Wikimedia Commons
Primary Source Article: Mucientes, G., Alonso-Fernández, A., Vedor, M., Sims, D. W., & Queiroz, N. (2025). Discovery of a potential open ocean nursery for the endangered shortfin mako shark in a global fishing hotspot. Scientific Reports, 15(1), 2190–13. https://doi.org/10.1038/s41598-025-85572-4
Secondary Source Articles:
- https://sharks.panda.org/conservation-focus/sharks-and-rays
- https://blog.marinedebris.noaa.gov/catching-marine-debris
- https://www.floridamuseum.ufl.edu/discover-fish/species-profiles/shortfin-mako
- https://www.worldwildlife.org/stories/sharks-are-key-to-the-health-of-our-oceans-and-climate
Special thanks to Julia Bebout, whose superpower is fast editing.
Sharks are vulnerable to many environmental stresses caused by climate change and human activities. Shark finning, bycatch, habitat loss, and pollution all have a negative impact on shark populations. The challenges in conservation are international cooperation, enforcement of regulations, and sustainable fishing practices that balance the needs of the environment and humanity. In particular, the biggest challenge to shark conservation is overfishing. Although fisheries are targeting other species such as tuna and marlin, sharks often get caught in the crossfire.
Understanding the vulnerable life cycle of sharks helps inform conservation policies associated with shark conservation. In a recent scientific report about the endangered shortfin mako, data obtained from a Spanish surface online vessel revealed the possibility that pregnant female sharks travel from the Southwest to the Southeast of the Pacific Ocean toward the coast of Peru and Chile to provide for their juvenile sharks. This small, but important detail is helping scientists to understand why shortfin makos are at an increased risk of being fished at a key early life stage in their development.
Importance of Sharks in Ecosystems
As apex predators, sharks play an important role in maintaining ecosystems. They help control other populations of smaller predators and herbivores. Downstream (pun intended), this helps maintain coral reefs and seagrass beds. In addition, they transfer nutrients through fecal matter (a nitrogen source) to different habitats for long distances.
The shortfin mako, Isurus oxyrinchus, is a vibrant metallic blue shark with white on its underbelly that enjoys travelling long distances in temperate and tropical waters. Their body shape is long and torpedo shaped, reaching up to 9 ft in length. From snout to tail all the edges (dorsal fin, pectoral fin, etc.) are built for speed. They can reach speeds of up to 43 mph. As a fast shark on the go, they like to eat fast moving fish like tuna and swordfish, but can also eat squid, other sharks, sea turtles, and marine mammals. It is likely that the sharks migratory nature and ability to feed on a wide variety of prey are some of the reasons why mako sharks are caught in longline fishing.
Longline Fishing and the Bycatch Problem
Pelagic longline fishing (such as the Spanish longline vessel) involves high-flyer buoys to observe position and bait such as squid, mackerel, and sardines are attached to the hooks to catch target species. Image Source: Public domain via NOAA Fisheries
Longline fishing is a fishing technique where a line of baited hooks are set either near the surface or at depths of 50-300 meters with floats that are spaced along the line. There are two types of longline fishing: pelagic and demersal. Pelagic longlines are used in midwater zones and demersal are used for deep water. Although longline fishing is intended for tuna, swordfish, and other commercial fish, this fishing technique can accidentally hook other species. These accidental catches are called “bycatch”. Sea turtles, whales, dolphins, and sharks have been documented as longline bycatch. Laceration, puncture wounds, and infections put these species at risk of death.
Report Provides New Insights on Migration
A new study approaches shark research in a different way. It gathers catch data from a Spanish surface longline vessel between (1996-2009). This vessel was traveling around the South Pacific Ocean. As they recorded female shortfins, they recorded body measurements of pregnant females to determine migration trends. For each pregnant female they were able to record location, length, liver mass, and number of embryos (through yolk sampling). Overall, the measurements revealed that migration occurs from the Southwest Pacific Ocean to the Southeast. Previously, it was thought that shortfin mako nurseries only occurred in the North Pacific Ocean. This is exciting but troubling news because the greatest overlap of commercial fishing with shortfin mako territory is occurring in areas with the highest number of juveniles.
Although these findings only came from one longline vessel, this practical approach to filling in gaps of data in shark conservation can assist in developing better management practices. Currently, the approaches to mitigating bycatch of endangered species are severely limited. Some of the solutions proposed have been limiting mainline lengths, safe handling, following release protocols, and advocacy. Many of these approaches are difficult to manage across international waters. It will take a global effort to protect these makos. Sharks are crucial to the health and balance of marine ecosystems—they can’t afford to wait.
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