First record of scoliosis in a free-swimming scalloped hammerhead shark (Sphyrna lewini) in the Galápagos Islands

This communication presents the first record of a dorsal deformity in a free-swimming scalloped hammerhead shark (Sphyrna lewini), observed in the Galápagos Islands. The individual was filmed on May 7, 2024, during a recreational dive at a popular dive site by the island of Santa Cruz. The female shark was diagnosed with scoliosis—a lateral spinal curvature, which impacted its swimming efficiency, resulting in slower and less coordinated movements compared to a healthy individual swimming in close proximity. The individual’s general anatomy appeared compromised due to the combination of deformities and lesions. Possible causes include predation attempt, injuries from fishing, diseases, coercive mating behavior, exposure to contaminants, vessel collisions, or congenital malformations, which may have led to tissue trauma and potentially subsequent vertebral malformation. This communication underscores the value of in situ observations to help the understanding of the impact of deformities in marine species, providing insights into their mobility and survival. It also provides an opportunity to reflect on the role of marine protected areas in mitigating potential fitness debilities.