OCEARCH genomics study finds sibling pairs among white sharks

OCEARCH, a Florida-based marine research nonprofit, has published preliminary findings from what it describes as the first genomic kinship study of white sharks in the Western North Atlantic, identifying multiple close family relationships within a tagged population and raising new questions about how genetic ties may shape migration and habitat use.

The study, conducted by researchers at Texas A&M University-Corpus Christi (TAMU-CC) using genetic samples gathered across nearly two decades of OCEARCH expeditions, identified three pairs of full siblings and seven likely half-sibling pairs. One full sibling pair was estimated to have come from the same litter; two others were estimated to have been born approximately five and nineteen years apart, based on growth-model-derived birth years. The genetic evidence is described by the team as overwhelmingly consistent with full sibling status, though additional sequencing is planned before the work is submitted for peer-reviewed publication.

Family connections and migration patterns

Among the named individuals in the preliminary findings are Jekyll, a male white shark tagged in 2022, and Olympia, a female tagged in 2021. The two were identified as full siblings, born an estimated five years apart. The connection emerged somewhat unexpectedly: researchers had initially wondered whether Jekyll and a different shark, Simon, might be related after the two were observed making nearly identical seasonal migrations along the Atlantic coast. Genetic analysis did not link Simon and Jekyll as siblings, but it revealed the connection with Olympia instead.

Researchers were careful to note that the findings do not conclude that related sharks travel together intentionally, recognise one another, or inherit migration routes. The results establish a scientific foundation for investigating those questions rather than answering them. Each of the full sibling pairs was sampled in seasonally distinct habitats, with one sibling typically recorded in the southeastern United States during winter or spring and the other in New England or New York during summer or autumn.

Principal investigator Dr David Portnoy of TAMU-CC said the study is "really the beginning, not the end," adding that integrating genomic data with years of satellite tracking will allow researchers to explore whether related sharks share patterns of habitat use or migration, while noting that further research will be required to understand the drivers of any such patterns.

Conservation implications and population structure

The study also found no detectable genetic population structure across sampled sharks ranging from South Carolina and Georgia through to New England and Nova Scotia, reinforcing the view that Western North Atlantic white sharks form a single, highly interconnected population undertaking extensive seasonal migrations from the Gulf of Mexico to Atlantic Canada.

A finding with more immediate conservation relevance is the relatively high frequency of close relatives within the sample. Identifying multiple full and half-sibling pairs, including one pair with the same parents but an estimated nineteen-year age gap, could indicate a smaller-than-expected breeding population in the region. The researchers acknowledged that, if supported by further analysis, this could carry significant implications for conservation policies aimed at rebuilding white shark numbers in the Western North Atlantic.

The broader significance of the work lies in its methodology as much as its results. Conservation genomics applied to large, highly migratory apex predators is technically demanding. White shark populations are difficult to sample systematically, and long-term satellite tagging datasets of the scale OCEARCH has built over nearly twenty years are rare. The integration of movement ecology with population genomics is an approach that has gained traction across marine biology in recent years, applied to species from bluefin tuna to humpback whales, and this study represents a meaningful extension of that framework to one of the ocean's most studied yet still poorly understood megafauna.

The full study is being prepared for peer-reviewed submission, with expanded genomic analyses and continued integration of satellite tracking data expected to yield further findings on family structure and population dynamics.