A preliminary genome analysis of white sharks in the western North Atlantic has identified three full-sibling pairs and seven probable half-sibling pairs. The results come from an ongoing project by OCEARCH and the Texas A&M University-Corpus Christi. A peer-reviewed scientific manuscript is not yet available, as explicitly stated by the OCEARCH announcement of August 25, 2026.
Among the known animals is the male great white shark Jekyll, which was tagged in 2022. According to the analysis, he is a full sibling of the shark tagged in 2021, Olympia. Another shark named Simon showed a similarly patterned migration as Jekyll, but genetically did not prove to be his brother.
Siblings from different year classes
One of the three full sibling pairs is said to come from the same litter. For the other two pairs, the team estimated an age difference of about five and 19 years, respectively, based on growth models. If this is confirmed in the complete analysis, at least one pair of parents would have successfully reproduced repeatedly over many years.
Full siblings share, on average, more genetic material than half-siblings. However, such an assignment requires high-quality genome data and an appropriate reference sample. OCEARCH therefore deliberately refers to the seven other pairs as probable half-siblings and plans additional sequencing.
No evidence of a family migration
The kinship data do not show that siblings migrate together, recognize each other, or learn their routes from one another. The three pairs of full siblings were indeed each sampled in similar seasonal habitats: one animal in winter or spring in the southeastern USA, the other in summer or autumn off New England or New York. However, no simultaneous travel can be inferred from this.
It is also known from other studies that great white sharks can temporarily show social relationships. However, the new genome analysis answers a different question. It assigns biological kinship, not the social behavior of the animals during their migrations.
One connected population
In the sample examined so far, the team found no recognizable genetic population structure between South Carolina and Georgia in the south, as well as New England and Nova Scotia in the north. This tentatively suggests a connected population in the western North Atlantic rather than several clearly separate breeding groups along the coast.
This statement does not mean that every animal is found with the same frequency everywhere. Satellite tagging shows individual migration routes and seasonal hotspots. Genetic mixing can still occur if animals from different habitats reproduce over generations.
What several close relatives in a small sample could mean
The fact that several close relatives appeared in a limited sample could indicate a relatively small breeding population. OCEARCH presents this as a possible interpretation, not as a definitive population estimate. For reliable statements, sample size, spatial selection, survival rates, and the probability of actually capturing and sampling related animals would need to be considered.
Especially in long-lived species, genetic relatedness can provide important information that sightings or tagging data alone do not reveal. Sibling pairs from different birth years can provide clues about repeated reproduction; half-siblings can help statistically narrow down the number of successful parent animals.
The findings remain preliminary
Project leader David Portnoy and his team want to sequence further samples and submit the complete study for review. Until the publication of a journal article, the complete methods, the exact sample size, and the uncertainty ranges of the kinship assignments, among other things, are missing.
The report is nonetheless remarkable because it makes concrete kinship relations among individually known white sharks visible. Its strongest finding at present is the combination of sibling pairs across multiple year classes and the lack of genetic separation along the studied Atlantic coast.
