Young white sharks may return to nursery waters with the same companions

Nine years of acoustic detections found recurring groups of tagged juveniles, though their associations were not clearly different from chance.

Editorial illustration — not from the study.

Researchers analysed hourly detections of tagged juvenile white sharks recorded by a passive acoustic array along one beach in a New South Wales nursery area from 2010 to 2018. They treated sharks as co-occurring when they were detected within the same hour and within 2 kilometres of one another, then used those records to map yearly patterns of association.

Sharks were no more likely to co-occur based on sex or age, and their overall co-occurrence was not significantly different from what would be expected from random association. However, sharks tagged at the same time and place showed a strong tendency to co-occur across all study years, suggesting that some cohorts may visit the nursery area at similar times.

Recurring shark cohorts

The study covered nine years of hourly acoustic detections from juvenile white sharks at a single beach in a New South Wales nursery area. The likelihood of two sharks co-occurring was not linked to their sex or age. Overall, the observed co-occurrences were not significantly different from those expected under random association. The clearest pattern was that individuals tagged at the same time and location tended to co-occur across all years, which may indicate that particular cohorts return to the nursery area on consistent schedules.

Why shared movements matter

White sharks are often described as mainly solitary swimmers and hunters, but juveniles gather in nursery areas. The recurring co-occurrence of sharks from the same tagging cohort raises the possibility that social behavior influences how some juveniles move through these areas. Understanding whether these gatherings involve active associations or simply shared timing and habitat use could improve knowledge of juvenile white shark behavior.

Evidence and open questions

The findings come from social network analysis of passive acoustic tracking data collected over nine years. The study observed only tagged sharks, used detections from one beach, and defined co-occurrence broadly as being within 2 kilometres during the same hour. These limits mean the data could not establish whether sharks were actively associating or avoiding one another at finer scales. The authors say further research using smaller spatial and time scales is needed to measure the role of sociality in nursery aggregations.

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