Survey counts of black abalone rise from 54 to 302

Scientists relocated 246 endangered black abalone to a protected coastal site in California in 2023 to restore a population devastated by disease. Surveys three years later counted 302 individuals, compared with 54 before the intervention, and found juveniles. Researchers said further monitoring was needed to establish sustained reproduction.

The animals came from a recovering population on Santa Cruz Island and were moved to California's Jack and Laura Dangermond Preserve. The receiving site had suitable rocky habitat, but its black abalone population remained depleted after earlier disease-related losses.

Black abalone reproduce by releasing eggs and sperm into the water, a process called broadcast spawning. Fertilization works best when animals live close together. When too few remain near one another, reproduction becomes less successful, hampering natural recovery even where suitable habitat remains.

Researchers counted 54 black abalone across 11,719 square metres of surveyed habitat in March 2022, before relocation. Counts reached 252 in March 2024 and 302 in February 2026. Density in high-quality habitat rose from 0.2 per square metre in 2022 to one in 2026.

The February 2026 survey found 12 juvenile black abalone measuring 18 to 40 millimetres and six small adults measuring around 50 millimetres. Juveniles had not been recorded at the site in monitoring and broader habitat surveys since the disease-related decline in 1993.

Researchers have not established whether the juveniles descended from the relocated animals. Genetic parentage analysis is needed to determine their origin. The findings suggest possible renewed reproduction, rather than proving that the relocated population is breeding successfully.