Mass seed production for aquaculture of the edible acorn barnacle, Balanus rostratus

Abstract Balanus rostratus , commonly known as “miné-fujitsubo” in Japan, is a large cold-water acorn barnacle that is a delicacy in northern Japan. The intensive harvesting of this species has led to the depletion of large individuals in the wild population. In order to ensure a sustainable supply, we aimed to develop a mass seed production technique for B. rostratus and to investigate the nutritional factors underlying larval success through fatty acid analysis. Stable larval rearing and settlement were achieved using Thalassiosira sp. collected from coastal waters in northern Japan as larval feed. In this study, a total of approximately 9.0 × 10 6 larvae were used across 15 tanks. In each trial, 6.0 × 10⁵ ± 2.3 × 10⁵ (mean ± SD) larvae obtained from broodstock were reared per 200-L tank, with Thalassiosira sp. maintained at 1.7–4.1 × 10 4 cells/mL. From December 2024 to February 2025, following the natural reproductive period of B. rostratus in November, an estimated 1.14 × 10⁶ settled barnacles were successfully produced from 9.0 × 10 6 hatched larvae. The average survival rate from the start to cyprid emergence was 44.3% within 19 days. However, in six of total 15 trials, the larvae failed to reach naupliar stage 6. Fatty acid and triacylglycerol levels were similar between naupliar stages 1–3 and post stage 4 in successful trials. In contrast, these levels significantly decreased after stage 4 in unsuccessful trials, suggesting that lipid nutrients may play an important role in promoting the successful settlement of B. rostratus . The mass seed production technique reported in this study could contribute to the sustainable aquaculture of this species.