Time-series growth estimation of sea cucumbers (Apostichopus japonicus) in co-cultivation with coho salmon using time-lapse cameras in field experiments

Abstract

As Integrated Multi-Trophic Aquaculture (IMTA) continues to gain attention, this study investigated the co-culture of coho salmon (Oncorhynchus kisutch) and juvenile Japanese sea cucumber (Apostichopus japonicus) in Kuji Bay, Iwate Prefecture, Japan. The sea cucumbers were housed separately in box cages below the coho salmon aquaculture cages, and the growth was monitored using an underwater time-lapse camera from December 2022 to May 2023. The time-lapse camera was used to monitor the small sea cucumbers with an average body weight of 1.2 g for the initial stage. Semantic segmentation using the Segment Anything Model (SAM) was then applied to the images to separate the sea cucumbers from the background. Body weights were converted from the area of the sea cucumbers in the images. The estimated body weights were plotted over time and compared with the measured body weights. From this, a time-lapse camera can be used to roughly estimate the growth of sea cucumbers over time, which will be helpful to understand the co-cultured sea cucumbers.