Growth and survival performance of European clam Ruditapes decussatus seed in suspended lantern nets in open sea, Bay of Monastir, Tunisia

The rearing of hatchery-produced European clams, Ruditapes decussatus (Linnaeus, 1758), was tested for the first time in suspended lantern nets deployed on a pre-existing offshore longline structure originally installed for mussel Mytilus galloprovincialis rearing within an innovative offshore Integrated Multi-trophic Aquaculture (IMTA) system. This approach was designed to evaluate the growth performance of clam seed reared offshore in suspended culture as a strategic storage and grow-out solution to address several major challenges facing shellfish aquaculture during critical warm periods, including summer heat waves, declining water quality, and pathological risks associated with climate change. Two lantern nets were deployed, and clam seed were assigned to two experimental groups according to shell length. The pre-fattening group included individuals with shell lengths below 13.28 ± 1.52 mm, whereas the fattening group consisted of individuals with shell lengths exceeding 15.90 ±1.53 mm. Each lantern contained two size classes per experimental group, and each size class was represented in duplicate. Both groups were reared simultaneously in suspended lantern nets over a 316-day experimental period extending from June 2023 to May 2024. Our results revealed a significant mean length gain reached 2.6 ± 0.86 mm in the pre fattening and 1.18 ± 0.36 mm in the fattening, respectively with a relatively low mortality (<36.13% for pre-fattening;<4% for the fattening). These findings highlight the feasibility of European clam rearing into a pre-existing offshore IMTA longline and support this approach as a sustainable storage strategy, particularly during the summer period.