Habitat suitability and ecological corridors for cuttlefish Sepiella japonica: Informing conservation and release strategies.

Global marine fisheries production remains at a high level of approximately 80 million tonnes, partly due to the significant increase in cephalopod catches, which exhibit rapid adaptation to changing marine environments. Since the implementation of stock enhancement in 2008, Cuttlefish Sepiella japonica populations in coastal China have rebounded, and the establishment of closed areas and spawning ground reserves has effectively ensured the spawning and reproduction of cuttlefish. However, how to effectively protect the cuttlefish throughout its life cycle is still an unresolved issue, especially considering its migratory nature. To determine the suitability and connectivity of cuttlefish habitats, a Habitat Suitability Index (HSI) model was constructed using spring and fall bottom trawl survey data of 120 stations collected in the coastal Zhejiang Province from 2017 to 2021. Resistance surfaces in the ocean were generated using the habitat suitability output from the model, and the least-cost paths between key habitat nodes along the resistance surfaces were simulated and calculated, thus identifying potential ecological corridors of cuttlefish. The suitable habitats for cuttlefish are found to vary significantly between seasons, with different environmental drivers of migratory behaviors. In the spring, the distributions of suitable habitats are more scattered and patchier, with a higher percentage of key habitat nodes, longer paths, and a wider range of potential ecological corridors. Conversely, in the fall, the distributions of suitable habitats exhibit a reversal of characteristics. We had further confirmation that small MPAs are not effective in protecting the overall dynamics of cuttlefish populations. Consequently, it is not feasible to carry out stock enhancement without a comprehensive plan, so it is necessary to optimize the stocking strategies in the spawning ground reserve according to the actual situation in a larger scale. These findings improve our understanding of the suitability and connectivity of cuttlefish habitats, highlighting the need for population conservation at larger scales and based on species' critical life histories. With the increasing of anthropogenic interventions via large-scale stock enhancement globally, these knowledges have valuable inspirations for guiding artificial releasing projects.