Developing habitat suitable model for Asian seabass (Lates calcarifer) culture in Southern, Sri Lanka

Abstract

Site selection in aquaculture is considered as a mandatory step before establishing farming facilities. Habitat Suitability Models (HSM) is an effective tool that can be used for site selection. In Sri Lanka, there is less attention on this subject. This study focuses on developing an HSM to identify suitable habitats on the southern coast of Sri Lanka, for Asian seabass. For this study, five environmental variables (temperature, salinity, dissolved Oxygen, Nitrate, and Phosphate) were considered as model inputs; key drivers of habitat quality for Asian seabass. Environmental data were extracted from two Copernicus data products, namely Global Ocean Physics Re-analysis (GLORYS12V1) data (salinity and temperature) and Global Ocean Biogeochemistry Hindcast data (dissolved Oxygen, Nitrate and Phosphate). The data covered 21 years from 2000–2021 across approximately 290000 km2 area between 2.5–6.5 °N and 78–84 °E, at resolution of 0.083° (~ 9 km) over 10 depth layers down to 13 m. Data were averaged on monthly basis and across the depth layers before running the HSM. The HSM was designed to exhaustively search the data to find optimal locations for Asian seabass culture in this study area and to classify the potential habitats into three different classes: 'Habitable', 'Moderately Habitable', and 'Uninhabitable' according to their optimal ranges and tolerance limits of each environmental variable. Profound seasonal variability was observed in the environmental dynamics in the study area, which drove corresponding variability in the model-predicted habitat suitability. A thorough sensitivity analysis revealed that the variability observed in temperature, dissolved Oxygen and Nitrate fell in the ‘Habitable’ range year-round. However, salinity and dissolved phosphate rendered the southwestern sector of the study area become seasonally ‘Moderately habitable’ or ‘Uninhabitable’. Further analysis revealed that no part of the study area was identified as ’Uninhabitable’ throughout the year. However, the result of this study suggests that offshore regions, particularly in the southeastern sector of the study area are more 'Habitable’ for Asian seabass year-round and are preferable to be utilized as potential Asian seabass mariculture sites in southern coast of Sri Lanka.