You can download FAO-ICLARM Stock Assessment Tools II (FiSAT II) from the official FAO website or through the ICLARM (International Center for Living Aquatic Resources Management) resources.
Here’s how you can find it.....
FAO Website: Visit the FAO Fisheries and Aquaculture Department's section.https://www.fao.org/fishery-divisional-structure/en/ They often have links to tools and software.
ICLARM Website: Check the ICLARM (now part of WorldFish) site https://worldfishcenter.org/ for resources related to stock assessment tools.