Fish inherits from template_gaia_fish.xml, not from template_unit_fauna.xml, therefore their current file names (fauna_fish*) are incorrect. This patch moves them into a subfolder of their own (gaia/fish/), because although only three types of fish exist right now, it's not inconceivable many more will be added in the future.
Cf. gaia/ruins/ and gaia/treasure/, which contain files that inherit from template_gaia_ruins.xml and template_gaia_treasure.xml, respectively.
Apply the patch, then run the following command to adjust all map files:
find binaries/data/mods/public/maps/ \( -name '*.js' -o -name '*.json' -o -name '*.xml' \) -print0 | xargs -0 sed -i \ -e 's,gaia/fauna_fish_tuna,gaia/fish/tuna,g' \ -e 's,gaia/fauna_fish_tilapia,gaia/fish/tilapia,g' \ -e 's,gaia/fauna_fish,gaia/fish/generic,g'
See also D2254.