Apple Script for Fish if it is Already installed to your /usr/local/bin directory and you don't want to chsh -s, derived from the original Fish.app script

fish.scpt

tell application "System Events"
	-- Don't create multiple windows if Terminal is not running
	-- For some reason this sometimes throws an error on SnowLeopard
	try
		set terminal_count to count (processes whose bundle identifier is "com.apple.Terminal")
	on error
		set terminal_count to 1
	end try
	if terminal_count is 0 then
		tell application "Terminal"
			activate
			try
				do script ("exec '/usr/local/bin/fish'") in window 0
			on error
				-- If there's no window 0, just have it do it
				do script ("exec '/usr/local/bin/fish'")
			end try
		end tell
	else
		-- Terminal was already running, open a new window
		tell application "Terminal"
			do script ("exec '/usr/local/bin/fish'")
			activate
		end tell
	end if
end tell