To use the mac ports system for custom software on MacOS you need to modify your local PATH variable for your used shell. For bash this is done in the ~/.profile configuration.
To archive the same if you're using the fish shell, you should use set -U fish_user_paths $fish_user_paths /opt/local/bin/
I added two path extensions by:
set -U fish_user_paths $fish_user_paths /opt/local/bin/ set -U fish_user_paths $fish_user_paths /opt/local/sbin/
This makes the mac ports commands available if you open a fish shell.