Conda's installer by default writes the init block to the ~/.bashrc or ~/.bash_profile by default - not fish's config. So fish never sources conda and it is therefor unavailable from the shell even if you restart the shell.
To solve this you can source where the conda package was installed. For me this time. it was installed to $HOME/miniconda3/bin this may not be the same every time so verify where it was installed. Here is a potential way to find it.Ls ~/miniconda3/bin/conda 2>/dev/null || ls ~/miniconda3/condabin/conda 2>/dev/null || find /home/slippy -maxdepth 4 -name conda -type f 2>/dev/null and run the executable ./miniconda3/bin/conda init fish