fitch: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/lib/phylip/bin/fitch - from package: phylip

You may install the required package with command apt-get install {package}

Error in other languages:
fitch: bevel nie gevind nie
fitch: comandă negăsită
fitch: comando não encontrado
fitch: commande introuvable
fitch: command not found
fitch: käsku ei ole
fitch: không tìm thấy lệnh
fitch: komanda nerasta
fitch: Kommando nicht gefunden.
fitch: kommandot finns inte
fitch: komut yok
fitch: nie znaleziono polecenia
fitch: níor aimsíodh an t-ordú
fitch: no se encontró la orden
fitch: no s'ha trobat l'ordre
fitch: opdracht niet gevonden
fitch: parancs nem található
fitch: perintah tidak ditemukan
fitch: príkaz nenájdený
fitch: příkaz nenalezen
fitch: команда не найдена
fitch: командата не е открита
fitch: 命令找不到
fitch: コマンドが見つかりません