I have installed the io-octave package on my Debian Jessie system as you can see here:
apt-get install octave-io
Reading package lists... Done
Building dependency tree
Reading state information... Done
octave-io is already the newest version.
However when I try to load it in octave I get the following error:
octave:1> pkg load octave-io
error: package octave-io is not installed
error: called from:
error: /usr/share/octave/3.8.2/m/pkg/private/load_packages.m at line 53, column 11
error: /usr/share/octave/3.8.2/m/pkg/pkg.m at line 412, column 7