I toyed with a cold water tank a couple years ago and posted some research results at the time.
In short, I contacted the DFO and was told collection is legal with a fishing licence and you must observe quotas. (The exact email is somewhere on this forum if I remember correctly.)
As for temperature and species selection, I found this a great site for potential species.
http://hmsc.oregonstate.edu/projects/msap/index.html
And for insperation,
http://www.racerocks.com/
Hope this helps. Hmmm got me thinking of doing this again. (And I blame you all!! LOL!)