Yes it's possible all year long and you can spear any species of fish. The water is never crystal clear, but it's so much fun and quite fishy.
Yes you need a license but it's easy to get and it doesn't cost 20 euro a day, but about 20 euro for
three months. When you get there, you must go to the Town Hall of the town where you're settling (ask for the Comune or Municipio) and ask for a touristic fishing license. Then you' ll start having fun: pikes, eels, tench, black bass, perch, trout, there's plenty.
some regulations:
-no scuba hunting
-no night hunting
-no lamp
-maximum 5kg fish per day + one single fish exceeding that limit (for instance, in a day, you may get a 7kg pike plus 4,99 kg of other mixed fish
-no spearing in ports, stay 500 meters away from beaches
-a buoy of float is compulsory
-no spearing fishes during the reproduction period of their species (I'll add a link below)
-no spearing undersized fish (I'll add a link below).
the links:
minimum size and reproduction periods:
http://www.pescare.com/Normative/Lom...isuretempi.htm
areas allowed in the 3 lakes and various regulations
Apnea Magazine - NORMATIVE, DIVIETI E DISPOSIZIONI PESCA IN APNEA LAGHI GARDA, COMO, ISEO
Just tell me exactly where on the lake you're planning to go (it's 160 kilometers of coast line!) and I'll give you some more specific tips on where to go, description of coastline and bottom, techniques, suggested gear and anything you need to know.
I'll be happy to help!