Cleaner Fish: Cleaner fish are species of fish which will eat the sea  lice off of infected fish, and are commonly called  wrasse. These fish can reduce the number or sea lice  significantly, however, they do not clean as effectively  in the winter and since they come from wild stock, they may carry harmful diseases such as furunculosis.
 

Fallowing:  Fallowing is a process by which farm sites raise one group of fish from smolt size to market size and then to wait several months (2-3) before restocking the pens with new smolt.  This will result in a much lower sea lice count on the second batch of fish but it can be difficult in areas with more than one individually owned sites.

Vaccines:  Although none are currently available for use against sea lice, research is underway in many parts of the world to find a vaccine.

Azamethiphos: This drug, also knows as Salmosan, is an organophosphate that is typically used as a bath treatment for the fish.  This drug is only effective against the mobile stages (preadult and adult).  It is approved for use in Canada.

Hydrogen Peroxide: Hydrogen peroxide is an agent that is used as a spray treatment, and it is environmentally sound, because it breaks down into water and oxygen.  Although it usually works against the chalimus and adult stages, some research shows that some of the treated lice recover.

Dichlorvos:  This was the first drug ever used against sea lice. It is another organophosphate, and it is administered as a bath treatment.  It kills adult sea lice by blocking acetylcholinesterase production, which leads to continuous neuromuscular activity causing the lice to die from exhaustion. It is only available in Norway and Scotland, and it only works on adult lice.

Pyrethroids:  These drugs have been used in bath treatments in the USA and Europe.  They kill the lice by interfering with sodium channels in nerve cell membranes. Examples are cypermethrin and deltamethrin.

Emamectin benzoate: Emamectin belongs to the same family of drugs as ivermectin, the avermectins. It is in the process of being approved by Health Canada under the tradename SLICE. It is also administered in the feed. It is effective against all stages of sea lice reproduction. It has a wider safety margin for both the fish and the environment than its cousin, ivermectin.

Teflubenzuron (Cal-X, Calicide): This drug inhibits the synthesis of chitin which is a vital component of the sea louse's exoskeleton. It appears to be more effective against earlier stages where the exoskeleton is not completely developed.  The drug readily attaches to marine particles and persists in the environment. There are environmental concerns for surrounding crustaceans. It is approved for use in Europe and Canada.