Use of substituted heterocyclic compounds to control sea lice on fish

1. A method of controlling sea lice in and on fish, which comprises treating the sea lice by an in-feed treatment, wherein an active substance is added to the feed provided to the fish, said active substance being a compound of formula

or

wherein R′, R″ and R′″ are each H, halogen or trifluormethyl, subject to the proviso that at least one of R′, R″ and R″′ is not H;

R 5 is methyl, halogen, CF 3 or cyano;

Q is a radical selected from the group consisting of:

(q8) —C(O)NH—CH 2 —C(O)NH—CH 2 CF 3 ,

(q9) —C(O)NH—CH 2 —C(O)NH—CH 2 CN,

(q10) —C(O)NH—CH 2 —C(O)NH—CH 2 C≡CH,

(q11) —C(O)NH—C═N—O—CH 3 ,

(q12) —C(O)N═C—N(CH 3 ) 2 ,

(q13) —C(O)N═C(NH 2 )—O—CH 3 ,

(q14) —CH 2 —NH—C(O)—C 1 -C 3 -alkyl,

(q15) —CH 2 —NH—C(O)-cyclopropyl,

(q16) —CH 2 —NH—C(O)—C 1 -C 2 -haloalkyl,

(q17) —CH 2 —NH—C(O)—CH 2 —S—C 1 -C 2 -alkyl,

(q18)—CH 2 —NH—C(O)—CH 2 —S(O) 2 —C 1 -C 2 -alkyl, and

(q19) —CH 2 —NH—C(O)—(CH 2 ) 1-2 —O—C 1 -C 2 -alkyl;

and wherein Q′ is a radical (q2) to (q19) above.

2. A method according to claim 1 , wherein R′ and R″ 40 are each independently of the other chlorine and R″ is H.

3. A method according to claim 1 , wherein the active substance is of formula (Ia′).

4. A method according to claim 1 , wherein the active substance is of formula (Ia″′).

5. A method according to claim 1 , wherein the fish are of the Salmonidae family.

6. A method according to claim 1 , wherein the sea lice are of the Copepodae class.

7. A method according to claim 3 , wherein the active substance is of formula

8. A method according to claim 4 , wherein the active substance is of formula

9. A method according to claim 5 , wherein the fish are selected from the group consisting of Salmo salar, Salmo trutta, Oncorhynchus mykiss, Oncorhynchus gorbuscha, Oncorhynchus keta, Oncorhynchus nekra, Oncorhynchus kisutch, Oncorhynchus tshawytscha, Oncorhynchus mamson, Salvelinus species and Salmo clarkii.

10. A method according to claim 6 , wherein the sea lice are selected from the group consisting of Lepeophtheirus salmonis, Caligus elongatus and C. rogercresseyii.