engleski

Deltamethrin efficacy in controlling parasite Ceratothoa oestroides in Dicentrarchus labrax farming

In the cage farming of sea bass (Dicentrarchus labrax Line, 1758) parasite isopod Ceratothoa oestroides (Risso, 1826) causes significant production losses, which are observed in reduced fish growth and low survival rate. Increased mortality were recorded on young fish up to 20 g. Deltamethrin is a synthetic pyrethrin showing good results in the control of the C. oestroides. The aim of this study was to determine the efficacy of deltamethrin (3.5 mg/m3 of sea water) in the control of the C. oestroides in production conditions. The experiment was carried out at Cromaris d.d. within 4 commercial net cages of 16 m diameter and per 200, 000 fish individuals of the same origin and initial weight. After 6 months of farming deltamethrin treatments were performed in two cages, while other two were control cages. The average fish weight during antiparasitic bath was 20 g. Two months after the treatments visual control of the entire population was carried out, and total of 100 infested individuals were excluded. Afterwards, biometric analyses were performed on infested fishes and on C. oestroides males and females. Sexual maturity and fecundity on C. oestroides females was determined. In addition, daily records of fish mortality and sea temperature were recorded. The results showed that the number of C. oestroides in treated cages was significantly lower (P<0.01) than the number of C. oestroides in control cages. Also, C. oestroides were smaller in treated cages than in control cages and they were not sexually mature. In control cages the number of sexually mature C. oestroides was 22.3 and 21.4%. The obtained results indicated the successful sea bass treatment with deltamethrin on C. oestroides removal. However, after 2 months period, new generation of immature C. oestroides appeared. These results showed possibility of C. oestroides infestation on sea bass greater than 20 g, but the absence of sexually mature females points the importance of this treatment to reduce the dynamics of C. oestroides population.

Deltamethrin ; Ceratothoa oestroides ; Dicentrarchus labrax ; farming

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