engleski

FECUNDITY OF THE CERATOTHOA OESTROIDES (Risso, 1816) ON FARMED SEA BASS (DICENTRARCHUS LABRAX) IN THE ADRIATIC SEA

Introduction: Ceratothoa oestroides (Risso, 1816) is an isopod parasite living in fish buccal cavity. Reproduction is usually present during whole year and knowledge of the parasite reproductive biology is an important tool to apply good preventive measures in aquaculture. Fecundity is one of the factors which is crucial for recruitment of parasite in fish population. The aim of the present study was to gain accurate information about fecundity of the isopod parasite C. oestroides. This study analysed fecundity of C. oestroides in relation to biotic (size of female parasite) and abiotic factors (temperature, photoperiod). Methodology: The study was carried out from January to December 2018. Samples of fish infected with C. oestroides were collected from three different fish farms in the Middle Eastern Adriatic Sea. Water temperature varied from 12.1 °C to 22.6 °C. A total of 850 fish were examined, average weight of fish were 413 ± 40 g and length 30.4 ± 3.6 cm (mean ± SD). Fecundity was determined according to the number of larvae with visible eyes in the marsupium. Results: Our results showed that there was no significant correlation between sea temperature and fecundity. However, there was a significant difference in parasite fecundity between different months through the year. The smallest fecundity was found in November (256 ± 115 pulli) while the largest fecundity value was determined in May (470 ± 124 pulli). There was very strong positive correlation between photoperiod and fecundity (r = 0.9 ; P < 0.05). Also, the relationship between female size and fecundity showed a positive strong correlation (r = 0.6 ; P < 0.05). Conclusion: The large-sized female parasites had larger ovaries than smaller individuals of the same species, which allowed them to produce and carry more larvae. Also, fecundity of C. oestroides was positively correlated with photoperiod.

Ceratothoa oestroides, sea bass, fecundity

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