A Comparative study on some biochemical and enzymatic parameters of plasma and mucus during reproductive stages in goldfish (Carassius auratus)

Determination of reproductive status and knowledge in physiological situations of fish is essential to manage brooders. So, in this study, the efficacy of skin mucosal layer was investigated as the important source of biochemical and also less-invasive method to know goldfish reproductive status. In our research, fish sampling was carried out during five months and according to the histological analysis of gonad, the fish were divided into 5 stages: primary growth (I), cortical alveoli (II), early-vitellogenesis (III), late-vitellogenesis (IV) and spawning (V). Total protein, calcium, lipids (cholesterol and triglyceride) and alkaline phosphatase (ALP) levels of mucus and plasma were measured and compared. Protein levels of mucus were significantly increased during late-vitellogenesis (P < 0.05). Mucosal calcium levels were lower than plasma. Cholesterol and Triglyceride of mucus showedsignificant enhancing during the late-vitellogenesis (P < 0.05). ALP activity was elevated in mucus more than plasma. In histological studies, the analysis of gonadosomatic index showed significant positive correlation between this factor and plasma protein as well as mucus (P < 0.01). ALP was the appropriate indicator to distinguishing vitellogenesis and spawning stages. In summary, the results of this study indicated that the biochemical factors in mucus is measurable and be considered as a less-invasive tool and alternative blood for monitoring the endocrine response, reproductive indices, and sexual stages, especially in the vitellogenesis stages.