Possible Effects of Manual Stripping on Stress Response and Reproductive Status in Captive Female Salmo carpio

Captive breeding programs are essential for conserving the endangered salmonid Salmo carpio. However, standard hatchery operations rely on manual stripping, whose effects on Carpione reproductive physiology and welfare remain poorly understood. This preliminary study investigated the physiological and reproductive responses of captive female S. carpio to manual stripping. Forty-five mature females were assigned to three groups: pre-stripping (PRE), 1 day post-stripping (POST1), and 21 days post-stripping (POST21). Plasma concentrations of 17β-estradiol, testosterone, progesterone, cortisol, glucose, and antioxidant enzyme activities (SOD, CAT, GPx) were assessed alongside ovarian histology. While no effects were detected on circulating steroid or glucose levels, POST21 females showed significantly higher cortisol and increased SOD and CAT activities than PRE and POST1 fish (p < 0.05), while both POST1 and POST21 showed higher GPx activity compared to PRE, indicating a delayed modulation of stress response and oxidative challenge after the stripping event. Ovarian histology revealed no evident histopathological alterations. PRE group ovaries were characterized by the presence of primary growth and tertiary vitellogenic oocytes. Primary growth oocytes were identified in all the experimental groups. Secondary vitellogenic oocytes, together with post-ovulatory follicles and atretic oocytes, were observed at POST1. At POST21, histological examination revealed primary growth and early vitellogenic oocytes, while mature oocytes were also identified macroscopically, supporting the persistence of ovarian reproductive activity during the reproductive season. Overall, females maintained ovarian activity throughout the examined period, while delayed systemic stress during post-spawning recovery was observed in the POST21 group. Broodstock management should therefore include adequate recovery periods and reduce handling to support welfare and reproductive performance.