72 JUNE 2025 • WORLD AQUACULTURE • WWW.WAS.ORG TABLE 1. Mean value (summary of the three trials) showing percentage motility, number of spermatozoa, fertilization rate and hatchability rate. Treatments T0 T1 T2 T3 T4 SEM (0hour) (3hours) (6hours) (9hours) (12hours) Sperm motility (%) 80.00A 50.33B 40.67C 25.33D 13.67E 1.422 Number of spermatozoa/ml 104.3 x 106A 85 x 106B 48 x 106C 33.6 x 106D 21.6 x 106E 2.50 x 106 Fertilization rate (%) 88.86A 73.81B 52.93C 36.77D 14.35E 1.446 Hatchability(%) 93.34 80.09 60.08 28.70 16.79 1.013 Means values in each row with the same superscript are not significantly different (P > 0.05). SEM: Standard error of the differences of mean. TABLE 2. Range of water quality variables recorded during the experimental period. Variable Dissolved oxygen (mg/l) pH Temperature (°C) Minimum 5.0 6.3 24 Maximum 6.7 6.8 28 sperm motility was recorded in T0 (control), while the lowest occurred in T4 (12 hours). The reduced sperm motility in T4 indicates that prolonged exposure of sperm cells to saline solution affects motility. This finding aligns with the results of Browne et al. (2015) and José et al. (2019), who reported that at room temperature, storage in isotonic solutions leads to a decline in sperm motility and quality over time in externally fertilizing fish species. Similarly, Leon et al. (2019) concluded that increased salinity negatively impacts fish sperm motility by disrupting osmotic balance. Although José et al. (2019) suggested that saline solutions with specific concentrations can serve as extenders in cryopreservation for certain fish sperm cells, limited research supports the use of saline solution alone as a preservation medium without freezing. The motility results from T1 (3 hours) and T2 (6 hours) indicate that six hours is the maximum duration within which the original sperm motility can be maintained using saline solution as a preservative medium. Spermatozoa concentration in fish ranged between 2 x106 up to 5.3 x1010 cells per ml. The highest number of spermatozoa obtained in T0 (104.3 × 106) can be attributed to the time factor (0 hour) while the lowest number of spermatozoa obtained in T4 (2.50 × 106) can be attributed to the prolonged time of storage (12 hours) as increased time in saline solution had an effect on the number of spermatozoa, in agreement with Adebisi and Ewuola (2019), who have suggested that osmotic stress, cell swelling/ shrinking and ion balance have effects on the number of spermatozoa. High fertilization rates obtained in the first three treatments (88.86, 73.81, 52.93) was due to their higher sperm motility as compared to T3 and T4 that recorded the lowest fertilization (36.77, 14.35) and motility (25.33, 13.67) rates. This suggests that the preservation time for milt using saline water must not be beyond 6 hours because longer intervals can lead to damage to sperm due to intrinsic fragility, osmotic stress, and sperm aging (Moshiur et al., 2022). High hatchability rates occurred in the first three treatments (93.34, 80.09, 60.08) (Figure 3) compared with those obtained in T3 and T4 (28.70 and 16.79). This was almost certainly due to the effect of storage time of fish milt in normal saline in agreement with results obtained by Moshiur et al. (2022). All the treatments had identical water quality parameters. Assessment of procedural stages did not differ in all treatments, as the same proportion of normal and abnormal sperm cells were recorded, 45 ± 5% and 55 ± 5%, respectively, during lab analysis. The motility, number, fertilization rate and hatchability rate of catfish sperm that were extracted and used immediately were relatively higher compared to the sperm of catfish that was extracted, kept in saline solution, and used at 3 h, 6 h, 9 h, and 12 h. Hence, it can be followed that there was a sharp decline in the milt quality at T3 and T4. Therefore, it may be stated that preservation of fish milt FIGURE 3. Recently hatched Clarias fry.
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