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The availability of mature broodstock that produces high-quality gametes is one of the vital issues with fish reproduction. The effects of multiple hormonal stimulations and continuous stripping of the same individual males on spermatozoa quality are unclear. Thus, this study aimed to investigate motility parameters and seminal plasma compositions of common carp sperm during out-of-spawning continuous stripping stimulated by multiple hormonal injections. Five mature males ∼3 years old, each approximately 1.7–2.3 kg bodyweight cultured in RAS at a stable temperature of 21 °C were used in this study. Fish were treated monthly (at the beginning of each month from August to October) with carp pituitary at 1.5 mg kg−1 (b.w.) dissolved in 0.9 % (w/v) NaCl solution 24 h before milt collection. The mean sperm concentration ranged from 17.55 to 20.19 × 109 mL−1 collected during the experiments and did not significantly vary among the sampling months (F = 2.352, p = 0.1374). However, the repeated measures ANOVA showed significant effects of sampling months (F = 25.24, p = 0.0001) and individual males (F = 7.50, p = 0.0001) on the motility parameters and seminal plasma compositions, but their interaction effects were not significant (F = 1.31, p = 0.079). One-way ANOVA revealed a significant difference in spermatozoa motility (F = 10.51, p = 0.0001) and pH of the seminal plasma (F = 90.00, p = 0.0001), but did not differ in curvilinear velocity (VCL), straight-line velocity (VSL), and ionic compositions (Na+, K+, Cl-, Ca2+, total protein, and osmolality) of the seminal plasma (p > 0.05). The mean spermatozoa motility in August (88.51–94.05 %) and September (89.88–96.00 %) was significantly higher than in October (83.99–89.58 %), but spermatozoa motility was >80 % in all males for the three consecutive months. The present study indicated that multiple hormonal stimulation and continuous stripping did not suppress common carp's spermatozoa production and quality parameters.

Considering endangered fish, storage of sterlet (Acipenser ruthenus) gamete is crucial, and investigating the most suitable extender for short-term storage of sperm is necessary. Therefore, the present study aimed to optimize suitable extenders for short-term storage of sterlet spermatozoa and determine the effects of storage periods and different extenders on spermatozoa motility parameters. The sperm of five mature males with good spermatozoa motility (∼80 %) were diluted with 20 different extenders having various Na+ and K+ concentrations and osmolality. Spermatozoa motility performances were assessed using a CASA system within 144 h storage at 0–2 °C. Undiluted sperm was used as a control. Seminal plasma Na+, K+, Ca2+ and Cl- concentrations were 17.56±10.12, 2.48±1.14, 0.11±0.06, and 6.20±3.42 mmol/L with osmolality of 35.60±20.70 mOsm/kg. A two-way ANOVA showed significant effects of storage time, extender, and their interaction on spermatozoa motility, curvilinear velocity (VCL), and straight-line velocity (VSL) (p3 mM resulted in lower spermatozoa motility performance. When the effects of storage time were studied, spermatozoa motility, VCL, and VSL in non-diluted sperm and those diluted with E18-E20 were decreased at 24–48 h and 72–96 h post-storage, respectively. This study shows that extenders with higher osmolality (39–62 mOsm/kg) and lower K+ (1 mmol/L) are the most suitable for storing sterlet sperm for a short period.

The bacterial population plays a crucial role in recycling the organic matter and metabolizing the toxic nitrogenous compounds under biofloc technology (BFT). The biofloc technology has been successfully implemented for several fish species, but not for shrimp culture in Bangladesh. The major objectives of this study were to determine the effects of stocking density on the growth performance of tiger shrimp Penaeus monodon under biofloc technology (BFT) rearing system using commercial probiotics and to investigate the abundance of total heterotrophic bacteria (THB) and vibrio-like bacteria (VLB) in different biofloc treatments and their water quality parameters. The experiment was conducted with three different stocking densities in three BFT tanks (2.5 × 2.0 × 1.0 m) with triplicate and three control tanks filled in clearwater. All these tanks were built with cement and can contain 5000 L of water. Visually healthy, disease-free P. monodon postlarvae (weighted 0.18 ± 0.02 g) were collected from a local hatchery and stocked in three different stocking densities, i.e., 400 PL/m3 (CW), 400 PL/m3 (BFT1), 450 PL/m3 (BFT2) and 500 PL/m3 (BFT3). Shrimps were fed four times a day with commercial feed (Biomer, 40 % crude protein) for 127 days. Significant differences (P < 0.05) in specific growth rate, food conversion ratio, and protein efficiency ratio of shrimp were found among the treatments and the control group. The overall final biomass in BFT1 (5.88 ± 0.12 kg m3) was significantly higher (P < 0.05) than that of other BFT groups and the control (3.40 ± 0.09 kg m3). The present findings showed that the biofloc technology with lower stocking density was reducing the total ammonia nitrogen, nitrite-N, and nitrate-N in water and significantly increased THB and reduced VLB populations.