Plastic pollution is one of the pressing issues in freshwater ecosystems that may further contribute to coastal pollution. The present study aimed to address the state of macroplastics pollution in the Surma River system, Bangladesh. Six sampling sites were allocated in the river starting from upstream to downstream, water parameters and fin fish assemblage were recorded, and plastic debris was collected from each site. Afterward, macroplastics were categorized and weighed to measure their abundance. Previous data on rainfall, water discharge, and depth were aggregated to study the trend of river depth changes. A survey was conducted to identify the possible sources of plastic pollution in the river and awareness of the pollution. The results showed that Kazir Bazar (Site 4) and Beter Bazar (Site 5), comparatively contained poor water quality, diverse macroplastics categories, and higher macroplastics abundance. The water pollution index (WPI) also ranked the above sites as extremely polluted. Similarly, biodiversity indices revealed lower diversity at Site 4 and Site 5. The river depth analysis revealed that there was no remarkable tendency to change the depth. To conclude, the Surma River system is being polluted due to inadvertent plastic dumping. Contemporary awareness is highly required, and proper policies should be implemented to minimize the detrimental effects of macroplastics.
An experiment was performed to observe the potentiality of synthetic hormone analogue in artificial propagation i.e., the embryonic and larval development of Heteropneustes fossilis. Broodfish were injected with S-GnRHa according to the following concentration: 1, 2.5 and 5 ml kg-1 of body weight (BW) to females and 0.5, 1.125 and 2.5 ml kg-1 BW to males, in treatment groups T1, T2 and T3, respectively each with three replicates. The fishes were ovulated at about 10-11 hours after the hormone injection. Result showed the highest fertilization (83.11±1.36) and hatching rate (89.56±1.04) in T2, whereas ovulation rate was 100% in all treatment groups. First cleavage was observed in 30 minutes of post-fertilization. Embryonic developmental period sequentially for 2-cell, 4-cell, 8-cell, 16-cell, 32-cell, 64-cell, Morula, Blastula, Gastrula, somatic formation, yolk-plug, twisting movement and pre-hatching were 00:30, 00:45, 01:10, 01:30, 02:00, 02:30, 03:00, 04:00, 06:40, 09:00-18:00, 19:00, 20:00-21:00 and 22:00 hours, respectively. Hatching occurred after 23:00 hours of fertilization. Finally, the current result suggested that S-GnRHa might be an effective synthetic hormone in artificial propagation of H. fossilis.
Lead (Pb) is one of the toxins responsible for the deterioration of ecological health in aquatic environments. The present study investigated the effects of Pb(NO3)2 toxicity on growth, blood cell morphology, and the histopathology of gills, liver, and intestine of juvenile Nile tilapia, Oreochromis niloticus. A 30-day long aquarium trial was conducted by assigning three treatment groups T1 5.20 mg L−1, T2 10.40 mg L−1, and T3 20.80 mg L−1, and a control 0 mg L−1 following the 96 h LC50 of 51.96 mg L−1 from acute toxicity test. Overall growth performance significantly declined in all the Pb(NO3)2 treated groups and the highest mortality was recorded in T3. Behavioural abnormalities were intense in all the treatment groups compared to the control. Hepatosomatic index (HSI) values were reported as higher in treatment groups. Reduced nucleus diameter and nuclei size in erythrocytes were reported for T2 and T3 groups. Dose-dependent histological alterations were visible in the gills, liver, and intestine of all the Pb(NO3)2 treated groups. The width of the intestinal villi was highly extended in T3 showing signs of severe histological alterations. In conclusion, Pb toxicity causes a negative effect on growth performance, erythrocyte morphology, and affected the vital organs histomorphology of juvenile O. niloticus.
The current study was carried out to optimize the dose of the synthetic hormone for induction, and to observe the embryonic and larval developmental in Gulsha, Mystus cavasius. Induced breeding was conducted by using Ovupin (S-GnRHa) hormone (each 1.5 ml vial contain 0.2 mg of an analogue of S-GnRHa) at four different doses i.e., 0.25, 0.5, 1.0-and 1.50-ml kg -1 body weight (BW) for females, and the half of these doses were applied to males. Among the applied doses, 0.5 ml kg -1 BW for female and 0.25 ml kg -1 BW for male provided the maximum fertilization (83.66%) and hatching (80.0%) rates. The eggs of M. cavasius were strongly adhesive, with covering on egg surface. The average diameter of fertilized eggs just after spawning was 85.58±5.87 µm. After fertilization, the first, second, and third cleavage stages occurred within 20-25, 35-40 and 60-65 min, respectively. The identity of blastomeres was gradually lost and appeared at 64-cell stage to 128-cell stage onwards. The 64-cell stage appeared at 150-160 min and the morula stage 3:00-3:20 h (blastomeres completely lost), respectively. The gastrula stage appeared at 5:0-5:30 h in which the blastoderm spread in both the sides covering about 60-70% area, together with a thread-like germinal ring. Afterward, twisting locomotion was recorded at 23:30 h. The larvae started hatching at 24:00 to 25:00 h. The barbells were partially visible when the larvae were 10-12 h of age. Finally, the yolk sac was fully absorbed in the end of Day 3.
Marine fish farm industries face ongoing challenges due to a lack of quality seed, a low survival rate and a slow growth rate of marine fish larvae. One of the most sensitive problems is a nutritionally balanced quality feed for rearing these larval fish at the first feeding stage. Many studies have reported high requirements of n-3 highly unsaturated fatty acids, mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for proper development, which have also been reported to increase the survival and growth status of larval fish. Marine fish larvae have difficulties accepting artificial feed at their weaning stage, so live food plays a vital role in the rearing process. Artemia is one of the most commonly used live food organisms in marine fish larvae production systems. However, they are deficient in EPA and DHA, which are most critical for larval development. Recent advancements in live food production systems have developed several techniques of bio-encapsulation and enrichment of nutrients in live food. But the instability of DHA and the high cost of enrichment procedures remain-bottlenecks for supplying proper nutrients through live food. This short review emphasizes challenges in marine fish larvae culture in terms of HUFAs nutrition with a comparative study on DHA requirements of marine larval fish and its availability in live food organism Artemia. We also highlighted several factors affecting DHA enrichment process and its degradation following enrichment procedures.
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