International Journal of Aquatic Biology
Volume:11 Issue: 4, Aug 2023

Biofloc technology is based on carbon metabolism and nitrogen immobilizing microbial activities. The present study aimed to maintain water quality and increase the production performance of guppy Poecilia reticulata(Peters 1859) in a zero-water exchangebrackish waterbiofloc system. Twenty P. reticulatawere stocked into each treatment and control tank in triplicate and fed a formulated diet at a rate of 3% of body mass daily. In control-1, 50% water was exchanged weekly following the industrial practice,and no water was exchanged in control-2 and the treatment. Depending on the concentration of total ammonia nitrogen (TAN) in water, rice bran as a carbon source was added to the treatment tanks to keep the C:N ratio at 20:1. Water quality in biofloc treatment and control-1 was within thefavorablerange for P. reticulata. TAN and pH in tanks with zero water exchange were significantly higher (P<0.05).Weight gain, specific growth rate, survival rate, final weight and length of P. reticulatain the biofloctreatment were significantly higher (P<0.05) than controls. Fish reared in the biofloc treatment had an intense bright red body and fin colorcompared to those in the controls. Biofloc technology can be adopted to maintain water quality and enhance the production performance of P. reticulatain zero-water exchangebrackish waterculture systems.

The population parameters of Gerres nigri Günther,1859from the Saloum estuary in Senegal were studied from September 2017 to January 2018. A total of 591 individuals were collected monthly by experimental beach seine. The monthly length-frequency data (total length in cm) were obtained and analysed using the FiSAT II software and its sub-program ELEFAN for the evaluation of population parameters. Asymptotic length (L∞) and growth coefficient (K) were estimated at 22.1 cm and 1.5 yr-1, respectively. The growth performance index (Φ’), longevity (tmax), and the theoretical age at birth (t0) were calculated as 2.86; 2.827yr, and -0.11yr-1, respectively. Total mortality (Z), natural mortality (M), and fishing mortality (F) were calculated at 3.57 yr-1, 2.48 yr-1,and 1.09 yr-1, respectively. The probability of capture was calculated as L25 = 13.45, Lc = 14.34 and L75 = 15.08 cm. The recruitment pattern is a continuous two-peak model, with the minor peak occurring in May and the major peak occurring in August. The current exploitation rate (Ecurrent) and maximum exploitation rate (Emax) were calculated as 0.31 and 0.421, respectively. Further, the current rate of exploitation of G. nigri was slightly lower than the maximum exploitation rate. The results showed that the G. nigristock was not overexploited.

It is here presented the first faunistic list of the marine Heterobranchia fauna of Lipari and Vulcano, the two southernmost islands of the Aeolian archipelago. Through the examination of ten dive sites (six in Lipari and four in Vulcano), it was found a total of 30 marine Heterobranchia species (1 Rhodopoidea, 1 Pleurobranchida, 21 Nudibranchia, 1 Cephalaspidea, 1 Umbraculida and 5 Sacoglossa). Specifically, in Lipari 26 species were found, while in Vulcano 18 taxa. This numerical difference between the two islands might be related to the higher presence of different environments and habitats in Lipari compared to Vulcano.

Cetobacterium someraeis a predominant bacterium found in the gut of freshwater fish. However, being an anaerobic bacterium, its survival is believed to be prevented in oxygen-rich environments. Therefore, in this study, we investigated the oxygen tolerance of 83 C. someraestrains collected from the guts of freshwater fish, rearing water, and sediment of culture ponds and tanks. When placed in sterile bottles containing common carp-and goldfish-rearing water, C. someraeshowed a 1-log decrease after 24 hours, suggesting that this organism faces challenges in growing in rearing water. Subsequently, we inoculated the bacterial strains onto agar plates and exposed them to air for 12 hours to measure the oxygen inhibition index (OII). The OII values ranged from 0.01 to 4.65 among different strains, indicating significant variation in oxygen tolerance within the bacterium. Furthermore, the OII values varied considerably depending on the isolation source, with sediment, rearing water, and gut samples showing increasing values in thatorder. This suggests that oxygen tolerance plays a substantial role in the ecological behavior ofC. somerae.

Mitochondria is the major source of ROS which is neutralized by antioxidant enzymes. However, if there is an imbalance between the prooxidants and the antioxidants, then mitochondrial oxidative stress may occur. This is one of the main reasons for mitochondrial damage and dysfunction. The present study attempts to understand whether environmental stressors like hypoxia and acidic ambiances induce oxidative stress in zebrafish, Danio rerio. The enhanced production of MDA clearly states that the zebrafish skeletal muscle and liver tissues undergo oxidative stress when subjected to environmental stressors. Further, the study also aims to explore the mitochondrial biogenesis in skeletal muscle and liver tissues by confocal microscopy visualization through IraZolve-mitostaining under oxidative stressed situations. Visualization of mitochondria from skeletal muscle and liver tissue through transmission electron microscopy (TEM) reveals that under oxidative stress, the structure of mitochondria is disorganized leading to reduced mitochondrial functioning and biogenesis. Through microscopic visualization, the study concludes that hypoxia and acidic ambiances can cause remarkable mitochondrial damage in tissues like skeletal muscle and liver.

The current work aimed to develop a framework for the estimation of the optimized catch limit of the Yellowfintuna(YFT),Thunnus albacaresstock using catch data in the Iranian southern waters.In this study, two methods were employed to determine the biological reference points (BRPs) of this species. Biometry data was collected for 18 years (1993-2019) and the optimized catch limit was estimated using the limited data approaches. In an estimation method of Length-based Bayesian biomass(LBB), the highest length of this species was calculated as 166 (163-169) cm. The estimate of F/M= 1.9 (1.35-2.5) confirms the overfishing of yellowfin tuna, but the estimate of B/B0=0.17 (0.109-0.238) shows the overfishing of the biomass. In an estimation method of length-based spawning potential ratio (LB-SPR), F/M>2.5 is upper the level that probably results in the maximum sustainable yield (F/M= 0.8-1.0). In the present study, the spawning potential level of the population was estimated at approximately 11%, which means over-exploitation of this species so far. The results showed that the exploitation ratio of YFTstock is overfishing (overexploitation) and a decrease in exploitation ratio and fishing effort are proposed. Regarding the condition of yellowfin tuna stock, both LBB and LBSPR methods confirmed each other and there is no big difference between them.

The cyanobacterial bloom leads to the deterioration of the aquatic environment because they release their secondary metabolic to the water, especially toxins. One of the important toxins is Cylindrospermopsin (CYN) which is one of the dangerous toxins that cause liver damage known as hepatic toxin, which poses great health risks to humans. Light plays an important role in the production of these toxins by cyanobacteria through its effect on the photosynthesis processand the gene regulator of these toxins. The current study tested the effect of different light intensities of 26, 52, 78, and 104 mol m-2s-1on hepatotoxic CYN production by cyanobacterium Nostoc ellipsosporum. The findings of this study showed that the highest inter and extracellular CYN reached 0.047 and 42.5 μg/ml, respectively with a total value of 42.547 μg/ml recorded at the light intensity of 78 μmol photons m-2s-1. The lowest production of intra and extracellular CYN was recorded at the light intensity of 26 μmol photons m-2s-1, which amounted to 0.0006 μg/mg and 7.73 μg/ml, respectively with a total value of 7.735 μg/ml. Also, the highest light intensity inhibited the CYN production which recorded 0.009 μg/mg and 26.39 μg/ml for intra and extracellular contents, respectively, and total production of 26.399 μg/ml. We conclude that light intensity has a vital role in CYN production especially in the optimal condition represented by moderate light, and this effect differs among different cyanobacterial species.

Pangasius nasutus is one of the popular freshwater fish species in Pahang River, Malaysia because of its economic value, however, the high exploitation rate, occurrence of invasive alien species in the same ecosystem, and habitat modification threatened its population sustainability. This study aimed to enhance the existing information database of a species that has limited data availability and to monitor its population status. The monthly samplings were conducted from the upstream to the downstream of the Pahang River for 12 consecutive months from May 2021 to April 2022. The FiSAT II software was used to analyse population parameters from the length frequency data. The results revealed the asymptotic length (L∞) = 661.50 mm, growth coefficient (K) = 0.18 year-1, growth performance index (Ø’) = 4.90, the maximum age (Tmax) = 16.67, total mortality (Z) = 0.61 year-1, natural mortality (M) = 0.25 year-1, fishing mortality (F) = 0.36 year-1 and exploitation rate (E) = 0.59 year-1. The results also showed that P. nasutusexhibits a slow growth rate, rendering it more susceptible to overfishing. This study alsoindicated that the current level of exploitation of P. nasutus population in the Pahang River appears to be appropriate. However, it is recommended that a precautionary strategy be adopted to mitigate the risk of overexploitation.

Considering the drought and lack of water in recent decades, effluent reuse has been suggested as an efficient way to save water sources. Also, reducing the amount of sewage before releasing it into the environment is necessary to decrease threats to human and aquatic organisms. In recent years, due to the emergence of the COVID-19 epidemic and following the massive production of alcohol, the dischargeof wastewater from these factories has increased. In this research, the performance of a particle trap system (PTS) was examined in treating the effluents of an alcohol factory as vinasse and stillage and the treated water with different concentrations of the wastewater was used forDaphnia (Daphnia pulex) and Zebrafish (Danio rerio)as model bioindicators. The performance ofPTS in reducing COD, BOD, and TSS for vinasse was 96.90, 97.44, and 88.43% and for stillage was 95.69, 96.77, and 90.15%, respectively. Based on the results, the LC50of vinasse for zebrafish and daphnia was 0.63 and 0.76%, and the LC50of stillage for zebrafish and daphnia was 0.6 and 0.65%, respectively. The mortality rate of daphnia and zebrafish was different based on wastewater concentration and duration of exposure. In high exposure concentrations, which were usually above 3%, death occurred in a shorter period of time. In conclusion, the PTS is an efficient and inexpensive system for the purification and recycling of effluent from alcohol factories

The aim of the present study was to predict future distribution change of the Mesopotamian barb species group or Capoeta damascinaspecies complex under different climate scenarios in Central Zagros, Iran. By collecting data on the species' presence and applying the Maximum Entropy (MaxEnt) algorithm with the help of R programming language, we were able to create models of the current habitats of the fishes. Then the distribution range shifts in the future were projected in two optimistic and pessimistic scenarios (Representative Concentration Pathways (RCP) 2.6 and 8.5) of 2050 and 2080. The results showed that the accuracy of the implemented model was excellent (i.e. AUC (Area Under Curve) was 0.906. Moreover, the range change of species in all scenarios was negative but in the pessimistic scenario (RCP 8.5), the impact seems to be higher than in the optimistic scenario (RCP 2.6). The results of this study are very important for conservation and management. Knowing the potential impacts of climate change on these fish species in Central Zagros in the present and future can help us make better decisions to protect fish diversity in this important region.

Bone tissue engineering is a rapidly expanding research areathat usesan artificial scaffold as a template for new tissue formation by culturing osteoblasts, along with adding regulating factors that promote cell recruitment, growth differentiation, and mineralized bone tissue.Different natural and syntheticmaterialsand their combinations are used for this purpose. However, polymers have many advantages to use as scaffolds in bone tissue engineering, and therefore, their application in tissue engineering has been widened in recent years.In this work, we aimed to review thosenatural polymersthat are used inbone tissue engineeringwith an emphasis on those originating from natural aquatic resources. In this regard, the recent findings in the applicationof those natural biopolymers and their characterization viz. hydroxyapatite, starch, fibrinogen, silk fibroin, alginate,gelatin, chitosan, and collagenfor useas scaffolds in bone tissue engineering were discussed