International Journal of Aquatic Biology
Volume:11 Issue: 1, Feb 2023

Centrocestus formosanus (Nishigori 1924) is a trematode parasite introduced into many parts of the world through the aquarium fish trade. Its infection causes high fish mortalities and economic losses to fish farmers worldwide. In this study, the efficacy of ethanol (95%) extract of Anacardium occidentale (Linnaeus 1753) apple to control C. formosanus infection in Xiphophorus hellerii (Heckel 1848) was investigated. According to Probit analysis, the estimated 96 h LC50 of plant extract for X. hellerii was 387.28 mgL- 1. Infected X. hellerii was treated with concentrations of 300, 320, 340, 360, and 380 mgL- 1 plant extract with exposure periods of 24 and 48 h. The behavior and mortality of treated and non-treated fish were observed for two weeks. Mortality and parasitic intensity of treated fish were significantly lower than that of non-treated fish during the experiment and recovery period. The parasitic intensity in treated fish decreased significantly with increasing concentration of plant extraction in 24 h and 48 h exposure. The lowest dose of A. occidentale apple extract needed to reduce more than 70% of metacercariae infected to gills of X. hellerii within 24 h was 340 mgL-1. According to the findings, A. occidentale apple extract can effectively control C. formosanus infections in aquarium fish.

This study aimed to study the concentrations of some trace elements viz. Pb, Ni, Cd, Co, and Fe in the water, sediments and muscle of three fishes of Liza abu, Mesopotamichthys sharpeyi and Carasobarbus luteus in the Tigris River by selecting six stations distributed along the Misan Governorate, southern Iraq. The study was conducted during two seasons, winter and summer. The concentrations of the studied trace elements in water followed the following order: Fe > Ni > Cd > Co > Pb. Fe had the highest concentration in the water (28.748), while the lowest onewas Pb (0.0523). The results also recorded the trace elements in order of Fe > Ni > Pb > Cd > Co. The highest concentration of Fe in the sediments was 9690.39, and the lowest was cobalt (8.612). The bioconcentration factor (BCF) values in the studied fish species were much higher than the biosedimentation factor (BSF). We conclude that the concentrations of trace elements in the sediments were more than in the waters of the Tigris River, as a storage place of pollutants in the aquatic environments.

Population dynamics of two sympatric cichlids, the native Etroplus suratensis and the alien Oreochromis mossambicus, were determined from the Vembanad Lake, the largest estuarine system of southern peninsular India. Based on annual length-frequency data, the results revealed that E. suratensis has a higher asymptotic length (L∞) (302 mm vs. 262mm), but a lower growth constant (K) (0.68 year-1 vs. 1.1 year-1) than O. mossambicus, suggesting the faster growth rate of the alien species. Natural mortality (M) rates recorded for E. suratensis (0.69 year-1) indicate lower levels of predation and other natural stressors in the lake. The exploitation ratio (E) was estimated to be 0.83 for E. suratensis and 0.78 for O. mossambicus, both values greater than the predicted optimum and suggestive of overexploitation. Our study provides the first information on the demography of wild E. suratensis, which would help inform future management strategies in the Vembanad Lake.

Length-weight relationships (LWRs) were evaluated for three endemic fish species collected from the north and south of inland waters of Oman in 2022 including Garra sindhae, G. smartae, and Oxyurichthys omanensis by using foldable shrimp and crab fishing traps (mesh size of 3*3mm) and hand nets (mesh size of 3*3mm). The parameter of b for all three species was between the estimated ranges of 2.5-3.5 as proposed for different other fish species, and there was high and significant coefficient of determination for all three species (0.87-0.984).

The Shatt Al-Arab River's water quality deteriorates naturally due to salinity intrusion, and freshwater sources decrease. Seven sampling locations along the Shatt Al- Arab River in southern Iraq were used to examine the level of six heavy metals, including Cu, Cd, Ni, Co, Mn, and Fe, during Januar-December 2021. Salinity levels in the study area ranged from 1.55 upstream to 35.15 g/L downstream of the study area. The pH of surface water ranged 7.545-8.325, indicating alkaline conditions. The concentrations of six heavy metals, viz Cu, Cd, Ni, Mn, Co, and Fe in the study area were 3.741±4.219, 3.654±4.169, 7.700± 6.251, 2.551±3.898, 2.292±3.996, and 18.236±5.583 μg/L, respectively, which decreased in the order of Fe > Ni > Cu > Cd > Mn > Co. There was a considerable change in the quantity of heavy metals throughout the year, with the summer months having the highest concentration. There is a correlation between seawater intrusion and the concentration of heavy metals in the surface waters. The mean levels of the heavy metals were below the allowed values of WHO drinking water guidelines.

Caspian Kutum, Rutilus frisii, is a valuable species in the Caspian Sea basin. With the aim of restocking, the Iranian Fisheries Organization (IFO) annually released millions of Caspian kutum larvae into the estuaries of the Caspian Sea. This study was conducted to evaluate the effects of starvation on fish during Caspian seawater (CSW) adaptation. Caspian kutum larvae (0.5±0.1 g) were divided into two groups; one was considered a control fed ad libitum during the experiment and another group was left food deprived. Both groups were continuously exposed to the CSW challenge (13 ppt) for 7 days and sampling was done on the second, third, fourth and seventh days after initiation of the CSW challenge. Different physiological factors, including hormones (cortisol, T3, and T4), gill Na+/K+-ATPase activity, whole body glucose and protein, gill protein, body moisture, and seawater preferences, were analyzed in each sampling time. The results showed that although fed larvae can successfully overcome the physiological changes imposed by the CSW challenge, the starved fish indicated significant failures in the most measured parameters and eventually demonstrated significantly lower salinity preferences. Therefore, it can be concluded that starvation may negatively affect the success of CSW adaptation. Since physiological impairment during the CSW adaptation period is directly related to the effectiveness of the restocking program, more studies about the feeding condition of Caspian kutum larvae pre and post-releasee and the nutritional status of recipient rivers are suggested.

Daily vertical migrations of hydrobionts are widespread in all water bodies, such as small wells and vast oceans. This phenomenon is most common among crustaceans, especially in amphipods. Lake Baikal is one of the most biodiverse freshwater centers containing 354 species and subspecies of amphipods, and almost all of them are endemics. The study’s goal was to follow the year-round dynamics of daily vertical migrations of amphipods and pinpoint various environmental factors that affect this process. Observations of amphipod migration were obtained using a remote video system. Based on the results, the vertical migratory activity of amphipods can be tracked during the year. The key factor that reduces migratory activity was found to be the start of the reverse stratification period. It is assumed that Lake Baikal amphipods have no single general reason for vertical migrations, and a few of the driving forces that make different amphipods groups migrate are accumulations of regions positive temperatures that facilitate sex development, food foraging, passive dispersal, search for a partner, and pairing.

A new locality was reported for Esomus metallicus in Kapalo Banda River, 50 Kota Regency, West Sumatra Province, Indonesia, about 74 km from Maninjau Lake. Identification of species was made by morphological and molecular methods using the COI gene. We also applied the Neighbor-Joining method to construct the phylogenetic tree. Based on morphological analysis, the specimens from Kapalo Banda River were E. metalicus with the unique feature of having long maxillary barbels. Based on the DNA sequence, specimens of West Sumatra were identical to E. metallicus sequence of Thailand specimens with a similarity of 99-100%, suggesting the probable origination of the Kapalo Banda River from Thailand.

This study was conducted to evaluate the water quality of the Um El-Naaj Marshes using the community of diatoms bioindicator and mapping them by remote sensing data. From November 2018 to April 2019, epiphytic diatoms were collected from host aquatic plants of Zannichllia palustnia from six sites in the Um El-Naaj Marshes. According to the results, the Diatom Index (DI) ranged from 3.5 in autumn 2018 to 2.4 in summer 2019, i.e in sites 3 and 2, respectively. The index of trophic diatoms (TDI) for the majority of study sites showed the mesotrophic state ranged from 47.5 to 62.5 in all seasons. Except for site 2, which had the lowest value (35) in the summer of 2019, and station 3 which had a greater value than 60 in the Autumn of 2018 and spring of 2019, other sites had oligo-mesotrophic states. The general diatomic index (GDI) values showed the lowest value (9.6) at site 2 in the summer of 2019 and the greatest value (14.4) at site 3 in the spring of 2019. In addition, in the current study, maps were produced using remote sensing methods to visualize the values close to the studied sites to show the quality state of the whole marsh.

Retinoic acid isomers such as 9 cis retinoic acid (9CRA) and all trans retinoic acid (ATRA) have been discovered in crustaceans. However, their physiological significance in the biological framework of crustaceans is unclear. The present study evaluates the effect of retinoic acid on the hemolymph glucose levels in the monsoon prawn, Macrobrachium malcolmsonii. Injection of 9CRA into intact prawns significantly elevated the hemolymph glucose levels in a dose-dependent and time-dependent manner. However, such hyperglycemic response in 9CRA-injected eyestalk ablated (ESX) prawns was not observed. No changes in the hemolymph glucose levels were noticed in ATRA-injected intact or ESX prawns. Bilateral ESX showed significant elevation in the total carbohydrates and glycogen levels with a significant reduction in the activity levels of phosphorylase activity in the crustacean hyperglycaemic hormone (CHH) target tissues, hepatopancreas and muscle of prawns. Injection of 9CRA into intact prawns showed significant elevation in the activity levels of phosphorylase activity with a concomitant decrease in the total carbohydrates and glycogen levels in the CHH target tissues compared to vehicle-injected prawns. No significant differences were observed in the selected biochemical variables in 9CRA-injected prawns over 9CRA-injected ESX prawns. The expression levels of CHH in the eyestalks of 9CRA-injected prawns were significantly elevated over its respective control. It can be concluded that 9CRA-induced hyperglycemia, at least in part, mediates CHH in M. malcolmsonii.