International Journal of Aquatic Biology
Volume:9 Issue: 5, Oct 2021

This work is a study of growth aspects and mortality of the Atlantic chub mackerel, Scomber colia, from the Mediterranean Moroccan coast. A total of 845 specimens were collected from commercial catches in M’diq Bay, whose total length ranged between 16.4 and 35.9 cm. The length-weight relationship was W = 0.0019 TL3.4527 (r = 0.97) for the whole population. The Atlantic chub mackerel displays positive allometric growth. Otolith edge analysis indicated that opaque zones were formed between April and September and translucent ones during the remaining months of the year. The oldest individuals in the sample were 5 years old for both sexes. Von Bertalanffy growth parameters estimated for this species were: L∞ = 37.30 cm, k = 0.26 year-1 and t0 = - 2.19 year. The difference in growth between sexes is not significant. The estimated natural mortality was 0.59 per year.

Management and preservation of aquatic environments are essential for their productivity and the maintenance of aquatic life. This study aims to characterize the trophic state of TohoTodougba lagoon complex which has been subject for several years, to an intense fish production in cages. For this purpose, physico-chemical parameters were measured from June 2019 to May 2020 as well as chlorophyll-α, phosphorus and nitrogen. The trophic characterization indices were calculated basedo n Carlson (1977), Burns and Bryers (2000), Neverova-Dziopak and Kowalewski (2018), Primpas et al. (2010) and CCME-WQI (2001). It appears that the temperature (29°C), dissolved oxygen (3.19 mg.L-1 to 4.33 mg.L-1) and pH (6.66 to 7.31) are those characteristic of tropical lake environments. The production parameters revealed that the chlorophyll-α concentration varies from 0.19 to 37 mg.L-1 (stations and months combined). The concentration of phosphorus ranged from 0.02 to 0.42 mg.L-1 while nitrogen varied from 1.91 to 4.03 mg.L-1. Only nitrogen is not in critical proportion for the ecosystem. It should be noted that with the exception of the Carlson index, all other indices revealed that the ecosystem is in a state of advanced eutrophication with a tendency to hyper-trophication according to the eutrophication index of Primpas et al. (2010). Consequently, Toho-Todougba lagoon complex is eutrophic and requires adequate measures for its restoration despite its good health revealed by the physico-chemical parameters.

The Indian Oyster, Crassostrea madrasensis are abundant in the coastal waters of Tamil Nadu and Kerala. Since, they are benthic filter feeders, the external environmental conditions impose ceaseless effects on their shell affecting one or more of size, sculpture, anatomy pattern, shape and colour resulting in ecophenotypic plasticity. However, the identification of Oyster species is still based on phenotypic characters that are highly plastic. Therefore, this study aimed to investigate the phenotypic plasticity of the Indian Oyster, C. madrasensis population of Ashtamudi Lake with respect to certain ecological parameters. Individuals were collected from the barmouth and upper reaches of Ashtamudi Lake, Kerala and apparent variations were measured. Significant variations were found in the Shell colour and shell pattern. Accordingly, two morphotypes of C. madrasensis were recorded. Since, the two population exhibit remarkable differences in morphology, species confirmation was made possible using mitochondrial 16S rRNA gene. Even though 2.7% genetic distance observed between the two morphotypes of C. madrasensis is not enough to consider them as different species, it calls attention to the possibility of evolutionary divergence in the near future.

Though sea cucumber is one of the key export-oriented fishery resources in Sri Lanka, there is some evidence for the population depletion of most of the sea cucumber species in the shallow coastal waters. The present study was aimed to study the status of the sea cucumber fishery in the Irrakkakandi coastal area, eastern Sri Lanka, and carry out a stock assessment on the critical sea cucumber species presently harvested in this area. In order to achieve the objectives, logbook records based survey was conducted to cover the fishing season in 2019, from late February to the end of September. The harvest was collected by skin diving from shallow nearshore waters and Scuba diving from distal coastal waters about 5 km away from the shore. Thelenota anax was the dominant species in the catch from both fishing grounds, with a relative abundance of 86.82% in shallow waters and 91.30% in distal waters. The average Catch Per Unit Effort (CPUE) during the fishing season in 2019 for SCUBA diving and skin diving was 50±8.59 individuals /boat/day and 8±1.12 individuals /diver/day, respectively. The dominant stock of the T. anax in the distal fishing ground was assessed using the depletion method. The initial stock size of T. anax at the onset of the fishing season was estimated at 112,067 individuals, and about 25% of the initial stock had been fished by the end of the fishing season in 2019. The estimated catchability coefficient (q) was 0.00046. The study revealed that the stock of T. anax along with other recorded threatened species in the Irrakkakandi coastal waters might be led towards extinction if the fishery prevails without proper management.

As a multinational river, the Naf River flows into the Bay of Bengal in the Indian Ocean, between the Cox's Bazar district of Bangladesh and the Rakhine state of Burma. In a multidisciplinary approach, several experiments were carried out to understand the seasonal diversity of the phytoplankton community structure. A total of four layers of water was sampled from four depths in the Naf River during monsoon (September) and winter (December) of 2016. 41 species of phytoplankton were identified, and 3 different dominant groups (Cyanobacteria, Diatoms, and Dinoflagellates) were found. Diatoms and cyanobacteria alone were found to be most prevalent. Higher species diversity was observed in the monsoon season, with Synedra sp. (1.84×105 cells L-1, 18.76%) and winter with Microcystis sp. (1.41×105 cells L-1, 17.74%), respectively. In monsoon, NO3-N and PO4-P were both higher than winter (450.9 and 34.4 µg L-1, respectively) especially, at downstream Naf River. Moreover, high diversity indexes (richness) of phytoplankton were recorded along with these estuarine stations. Significant correlations (P<0.01) of nutrients with phytoplankton may liable behind these scenarios. An analysis of principal component analysis (PCA) and linear regression supported this correspondence. In the monsoon season, the concentration of Chlorophyllα reached the highest level (165 µg L-1) at a depth of 1.5 m, in Station-D. Cluster analysis based on the nutrient content of the Naf River was found two (upstream and downstream) mentionable zones during the winter and monsoon seasons. The results of the present study indicate that estuarine downstream areas are more productive than upstream areas of the Naf River at the southwest coastal zone of the Bay of Bengal.

One of the most important challenges lies in the microalgae mass production is the high cost of harvesting process which is the separation of a low amount of biomass consisting of small individual cells from a large volume of culture medium. Therefore, finding an efficient and costeffective technique for harvesting microalgae is important issue. In the current study, pH-induced flocculation method was tested for microalgae Cyanothece sp. harvesting. The halophilic microalgae were cultured and grown in laboratory with hypersaline water in F/2 medium. After reaching the stationary phase, the impact of pH induction (from natural medium culture pH:8.2 to pH:11) on flocculation efficiency, chlorophyll a, chlorophyll b, total carotenoid, β-Carotene and phycocyanin component and the possibility of reuse flocculated medium of microalgae Cyanothece sp. were evaluated. The results indicated that the increasing the medium pH value by adding NaOH from pH natural at 8.2 to 9.4 increased flocculation efficiency significantly from 10 up to 90% (P<0.05), but after that remained stable up to pH: 11. Regarding the pigment content, the increase in pH value from natural pH: 8.2 to pH: 9.1 had a relatively a medium effect on pigment components, including chlorophyll a, chlorophyll b, total carotenoid, β-Carotene and phycocyanin amount of the harvested biomass of Cyanothece sp, but after that from pH: 9.4 to 11 the reduction was severe. The medium culture from pH: 8.5 to pH: 11 was reusable for new culture of microalgae. Thus, the flocculation induced by pH increase up to pH: 9.1 is a suitable method for harvesting microalgae Cyanothece sp. with no serious adverse effect on pigment component.

In the present study, the effects of ZnO nanoparticles (NPs) on marine rotifer, Brachionus plicatilis, was investigated in three separate experiments. Firstly, the sensitivity and reproductive characteristics of B. plicatilis were studied at concentrations of 0, 0.1, 0.5, 1, 3, 5 and 10 mg L-1 of ZnO-NPs for 10 days. Based on the results, the total number of rotifers (TNR) significantly decreased at 5 and 10 mg L-1 of ZnO-NPs. In addition, the specific growth rate (SGR) of animals was negative at two of the concentrations of ZnO-NPs. In the second experiment, the TNR at 4 concentrations of ZnO-NPs (0, 10, 13, 17, and 19 mg L-1) during 72 h were tested and the 24-72 h LC50 of ZnO-NPs was calculated. After three days, the entire population of rotifers was generally lost at 19 mg L-1 of ZnO NPs. The LC50 of ZnO-NPs in animals at 24, 48, and 72 h intervals was registered as 18.2±1.34, 12.43±0.08, and 9.63±0.26 mg L-1, respectively. Finally, the zinc accumulation in rotifers was measured at different concentrations (0, 0.1, 0.5, and 1.3 mg L-1) of ZnO-NPs and maximum zinc (123 μg g-1 of rotifer DW) uptake by rotifers was observed in treatment 3 mg L-1 of ZnO-NPs. In sum, it can be concluded that the B. plicatilis can be used as a biological model for studying marine water contaminants with nanoparticles, especially ZnO-NPs.

Fishery wastes are one of natural resources to extract bioactive substances such as collagen and glycosaminoglycan (GAG). The anticoagulant activity of glycosaminoglycans extracted from Binni fish, Mesopotamichthys sharpeyi scales was the aim of this study. The cationic salt of cetyl pyridinium chloride was used to extract the glycosaminoglycan. The structure of the isolated glycosaminoglycan was identified by ELISE glycosaminoglycan kit and compared to that of heparin. Prothrombin time (PT), and thrombin time (TT) on plasma of male mice at three concentrations of 20, 40, and 100 g/ml were used to determine the coagulant property of the extracted substance. The extracted glycosaminoglycan was calculated to be around 27.7 mg/g of dry tissue. The presence of heparin-like molecules in the glycosaminoglycan isolated from fish scales was confirmed by ELISE GAG kit. When the concentration of isolated glycosaminoglycan was increased, the time to coagulate rose. The PT and TT coagulation times were 4:1 and 2:1. Times faster than the control at 100 g/ml. When compared to synthetic anticoagulant substances like heparin, the glycosaminoglycan isolated from fish scales displayed good anticoagulation qualities.