Background and Objective: Aquatic plants are the main components of aquatic ecosystems. They play an important role in aquatic environments, reproducing and reconstructing stocks of all aquatic animals. In addition, some animals feed on aquatic plants.Macrobrachium nipponense is an aquatic species that use the aquatic plant as food and a place for reproducing. Therefore, determining the distribution of aquatic plants with the abundance of M. nipponense was essential for a better understanding of the aquatic plant roles in the M. nipponense life cycle. Materials and Methods: In this study, a sample of aquatic plants and M. nipponense during 2017 were taken. Identification and determination of dominant aquatic plants were made in the Anzali Lagoon. Results: The results showed floating macrophytes (Azolla filiculoides, Nelumbo nucifera, Trapa natans, Hydrocotyle vulgaris, Hydrocharis morsus-ranae and Eichhornia crassipes) and submerged macrophytes (Ceratophyllum demersum, Myriophyllum spicatum, Stuckenia pectinata and Potamogeton crispus) were in all of the sampling sites. Canonical correspondence analysis explained 100% of the total variance that correlated with the number and weight of M. nipponense with aquatic plants. The CCA analyses showed the number of M. nipponense was more affected by T. natans and C. demersum while the weight of M. nipponense was more affected by A. filiculoides, Algae and P. crispus. Conclusion:The correlation between aquatic plants and M. nipponense showed a significant correlation among all aquatic plants and the number and weight of M. nipponense. That means all aquatic plant effects on M. nipponense. But Azolla filiculoides (0.96), Trapa natans (0.97) and Algae (0.97) had more correlation coefficients compared to the other aquatic plants.

Background and Objective: Water quality in freshwater bodies is involved with multiple aspects such as physical, chemical and biological processes and their interactions. Due to the vulnerability of water resources, quality control of surface water is one of the key issues in environmental conservation programs. The objectives of the present work were to study the water quality in the Anzali Lagoon and to study the classification of water based on the water quality index in different parts of the Anzali Lagoon. Materials and Methods: In this study, we sampled water from January to December, 2015 in the Anzali Lagoon. All physicochemical parameters were sampled and determined according to standard methods. Results: The Water Quality Index results showed the Anzali Lagoon water quality had been "medium" in site 1 and "bad" in sites 2, 3 and 4. The result showed a significant difference between sit 1 and sites 2, 3 and 4 (p<0.05). However, there was no significant difference between sit 2, 3 and 4 (p>0.05). The result showed a clear spatial separation among parts in the Anzali Lagoon. The Eastern part of the Anzali Lagoon showed lower water quality compared to the central and western stations. Conclusion: This study showed that the level of pollution was different on all of the Anzali Lagoons. The water of the Anzali Lagoon has different quality classes according to the aggregation methods employed. Nutrient loadings from the adjacent agricultural lands combined with high mean salinity values affect all organism conditions. The three primary sources of nutrients, including fertilizers used in agriculture, household waste and livestock waste, reduced the water quality of the Anzali Lagoon.

Background and Objective: Studies on fish biology are essential for the sustainable management and conservation of fish biodiversity.This study observed the length-weight relationships and condition factors of common rudd fish, which give us some information about the ecological and nutritional conditions of fish. This information is crucial to fishery management. Materials and Methods: The length-weight relationship (LWR) and condition factors (K) of 270 Scardinius erythrophthalmus caught in Anzali Lagoon from April to August, 2015. Results: The total length and body weight of S. erythrophthalmus ranged from 94-179 mm and 11.98-98.5 g, respectively.A strong positive relationship was observed between length and weight (r = 0.96). There were no significant differences in the condition factors of males and females (p>0.05). The lowest K value was observed in April (K = 1.5±0.04) and the highest in July (K = 2.25±0.34). The sex ratio of 1.0 male: 1.15 female was observed, with no significant difference between males and females (p>0.05). Conclusion: In this study, the regression coefficient (b) in males and females was 3.35 and 3.29, respectively, more than 3.0, which means they have positive allometry growth in both sexes.