Impacts of Water Quality, Excessive Fishing Effort and Sediment Composition on Some Edible Bivalves in Suez Canal Lakes, Egypt

Fish production from natural resources has been facing countless challenges, primarily pollution, excessive fishing effort, unlawful gathering of fish fry in addition to food accessibility. Suez Canal lakes, Bitter and Timsah lakes are among the essential lakes in Egypt, producing commercial species with a mean annual fish production of 4000 tons (2005- 2021).  In the last 17 years, a severe decline in the fish production from the Suez Canal lakes was recorded. Fishery statistics of the Suez Canal lakes were collected from 2005 to 2021 to track the total catch, bivalve catch, and fishing effort during that period. Sediment and water samples were collected at 24 stations around the Great Bitter and Timsah lakes during 2022 and 2023. The grain size analyses designated that the bottom sediments of the Suez Canal lakes were principally composed of sand, with minor ingredients of gravel and mud. The concentration of heavy metals revealed that Fe has the highest concentration in the water and sediments of both lakes, while that of Cd was the lowest. The soft tissues of 105 individuals of Paphia undulata (Born, 1778), 100 individuals of P. textile (Gmelin, 1791) and 200 individuals of Donax trunculus (Linnaeus, 1758) from Lake Timsah were used for assessing heavy metal concentrations. Results showed that the concentration of all metals in the soft edible parts of the considered bivalve species were within the safe levels, except for lead (Pb) and zinc (Zn) that recorded higher levels than the permissible ones. A production model was used to evaluate the fishery status of the studied species in the Bitter and Timsah lakes. Based on the results, the main reasons for the production depletion of the studied species in the Suez Canal lakes are the overfishing and pollution. Therefore, the fishing effort control and pollution mitigation are strongly recommended in the lakes.