Sex-Specific Vulnerability of Fish to Dredging in the Mediterranean Coastal Lagoon (Lake Manzala, Egypt)

Year 2025, Volume: 40 Issue: 3, 153 - 162, 29.07.2025

Kariman Shalloof , Azza El-ganainy , Walid Aly

https://doi.org/10.26650/ASE2025.1693187

Abstract

Lagoon dredging disrupts aquatic ecosystems and fish populations. A study in Lake Manzala, Egypt, assessed these impacts by analyzing 2616 fish across ten species. Results showed significant variation in the condition factor (K) between sexes, ranging from a low of 0.220 in male European eels (Anguilla anguilla) to a high of 1.794 in female redbelly tilapia (Coptodon zillii). Sex ratios were predominantly male-biased. The male-to-female ratio was approximately 3:1 in C. zillii, Chelon ramada, and Chelon auratus, and 2:1 in Dicentrarchus punctatus, with males also dominating in Dicentrarchus labrax and A. anguilla. Only three species were female-biased: Oreochromis niloticus (1:1.40), Sarotherodon galilaeus (1:1.34), and Clarias gariepinus (1:3.31). These imbalances suggest dredging may negatively impact female populations, potentially reducing overall fish production. Therefore, incorporating sex ratio data into conservation management for Lake Manzala is crucial. Further research on species' reproductive biology is recommended post-dredging.

Keywords

Length weight relationship , Condition factor , Sex ratio , Length frequency

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