Introduction
Aquaculture is a cornerstone of food security in Egypt, the largest producer in Africa, yet its expansion along the Mediterranean coast has intensified conflicts with piscivorous birds. Despite the global recognition of bird predation as a major economic constraint—with documented losses exceeding 30% of production in some regions—Egypt lacks empirical data on this conflict. The northern Delta lakes, including Lake Manzala adjacent to Port Said, are critical wetlands along the African-Eurasian flyway, hosting millions of migratory waterbirds. Concurrently, climate change, wetland degradation, and overfishing are eroding natural prey bases, potentially forcing birds toward aquaculture ponds. This study aims to conduct the first comprehensive assessment of piscivorous bird impacts on brackish-water aquaculture in Port Said, quantifying species-specific predation, economic losses, and the efficacy of current mitigation strategies within the context of global environmental change.
Materials and Methods
A 24-month mixed-methods case study (January 2024–December 2025) was conducted across 35 aquaculture farms in Port Said Governorate. Systematic ornithological surveys (point counts, transects, and 520 hours of focal behavioral sampling) were performed to characterize bird communities and foraging strategies. Exclusion experiments compared fish survival between netted (n=15) and open ponds. Bioenergetics modeling estimated consumption rates, while production records from 10-hectare seabass (Dicentrarchus labrax ) operations quantified economic losses. Farmer interviews (n=50) assessed perceptions, mitigation costs, and management challenges. Spatial analysis using GIS mapped bird distribution relative to Lake Manzala .
Results
Thirty-three piscivorous bird species were documented, with three species dominating predation: Little Egret ( Egretta garzetta) (28.5% of observations), Slender-billed Gull (Chroicocephalus genei) (18.7%), and Grey Heron (Ardea cinerea ) (9.1%). Winter congregations reached exceptional densities: 48,266 birds at Lake Manzala North East and 28,555 at Port Fouad El Malaha. Direct economic losses averaged 12.7% of stocked biomass per cycle (range: 5–31%), equivalent to EGP 148,750 (USD ~4,950) per hectare per cycle. For a 10-hectare seabass operation, feeding-time predation alone caused seasonal losses of EGP 10,800–27,000. Extrapolated regionally, total annual losses reach approximately EGP 11.25 million (USD ~360,000). Indirect impacts included 220% higher cortisol levels and a 15.7% reduction in growth. Current deterrents were largely ineffective (mean efficacy 2.8/5); 65% of farmers admitted to lethal control despite legal protections.
Discussion
This study provides the first empirical evidence that piscivorous birds cause substantial economic losses to Egyptian aquaculture, with impacts exacerbated by climate-driven degradation of natural habitats. The convergence of migratory birds at aquaculture ponds reflects broader ecosystem stress—birds are increasingly ’squeezed’ between a degraded Lake Manzala and an overfished Mediterranean Sea. The identification of species-specific foraging strategies and risk classifications enables targeted management. Cost-benefit analysis reveals that targeted netting of feeding areas (3.6-year payback) and automated laser systems (3.2-year payback) offer economically viable alternatives to current ineffective practices. These findings highlight the need for an Integrated Bird Management framework balancing aquaculture productivity with avian conservation obligations under Egyptian Law 4/1994 and international agreements.
Acknowledgment
This work was funded by Suez Canal University, Egypt.
References
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