Two islands, one ray: Age and growth pattern of the common eagle ray (Myliobatis aquila) in the Central Mediterranean (Sicily and Sardinia)

The common eagle ray represents one of the most threatened batoid species inhabiting the Mediterranean Sea. Despite its low commercial value, the species is frequently encountered in both commercial and artisanal fishery bycatch. Nonetheless, the information available on its life history, especially its growth pattern, are rather scarce. Given the importance of growth data for accurately assessing the status of a species' population and informing its management, this study aims to provide new insights into the growth patterns of the common eagle ray in the western-central Mediterranean Sea. Between 2014 and 2024 a total of 200 vertebral centra were analysed from specimens caught along the coast of the two major Mediterranean islands (Sicily and Sardinia). Vertebrae were only extracted from specimens that were found to be already dead at the time of the capture, while live individuals have been released. To accurately describe the species' growth, different models were fitted to age-at-length data in a multi-model inference analysis. The von Bertalanffy growth function was indicated by the corrected Akaike’s Information Criterion as the most accurate in describing the species' growth. Results indicated that females reaching larger sizes (in disk width, DW) and greater longevity (DW: 189–737 mm; age range: 0–10 years) but growing at a slower rate (DW∞ = 872.9 mm; k = 0.11 y⁻¹; t₀ = −2.36) compared to males, which showed smaller maximum sizes and shorter lifespans (DW: 250–567 mm; age range: 0–7 years; DW∞ = 511.1 mm; k = 0.36 y⁻¹; t₀ = −1.36).