Metal bioaccumulation in commercially important fish species, such as Sarda sarda, is significant for both ecosystem health and the integrity of food chains [1], [2], [3]. Sarda sarda, a pelagic predator at a high trophic level, serves as a critical bioindicator for assessing metal contamination due to its biomagnification potential [4]. These metals, originating from anthropogenic sources, have the potential to exert deleterious effects on fish physiology, reproductive success and population dynamics [5], [6], [7], [8], [9]. Furthermore, these contaminants further threaten human health via dietary exposure, with chronic intake linked to neurological disorders, cardiovascular diseases, and carcinogenicity [10].

The Black Sea, a semi-enclosed basin with limited water exchange, faces heightened vulnerability to metal pollution due to concentrated anthropogenic pressures from coastal industries, agriculture, and urbanization [11], [12], [13]. The extant literature about metal bioaccumulation in Sarda sarda is scant; nevertheless, extant studies suggest that this species may serve as a valuable bioindicator for assessing the health of marine ecosystems [14], [15]. Acknowledging the significance of seasonal fluctuations in mental concentrations is imperative for a comprehensive understanding of bioaccumulation dynamics [16]. This is so because factors such as reproductive cycles and environmental conditions can influence metal uptake. This study aims to fill the existing gaps in literature by providing comprehensive data on metal concentrations during the peak fishing season (September-November 2023) in the Sarda sarda fishery in Sinop. The methodology used is designed to provide robust and reliable results. The fish were directly purchased from local markets to minimise pre-analytical variability and ensure samples integrity. Fish were systematically categorised into size classes (small, medium, large) to evaluate how growth phases and seasonal shifts influence bioaccumulation. While the current study assessed the relationship between fish size and metal concentrations using a systematic categorisation of fish according to size, the results of this study can be used as a source of information for other research efforts that do not account for size variation. Furthermore, we integrate health risk assessments—including estimated daily intake (EDI), target hazard quotient (THQ), and Se health benefit value (HBVSe) to evaluate both toxicological risks and nutritional benefits for consumers.

Consequently, this study addresses critical gaps in the existing literature while utilising rigorous methodologies to ensure the reliability of its findings. By focusing on recent data and examining the influence of fish size and environmental factors, this research will provide key insights into the dynamics of metal accumulation in marine species and ultimately support better management practices and public health recommendations related to fish consumption.