In chondrichthyans, despite males in ex situ conservation programs exhibiting good sperm quality, offspring production is confined to specific species. This study hypothesizes that the aquarium's environmental footprint may contribute to this loss of reproductive capacity. Consequently, the research initially focused on comparing the blood metabolomic profiles of the Small-Spotted Catshark (Scyliorhinus canicula) in both an aquarium environment at Oceanogràfic of Valencia and in wild populations along the Valencia Region coast (Spain). Furthermore, the study compared the blood metabolomic profiles with those of seminal plasma. This comparison aimed to identify potential variations in seminal plasma composition and its relationship with in vitro seminal characteristics. Samples were collected from S. canicula present in the aquarium (n = 7) and wild captured individuals (n = 12). Despite conventional semen quality assessments showing no significant disparities in semen volume and sperm concentration, considerable differences were observed in sperm motility and viability rates. Specifically, aquarium specimens showed slightly reduced metrics. The untargeted metabolic study in blood revealed significant differences between aquarium and wild individuals, with 158 semi-polar and 233 non-polar differential metabolites. A parallel analysis of seminal plasma similarly revealed substantial differences, with 2 semi-polar and 74 non-polar differential metabolites. Additionally, the analysis showed 104 semi-polar and 188 non-polar metabolites shared between the blood and seminal plasma of both animal groups. A further targeted analysis of 28 metabolites in blood identified significantly lower concentrations of phenylalanine, tyrosine, lysine, taurine, arginine, N-acetyl-L-glutamate, and creatinine in aquarium sharks. In seminal plasma samples, aquarium animals exhibited elevated levels of 7-Dehydrodesmosterol but reduced levels of phenylalanine, pantothenic acid (Vit B5), and spermine. In conclusion, these findings highlight alterations in both the blood and seminal plasma metabolomic profiles between aquarium-housed and wild animals, demonstrating the impact of the aquarium's environmental footprint, which could partly explain the reduced reproductive success of sharks in captivity. © 2024 The Authors

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