Unveiling knowledge gaps in non-indigenous fish species: A systematic review of growth and length–weight data across the Mediterranean basin

This study aims to identify the non-indigenous fish species for which significant knowledge gaps persist by evaluating the existing scientific literature on their fundamental biology (age-growth and length-weight relationships). Data were synthesized descriptively following PRISMA 2020 guidelines. In the study, a list of 177 non-indigenous fish species recorded in the Mediterranean was compiled, and a systematic literature survey was conducted to identify scientific publications containing length-weight relationship (LWR) and age-growth (AG) parameters for these species. Studies outside the Mediterranean or on non-fish taxa were excluded. Databases were searched up to November 2025. Data were synthesized descriptively by species, country, and study type. Risk of bias was not formally assessed in this review. A total of 143 studies were identified. The analyses revealed an uneven geographical distribution of research, with Türkiye leading by a wide margin with 84 (58.86%) studies. Lagocephalus sceleratus with 25 studies for LWR, and Saurida lessepsianus with 11 studies for AG, stood out as the most researched species. However, it was determined that fundamental biological data are still unavailable for many non-indigenous species. These findings reveal critical knowledge gaps that need to be urgently addressed for the sustainable management of increasing non-indigenous fish populations and highlight the urgency of expanded scientific research on these species.