An experimental approach to non-indigenous species management: testing the selectivity and capture efficiency of thick trammel nets for lionfish Pterois miles in the southern Aegean of Türkiye

Managing non-indigenous species (NIS) is a key priority for natural resources managers, particularly as climate change increases the risk of these species becoming invasive.The lionfish (Pterois miles), an invasive NIS in the eastern Mediterranean and southern Aegean seas of Türkiye, has become a target for small-scale fishers (SSF) due to declining native fish stocks and NIS control efforts.A market-based approach to exploiting lionfish is a promising strategy, given the challenge of complete eradication in marine ecosystems -even though its commodification may carry unintended ecological and socio-economic risks in the long term.In Türkiye, despite market demand, fishers hesitate to supply lionfish due to potential gear damage and safe handling.This study examines the size selectivity and catch efficiency of thick trammel nets (TTNs), commonly used by SSF in Türkiye to overcome this barrier.Fishing trials from 2022 to 2024 mainly in the summer using TTNs with varying mesh sizes in the southern Aegean Sea caught 771 lionfish (18.2-42.7 cm total length).Results showed significant differences in mean total lengths across mesh sizes, with optimal model lengths exceeding the species' first maturity length (L 50 ).Larger mesh sizes may meet market demand but are insufficient for population control, while smaller mesh sizes have an increased risk of bycatch of native species.Nevertheless, since TTNs generally have limited bottom contact compared to more destructive gear types such as trawlers and purse seiners, defining an optimal mesh size targeting lionfish has been the main aim of this study to inform decisionmakers and SSF on best means available to tackle lionfish invasion in a collaborative way.