Potential contribution of foreign-flagged recreational and craft vessels to the introduction and spread of non-indigenous species: A preliminary assessment for Brazil.

The role of recreational boats as pathways for the introduction and spread of non-indigenous species (NIS) has been regarded as a secondary concern by international regulations. Nonetheless, recent studies indicated that recreational crafts may cause up to 60 % of introductions in some regions. By keeping official records of foreign crafts transiting in its jurisdictional waters, the Brazilian Maritime Authority has a useful database. The present study combines these data with environmental parameters to map and assess the biofouling-mediated risks associated with recreational boats entering Brazilian Jurisdictional waters (BJW). Eight regional captaincies were selected as the main entry gates for BJW. Across five years (2019-2024), each route used by foreign recreational boats to reach these captaincies was mapped and had an associated NIS introduction risk calculated through a modified version of GloBallast Risk Assessment Approach (GRAA). The analysis of records identified 84 entry routes for recreational boats in BJW. The captaincies of Rio Grande do Sul (CPRS) and Rio de Janeiro had the highest connectivity, with 20 and 15 routes, respectively. In contrast, the captaincies of Maranhão and São Paulo were the least connected, each with five routes. Risk values ranged approximately from 0.1 for the route from Isle of Man to captaincy of Santa Catarina to 7.5 for the route from Buenos Aires to CPRS. The findings allow management to direct resources to higher-risk areas, reaching more effective results. Future work will involve cataloging fouling species on recreational vessels to refine risk assessments and management strategies against NIS.