Dispersal of floating seaweeds contributes to the connectivity of marine communities. Little is known about the harvest of natural populations by fishermen on the dispersal capacity of these species. Harvesting decreases the available biomass and the size of individuals. Therefore, it can be hypothesized that the availability of floating specimens will be lower at sites with the highest harvesting intensity compared to sites with low intensity harvesting. Using the floating seaweed Durvillaea incurvata as a model, the relationship between the harvest of its benthic populations and the strandings on adjacent beaches was examined. Surveys were carried out during summer and winter from 2021 to 2023 at sites along the coast of Chile (33°S - 42°S) with different management administrative strategies and seaweed harvesting intensity: (a) Marine Protected Areas (MPA, low level), (b) Territorial Use Rights for Fisheries (TURF, intermediate level), and (c) Open Access Areas (OAA, high level). Measurements of biomasses, size structure, reproductive stage, potential buoyancy and floating times (using attached Lepas spp. as proxy) of the specimens from benthic populations and strandings on adjacent beaches were made. Benthic biomasses and sizes of D. incurvata specimens were higher in MPA compared to TURF and OAA, which were consistent with strandings on nearby beaches. Benthic and stranded biomasses, densities, lengths and percentages of reproductive individuals were higher in winter compared to summer. The presence and sizes of Lepas spp. indicated short floating times of stranded individuals. Significant relationships between biomasses, densities, and lengths of benthic and stranded D. incurvata specimens were observed, according to harvest intensity levels and seasons. Our results suggest that the harvest of benthic populations can affect the dispersal potential of D. incurvata. Exploitation of natural populations of floating seaweeds should consider their dispersal capacity, which may be useful for the recovery of over-exploited areas.
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