Climate-Driven Changes in Freshwater Inputs to a northern Patagonia Fjord and overfishing of wild mussel seed could threaten Chilean mussel farming

Abstract Chile is the first world exporter of farmed mussels with an annual harvest about 400000 tones, such production is based on the capture of wild seed which availability may be threatened by climate change and overfishing. Climate change-induced decreasing trends in annual precipitation, which increases water column salinity and this could be affecting the vertical distribution of mussel populations in fjords. In the Reloncaví Fjord, Chile, the observed changes in precipitation reduce the freshwater inputs, leading to potential shifts in the habitat and distribution of the economically significant Chilean mussel (Mytilus chilensis) and a competing species, Aulacomya atra. This research analyzes mussel beds' vertical dynamics in relation to changing environmental conditions, including freshwater inputs, salinity, and hydrological regimes in an exploited fjord for mussel seed collection. The findings suggest that decreasing trends in precipitation could result in increased surface salinity, reducing M. chilensis beds while favouring A. atra, with negative consequences for wild seed collection therefore threatening the Chilean mussel farming industry, projecting socio-economic impacts for small-scale aquaculture. Also, this study describes the increasing fishing pressure for wild mussel larvae and suggesting joint effects which are not possible to untangle with the present information and represents a key challenge for the design of adaptation measures for climate change. Therefore, this study emphasizes the need for better monitoring of mussel beds along with seed production and oceanographic conditions as well as improving aquaculture practices that reduce unnecessary pressure on mussel beds through seed collection in the face of changing environmental conditions.