Coastal fish assemblages and predation pressure in northern-central Chilean Lessonia trabeculata kelp forests and barren grounds.

Kelp forests are declining in many parts of the globe, which can lead to the spreading of barren grounds. Increased abundances of grazers, mainly due to reduction of their predators, are among the causes of this development. Here, we compared the species richness (SR), frequency of occurrence (FO), and maximum abundance (MaxN) of predatory fish and their predation pressure between kelp forest and barren ground habitats of northern-central Chile. Sampling was done using baited underwater cameras with vertical and horizontal orientation. Two prey organisms were used as tethered baits, the black sea urchin Tetrapygus niger and the porcelanid crab Petrolisthes laevigatus. SR did not show major differences between habitats, while FO and MaxN were higher on barren grounds in vertical videos, with no major differences between habitats in horizontal videos. Predation pressure did not differ between habitats, but after 24 h consumption of porcelanid crabs was significantly higher than that of sea urchins. Scartichthys viridis/gigas was the main predator, accounting for 82% of the observed predation events on Petrolisthes laevigatus. Most of these attacks occurred on barren grounds. Scartichthys viridis/gigas was the only fish observed attacking (but not consuming) tethered sea urchins. High abundances of opportunistic predators (Scartichthys viridis/gigas) are probably related to low abundances of large predatory fishes. These results suggest that intense fishing activity on large predators, and their resulting low abundances, could result in low predation pressure on sea urchins, thereby contributing to the increase of T. niger abundances in subtidal rocky habitats.

Exploring determinants for the implementation of mixed TURF-aquaculture systems.

Territorial use rights in fisheries (TURFs) have been highlighted as a means to deter the race for fish. Nevertheless, in many situations TURFs are not able to meet all their goals, jeopardizing their continuity. Here we explore one of several innovations on TURFs, mixed TURF-aquaculture systems, which can help overcome the challenges of maintaining sustainable socio-ecological systems. We analyzed the history of mixed TURF and small-scale aquaculture systems in Chile, particularly 8 recent learning platforms in the Coquimbo region. Additionally, we assessed the impact of 6 variables, from multiple spheres, on the implementation of mixed TURF-aquaculture systems. Despite low values in several variables, 75% of the learning platforms managed to implement aquaculture systems and 38% have been successful in developing monitoring efforts. Social capital was key in the implementation of the mixed systems. By investing in social capital policy makers can contribute to the successful implementation of mixed TURF-aquaculture systems, thus promoting a livelihood diversification strategy for fishing communities that encompasses the economic benefits of aquaculture with the socio-ecological benefits of TURFs. However, their development and enabling conditions must be monitored to embrace their synergies.

Butyltin contamination in Northern Chilean coast: Is there a potential risk for consumers?

Imposex is the superimposition of non-functional male sex organs in gastropod females. This syndrome is a hormonal imbalance induced by tributyltin (TBT) which have been used in antifouling paints formulation. The present study aimed to perform an integrated environmental assessment of imposex and butyltin (BT) contamination using surface sediments and tissues of Thaisella chocolata (an edible gastropod) from northern Chile. The results showed imposex incidence in 11 out of 12 sites. In the most contaminated sites, which are areas under the influence of maritime activities, and also used for fishing and aquaculture, RPLI were over 60 and VDSI over 4 (high incidence of sterile females). Exceptionally high contamination levels and evidences of fresh inputs of tributyltin (TBT) were detected along the studied area. TBT levels above 300 and 90ngSng-1, respectively, were recorded in sediments and edible gastropod tissues of 6 sites. Thus, a daily ingestion of 90 to 173g of T. chocolata foot (4 to 8 organisms) from the most contaminated sites will certainly lead to the consumption of BT exceeding the tolerable daily intake recommended by European Food Safety Authority. It is reasonable to consider that human risk is even higher if daily consumption of additional seafood is considered. Moreover, some contaminated sites were located within the marine reserve "Isla Grande Atacama", indicating that even marine protected areas are under the influence of TBT contamination. These findings suggest that current levels of TBT in the studied area are sufficient to induce harmful effects on the environment and constitutes a potential threat to seafood consumers. Thus, national regulatory actions toward environmental protection and food safety of local populations are still mandatory, even after 8years of the TBT global ban by IMO.