Characterization of the welfare conditions of salmonids reared in freshwater in southern Chile

A study was conducted to collect information on the welfare status of salmonids reared in freshwater in southern Chile and to identify the most suitable operational welfare indicators (OWIs) for application in hatcheries. The study was carried out with the voluntary participation of 54 hatcheries that represent 36% of the total number of freshwater hatcheries operating in Chile, which were classified according to the production stage and comprised 12 hatcheries with recirculation system (RAS); 32 hatcheries with flow-through system (FTS); 7 hatcheries with water reuse system (REU) and 3 hatcheries with mixed system (FTS+RAS). Thirty OWIs were selected as the most suitable from the consulted literature and from a questionnaire administered to the fish farmers participating in the study. Three aspects were considered: animal welfare, feasibility, and economic cost, which were grouped into indirect (15) and direct OWIs (15). The OWIs were validated in 16 hatcheries where incubation, fingerling, and smoltification steps were covered. The results enabled the identification of critical conditions for the welfare of farmed fish, both in flow-through hatcheries and recirculation hatcheries, for the three salmonid species reared in Chile (Atlantic salmon Salmo salar, coho salmon Oncorhynchus kisutch, and rainbow trout Oncorhynchus mykiss). Water quality was considered the most critical issue for smolt production in freshwater, followed by precocious maturation in Atlantic salmon males, observed primarily in RAS hatcheries, and mortality classified as non-infectious. The latter included the culling of fish that are considered not suitable for commercial production.