Effects of salmon farming density on wild cod reproductive fitness
Sea cage fish aquaculture attracts large aggregations of wild fish that opportunistically feed on farm waste. Over time, these fish can undergo physiological changes, and captive feeding trials indicate possible negative effects on their reproductive fitness. However, not much is known about the significance of this phenomenon for reproduction in wild fish over larger spatial scales. Dr. Luke Barrett with researchers from the University of Melbourne and the Institute of Marine Research investigated if coastal areas with intensive aquaculture impacts the fitness of wild fish. They collected Atlantic cod in southwestern Norway from two neighbouring areas with either a high or low density of Atlantic salmon farms, and compared a range of reproductive fitness metrics via a captive spawning trial. They found evidence that cod from the area with a high density of salmon farming produced smaller eggs which led to smaller larvae, indicating a possible reduction in reproductive investment among cod from the intensive salmon farming area.