Ranching of wild cod in ‘herds’ formed with anthropogenic feeding

Anthropogenic feeding was carried out for 21 months in a fjord in Northwest Iceland to assess the potential of aggregating and growing free-ranging cod (Gadus morhua). Practical feeding and harvesting methods were developed and four sizable herds of wild cod formed at four feeding stations, where net bags with frozen trash fish were deployed 2–5 times per week. Commercial fishing was prohibited in a 30 km2 area around the feeding stations, where a total of 262 metric tons (t) of feed was dispensed. In August 2005, when the monthly feeding peaked at 27.2 t, the biomass of cod in the herds was estimated to be 70–100 t, mainly fish > 40 cm. The biomass of cod in the fjord was estimated as approximately 2000 t. The conditioned fish showed high fidelity to a given herd and their growth rates approximately tripled. A total of 171 t of cod and 82 t of haddock (Melanogrammus aeglefinus) were harvested in the project. Ranching of cod in herds has the potential of reducing the cost and energy consumption of fishing, and on-growing wild cod on a large scale without the cost associated with sea cages.