Symposium Abstract: The Impact of Oyster Dredging on Blue Cod in New Zealand
Little is known about the potential impact of dredging on the growth and abundance of demersal fishes. Observations of blue cod (Parapercis colias) and oyster Ostrea chilensis fishing patterns indicate that dredging by the oyster fishery reduced localized catches and changed fishing patterns of blue cod fishers in Foveaux Strait, southern New Zealand. Towed underwater videos were then used to confirm the impact of dredging on habitat complexity and numbers of blue cod. An analysis of the diet and growth of blue cod from undisturbed biogenic reefs and reefs modified by oyster dredging further showed that diet complexity and growth of juvenile blue cod are reduced by dredging for oysters. However, stabilizing dredged habitat with fresh processed oyster shells shows promising signs of regeneration of blue cod populations in only a few years.