Blue cod is a fish found only in the ocean waters surrounding the rocky coastlines of New Zealand. It is fished heavily both commercially and for recreation, leading to its placement on a quota management system in 1986. Depending on age and gender, the fish range in color from blue-green to brown-blue. Size and weight also vary, up to 23.6 inches (60 cm) in length and averaging 8.8 pounds (4 kg) in weight.
These fish have always been an important food source for people living in New Zealand. Native Maori used the fish as a staple part of their diet, calling it raawaru. Archaeologists located blue cod fish bones at ancient dig sites. These bones contributed to data tracking average length over time, numbers that suggest the cod has grown in size despite over-fishing.
New Zealand has a quota management system put in place by the government to monitor and restrict commercial and recreational fishing. Blue cod was one of the first 28 fish species placed on this program in 1986. The number of fish that can be caught per person ranges from 10 to 30 daily, and the number changes based on region and current fish population. All fish must be at least 11.8 inches (30 cm) when caught, otherwise they must be released back into the ocean.
Most of the blue cod population is concentrated in several areas, including the Cook Strait, Southland, Fiordland, and the Chatham Island. As bottom dwellers, the fish live in sand and weeds in shallow depths of water up to 492 feet (150 m) deep. Tracking studies of blue cod over time revealed that the fish usually stay in the area they are born and do not travel far over the course of their lifetime.
Breeding season begins in late winter and lasts until late spring. Eggs are spawned near the surface of the water, hatching after floating for five days. The blue cod larvae stay near the surface for another five days, finally leaving afterwards to begin their lives of bottom dwelling.
This species of cod can be hermaphroditic, switching from female to male after reaching maturity. Male fish grow faster than females, and the males are the only ones to appear a true deep blue in color. Female fish are more brown in appearance, and juvenile fish have a green tint to their blue coloration. The fish reach a size they can be legally caught at around 7 years of age, with a lifetime that can last up to 17 years.