Snapper seagrass nurseries

NIWA research has found that seagrass nurseries have a significant role in the growth and condition of juvenile snapper.

The research compared young snapper from several locations in eastern Northland and found that fish from three subtidal seagrass nurseries did significantly better than fish from non-seagrass nursery areas.

Researcher Christine Stewart’s BSc (Hons) thesis examined the role of seagrass nurseries in the physical development of snapper – an important northern New Zealand coastal fishery. Her work was supported by the Ministry for Business, Innovation, and Employment (MBIE) ‘Juvenile fish habitat bottlenecks’ programme.

The project involved ageing 113 juvenile snapper from the area using daily growth rings and calculated body condition indices, to see how fish growth and condition varied across different environments/nurseries. This included three subtidal seagrass dominated nurseries (Parengarenga, Rangaunu, and Whangarei harbours), and six non-seagrass nurseries (Whangaroa Harbour, Bay of Islands (Te Puna, Kerikeri, and Opua Inlets, and Te Rawhiti Strait), Whangaruru Harbour), as well as lesser nursery areas of Rangaunu and Doubtless Bays.

Fish in subtidal seagrass nurseries grew significantly faster and were heavier for their length than fish in other habitats. For example, at 40 days of age post-settlement, juveniles from seagrass areas weighted 1.45 times more than non-seagrass fish; this increased to 1.87 times by 70 days age.

Christine’s work was supervised by Dr Richard Taylor at the University of Auckland’s Leigh Marine Laboratory. She is now working on ageing Hauraki Gulf juveniles, which will further extend our knowledge of juvenile snapper nursery habitat quality effects. These data will be important inputs into a nursery habitat simulation model being developed in the MBIE programme.