Determining the sustainability of restored soft-sediment mussel beds in the Hauraki Gulf, New Zealand

Green-lipped mussel beds (Perna canaliculus) once covered vast areas of soft-sediment sea floor throughout the Hauraki Gulf, New Zealand, until their near extirpation, largely due to dredge fishing. Since the closure of the... [ view full abstract ]

Green-lipped mussel beds (Perna canaliculus) once covered vast areas of soft-sediment sea floor throughout the Hauraki Gulf, New Zealand, until their near extirpation, largely due to dredge fishing. Since the closure of the fishery in 1969, there has been little evidence of recovery in these populations, spurring efforts to restore these productive habitats and the many ecosystem services they once provided. With the creation of four experimental mussel beds, we attempted to determine if mussel beds could be sustainable within the current environment in the Hauraki Gulf. We monitored settlement, growth, and population size across these restored beds to assess sustainability and identify particular stressors to establishing sustainable beds. Each mussel bed contained on average 20550 mussels at the initial survey and covered an average area of 33.5 metres squared. Settlement was found to occur year round within the mussel beds, however only a small amount of recruitment (average of 3 individuals per metres squared) was observed on the most recent survey at one year. Across all beds, mussels showed evidence of individual growth while the population as a whole declined over each of the surveys to an average of 39%. With one year into the study, although larval supply is present and recruitment occurring, it is currently of insufficient magnitude to balance the natural mortality within these beds. If we are to develop restoration strategies that will be sustainable, we will require a greater understanding of recruitment and survival of mussels in this system, and factors such as the influence of predator intensity and larval sources on these processes.