Mr Finn Ryder1,2, Dr Gaya Gnanalingam1,2, Associate Professor Keith Sainsbury3, Dr Daniel Pritchard2, Professor Christopher Hepburn1,2
1Department of Marine Science, University of Otago, Dunedin, New Zealand, 2Coastal People Southern Skies Centre of Research Excellence, University of Otago, Dunedin, New Zealand, 3Institute of Marine and Antarctic Studies, University of Tasmania, Hobart, Australia
Blackfoot abalone (Haliotis iris), commonly known as pāua, are a highly prized cultural, recreational, and commercial resource in New Zealand. In recent years, due to multiple stressors, pāua stocks have undergone considerable declines. Despite this, there has not been a fine scale study of a single pāua population over a long timescale. From 1973 to 1976, Keith Sainsbury comprehensively studied a pāua population in Peraki Bay, Banks Peninsula. Using this historical data and similar methods, this study investigates how the population dynamics and size structure of pāua have changed over an extended period. As pāua in Peraki Bay have experienced little fishing pressure, this provided a unique opportunity to assess change. By re-surveying Peraki Bay 45 years after it was first surveyed, a large change in population size and structure was observed. Since 1976, there has been an 84 % decrease in estimated population size. Growth rates showed no change, but mean adult shell length decreased by 16.3 mm. No spawning events were observed during this study; however, recruitment occurred episodically. In addition to a large population decrease, our findings indicate that individuals are no longer reaching the size they once were, and that spawning may not be annual in Peraki Bay. Pāua may be susceptible to multiple stressors that are causing habitat loss and low and inconsistent recruitment. Being the first multidecadal study on a pāua population, and with very little fishing in Peraki Bay, this study helps clarify the rate and causes of population change driven by environmental stressors.
Presentation Slides – Finn Ryder
Biography:
Finn is currently a PhD candidate at the University of Otago in Dunedin, New Zealand. Finn’s research focuses on the spatial and temporal drivers of population dynamics and size structure of abalone.
