Science Centres: Aquatic Biodiversity and Biosecurity

Sometimes populations of invasive species take a natural downturn. Can selective fishing be used to hasten their demise?

To answer this question, NIWA scientists developed a population model to evaluate the impact of selective fishing on a declining population of the invasive crab Charybdis japonica in Waitemata Harbour.

The model was based on catch data from eight trapping surveys carried out by NIWA and Biosecurity New Zealand in 2002–04. It incorporated the effects of variation in sea surface temperature on larval survival and post-settlement mortality of the crab population.

Forecasts of crab numbers over 25 years suggested a high probability of extinction in six to eight years. They also showed that intense fishing could accelerate this process. However, more accurate estimates of recruitment and growth within the population are needed to calculate the fishing pressure (and investment) required to have an impact.