Project 4.8.1

No-take (green) zones replenish fish populations in fished (blue) zones in the Great Barrier Reef Marine Park

Project Leader: Prof Terry Hughes, JCU

Understanding patterns in larval dispersal - connectivity between reefs and the capacity to replenishment stocks - is a major challenge in both marine ecology and fisheries management. Other MTSRF-funded work has shown that green (no-take) zones in the Great Barrier Reef Marine Park promote the abundance, size and reproductive potential of exploited fishes within their boundaries, but an important question remained unanswered: does the reproductive output of fish living within no-take areas contribute to the replenishment of populations in fished areas, particularly for sought after species such as coral trout? This MTSRF project investigated this question in two ways: by developing a detailed model for larval dispersal between reefs in the Great Barrier Reef Marine Park, and by extensive parentage analyses of targeted reef fish species inside and outside green (no-take) zones. The model results indicated that more than half of the larvae produced within green (no-take) zones on the Great Barrier Reef were likely to be exported to other zones. Seeking confirmation in the field, researchers enlisted the help of local recreational fishers in obtaining DNA samples from a large number of adult and juvenile coral trout living on reefs in the Keppel Group. Preliminary genetic analyses have determined that 85 of the sampled juveniles were produced from adults living in green (no-take) zones. Over two-thirds of these identified juveniles were sampled in blue zones; that is, they had dispersed from their parental green (no-take) zones into blue (fished) zones. Observed dispersal distances ranged from 100 m to 24 km, with an average of 6-8 km. This research has demonstrated empirically for the first time that fish protected within green (no-take) zones in the Great Barrier Reef Marine Park make a positive contribution to stocks in adjacent (blue) zones where fishing is permitted. Green (no-take) zones not only promote ecosystem resilience through larval connectivity, but improve the sustainability of fishing in adjacent blue zones.