Linking scallop distribution and abundance with fisher behaviour: implication for management to avoid repeated stock collapse in a recreational fishery

The scallop fishery in southern Tasmania is one of the oldest in the world with harvest records dating back for over a century. This fishery has been plagued by episodic boom and bust cycles, a feature common to many fisheries targeting sessile marine invertebrates. In 2005, after a closure of 12 years, the fishery was once again opened to harvest, but access was only granted to recreational fishers and conservative management arrangements were implemented with an expectation of providing longer-term sustainability for the fishery. This study used dive surveys combined with telephone surveys of licenced fishers to monitor the fishery and resource status over between 2005 and 2009. Results indicated that, despite the conservative management approach, scallop stocks declined markedly over the study period, in part because of serial depletion of dense beds by recreational diving effort. This was set against the perception by the majority of divers who had participated in the fishery for multiple years that the stock levels had been maintained if not improved over the 4 years. This misperception reflects a shifting baseline phenomenon whereby divers progressively moved into new areas and switched target species, overlooking the lack of scallops in areas fished previously.