Australia’s comparatively young orange roughy fishery attracted recent community, industry and scientific interest because of questions about its sustainability, in particular for fish stocks which straddle Australian and international waters.
The Orange Roughy fishery has been boom and bust. The ‘hotspots’ initially discovered yielded such high volumes of fish that they overwhelmed handling capacity and much of the first catches were dumped. Within just a couple of years the fish were gone and a series of hotspots were no longer producing commercial catches.
The ecology of deep-sea fish is different and scientists believe that each fished out hotspot may never recover.
As with many other deep-sea fish, Orange Roughy are long lived. Studies show that they may commonly live more than 100 years (data from both otolith zone counts and radio-isotope ratios). The long life-time implies that they are late to mature (23-40 years of age), that they grow slowly (with an average size at maturity of 24 cm off South Africa and 42 cm in the NE Atlantic). They also have a low fecundity (reproductive rate) and may spawn irregularly. Even considering deep-sea fish species have these life history tendancies, researchers believe that Orange Roughy are the extreme low end of the productivity and high end of the longevity scales.
Orange Roughy populations may also be endemic, localised or resident, associated with specific topographic features and not tending to migrate over large distances.
All of these characteristics make the Orange Roughy highly vulnerable to exploitation. Field experience gained over the fishery’s 25 year history suggests that it is very difficult, if not impossible for local populations to recover from over-fishing.
It is not only the Orange Roughy themselves that are being destroyed. The fishery has very high by-catch levels. Mortality is nearly 100% for the deep water species dragged up and the understanding of the ecosystem effects of this and other deepsea fishing practices are largely unknown.
The mechanical effects of the fishery effort are also devastating to the deep-sea environment. Not only are the fragile, slow-to-recover, sea-floor communities of the trawl path destroyed, but the disturbance to the sea-floor sediments may spread the destructive effects over large areas.