Magazine article Ecos

Age Riddle Confounds Fair Fishing for Krill. (Spectrum)

Magazine article Ecos

Age Riddle Confounds Fair Fishing for Krill. (Spectrum)

Article excerpt

Antarctic krill was once considered a vast untapped source of protein for the `starving masses'. But trawling in the Southern Ocean is expensive and logistically difficult, so krill has been fished in relatively low volumes, for high-value products such as food additives, sport-fishing bait and feeds for farmed fish.

As a result, Antarctic krill may be one of the last substantial marine living resources that is not over-exploited.

But there are plans to expand the fishery as the technology becomes available to make high-value products more cheaply, and the value of krill as feed for the rapidly growing aquaculture industry begins to rise. Scientists estimate that the world catch of krill--of which there are 85 species--may increase from 150 000 tonnes a year to more than five million tonnes.

To ensure krill fisheries remain sustainable under expansion, more information about their biology is needed. At the Australian Antarctic Division in Kingston, near Hobart, Dr Stephen Nicol and PhD student Angela McGaffin are attempting to age Antarctic krill (Euphausia superba), to gain a better understanding of their life span and population structure.

`Krill were thought to live for two years, but at the division we've kept them alive for up to 10 years,' Nicol says.

`This means they live five times longer than previously thought, so their production rate is one fifth what was initially estimated. This slower turnover could have implications for the amount of krill that can be commercially harvested.'

While size is often a good indication of age, krill can actually shrink in winter and grow rapidly in summer. Their growth rate is related to the amount of food available, but may also depend on temperature and light cycles. This variability confounds the ageing process.

So rather than rely on size as a clue to age, McGaffin is evaluating a biochemical technique that measures the accumulation of pigments in the animals' brains with time. …

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