Reference points

Reference points

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Reference points

Biological reference points provide guidance on determining whether stock abundance is too low or fishing pressure is too high. Reference points in a fishery generally include targets to indicate where we would like to be, and limits to show what to avoid. Stock assessments usually produce estimates of abundance and fishing pressure over time, which can be assessed against biological reference points. The use of reference points to guide management decisions is consistent with the FAO Code of conduct for responsible fisheries.

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Limit reference points

The limit reference points used to determine stock status for management response have historically varied across the Australian jurisdictions. For example, Commonwealth fish stocks with a biomass below 20 per cent of the unfished abundance (biomass) level are generally classified as overfished, whereas, in New South Wales, stocks are generally considered overfished when they are below 30 per cent of the unfished abundance (biomass). The reference points for Commonwealth fisheries are specified in the Commonwealth Fisheries Harvest Strategy Policy (which underwent a review from March 2012 to March 2013), and Commonwealth fisheries are assessed against these reference points. Most other Australian jurisdictions have similar policies or legislative frameworks.

For assessing fish stock status nationally, 'recruitment overfished' was agreed as the biological limit reference point for determining whether or not a fish stock is overfished. 'Recruitment overfished' is defined as follows:

The point at which a stock is considered to be recruitment overfished is the point where the spawning stock biomass has been reduced through catch, so that average recruitment levels are significantly reduced.    

The percentage of the unfished abundance that is considered to represent a recruitment overfished state varies across species and stocks, based on differences in biology. The recruitment overfished limit reference point for abundance in the Status of Australian fish stocks reports is different from the limit reference points defined in some jurisdictions, which may include economic considerations or a precautionary buffer against measurement uncertainty. Reference points that include economic considerations or precautionary buffers can be very useful in particular decision-making contexts. However, it is intended that the national reporting be based solely on biological considerations, and these other considerations and buffers are therefore not included in the biological limit reference points used in the .

With respect to fishing pressure, for a stock to be classified as a sustainable stock in the Status of Australian fish stocks reports, the current level of fishing pressure must be at a level considered to be unlikely to cause the stock to become recruitment overfished—that is, recruitment overfishing should not be occurring (see glossary for a more detailed explanation of recruitment overfishing).

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Target reference points

Target reference points correspond to levels of biomass and fishing pressure that are considered to provide for optimal harvests, taking into account economic considerations and/or the ecological requirements for each fish stock. Generally, fisheries management aims to ensure that stocks are maintained near target levels and away from limit levels. Target reference points commonly incorporate management objectives, such as maximising the sustainable yield or economic returns. For example, the Commonwealth Fisheries Harvest Strategy Policy seeks to maintain fish stocks, on average, at a target biomass equal to the biomass that would produce maximum economic yield. As with limit reference points, a range of target reference points is currently used in the different fisheries and jurisdictions across Australia.

There is no single agreed national target level and these may vary substantially between stocks, so it is not challenging to include status classifications based on targets in stock status determinations. Although the stock status determinations provided in these reports report against limit reference points, it is envisaged that, in the future, stock status classification will consider stock status in relation to targets as well as limits.