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Fish stocks under the Quota Management System (QMS)

To report on fish stocks under the QMS, the following two aspects are measured:

Assessing stocks

Assessments of fish stock status are one of the key information sources for reviewing catch limits for species subject to quota. Safe fishing levels are worked out by determining the largest average annual catch that can be taken over time without decreasing a stock’s productive potential (maximum sustainable yield).

Science working groups estimate the status of each stock, to determine whether current TACCs and actual catch levels are meeting targets and avoiding limits.

When new information results in substantial changes to previous assessments, a report is referred to the Fishery Assessment Plenary for further consideration and a document is prepared summarising the state of each stock.

Economic, social and environmental considerations are then taken into account to determine whether TACCs should be adjusted, and if so how quickly. Ongoing assessments and management actions are needed to respond to fluctuations in stock size.

Status classes

The 2009 fishing year was the first year for assessing status of stocks relative to soft and hard limits and overfishing. The New Zealand Harvest Strategy Standard 2008 defines two biomass limits: a soft limit as a trigger for a formal, time-constrained rebuilding planning and a hard limit, below which managers should consider closing a fishery. Additionally, overfishing is said to be occurring when the rate at which fish are extracted exceeds the rate associated with maximum sustainable yield.

The number of stocks assessed against the soft and hard limits differs from the number assessed relative to management targets. All stocks determined to be at or above the target are, by definition, also above both the soft and hard limits. However, stocks that are below targets or of unknown status relative to targets may or may not be able to be assessed against the soft and hard limits. In general, it is easier to assess the status of stocks relative to the hard limit than relative to management targets.

Stock status indicators describe the present status of the stock relative to its target level (usually the biomass needed to produce maximum sustainable yield or an appropriate surrogate), and to soft and hard biomass limits. Management targets represent a balance between what we can take from the current population, and what we leave in the water to grow and breed for the future. Catch limits are set to ensure fish stocks fluctuate around target levels while avoiding falling below limits.

The status of New Zealand fish stocks are classified as:

  • at or above target levels: at or above the biomass needed to produce maximum sustainable yield (or, in some cases, at or below the fishing mortality needed to produce maximum sustainable yield)
  • below target levels: below the biomass or above the fishing mortality needed to produce maximum sustainable yield
  • depleted: below the soft limit, which is 20 per cent of the pre-fishing biomass or half of the biomass needed to produce maximum sustainable yield, whichever is higher
  • collapsed: below the hard limit, which is 10 per cent of the pre-fishing biomass, or quarter of the biomass needed to produce maximum sustainable yield, whichever is higher
  • overfishing: overfishing is said to be occurring when the rate at which fish are extracted exceeds the rate that produces maximum sustainable yield.

Example of a fish stock assessed against management target and hard and soft limits

Figure 1 Landed commercial catch by species groups, 1990–2009

Text description: This graph shows where the management target level (usually the biomass needed to produce maximum sustainable yield) sits in relation to the soft and hard limits. The soft limit is 20 per cent of the pre-fishing biomass or half of the biomass needed to produce maximum sustainable yield. The hard limit is 10 per cent of the pre-fishing biomass, or quarter of the biomass needed to produce maximum sustainable yield.

This information has come from the latest fish stocks report card.

Last updated: November 2010