There is evidence that competition for krill between fishing vessels and krill predators already exists in some areas. This evidence is especially based on consumption rates in local areas and at particularly critical times of the year for predators (SC-CCAMLR WG-EMM 2003).

In addition, recent research has shown that demand for krill has begun to exceed supply in some areas of the southwest Atlantic. As a result, it is thought that penguins and albatrosses might be having difficulties in rearing offspring successfully. Twenty years of long-term monitoring of seabirds and seals on South Georgia has revealed an increase in the frequency of years when there is insufficient krill to feed seal pups and seabird chicks. This discovery is now putting into question the apparent super-abundance of krill over all of the Southern Ocean and reinforces the need to manage the krill fishery in a way that takes into account the needs of predators in different Antarctic areas (British Antarctic Survey 2002).

The impact of high krill catches taken in a small area, close to land-based predator colonies, also needs to be considered in relation to breeding times. Concentrated fishing may have its maximum impact on predator breeding success, when fishing takes place on the immediate foraging area and at the critical breeding time. For example, in the Antarctic Peninsula, the summer fishery takes place at the same time and in the same areas where penguins and seals are foraging to rear their young.

CCAMLR has attempted to consider the needs of krill predators at the time of establishing decision rules for setting up catch limits for the krill fishery.  These rules allow fishing quotas to be set at lower levels in order to secure more quantities of krill be left for predators than if single-stock management principles were applied. In spite of this innovative approach, current management of Antarctic krill is still occurring on the basis of large sections of the Southern Ocean.  These sections have been identified as “harvesting units”, and have been described as large-scale areas circumscribing the managed population of the harvested species –for example, Antarctic krill is commonly assessed at the scale of the South Atlantic.   Harvesting units are likely to comprise a number of fishing grounds and are usually adequate for the management of target stocks when a single species management is considered.  This type of management does not take into account complex predator-prey-fishery interactions, which occur at much smaller scales (Constable & Nicol 2002).

At the level of harvesting units, CCAMLR has been applying the Statistical Subareas defined by FAO, in the same way as it is done with other Antarctic fisheries.  In 2000, CCAMLR adopted a subdivision of the krill catch limit in Area 48, pending a further review of catch quotas in localized areas. In the case of krill, there is a particularly imperative need to identify a different type of management unit, since a harvesting unit will inevitably include a number of foraging areas of krill predators.  In order to ensure the application of an ecosystem-based management, it is important to identify predator-prey-fishery systems, relatively independent from each other. These have been referred to as “predator units” (Constable & Nicol 2002).

It has been acknowledged that the current management that sets limits for harvesting units involves a great potential for localised impacts on krill-dependent predators  (Constable & Nicol 2002). This impact is more likely to occur if large portions of the actual quota are taken within a small portion of a Subarea. It is important to highlight that an important portion of the historical krill harvest has been taken from a small number of areas, which coincidently also concentrate a high percentage of the estimated predator demand for krill in the Southern Ocean (Hewitt et al. 2004).

CCAMLR has responded to the risk of competition between krill fisheries and predators by sub-diving the Subareas in the South Atlantic into 15 SSMUs (“Small-scale Management Units”) that respond to the concept of predator units.  The delimitation of these SSMUs was the result of a process in which land-based predator foraging areas, krill distribution, and the behaviour of the fishery were considered (Hewitt et al. 2004).  The next challenge for CCAMLR is to subdivide the current catch limits applicable to Area 48 among the SSMUs, in order to avoid excessive localised effort that could affect krill availability in predator foraging areas.  Another measure taken by CCAMLR to avoid this type of localised impact is the requirement that the total catch in the South Atlantic should not exceed 620,000 tonnes until this subdivision has been completed.

References:

• British Antarctic Survey. Annual Report 2000-2001. Natural Environment Research Council, UK.
• Constable, A.J. and Nicol, S. 2002. Defining smaller-scale management units to further develop the ecosystem approach in managing large-scale pelagic krill fisheries in Antarctica. CCAMLR Science, Vol. 9: 117-131.
• Hewitt, R.P., Watters, G., Trathan, P.N., Croxall, J.P., Goebel, M.E., Ramm, D., Reid, K., Trivelpiece, W.Z., Watkins, J.L. 2004.  Options for allocating the precautionary catch limit of krill among small-scale management units in the Scotia Sea.   CCAMLR Science, vol. 11: 81-97.
• SC- CCAMLR WG-EMM. 2003. Report of the Meeting of the Working Group on Ecosystem Monitoring and Management, Cambridge, UK, 18-29 August 2003.