Last updated on 7 May 2019
The last reported synoptic survey of Antarctic krill was conducted in 2000 (Hønneland et al. 2015a); since then there has been no annual or updated stock assessment of krill available. However, a new synoptic krill survey for 2019 has been planned due to the long gap (19 years) since the last synoptic survey and the environmental conditions have been changing since the early 2000s (e.g. climate change, ice-coverage) (SC-CAMLR-XXXVI 2017). Six vessels will spend nearly 2 months mapping the abundance of krill in and around the Scotia Sea (Stokstad 2019). The 2019 survey will use a different acoustic analytical approach (the swarm-based approach) compared with that used for the CCAMLR 2000 Krill Synoptic Survey of Area 48 (the dB-difference window approach) for the identification of Antarctic krill (SC-CAMLR-XXXVII 2018).
The Scientific Committee for the Conservation of Antarctic Marine Living Resources (CCAMLR) sets a precautionary catch limit based on the potential yield of the stock as determined from the synoptic survey carried out in 2000, to evaluate the stock condition. The initial limit to yield is determined on the basis of estimated potential yield, based on a Generalized Yield Model. This model uses standard population model equations but allows the population dynamics to represent particular stocks by setting appropriate parameter values for growth, natural mortality, and recruitment. The initial estimate of krill standing stock (B0) was calculated as 44.29 million tonnes, but a range of values have been estimated, highlighting the uncertainty around this value (SC-CAMLR-XXIX, 2010). Commercial catch per unit effort (CPUE) data is not considered appropriate as an index of abundance (Hønneland et al. 2015a). Large-scale surveys provide information to the understanding of variability and trends at subarea-scales and possible impacts of climate change (SC-CAMLR-XXXIV 2015). A recent study indicated that krill’s distribution has contracted southward over the past 90 years due to climate change (Atkinson et al. 2019).
In recent years, there have been some new analysis and interpretations of the previous assessment (SC-CAMLR-XXXIII 2014; Kinzey et al., 2015). A recent approach developed an integrated stock assessment model for krill that combines an age-structured cohort model with survey observations (WG-SAM-14/20). However, some more spatial restricted surveys are undertaken annually by the UK, USA and most recently by Norway providing interannual variability information on the status of the ecosystem (Watkins et al., 2015). An important acoustic survey for krill biomass was conducted around the Balleny Islands during the 2015 austral summer (SC-CAMLR-XXXIV 2015). In 2016, a new model was fitted based on time series of survey biomass indices and length-composition data from research surveys and on catches and length compositions from the krill fishery. However, this model was considered as not able to provide management advice (WG-SAM-16/37). Reanalyses of the krill biomass index in Area 48 based on KrillBase data and local acoustic surveys show no evidence of a systematic change in krill biomass since 2000 (SC-CAMLR-XXXIV 2015; Hill et al. 2016). Moreover, a recent study indicated that average krill density appears to have been stable but with considerable inter-annual variability (Cox et al. 2018). More studies on the influence of krill recruitment into the subsequent spawning biomass are needed since it is not clear its role for the inter-annual variability of the biomass (WG-EMM-18 2018; Kinzey et al. 2018).
The spatial/temporal accuracy of the catch reporting for the continuous fishing system (based on 2 hours of haul duration) needs to be improved as required by the Conservation Measure (CM) 21-03 but Norway has been working to solve this issue (SC-CAMLR-XXXVI 2017).
Acoustic data from fishing vessels is collected to provide qualitative and quantitative information on the distribution and relative abundance of Antarctic krill and other pelagic species (Watkins et al. 2016). Recently, swarm analysis has been used for krill density estimation from data collected by fishing vessels along transects, as well as during fishing operations. This approach has been considered very useful in understanding seasonal cycles in krill habitat use and might be useful for management (SC-CAMLR-XXXVI 2017). Progress on methods for the collection and analysis of krill acoustic data from fishing vessels, including the comparison of the two acoustic methods (swarm-based and dB-difference window target identification) have been undertaken (SC-CAMLR-XXXVII 2018). However, the accuracy issues of the catch reporting for the continuous systems need to be solved before this approach can be applied (WG-EMM-17 2017).
Catches represent a minimal part (0.4%) of the total krill consumption by predators. CCAMLR monitors krill predator populations, makes catch reports and supports periodic fisheries-independent surveys of local biomass. However, these variables were not tested yet to assess if they will be sufficient to detect the impacts of fishing (Hønneland et al. 2015a). The Working Group suggested that age- or length-specific natural mortality may be explored as well as include environmental correlates with biomass in the model to allow future projections of biomass.
The Working Group commended to recording krill carapace lengths during measurement of krill and to extend by-catch monitoring (e.g. invertebrates) (WG-EMM-17 2017).
A new risk assessment framework for Area 48 has been developed and annual updates should be made to provide advice on the spatial distribution of the trigger level (CCAMLR-XXXV 2016). Fishing in Subarea 48.1 has taken place primarily in the summer, but for the past few seasons fishing in this area had been occurring throughout the austral summer and winter. Also, the fishery was regularly operating in areas in the southern part of Subarea 48.1 where no regular krill surveys are conducted (WG-EMM-16 2016). Recent studies indicated that in most years krill abundance in the subarea 48.1 was higher in autumn than in the summer season (WG-EMM-18 2018).
In the fishing season 2016/2017, the krill fishing re-started in the divisions 58.4.1 and 58.4.2 and Australia developed a preliminary risk assessment for this region (SC-CAMLR-XXXVI 2017) but more recent layers of information are needed (WG-EMM-17 2017). The regional risk of the current conservation measures in Divisions 58.4.1 and 58.4.2 are higher than the baseline regional risk. Collection of additional information from updated surveys and adaptions of the risk assessment framework are some of the recommendations of the Working Group (WG-EMM-18 2018).
Last updated on 7 May 2019
The Scientific Committee advises the Commission with the best available scientific information on harvesting levels and other management issues. In turn, the Convention established the Commission to take full account of the recommendations and advice of the Scientific Committee (Hønneland et al. 2015a).
There are no biologic and fishing reference points in place. In 2010, CCCAMLR agreed that the best estimate of krill standing stock (B0) was calculated at 60.3 million tonnes. Based in the krill stock assessment model, CCAMLR (Conservation measure CM 51-01) agreed that the current precautionary catch limit (PCL) for krill is 5.61 million tonnes per season (December 1st to November 30th of the following year) in Subareas 48.1, 48.2, 48.3 and 48.4 combined (Krill Fishery Report 2016). However, until the Commission decides to allocate this total catch limit between small-scale management unit (SSMU), the total combined catch is limited to 620,000 tonnes (trigger level). This trigger level is not related to the status of the krill stock (Conservation measure 51-07, 2014). However, the catch trigger level is well below the precautionary catch limit, which acts as an effective risk-limit reference point (Hønneland et al., 2015a). The trigger level (CM 51-01) was based on the highest aggregated catch of the historical time series (SC-CAMLR-XXXIV 2015) and corresponds to less than 2% of krill biomass estimated in any year between 2000 and 2011 (SC-CAMLR-XXXIV 2015).
Krill biomass is not homogeneously distributed within the subareas (Krafft et al. 2015), and the fishery has become concentrated in some SSMUs in recent years (WG-EMM-15 2015). The Scientific Committee agreed that the spatial distribution of the trigger level should be continued to avoid further harvesting concentration and that it does not impact adversely on predators. However, there are some concerns on SSMU-scale since results from surveys demonstrated a huge variability and fishing activity has become more concentrated into some SSMUs (SC-CAMLR-XXXIV 2015).
The harvest control rule for krill in Area 48 is a precautionary catch limit that has the objective to constrain exploitation to a safe level (Hønneland et al. 2015a). However, absolute estimates of krill biomass in the whole Area 48 are unlikely to be available on a regular basis, and management approaches will need to take this into account (SC-CAMLR-XXXIV 2015).
In 2014, the Scientific Committee agreed to develop a feedback management (FBM) approach to the krill fishery (CCAMLR-XXXIII, 2014) to improve understanding of potential impacts of fisheries and predators on krill stocks. Since surveys occur in a limited period of the year, the potential to use fishing vessels to provide key information on the distribution and abundance of Antarctic krill is being considered. The Scientific Committee settled that krill consumption by baleen whales and the collection of appropriate acoustic information from fishing vessels should be included in the development of an effective FBM regime (SC-CAMLR-XXXV 2016). The Subgroup on Acoustic Survey and Analysis Methods (SG-ASAM) is in charge to develop advice on how to best collect and evaluate fishing-vessel-based acoustic data on krill and other pelagic species, contributing in this way to the development of the FBM approach (Watkins et al., 2015; CAMLR-XXXIV 2015). The Scientific Committee also agreed that the data on krill catch by month and SSMU should be included in the Statistical Bulletin (SC-CAMLR-XXXV 2016). A coordinated effort is as well suggested between members to move on with experimental work needed for the development of an FBM approach and the engagement of the fishery sector is crucial (SC-CAMLR-XXXVI 2017).
Recently, a spatial concentration of krill catches has been observed, including in summer months and in near-shore areas where krill-dependent species forage. Based on the results of the risk assessment, the Scientific Committee agreed that the risks of localized effects of fishing were increasing, supporting the continuation of the CM 51-07 for a minimum period of three years. The Working Group agreed that a revision of CM 51-07 should consider how catch limits could be spatially and temporally apportioned within subareas to avoid negative impacts on predator populations at smaller spatial scales, particularly in Subarea 48.1 (WG-EMM-16 2016). Additionally, the implementation of coastal buffer zones can also be considered (SC-CAMLR-XXXV 2016). The increase in catches and the seasonal distribution of the fishery during the last season (2017/2018) raise the need for progressing with the development of the management scenarios for this fishery. The recent changes in fishing patterns were attributed to a combination of factors that included management restrictions (i.e. fishery closures), abundance of krill and other operational considerations (SC-CAMLR-XXXVII 2018).
There are in place several programmes to collect appropriate data for the effective management of the Southern Ocean, including fisheries monitoring, scientific observers on fishing vessels and ecosystem monitoring (Hønneland et al. 2015b). Kinzey et al. (2013) concluded that better information is required about krill recruitment variability and natural mortality before increasing catches much beyond the trigger level (WG-EMM-15 2015).
Last updated on 7 May 2019
There is no recent stock assessment, thus there is some degree of uncertainty around the current status of the stock. Previous research (in 2006) on the stock status suggested krill biomass to be in good shape and in the range of 37–208 million tonnes, i.e., well above 75% B0 (original biomass before the fishery has started) (Hønneland et al. 2015a). Reanalyses of the krill biomass index in Area 48 based on KrillBase data and local acoustic surveys (2015) showed no evidence of a systematic change in krill biomass since 2000 (SC-CAMLR-XXXIV 2015).
The fishery is operating at catch levels well below what would generally be regarded as a precautionary upper level relative to the best estimates available of stock size (i.e. a precautionary catch limit or PCL). Catches have been increasing in the last 10 years but were still lower than in the period from 1986 to 1991. However, total catches for the season 2017/2018 increased 29% in relation to the previous year and it was the highest level of catch since the early 1990s. The global catch in Area 48 is currently at about 39% of the trigger level and 5.5% of the precautionary catch limit; catches are currently around 0.5% of biomass estimate from the CCAMLR-2000 Survey.
The management measures and controls in place give good confidence that current catch levels will not affect the total krill biomass adversely even if adverse ecosystem and oceanographic/climate conditions occur (Hønneland et al. 2015). However, there are indications of an increased risk of localized effects of fishing (SC-CAMLR_XXXV 2016) which some additional measures should be considered.