Commercial fishing vessel as research vessels in the Antarctic – requirements and solutions exemplified with a new vessel

The climate-induced changes presently seen in the ecosystems of the Antarctic region require a precautionary approach with respect to the human use of these ecosystems. In particular, resource harvesting requires enough basic knowledge, as well as adequate monitoring, to avoid unintended impacts on the harvested stocks and the associated ecosystem. Due to the vastness and remoteness of the Antarctic region, research vessel capacity is not readily available for conventional coverage of harvested stocks and their ecosystems. This paper describes the potential of using commercial fishing vessels to bridge the gap in research vessel capacity. The various tasks and required instrumentation are presented and discussed. To illustrate this concept a description of a Norwegian krill fishing vessel now under construction is presented. This type of combined fishing and research vessel could make a large amount of important data available for both management, through CCAMLR, and the broader scientific community and thus improve the basis for resource evaluation and management

Is current management of the Antarctic krill fishery in the Atlantic sector of the Southern Ocean precautionary?

This paper explains the management of the Antarctic krill (Euphausia superba) fishery in the Atlantic sector of the Southern Ocean, and current knowledge about the state of the regional krill stock. In this region, krill fishing is permitted in an area of approximately 3.5 million km2 which is divided into four subareas (labelled Subareas 48.1 to 48.4) for management and reporting purposes. The effective regional catch limit (or ‘trigger level’), established in 1991, is 0.62 million tonnes year–1, equivalent to ~1% of the regional biomass estimated in 2000. Each subarea has also had its own catch limit, between 0.093 and 0.279 million tonnes year–1, since 2009. There is some evidence for a decline in the abundance of krill in the 1980s, but no evidence of a further decline in recent decades. Local-scale monitoring programs have been established in three of the subareas to monitor krill biomass in survey grids covering between 10 000 and 125 000 km2. Cautious extrapolation from these local monitoring programs provides conservative estimates of the regional biomass in recent years. This suggests that fishing at the trigger level would be equivalent to a long-term exploitation rate (annual catch divided by biomass) of <7%, which is below the 9.3% level considered appropriate to maintain the krill stock and support krill predators. Subarea catch limits exceed 9.3% of conservatively estimated subarea biomass in up to 20% of years due to high variability in krill biomass indices. The actual exploitation rate in each subarea has remained <3% because annual catches have been <50% of the trigger level since 1991. Comparison with the 9.3% reference exploitation rate suggests that current management is precautionary at the regional scale. The subarea catch limits help prevent excessive concentration of catch at the subarea scale. Finer-scale management might be necessary to manage the risk of adverse impacts which might occur as a result of concentrated fishing in sensitive areas or climate change. Frequent assessment of the krill stock will enhance CCAMLR’s ability to manage these risks. Continuing the local monitoring programs will provide valuable information on krill variability, but more information is required on how the monitored biomass relates to biomass at the subarea and regional scales

Are stock assessment methods too complicated? A critical review central on North Sea demersal stocks.

This critical review argues that several methods for the estimation and prediction of numbers-at-age, fishing mortality coefficients F, and recruitment for a stock of fish are too hard to explain to customers (the fishing industry, managers, etc.) and do not pay enough attention to weaknesses in the supporting data, assumptions and theory. The review is linked to North Sea demersal stocks. First, weaknesses in the various types of data used in North Sea assessments are summarized, i.e. total landings, discards, commercial and research vessel abundance indices, age-length keys and natural mortality (M). A list of features that an ideal assessment should have is put forward as a basis for comparing different methods. The importance of independence and weighting when combining different types of data in an assessment is stressed. Assessment methods considered are Virtual Population Analysis, ad hoc tuning, extended survivors analysis (XSA), year-class curves, catch-at-age modelling, and state-space models fitted by Kalman filter or Bayesian methods. Year-class curves (not to be confused with ‘catch-curves’) are the favoured method because of their applicability to data sets separately, their visual appeal, simple statistical basis, minimal assumptions, the availability of confidence limits, and the ease with which estimates can be combined from different data sets after separate analyses. They do not estimate absolute stock numbers or F but neither do other methods unless M is accurately known, as is seldom true