ICES Journal of Marine Science: Journal du Conseil

Cury, Philippe M.; Christensen, Villy

doi: 10.1016/j.icesjms.2005.02.003pmid: N/A

Garcia, Serge M.; Cochrane, Kevern L.

doi: 10.1016/j.icesjms.2004.12.003pmid: N/A

The FAO and other guidelines available for the implementation of the ecosystem approach to fisheries are briefly reviewed. The paper recalls the high-level policy foundations and the main issues, related to fisheries and non-fishing impacts as well as to natural variability. It reviews the central paradigm and the extension of the conventional management required to better account for ecosystem considerations. It focuses on the policy, strategy development, and implementation processes required to adapt the fuzzy principles and conceptual goals to the reality of specific situations, addressing briefly the central issues of capacity-building, management costs, realistic time frames, and the role of science, and concludes with comments on the respective roles of the various types of stakeholders.

Polovina, Jeffrey J.; Howell, Evan A.

doi: 10.1016/j.icesjms.2004.07.031pmid: N/A

Satellite remotely sensed oceanographic data provide reliable global ocean coverage of sea surface temperature, sea surface height, surface winds, and ocean colour, with relatively high spatial and temporal resolution. We illustrate approaches to use these data to construct indicators that describe aspects of ecosystem dynamics in the North Pacific. Specifically, altimetry data are used to construct regional indicators of the ocean vertical structure, ocean colour data to describe the temporal chlorophyll dynamics of the coastal zone, ocean colour, sea surface temperature, and altimetry data to develop indices of biologically important ocean features, and finally altimetry data to drive a larval transport model and develop an index of larval retention. Recent changes in the North Pacific based on these indices are discussed.

Rodionov, Sergei; Overland, James E.

doi: 10.1016/j.icesjms.2005.01.013pmid: N/A

A common problem of existing methods for regime shift detection is their poor performance at the ends of time-series. Consequently, shifts in environmental and biological indices are usually detected long after their actual appearance. A recently introduced method based on sequential t-test analysis of regime shifts (STARS) treats all incoming data in real time, signals the possibility of a regime shift as soon as possible, then monitors how perception of the magnitude of the shift changes over time. Results of a STARS application to the eastern Bering Sea ecosystem show how the 1989 and 1998 regime shifts manifest themselves in biotic and abiotic indices in comparison with the 1977 shift.

Beaugrand, Grégory

doi: 10.1016/j.icesjms.2005.01.002pmid: N/A

Planktonic organisms are an important food resource of pelagic ecosystems, but they also serve as an integrator of hydroclimatic forcing. Four types of recently developed plankton indicator, based on the Continuous Plankton Recorder survey, are summarized here: indicators based on individual taxa; indicators based on functional attributes of the ecosystem (diversity); species assemblage indicators; and indicators of larval fish survival. All provide information on the state of a pelagic ecosystem, but have different limitations. Therefore, their combined application provides the most accurate diagnosis of ecosystem state. In most of the examples described, statistical analyses help to identify major spatial and temporal patterns, and may allow future ecosystem changes to be anticipated.

Brander, Keith M.

doi: 10.1016/j.icesjms.2004.07.029pmid: N/A

Stocks of Atlantic cod (Gadus morhua) have been declining over much of the North Atlantic for the past 30 years, owing to a combination of overfishing and adverse changes in their environment. In a previous study, environmental effects were introduced as an extra parameter in the stock-recruit relationship, where they act as a multiplier, independent of the level of spawning-stock biomass (SSB). Using a non-parametric pooled analysis of all cod stocks on the European Shelf south of 62°N, it is shown here that environmental variability (as represented by the North Atlantic Oscillation) only has a significant effect on recruitment when the spawning stock is low. This has implications for fisheries management strategies, and for rates of stock recovery, which will be very dependent on environmental conditions.

Mueter, Franz J.; Megrey, Bernard A.

doi: 10.1016/j.icesjms.2004.11.006pmid: N/A

Ecosystem-based approaches to fisheries management require researchers and managers to take into account effects of fishing on other components of the ecosystem, including non-commercial species. Currently, stock assessments in the Northeast Pacific are limited to the most important commercial species, little being known about the status of non-commercial species. Nevertheless, standardized bottom-trawl surveys conducted in the eastern Bering Sea (EBS) and Gulf of Alaska (GoA), although primarily designed to assess commercial species, provide valuable information on the abundance, distribution, and mean weight of numerous taxa. Using a novel statistical approach and survey data for the years 1993–2003, we examined trends in catch per unit effort (cpue), frequency of occurrence, and mean weight of individuals for each taxon. Time trends were computed as the slope of a linear regression of each indicator on year, and were summarized separately for the eastern and western GoA and for the EBS. Within each system, trends were further compared between commercial and non-commercial taxa. Simulations were used to obtain reference distributions for the expected distribution of slopes across many dependent populations. Observed distributions of trends were compared with simulated distributions, suggesting that more taxa than expected showed a decreasing trend in cpue in the EBS, but not in the GoA. These trends likely resulted from low groundfish productivity in the EBS during the 1990s. At the same time, the frequency of occurrence of significantly more taxa than expected increased in the EBS and, to a lesser extent, in the western GoA. Increases in frequency of occurrence were much more common among non-commercial, invertebrate taxa, and may be a response to reductions in trawl fishing effort during the 1990s.

Erzini, Karim; Inejih, Cheikh A. O.; Stobberup, Kim A.

doi: 10.1016/j.icesjms.2004.12.009pmid: N/A

Min/max autocorrelation factor analysis (MAFA) and dynamic factor analysis (DFA) are complementary techniques for analysing short (>15–25 y), non-stationary, multivariate data sets. We illustrate the two techniques using catch rate (cpue) time-series (1982–2001) for 17 species caught during trawl surveys off Mauritania, with the NAO index, an upwelling index, sea surface temperature, and an index of fishing effort as explanatory variables. Both techniques gave coherent results, the most important common trend being a decrease in cpue during the latter half of the time-series, and the next important being an increase during the first half. A DFA model with SST and UPW as explanatory variables and two common trends gave good fits to most of the cpue time-series.

Underhill, L.G.; Crawford, R.J.M.

doi: 10.1016/j.icesjms.2005.01.005pmid: N/A

Time-series of the sizes of breeding populations of 10 species of seabird were used to develop indices of the health of the Western Cape seabird community of South Africa. For each species, a target range was defined running from some minimum value to infinity or to some maximum value for species that may cause harm to other species or be a nuisance to humans. If populations were within the target range, their individual health index was set at 1, whereas outside the range, this index decreased linearly with population size. These individual indices were integrated into one for the total community, also running from 0 to 1 and therefore allowing representation as a percentage of the overall management target (=1). Three indices were developed, weighting each species equally and using different weighting methods to account for the IUCN conservation status of the species. All indices increased between the 1950s and 1970s and then decreased again, the lowest values being observed in the late 1990s.

Reid, Keith; Croxall, John P.; Briggs, Dirk R.; Murphy, Eugene J.

doi: 10.1016/j.icesjms.2004.11.003pmid: N/A

The utility of upper-trophic-level species as ecosystem indicators is determined by our ability to relate changes in indices of their performance to changes at lower trophic levels. Such relationships were assessed using indices of predator performance (response vectors) for four predator species, together with independent ship-based acoustic estimates of abundance of their main prey, Antarctic krill (Euphausia superba), from South Georgia in the South Atlantic Ocean. Out of 32 response vectors investigated, 13 showed a significant non-linear relationship, based on a Holling Type II response, to krill abundance, and just five showed a significant linear relationship. Predator responses reflecting the processes during summer, when prey surveys were undertaken, showed the closest relationship with prey abundance. Distinct relationships existed between the variability of indices and the biological processes they measured. Body mass variables had the lowest variability (CVs <10%), whereas those measuring breeding success showed the greatest variability (CVs >50%). Multivariate indices, produced by combining response vectors from all four predator species into a single combined index, provided a better fit with krill data than any of the individual vectors. Whereas population size parameters for individual species showed no relationship with annual estimates of krill abundance, a combined, multispecies population size index did show a significant response. Understanding the form of the relationship between concurrent indicators of prey abundance and key ecosystem metrics/reference points, such as population size, is crucial to the application of monitoring data to management action.