Report of the Working Group on the Ecosystem Effects of Fishing Activities (WGECO). 8–15 April 2014. Copenhagen, Denmark
| Type | Report | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Date | 2014 | ||||||||
| Language | English | ||||||||
| Ref. | ICES CM 2014/ACOM:26 | ||||||||
| Other localization | http://www.ices.dk/community/groups/Pages/WGECO.aspx | ||||||||
| Author(s) | ICES | ||||||||
| Contributor(s) | Rochet Marie-Joelle | ||||||||
| Publisher | ICES | ||||||||
| Note | ICES WGECO REPORT 2014 ICES ADVISORY COMMITTEE | ||||||||
| Abstract | The 2014 meeting of WGECO was held at the ICES HQ in Copenhagen, Denmark from the 8–15 April 2014. The meeting was attended by 20 delegates from 15 coun-tries, and was chaired by Anna Rindorf (Denmark). The work conducted was centred on six Terms of Reference concerning foodweb indicator development, the develop-ment of Large Fish Indicators (LFIs), possible consequences of “balanced fishing” re-gimes, effects of fishing on the seabed, ecosystem effects of a landing obligation, ecosystem consequences of rebuilding predatory stocks and two incoming requests from other working groups. WGECO reviewed the progress on foodweb indicators, including the preliminary results of WKFooWI. The group found that indicators tended to fall into two classes, surveillance indicators and indicators for direct management action. Surveillance in-dicators play an important role in assessment and management of foodwebs, where relations between pressures, drivers, state, and function can be complex and indirect. Further, in line with the results of WKFooWI, WGECO continued work on indicators of functional groups (guilds) and continued the development and testing of foodweb indicators by introducing a new size-based indicator called “Typical Length”. The formulation and interpretation of the LFI was discussed, highlighting a need for con-ceptual clarification of the role of this indicator as a foodweb indicator. The discus-sion of foodweb indicators was closed with a note on the need for indicators addressing the role of benthos in the food chain. The progress in the development of regional and subregional LFIs was reviewed by the group. General guidelines were made for the frequently encountered problem that only selected fish species are weighed during surveys, creating a need to esti-mate weight at length by other means. A total of ten LFIs were reviewed covering the regions North Sea, Celtic Sea, Southern Bay of Biscay, Central-Southern Tyrrhenian Sea, Baltic Sea, Poland EEZ, Kattegat North, Kattegat South, The Sound and Gulf of Cádiz. Of these ten LFIs, four had specific thresholds and reference levels assigned and hence can be considered fully developed. An analysis of subregional LFIs in the North Sea showed that the temporal development in larger scale regional indicators is not necessarily related to the development of subregional indicators, and hence regional indicator results cannot be derived from subregional results and vice versa. To ensure that the LFI is above reference levels in all subregions, the analysis must be conducted by subregion, leading to a trade-off between the number of subregions and data support within each subregion. WGECO considered “balanced harvesting” as the adjustment of exploitation pat-terns to balance the pressures of all fisheries in an area with the relative productivi-ties of the species and sizes of fish. Size-based and other models used to predict the consequences of contrasted fishing regimes have produced nuanced results: Less se-lective (including balanced) fishing regimes tend to produce higher yields with lower ecosystem impacts in most studies, but the magnitude of the predicted differences varies. The few empirical studies available provide weak evidence that fishing pat-terns affect community dynamics and biodiversity; the size of the effects is presuma-bly insufficient for a strong signal to be detected among the noise of the many other factors. Balanced fishing may be difficult to implement, both due to less predictable ecosystem dynamics, and due to the complexity of translating the concept into practi-cal management measures. Though it may be precautionary to avoid too selective The 2014 meeting of WGECO was held at the ICES HQ in Copenhagen, Denmark from the 8–15 April 2014. The meeting was attended by 20 delegates from 15 coun-tries, and was chaired by Anna Rindorf (Denmark). The work conducted was centred on six Terms of Reference concerning foodweb indicator development, the develop-ment of Large Fish Indicators (LFIs), possible consequences of “balanced fishing” re-gimes, effects of fishing on the seabed, ecosystem effects of a landing obligation, ecosystem consequences of rebuilding predatory stocks and two incoming requests from other working groups. WGECO reviewed the progress on foodweb indicators, including the preliminary results of WKFooWI. The group found that indicators tended to fall into two classes, surveillance indicators and indicators for direct management action. Surveillance in-dicators play an important role in assessment and management of foodwebs, where relations between pressures, drivers, state, and function can be complex and indirect. Further, in line with the results of WKFooWI, WGECO continued work on indicators of functional groups (guilds) and continued the development and testing of foodweb indicators by introducing a new size-based indicator called “Typical Length”. The formulation and interpretation of the LFI was discussed, highlighting a need for con-ceptual clarification of the role of this indicator as a foodweb indicator. The discus-sion of foodweb indicators was closed with a note on the need for indicators addressing the role of benthos in the food chain. The progress in the development of regional and subregional LFIs was reviewed by the group. General guidelines were made for the frequently encountered problem that only selected fish species are weighed during surveys, creating a need to esti-mate weight at length by other means. A total of ten LFIs were reviewed covering the regions North Sea, Celtic Sea, Southern Bay of Biscay, Central-Southern Tyrrhenian Sea, Baltic Sea, Poland EEZ, Kattegat North, Kattegat South, The Sound and Gulf of Cádiz. Of these ten LFIs, four had specific thresholds and reference levels assigned and hence can be considered fully developed. An analysis of subregional LFIs in the North Sea showed that the temporal development in larger scale regional indicators is not necessarily related to the development of subregional indicators, and hence regional indicator results cannot be derived from subregional results and vice versa. To ensure that the LFI is above reference levels in all subregions, the analysis must be conducted by subregion, leading to a trade-off between the number of subregions and data support within each subregion. WGECO considered “balanced harvesting” as the adjustment of exploitation pat-terns to balance the pressures of all fisheries in an area with the relative productivi-ties of the species and sizes of fish. Size-based and other models used to predict the consequences of contrasted fishing regimes have produced nuanced results: Less se-lective (including balanced) fishing regimes tend to produce higher yields with lower ecosystem impacts in most studies, but the magnitude of the predicted differences varies. The few empirical studies available provide weak evidence that fishing pat-terns affect community dynamics and biodiversity; the size of the effects is presuma-bly insufficient for a strong signal to be detected among the noise of the many other factors. Balanced fishing may be difficult to implement, both due to less predictable ecosystem dynamics, and due to the complexity of translating the concept into practi-cal management measures. Though it may be precautionary to avoid too selective |
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