Report of the Study Group on Biological Characteristics As Predictors of Salmon Abundance (SGBICEPS)
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ICES SGBICEPS REPORT 2010 SCICOM STEERING GROUP ON ECOSYSTEMS FUNCTION ICES CM 2010/SSGEF:03 REF. WGNAS, WGRECORDS, SSGEF SCICOM, ACOM Report of the Study Group on Biological Characteristics as Predictors of Salmon Abundance (SGBICEPS) 24–26 November 2009 ICES Headquarters, Copenhagen, Denmark International Council for the Exploration of the Sea Conseil International pour l’Exploration de la Mer H. C. Andersens Boulevard 44–46 DK‐1553 Copenhagen V Denmark Telephone (+45) 33 38 67 00 Telefax (+45) 33 93 42 15 www.ices.dk [email protected] Recommended format for purposes of citation: ICES. 2010. Report of the Study Group on Biological Characteristics as Predictors of Salmon Abundance (SGBICEPS), 24–26 November 2009, ICES Headquarters, Copen‐ hagen, Denmark. ICES CM 2010/SSGEF:03. 158 pp. For permission to reproduce material from this publication, please apply to the Gen‐ eral Secretary. The document is a report of an Expert Group under the auspices of the International Council for the Exploration of the Sea and does not necessarily represent the views of the Council. © 2010 International Council for the Exploration of the Sea ICES SGBICEPS REPORT 2010 | i Contents Executive summary ................................................................................................................ 3 1 Introduction .................................................................................................................... 4 1.1 Main tasks .............................................................................................................. 4 1.2 Participants ............................................................................................................ 4 1.3 Background ........................................................................................................... 5 2 Summary of literature ................................................................................................... 6 2.1 Salmon life history strategies .............................................................................. 6 2.2 Salmon in the Sea .................................................................................................. 8 2.3 Climatic/oceanic factors ..................................................................................... 18 2.4 Salmon in Freshwater ......................................................................................... 22 3 Data sets ......................................................................................................................... 32 3.1 Data sources and requirements ........................................................................ 32 3.2 Data on biological characteristics – update on developments ...................... 33 3.3 Data quality issues – caveats and limitations ................................................. 35 3.4 Environmental data sets .................................................................................... 39 4 Case Studies .................................................................................................................. 40 4.1 Long‐term changes in biological characteristics of smolts on the River Bush, N. Ireland and associations with environmental parameters ........................................................................................................... 40 4.2 Update on biological characteristics of salmon from the River Dee, North Wales and other monitored rivers in UK (England & Wales) and associations with environmental parameters .......................................... 44 4.3 Biological characteristics of salmon from the River Frome – UK (England & Wales) .............................................................................................. 50 4.4 Biological characteristics of salmon from the River Test – UK (England & Wales) .............................................................................................. 50 4.5 Evidence for later age at maturity in Norwegian salmon stocks in recent years .......................................................................................................... 51 4.6 Baltic Sea – changes in post‐smolt survival and the factors affecting it ............................................................................................................................ 52 4.7 Baltic Sea – review of Swedish tagging experiments and implications for estimating post‐smolt survival ............................................. 62 4.8 Fecundity of Penobscot River broodstock ....................................................... 62 4.9 Smolt summary data for two monitored river sites in UK(Scotland) .......... 62 4.10 Burrishoole wild salmon census programme ................................................. 65 5 Exploratory analyses ................................................................................................... 69 5.1 Analyses of long‐term variation in condition factor in relation to ocean climate ....................................................................................................... 70 ii | ICES SGBICEPS REPORT 2010 5.2 Biological characteristics data sets – temporal trends ................................... 71 5.3 Biological characteristics data sets – spatial patterns..................................... 73 5.4 Overview of preliminary analyses of temporal and spatial trends ............. 81 5.5 Exploration of two‐way relationships ............................................................. 88 5.6 Long‐term variation and changes in age at smoltification in four major Scottish salmon rivers ........................................................................... 100 5.7 Among‐river comparisons of mean river age and proportional river age composition in four major Scottish salmon rivers: 2SW “summer” salmon (returning May‐August/September) ............................. 107 5.8 Among‐river comparisons of mean river age and proportional river age composition in four major Scottish salmon rivers: 1SW grilse (returning April–August/September) .................................................. 113 5.9 Analysis of the time‐series of the emigrant smolt run, River North Esk (1964–2008) ................................................................................................. 119 5.10 Correlations between the length of returning 1SW salmon and the PFA of maturing (1SW) salmon ...................................................................... 123 5.11 Is there evidence of a change in overall (egg‐adult) mortality over time? ................................................................................................................... 126 6 Overview and recommendations ............................................................................ 137 Annex 1: List of participants ............................................................................................. 139 Annex 2: List of working documents/presentations and data sets ............................ 141 Annex 3: References ........................................................................................................... 143 ICES SGBICEPS REPORT 2010 | 3 Executive summary A second meeting of the Study Group on the identification of biological characteristics for use as predictors of salmon abundance [SGBICEPS] was agreed by ICES at the 2009 Annual Science Conference (C. Res. 2009/2/SSGEF03) and met at ICES HQ, Co‐ penhagen from 24 to 26 November, 2009. The meeting was chaired by Ian Russell, UK and attended by 11 people from five European countries. Data were made available for stocks throughout the geographic range of Atlantic salmon ‐ Canada, USA, Iceland, Russia, Finland, Norway, Sweden, UK (Scotland), UK (England & Wales), UK (N. Ireland) and France. The main objectives of the meeting were to identify and compile time series of data on biological characteristics of Atlantic salmon and conduct preliminary analyses on these data as a basis for developing, and where possible testing, hypotheses relating any observed changes in these characteristics to trends in freshwater/marine mortal‐ ity and/or abundance of Atlantic salmon stocks and/or environmental changes. The Study Group report, in addressing the ToR, provides: (1) an updated summary of the available literature; (2) a description of the available data sets and how these were compiled; (3) a number of case studies; (4) details of exploratory analyses of the full data set; and (5) an overview and recommendations. In brief: Literature ‐ the review summarises the life history strategies of salmon and changes in biological characteristics of different life stages across the geo‐ graphic range of the species in relation to key environmental variables. A number of existing, and sometimes conflicting, hypotheses relating to factors regulating the mortality of salmon are considered. Data sets – additional data sets providing time series of various biological characteristics were made available to the Study Group. Information was also compiled in relation to the various sampling programmes from which data were derived, and methodological differences noted. Case studies ‐ information from a number of new river or area‐specific inves‐ tigations were presented and reviewed and other case studies updated. A number of hypotheses were investigated. Exploratory analyses ‐ the extended data sets of stock‐specific biological characteristics were re‐examined for possible temporal trends and to explore changes in biological characteristics over broader spatial scales.