A statistical summary review of the NRW technical conservation case for introducing THE WALES ROD AND LINE (SALMON AND SEA TROUT) BYELAWS 2017 THE WALES NET FISHING (SALMON AND SEA TROUT) BYELAWS 2017 Presentation by Mike Ashwin, as part of WPWF objections by Chris White, John Eardley & Rueben Woodford
In the short window period (20-30 years) since formal stock assessments were introduced, fisheries scientists, teams and experts have yet to encounter or monitor the longer span climatic and ecological impacts on our migratory stocks We are only now only beginning to see the major 1SW & MSW component transitions emerging and predicted over 50 – 60 year cycles, associated with the North Atlantic oscillation of cooling and warming currents and availability of food sources Our monitoring of migratory life cycle populations is at best incomplete, with little if any conclusions or actions taken for the important marine phase of their life cycle. There are major resourcing issues to overcome and parties at all levels need to work together. Monitoring and stock assessment reporting systems must be reviewed and tuned in to adapt to these trend changes if individual river stock performance data is to be used with confidence to guide and set Regulatory measures
Significant trend changes reported in the 2017 national Cefas, NRW & EA Salmon Stocks & Fisheries and Fisheries Statistics reports “ True” exploitation by Net & Rod fisheries ( salmon caught and killed) has reduced by 90% from the early 1970`s (page 23 - ACC/28) In Wales the number of rod caught salmon released annually has improved dramatically from 7% in 1993 to 86% in 2017 (page 27 - ACC/28). CPWF maintain that Anglers are adopting conservation codes and being guided by peer pressure and advice from Regulatory & conservation bodies In the same period Angler days fished for Salmon & Sea Trout in Wales has dropped by 60% from 118,862 (1994) to 47,092 in 2017 (page 17 ACC/28) Yet over the long term combined annual and short term salmon & migratory trout rod licence sales in England & Wales have remained reasonably constant 37,728 in 1994 compared with 35,162 in 2017 (page 15 ACC/28) Marine smolt survival rates are reported have crashed by 90% - WHY ? 1970`s 1SW - 25% & MSW - 15% 2011 – 15 !SW - 2.5% & MSW - 2% (Dee, Tamar, Frome estimates 5 yr mean, page 56 – ACC/28 )
CPWF Objections and concerns are presented in four sections. In simple terms the four stages of determining a rivers stock status & implementation of measures where appropriate 1. the principles and methods adopted for setting and monitoring conservation targets - Conservation limit setting (CL) and influence of salmon stock dynamics and recent River smolt deficits 2. identifying and highlighting concerns with the capture and use of core data for reporting Annual River egg deposition estimates to Conservation limit (CL) 3. explaining weaknesses and flaws in the methodology and systems procedures where the national River Classification model is used to designate River Stock status 4. the final decision structure process and measures applied The report will conclude with presentational issues and a short analysis of alternate modelled systems - summarising CFWF & NWATFCC recommendations made to Defra and Welsh Ministers to improve and harmonize Welsh & English systems and introduce a single conservation strategy. Precautionary principles are considered also.
1. Conservation Limits, salmon stock dynamics and smolt deficits Conservation targets and Biological Reference Points (BRP`s) for managing and maintaining sustainable salmon stocks were adopted in England & Wales for monitored salmon rivers, following transportation of the River Bush statistical model in the 1990`s. Revised model principles being adopted from the 1997 EA commissioned Wyatt & Barnard Technical reports BRP`s and minimum sustainable CL targets (River egg depositions and juvenile recruitment from spawning stock) were set above which, stocks should be maintained in the long term. Management Targets (MT) being a higher management target to aim for. In terms of accurately assessing stocks we cannot physically count a River spawning egg depositions or how many actually successfully fertilize and develop to juvenile stage. What are used are estimates, either :- - based on declared Welsh rod angler catches (21 of 23 individual Rivers) and corrections with total spawning fish estimated using a variable factor expressed as the rod exploitation rate or multiplier - or for two Welsh rivers, that the “efficiency” of counters or trap is accurately monitoring a proportion of the “validated” adult run estimate
The conservation model in England & Wales was introduced in the 1990`s and a River Classification 10 year trend model incorporated to this in 2003. The 2003 trend model did not undergone Validation and its use for designating five year forward River “trends” and a Rivers stock status in the proposed regulatory measures is hotly contested and under scrutiny Today the Conservation model uses Sea Survival (Replacement Line) estimates that are out of alignment with current forecasts and rod catch and exploitation estimates that can require significant correcting or in some cases cannot correct for important seasonal factors (e.g. rod effort, river flows, closed season runs) The threats and & challenges that our salmon stocks face are set out in the NRW conservation case BUT the Technical case document does not assess or quantify “Life Cycle” stage impacts or prioritise these in terms of their total impact on stocks. Doing so would identify strategies that should be prioritised above others Rod exploitation (retained fish) would appear well down that list (estimates of 1- 2% of spawning stocks) and CPWF maintain Rod fisheries actually do and can have a positive impact on fish stocks – Anglers guarding stocks against poaching, avian predators, unlawful river polluters, unregulated abstraction and contributing to habitat improvements before even the socio/economic benefits
Salmon population dynamics and use of graphs and trends as indicators of stock health Migratory (Anadromous - river and sea) salmon & sea trout have populations that naturally fluctuate, as do most species Salmon have a propensity to fluctuate in cycles of high and lows that mirror the 4/5 year and life cycle stage of eggs to returning adult spawning maturation On many Rivers Salmon peaks and abundance often repeat in 5 or longer 10 year cycles peaks/troughs, with even longer 50 – 60 year population abundance associated with the transition of different component groups or stocks of that annual spawning run – this is the Rivers proportion or dominance of either 1SW (returning one sea winter adults) and MSW (multi sea winter adults) Higher stock proportions of longer sea phase MSW make that pattern more complex Yearly graphs – depicting 10 years or more of a rivers estimated egg deposition depicts the “health of stocks” and a trend over the time series is used to indicate salmon health or that “estimated trend” The wide scatter and random nature of some river estimates of egg deposition causes difficulties of interpretation and confidence in these trends and future stock predictions. Conversely, more regular River populations with small annual variability make trend predictions easy & accurate to forecast going forward
Refer to Flip charts Depicting time series trends & Actual River egg deposition trends as opposed to Modelled Regressed Linear trends and use of the 20 th percentile as expressed as Rivers “regressed 10 year historic & projected linear 5 year forward predictions ” What is a 20 th percentile ? It is a trend used in a Rivers formal stock assessment compliance that is widely misunderstood and difficult to grasp or explain IT IS NOT as many think - a rivers historic actual performance to CL expressed as its 4 out of 5 years or 80% trend IT IMIGHT BEST be described as the Rivers actual 10 year historic trend lowered or regressed to reflect a higher management target for the River. In effect the Precautionary Approach that is already being applied in the Assessment
Recommend
More recommend
