| 1. |
- Ahlbeck Bergendahl, Ida, et al.
(författare)
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Fisk- och skaldjursbestånd i hav och sötvatten 2016 : Resursöversikt
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I rapporten kan du ta del av bedömningen som görs av situationen för bestånd som regleras inom ramen för EU:s gemensamma fiskeripolitik (GFP). Bedömningarna baseras på det forskningssamarbete och den rådgivning som sker inom det Internationella Havsforskningsrådet (ICES).De bestånd som förvaltas nationellt baseras på de biologiska underlagen, och rådgivningen i huvudsak på den forskning och övervakning samt analys som bedrivs av Institutionen för akvatiska resurser vid Sveriges lantbruksuniversitet (SLU Aqua) samt yrkesfiskets rapportering.Rapporten omfattar 41 fiskarter uppdelade i olika bestånd, samt sju skal- och blötdjursarter.Nytt för årets upplaga är kapitlet om ekosystemtjänster. Avsnittet beskriver de fördelar människan får genom ekosystemen, till exempel hur fisk och skaldjur kommer till nytta för människan genom föda, rekreation och biologisk mångfald. Nytt för i år är också att rapportens diagram och figurer anpassats för läsare med defekt färgseende.Översikten är utarbetad av SLU Aqua på uppdrag av Havs- och vattenmyndigheten.
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| 2. |
- Andersson, Jan, et al.
(författare)
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Assessing the dynamics of the European eel stock along the Swedish west coast
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The stock of the European eel (Anguilla anguilla) has been at a critical state for the last decades, prompting strict conservation measures. This study investigates local stock dynamics along the Swedish west coast where fishing was banned in 2012. The local stock is truly marine, which is quite unique for the species. Results of ongoing monitoring programmes are presented, and options for the assessment of the status of the stock are discussed. Results show contradictory trends over time: recruitment followed the general downward trend found throughout Europe. Catch-per-unit-effort (CPUE) for eels < 37 cm appears to decrease over time, while CPUE for size-classes > 49 cm tends to increase, especially since after the fishing ban. In the absence of information on essential processes – in particular the migration into and out of the area – it is currently impossible to assess the status of the local stock (abundance, impacts), but continued monitoring will provide indicators for the further recovery of the stock after the fishing ban.
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| 3. |
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| 4. |
- Dekker, Willem
(författare)
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Assessment of the eel stock in Sweden, spring 2015 : second post-evaluation of the Swedish Eel Management Plan
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The population of the European eel Anguilla anguilla (L.) is in severe decline. In 2007, the European Union decided on a Regulation establishing measures for the recovery of the stock, which obliged Member States to implement a national Eel Management Plan by 2009. Sweden submitted its plan in 2008. According to the Regulation, Member States will report to the Commission every third year, on the implementation of their Eel Management Plans and the progress achieved in protection and restoration. The current report provides an assessment of the eel stock in Sweden as of spring 2015, intending to feed into the national reporting to the EU; this updates and extends the report by Dekker (2012). In this report, the impacts on the stock are assessed - of fishing, restocking and of the mortality related to hydropower generation. Other anthropogenic impacts (climate change, pollution, spread of parasites, disruption of migration by transport, and so forth) probably have an impact on the stock too, but these factors are hardly quantifiable and no management targets have been set. For that reason, and because these factors were not included in the EU Eel Regulation, these other factors are not included in this technical evaluation. Our focus is on the quantification of biomass of silver eel escaping (actual, potential and pristine) and mortality endured by those eels during their lifetime. The assessment is broken down on a regional basis, with different impacts dominating in different areas. In recent years, a break in the downward trend of the number of glass eel has been observed throughout Europe. Whether that relates to recent protective actions, or is due to other factors, is yet unclear. This report contributes to the required international assessment, but does not discuss that recent recruitment trend and the overall status of the stock. On the west coast, a fykenet fishery on yellow eel was overexploiting the stock, until this fishery was completely closed in spring 2012. Though research surveys using fykenets continued, insufficient information is currently available to assess the recovery of the stock. Obviously, current fishing mortality is zero, but no other stock indicators can be presented. It is recommended to develop a comprehensive plan for monitoring the recovery of the stock. In order to support the recovery of the stock, or to compensate for mortality elsewhere, young eel has been restocked on the west coast. No follow-up monitoring has been established. Noting the small expected effect – in comparison to the potential natural stock on the west coast, when recovered – it is recommended to reconsider this programme, or to set up adequate follow-up monitoring. For inland waters, this report presents a major update of the 2012 assessment. In the 2012 assessment, eel production estimates were based on information from past restocking, but natural recruitment and assisted migration were ignored; these have now been included. Additionally, the impact of hydropower is now assessed in a spatially explicit reconstruction. Based on 75 years of data on natural recruitment into 24 rivers, a statistical model is developed relating the number of immigrating young eel caught in traps to the location and size of each river, the distance from the trap to the river mouth, the mean age/size of the immigrating eel, and the year in which those eels recruited to continental waters as a glass eel (year class). Further into the Baltic, recruits are larger (exception: the 100 gr recruits in Mörrumsån, 56.4°N, where only 30 gr would be expected) and less numerous; distance upstream comes with less numerous recruits, but size is not related. Remarkably, the time trend differs for the various ages/sizes. Oldest recruits (age up to 7) declined already in the 1950s and 1960s, but remained stable since; youngest recruits (age 0) showed a steep decline in the 1980s and a little decrease before and after. In-between ages show in-between trends. Though this peculiar age-related pattern has been observed at other places in Europe too, the cause of this is still unclear. Using the results from the recruitment model, in combination with historical data on assisted migration (young eels transported upstream, across barriers) and restocking (imported young eels), the production of fully grown, silver eel is estimated for every lake and year separately. Subtracting the catch made by the fishery and down-sizing for the mortality incurred when passing hydropower stations, an estimate of the biomass of silver eel escaping from each river towards the sea is derived. Since 1960, the production of silver eel in inland waters has declined from 500 to 300t/a, and natural recruitment (assisted or not) has gradually been replaced by restocking for 90%. Fisheries have taken just over 30% of the silver eel, while the impact of hydropower has ranged from 20% to 60%. Escapement is estimated to have varied from 10% (35t) in the late 1990s, to 30% (100t) in the 2010s. The biomass of current escapement (including eels of restocked origin) is approx. 1015% of the pristine level, that is 28% of the current potential. This biomass is below the 40% limit of the Eel Regulation, and anthropogenic mortality exceeds both the short-term limit establishing recovery (15%) and the ultimate limit (60% mortality, the complement of 40% survival). The temporal variation (in production, impacts and escapement) is largely the consequence of a differential spatial distribution of the restocked eel over the years. Natural (not assisted) recruits were far less impacted by hydropower, since they could not climb the hydropower dams when immigrating. Later, restocking has been practised in unobstructed lakes (primarily Lake Mälaren, 1990s), and is now concentrated in obstructed lakes (primarily Lake Vänern, to a lesser extent Lake Ringsjön, and many smaller ones). Trap & Transport of silver eel - from above barriers towards the sea - has added 1-6% of silver eel to the escapement. Without restocking, the biomass affected by fishery and/or hydropower would be only 10% of the currently impacted biomass, but the stock abundance would reduce from 10% to less than 2only 3% of the pristine biomass. It is recommended to reconsider the current action plans on inland waters, to take into account the results of the current, more comprehensive assessment. It is further recommended to ground-truth the current assessment on independent stock surveys. For the Baltic coast, the 2012 assessment has been updated, using information from re-continued mark-recapture experiments. Results indicate that the impact of the fishery is rapidly declining over the decades – even declining more rapidly towards the 2010s than before. The current impact of the Swedish silver eel fishery is estimated at 2%. However, this fishery is just one of the anthropogenic impacts (in other areas/countries) affecting the Baltic eel stock. Integration with the assessments in other countries has not been achieved. Current estimates of the abundance of silver eel (biomass) are in the order of a few thousand tonnes, but these estimates are highly uncertain due to the low values for catch and mortality (near-zero estimation problems). An integrated assessment for the whole Baltic will be required to ground-truth these estimates. It is recommended to develop an integrated assessment for the Baltic eel stock, and to coordinate protective measures with other range states. Considering the international context, the stock indicators – in as far as they could be assessed – fit the international assessment framework, but inconsistencies and interpretation differences at the international level complicate their usage. International coordination and standardisation of the tri-annual reporting is therefore recommended. Additionally, it is recommended to initiate international standardisation/inter-calibration of monitoring and assessment methodologies among countries, achieving a consistent and more cost-effective assessment across Europe.
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| 5. |
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| 6. |
- Dekker, Willem
(författare)
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Climbing back up what slippery slope? Dynamics of the European eel stock and its management in historical perspective
- 2016
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 73, s. 5-13
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Tidskriftsartikel (refereegranskat)abstract
- Fewfish stocks are as influenced by (intentional and inadvertent) human impacts as the European eel, all across the continent. The dynamics of this stock, however, are poorly understood—neither the causes of the historically lowabundance, nor minimal protection levels, are beyond discussion. Rather than analysing contemporary processes, this article turns back in time—two centuries or more—unravelling historical abundances and distribution patterns; reviewing historical actions and objectives; and discussing technical developments and scientific advice—picturing the slippery slope the eel stock has come down from. The first claim, that the continental stock was in decline, dates from the early 1800s; stock-enhancement actions were initiated shortly after. Diffuse objectives, technical innovations, eternal optimism, and—above all—no quantification impede the exact evaluation of historical reports. After 1950, when quantification improved, a slow but consistent decline was observed, but it is only two decades after the crash in glass eel recruitment (in 1980), that protection plans addressed the bad status of the stock. A slippery slope, full of pitfalls—yet, we now observe several years of increasing recruitment.
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| 7. |
- Dekker, Willem
(författare)
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Faire mieux que la nature? The History of Eel Restocking in Europe
- 2016
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Ingår i: Environment and History. - 0967-3407. ; 22, s. 255-300
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Tidskriftsartikel (refereegranskat)abstract
- Young eel, recruiting from the ocean towards Europe, are most abundant along the Atlantic coast of France. Since 1840, attempts have been made to redistribute them from the areas of highest abundance to other countries and farther inland. This 'restocking' has been troubled by technical constraints (e.g. mode of transport and maximum distance eel can be shipped alive), wars (e.g. the Franco Prussian War and World Wars One and Two) and, in recent decades, by shortage of supply due to the general decline of the eel stock all across Europe. Though objectives and procedures have changed considerably over the years, the recurring aim has been to increase production and, in that way, to 'faire mieux que la nature'. We document the historical development of these efforts from their inception, and contrast the achievements to the objectives. Except for the 1952-1990 period in Eastern Europe, restocking has probably added only slightly to the natural production. As successful as restocking might have been locally, it has not markedly changed the overall trends and distribution patterns or halted the general decline of the stock and fishery. Poor post-evaluation, frequent technical innovation and a constant renewal of the countries and people involved have kept the promise of a better future alive for 175 years.
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| 8. |
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| 9. |
- Dekker, Willem
(författare)
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Management of the eel is slipping through our hands! Distribute control and orchestrate national protection
- 2016
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Ingår i: ICES Journal of Marine Science. - : Oxford University Press (OUP). - 1054-3139 .- 1095-9289. ; 73, s. 2442-2452
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Tidskriftsartikel (refereegranskat)abstract
- Following a multi-decadal decline of the European eel stock all across the continent, the EU adopted a protection and recovery plan in 2007, known as the Eel Regulation. Implementation, however, has come to a standstill: in 2015, the agreed goals had not been realised, the required protection had not been achieved, and from 2012 to 2015, no further reduction in mortality has been accomplished-while the stock is at a historical minimum. To analyse this manifest impasse, this article characterises the steering framework of the Eel Regulation as a governance problem. The Eel Problem is found to be extremely complex, due to many knowledge uncertainties and countless societal forces having an influence. The Eel Regulation divides this complexity along geographical lines, obliging national governments to implement national protection plans. This deliberate distribution of control has improved communication between countrymen-stakeholders, and has stimulated protective action in most EU Member States and elsewhere. In the absence of adequate international coordination and feedback on national plans, however, coherence is lacking and the common goals are not met. Actions and achievements have been assessed at the national level, but these assessments have not been evaluated internationally. Full geographical coverage has not been attained, nor is that plausible in future. Meanwhile, ICES' advice remained focused on whole-stock management, a conservative approach not matching the structure of the Eel Problem or the approach of the Eel Regulation. Hence, essentially localised problems (non-reporting, insufficient action) now lead to a hard fail, paralysing the whole European eel recovery plan. Here, I argue that immediate re-focusing protective actions, assessments, evaluations and advice on mortality goals and indicators, for each management area individually, will enable feedback on national protection plans, and in that way, will break the impasse.
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| 10. |
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