鰻魚列瀕危物種 相關貿易恐受限
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http://www.appledaily.com.tw/realtimenews/article/recommend/20140612/414679/)
2014年06月12日
世界自然保護聯盟(IUCN)宣佈，確定將鰻魚列入介紹瀕危物種的紅皮書。報導指出鰻魚將被指定為瀕危物種。雖不會直接導致鰻魚買賣與食用的禁止，但今後鰻魚的國際貿易等將有可能受到限制。
在日本大部分用於食用的鰻魚，有來自日本國內捕獲或進口的魚苗後進行養殖的日本鰻，另外還有直接從國外進口的烤鰻魚。今年日本國內魚苗的捕獲量雖時隔數年有所恢復，但長期來看還是處於銳減趨勢。半個世紀前，日本魚苗的年捕獲量約為200噸，但到2012年為止的3年內，該數量僅為3至6噸。天然鰻魚的捕獲量也呈現銳減趨勢。
世界自然保護聯盟是由國家和自然保護組織加盟、世界最大的國際自然保護組織。世界自然保護聯盟紅皮書按照危機程度將物種分為「滅絕」、「瀕危」以及「資料缺乏」等8個等級。為將包含日本鰻在內的19種鰻魚列入紅皮書中，專家們自去年7月開始進行了科學評估。
鰻魚被列入紅皮書與管制並無直接關聯。但在對野生動植物國際貿易加以規定的《華盛頓公約》中，往往將世界自然保護聯盟紅皮書作為進行管制的重要參考資料，並將於2016年召開的下屆國際會議上，如果與會國提議管制政策，並且投票國中有3分之2表示贊成的話，用於商業目的的國際鰻魚貿易將可能被列入禁止貿易，或被列入需出口國許可。
Justification: (http://www.iucnredlist.org/details/60344/0)Anguilla anguilla exhibits facultative catadromy, has multiple life stages, and is semelparous and panmictic; these life history traits made application of the IUCN Red List criteria more challenging. Anguillids are often referred to as ‘freshwater eels’, however, it is known that they can exhibit inter-habitat migration and that a proportion may stay in estuaries, lagoons and coastal waters, rarely, if ever, entering freshwater: this element of the population is particularly poorly understood.
Ideally, the IUCN Red List criteria would be applied to mature eels at their spawning grounds, and in the absence of such data, the criteria would be applied to silver eels starting their spawning migration (in the case of European Eels, leaving ‘continental’ waters), as these represent the maximum estimate of spawning stock biomass, but data sets for this are very rare. The majority of available data relates to glass eels and yellow eels but the relationships between recruitment, yellow eel populations, silver eel escapement, and spawner stock biomass are poorly understood. As such, the IUCN Red List criteria have to be applied to an amalgamation of multiple life stages, which may not exactly mirror the mature spawning stock but can be used as the current best estimate. Finally, the European Eel is a panmictic species, i.e. they come from one spawning stock. Taken literally, this assumes equal importance of the continental populations, and as such escapement from a specific river/country/region is not equivalent to the subsequent recruitment as this relies on the spawning stock as a whole, irrespective of escapement location. However, there are hypotheses that certain regions may have greater importance for the spawning stock, e.g. males primarily escaping from North Africa (Kettle
et al. 2011), and as data are only available from certain parts of the species' range - data are particularly sparse for Mediterranean and North African populations - it is important that conservation initiatives and management actions are adjusted as new data become available.
In relation to
A. anguilla, only a very small amount of data are available for silver eels, and while this is not geographically representative of the stock as a whole, a cursory analysis of this alone indicates that the mean decline in silver eel escapement is estimated to be 50-60% over the period of three generations (45 years), just placing them in the Endangered category. There is a similar dearth and uneven geographical spread in the data that relates to yellow eels; however, taking these limitations into account, analysis indicates that there has been a slightly greater decline in this life stage compared to silver eels. Compounding these declines in escapement of maturing eels, according to the available data, there has been substantial declines (90-95%) in recruitment of the European Eel across wide areas of its geographic range during the period of the last 45 years (or three generations) due to a range of threats facing freshwater eels at multiple life history stages. Recruitment has fluctuated during the last century. However, the analysis carried out as part of the IUCN Red List assessment mirrors the WGEEL recruitment index (five year average) which, despite increases in recruitment during the last few years, is currently at its lowest historical level of 1-10% the recruitment of the 1980s, (ICES WGEEL 2013). Further, there is concern that due to the period of time eels spend feeding and growing, prior to silvering and migrating to spawn, that silver eels may continue to decline, even if recruitment is showing recovery.
There is a suite of threats that have been implicated in causing the decline in European Eel recruitment and stocks: barriers to migration – including damage by hydropower turbines; poor body condition; climate change and/or changes in oceanic currents; disease and parasites (particularly
Anguillicola crassus); exploitation and trade of glass, yellow and silver eels; changing hydrology; habitat loss; pollutants; and predation. The impact of these threats individually or synergistically, are likely regionally specific; however, more broadly, climate and ocean currents have been suggested to play an important role in the survival and transport of the leptocephalus larvae and recruitment of glass eels to coastal, brackish and freshwater habitat. Further research is required to fully understand the complexities of this particular aspect of the eel's life history but there are conflicting opinions as to the degree, if any, which oceanic factors contribute to broad fluctuations in eel numbers.
Eel Management Plans (EMPs) have been developed in European countries since 2007 as a stipulation of the EU Council Regulation No 1100/2007 relating to the recovery of the European Eel. Currently, more than 50% of the 81 EMP progress reports across Europe are failing to meet their target silver eel biomass escapement of 40% in accordance with the regulation, indicating that more work is required (WKEPEMP 2013). Further, international regulation was enforced for this species in 2007 when CITES (the Convention on International Trade in Endangered Species of Wild Fauna and Flora) listed
A. anguilla on Appendix II (this came into force in March 2009). Since this time, exports outside of Europe have been banned due to concern over the decline in recruitment and stocks, however, trade continues within the EU and from non-EU countries within its range to other non-EU countries.
A number of management measures are being implemented in line with EMPs, for example easing of barriers. The influence of these measures, however, will take time to determine as they have only very recently been implemented and very much focus on the freshwater component of the eel's life-history. Arguably the most widely practised measure is restocking; however, there remains a great deal of debate as to whether this benefits eel spawning stocks and thus enhanced future recruitment. Measures that apply to silver eels, such as fisheries management, and/or trap and transport programmes, can theoretically have an almost immediate effect on the potential spawning stock, although when carried out in isolation, their benefit is significantly reduced.
As stated above, the relationship between life-stages is poorly understood, but it was generally agreed that it is very likely that the low recruitment will ultimately translate, though not linearly, to reduced future escapement for, at best, one generation length (15 years). Further, low recruitment has been proposed to be indicative of low historical breeding stock due to the relatively short time period (~2 years) between spawning and subsequent glass eel abundance. As such it was deemed appropriate to assign
A. anguilla a Critically Endangered listing under current observations and future projected reductions of mature individuals (A2bd+4bd).
While this status is unchanged from the previous assessment, it is important to highlight that the process of this designation was very different in that it was carried out as part of an anguillid specific workshop, and that new data were incorporated – for example the generation length was reduced. There was general agreement that the situation had improved, albeit slightly, for this species both as far as recruitment and implementation of management measures was concerned. As such it is imperative to highlight that this listing is borderline, and that if the recently observed increase in recruitment continues, management actions relating to anthropogenic threats prove effective, and/or there are positive effects of natural influences on the various life stages of this species, a listing of Endangered would be achievable. Further, a drive to fill data gaps – particular in relation to the southern range of this species – would allow an even more robust assessment, and we strongly recommend an update of the status in five years.
