1 research outputs found
2020 Report of the EIFAAC/ICES/GFCM Working Group on Eels (WGEEL)
The Joint EIFAAC/ICES/GFCM Working group on eels (WGEEL) met by correspondence and
video conference from September 21â28 in 2020 to assess the state of the European eel, investigate
the effects of habitat loss on the eel stock and its management, review and update the Stock
Annex, prepare the 2021 Data Call and report on any updates to the scientific basis of the advice,
new and emerging threats or opportunities. Furthermore, data on fisheries landings, aquaculture
and restocking are presented.
Analyses were carried out on two glass eel recruitment indices (comprising 28 time-series in the
Elsewhere Europe area and 24 time-series in the North Sea) and one yellow recruitment index
(comprising 16 time-series). Note, that some data from the current year are always provisional
to allow for a small proportion of late reporting series, but this is not considered to materially
affect the trends. The potential impacts of COVID-19 on the data collection and quality were
noted by the WG and described in detail in the report.
The recruitment of European eel strongly declined from 1980 to 2011. The glass eel recruitment
compared to that in 1960â1979 in the âNorth Seaâ index area was 0.5% in 2020 (provisional) and
1.4% in 2019 (final). In the âElsewhere Europeâ index series it was 6.5% in 2020 (provisional) and
5.6% in 2019 (final), based on available dataseries. For the yellow eel dataseries, recruitment for
2019 was 17% (final) of the 1960â1979 level; the 2020 data collection for yellow eel is ongoing.
Statistical analyses of the time-series from 1980 to 2020 show that recruitment has stopped decreasing in 2011 but the trend thereafter is rather unclear.
A Bayesian assessment model (GEREM), structured to allow the existence of potential different
trends among regions, and provide absolute recruitment per zone has been run. While still preliminary, this model confirms the trend in recruitment, points out the need of new time-series of
recruitment, and could in the future allow a part of the analytical assessment of the stock.
The collection of yellow and silver eel series and their biometric data, started last year, has continued and a first analysis has been run. There is a large spatial variability in trends of abundance
among locations but the analysis of the long-term time-series shows that current silver eel abundance is low when compared to the pre-1980 levels. The analysis of biometric data allows a first
analysis of the biological characteristics of the series and points out missing fields in data collection.
Emerging threats and opportunities that have been reported over the past decade were reviewed,
and diseases, parasites, contaminants and hydropower were identified as routinely reported and
thus established. Climate change was repeatedly reported in the past; yet knowledge remains
limited. Moreover, the threat of the EU exit of the UK raised concerns regarding the accessability
of glass eels for stocking and the potentially increased availability of glass eel from the UK being
traded illegally to Asia The issue of COVID-19 was addressed and impacts were found to fall
largely in three categories: i) scientific monitorings, ii) restocking programmes and iii) closures/delays in commercial fishing and loss of markets.
The WG has a new standing annual activity to examine quantification of the impacts of nonfishery factors and in 2020 i) reviewed the literature on the effects of habitat loss with a focus on
the biological processes operating, ii) the national Eel Management Plans and (latest) triannual
assessments identifying whether and to what extent the effects of habitat loss have been taken
into account, iii) develop a workplan aiming at the quantification of habitat loss and its effect on
eel production in the coming years, and iv) present a number of actual case studies. Due to the
lack of appropriate data, a meaningful quantitative assessment is not possible at the moment.
Overall, the working group has made progress towards the assessment of the standing stock and
spawningâstock biomass (i.e. yellow and silver eel time-series) and the implementation of an
additional model for the recruitment data provides towards further analyses (e.g. with respect
to regional differences). The WG identified relevant issues for future research, highlighting the
limited knowledge on the complex effects of climate change as well as the need for additional
and specific data collection to quantify the effects of habitat loss