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Championing a Sustainable Eel Fishery

The Biology of the eel – an extraordinary life history

The European eel is a catadromous fish species, long lived (on average males 8-11 years, females 12-18 years in northern Europe but significantly shorter in the Mediterranean and North Africa) and the life cycle involves several metamorphic changes before the final adult spawning migration to the Sargasso Sea. Reproduction:, whilst still to be observed in the wild (indeed neither spawning adults nor eggs have ever been seen), is a singular event. The life cycle has still not been resolved and consequently critical and determining factors remain unproven.  However this is not a reason to abandon efforts to find easy and low cost solutions to some of the more obvious problems.

Eels often dominate the fish fauna in lower rivers and estuaries, where it represents a considerable component of the aquatic ecosystem, and constitutes a major part of the diet of many other fish and semi-aquatic predators such as otters, cormorants and herons.  There is also a coastal population that is largely unrecognised and undetermined.

Glass eels arrive along the coastal waters in winter in southern Europe to late spring in most northern regions.

Present status of eel stocks

The recruitment of glass eels compared with the 1980’s has been stated by ICES to be 1% of former levels. Specific structures for the management of eel stocks have been developed at an international level (EU Council Regulation EC No 1100/2007; CITES, 2007), establishing measures for the recovery of the stock of the European Eel, protection and sustainable exploitation.  Starting 1st January 2009 and by 31st July 2013, 60% of eel stock less than 12 cms in length caught annually (the majority being glass eels) should be reserved for restocking.  In addition there will be a common management objectives set at National levels.


Our experience in the UK would suggest a recruitment figure of between 10%-15% of former levels.  Local and regional environmental conditions have a marked impact on capture results.  However, it would appear that the decline in recruitment has occurred over the whole distribution area.  The causes for the decline are not understood but are believed to be multi-factorial and include loss of migratory pathways, habitat, and climatic changes.  Many other hypotheses such as exploitation, pollution and various pathogens have been proposed but the reality is that these things are not quantifiable.  Catch data would indicate that glass eel recruitment from the 1980s to the present time was lowest in 2008-9 with a significant increase for 2010-11.  Anecdotal evidence would indicate that there have been other historical lows and highs. We are fortunate that the Severn Estuary is one of the major glass eels fisheries in Europe still viewed to have a surplus supply of glass eels.  Severn River Basin Plan. To date there has not been a similar decline in adult eels.  .An extensive review of 54 data sets (including 31 time series) for various stocks in NW Europe (dating from the 1970s onwards) was provided to WGEEL in 2007 and again in 2008 (Knights & Bonhommeau).  but has not been considered  (Analyses indicate that 61% of the data sets showed no significant temporal changes, 35% showed significant declines and 4% showed significant increases.  Comparable trends in 31 of these data sets comprising continuous time series were 52, 42 and 6% respectively.  Combined time series showed a peak in 1982 but stock levels appeared to have been as low in the 1970s as in the 1980s.  On the River Severn studies suggest that the population is similar to those of 1980's and that there is no direct link between volume of Glass Eel arrival recruitment and adult stock.

Eels are cultured to a significant degree in Europe but unlike the other major cultured species, the juvenile stock is still obtained by capture from the wild and there is no closed cycle of production as exists for the fully domesticated fish species.

Developing a Europe Wide Sustainable Fishery

For many decades we have been at the leading edge of Glass Eel Fishery management and innovation have pioneered many techniques to make our industry more complete and effective.  We recognise that sustainability is the key not only for the future of the glass eels fishery and the future of the European aquaculture industry (until it is possible to reproduce the eel in captivity).  It is therefore not surprising that we have been directing our resources and energies to promoting a sustainable fishery since 2006.  Carrying on as before, with the various European fishery and environmental practices can only lead to further eel loss and ultimately end the livelihoods of all those engaged in this historic European industry.  We have been working over the last five years to introduce and support effective, immediate and concerted action to introduce change.  Initially we reviewed our own practices at UK Glass Eels, compared them with others and then tested them against a yardstick for sustainable fishery management.  Initially under the Marine Stewardship Council and subsequently we have reviewed our operation and practices using Professor Callum Roberts “straight forward and common sense reforms” for the worlds fisheries.  These were modified under the direction of Dr Gascoigne from MacAllistair Eliot.  There has, in the last two years been further development of the sustainable fishing practice under the guidance of the Sustainable Eel Group.

Callum Robert’s Common-Sense Reforms

“Reduce the present fishing capacity”

In the Severn River Basin glass eel fishing has been reduced year on year not only by the decline in overall numbers of licensed fisherman,  the use of bye laws to enforce sensitive hand netting techniques and principally by persuading fishermen to understand and cooperate in developing new practices.   Additionally in the UK the byelaws limit fishing to traditional fishing areas (just 2% of the coast) only and no new areas for exploitation.  For the Severn River there is no longer a commercial eel fishery.  The Severn river basin district is currently achieving the 40% silver eel escapement level as set out in the European regulations.  The consequence of all these measures and approaches is that the published eel management plan for the Severn River Basin states that adult / silver eel output is similar to that of the early 80’s and accordingly are subscribing to the view that the problem is more likely from loss of habitat and blocked migratory pathways than any other factors.  The plan is not recommending any additional actions to reduce glass eel fishing.  

All these measures are in contrast to some other countries where fishing boats and more intensive technologies are applied.  It has been much more difficult to manage these changes in the rest of Europe.  The majority of fishermen have yet to engage in a sustainable agenda.  However new strategies are emerging.  For example in France under the direction of the National and River Basin District Plans catch quotas and a boat scrappage scheme has significantly reduced fishing capacity and catches (the number of boats has been halved).  There has been and probably will be further reductions in catch quotas for successive years.  For some river basins there are opportunities to develop more responsible and sustainable fishing practices.  

The listing of the eel Annex B list II by Cites has for the moment restricted trade to within the European community.  Without the Asian market there are no longer the financial incentives that encourage extreme and insensitive fishing practices.

“Eliminate risk prone decision making”

This is a call by the professor to end the political and high level decision on quotas and to get away from national politics driven from a centralized and short term approach.  Instead he advocates giving decision making on fishery management to local bodies that operate within frameworks designed to achieve long term and sustainable objectives – this matches the words and sentiments of the European Fisheries Fund.  The Sustainable Eel Group is the new stakeholder grouping representing a range of interested parties from Europe that include government organisations, scientists, nature conservationists and industry stakeholders that wish to make sustainable decisions that meet long term social, environmental and commercial needs.

It is also important that there is co-ordination and co-operation between the River Basins of Europe.  It is generally accepted that the eel constitutes one panmictic stock found all over Europe, Northern Africa and the Mediterranean.  This wide distribution area, however, is effectively fragmented over thousands of river catchments, with little or no natural interaction in-between while protecting the species to some extent it does produce an anomaly that a sustainable river basin could easily be supporting an unsustainable one.

Eliminate Catch Quotas and instead implement controls on the amount of fishing and to require people to keep what they catch

This theme of Callum Roberts is aimed at ending the huge and pointless waste of fish being caught and then dumped at sea because the landing quota had already been achieved.  These sort of practices because of the very specialist techniques involved has not been directly applicable to the eel industry.
Currently there is no quota system for eels in operation in the UK.  At the present time as there is only limited commercial exploitation of adult eels in England and Wales.  There is merit in controlling or temporarily stopping the recreational fishing for adult eels.  It is highly desirable to increase the numbers that successfully return to breed in the Sargasso Sea.  The demand for eels can be met through aquaculture where the survival of glass eels to market weight is significantly greater than in nature.

UK Glass Eels greatly favours the suspension of exports of glass eels to Asia during the recovery period.

There is also a case to be made for using aquaculture to take glass eels and over a few months grow them into fingerlings with their far higher survival rate and release them into wetland habitat above the obstructions on ecologically sound river systems. Whilst this is not a long term solution (unblocking and passes would be) it is a cost effective and faster way of using the available habitat. (The choice of site would need careful planning). The larger eels have a greater ability to negotiate many but not all of the typical barriers The Sustainable Eel Group team in conjunction with the UK Environment Agency and  local  Rivers Trust using a revised  habitats model has been able to set  priorities for removing these obstructions.

Require fishers to use gear modified to reduce by catch and Ban or restrict the most damaging fishing gear

The traditional hand net is the only legal fishing instrument on the Severn. It is an environmentally sensitive fishing method. The catching is very species specific. There is no by-catch and no impact on larvae or other aquatic life. There is a 98% survival of the catch. UK Glass Eels is very aware that glass eels are sentient animals that require a high degree of management and husbandry by skilled trained staff from their point capture to their point of release.

Though we do not have data for the carbon foot print of fishing activity it is highly probable that one person fishing with a hand net has a significantly lower foot print than a 15 meter 300 HP trawler.
While attempts are now being made to develop new nets and fishing practices there is a huge body of evidence to show that most of the French Fishery does not meet these basic sustainable criteria.  Glass eel mortality could be as high as 50% from point of capture to point of release. We are highly critical of the current French fishery practices and standards and we welcome the latest initiative on the Loire to reduce catch mortality. However this initiative is handicapped by the regulatory authorities who will not relax rules on net design.

Implement extensive network of marine reserves that are off limits to fishing

For the eel reserves this would mean both marine and freshwater –  with regard to the former little is known about the marine life cycle there is an undetermined resident coastal marine population that is largely unexploited with only limited knowledge of the life cycle.

For the UK under the national eel plan an area of the UK has already been reserved for glass eel recruitment.   

The terrestrial programmes of land management and water framework directive is promoting a more sustainable future – The immediate challenge is to get enable more glass eels to pass the barriers and on into the wetlands and to maximise the number of silver eels returning to the oceans to breed.  In the short term restocking with glass eels or juvenile eels will increase the local population.

Hand net fishing – Trawling. Understanding the methodology and outcomes.

The principal driving force for glass eel migration depends largely on the tidal ratchet mechanism which can transport glass eels upstream several kilometres a day.  It is  during this period of immigration that the glass eels are to be found in the water column and are easily captured by mid water trawls..

There is however an additional active sub-migration stimulated by tide and specific local conditions that can be exploited using traditional hand nets. When the tide starts to ebb the glass eels drop out of the water column and congregate close to the river bank.  Under certain conditions the glass eels will then actively swim upstream in a column 10 to 20 cms wide close to the bank.  It is only under these very special conditions that the traditional hand net is effective.  The hand net is placed on its side close to the bank, with the mouth of the net facing down stream against the migration.  The glass eels will swim into the hand net and providing there is sufficient water flow through the back of the net, to stimulate the migration, the glass eels will continue to swim against the back of the net as opposed to round it.  The glass eels are not caught by any active scooping action. It is a completely passive method of fishing.  This active migration will last for just a few minutes to a few hours depending on local conditions.

Unlike hand net fishing, trawling for glass eels offers a greater opportunity to fish. It is much less affected by local conditions such as light, temperature, water flow and river conformation. A mechanised fishing system is much easier to manage and is more likely to be prolonged. Fishing effort is principally limited on an economic return based on the cost of oil.

The hand net has a significant number of constraints when compared with trawling. The successful use of a hand net requires a high degree of skill.  There is only a very small window of opportunity of the hand net to be effective.  It is highly dependant on local conditions.  The fishing effort is constrained by human endeavour and physical strength.

Based on this analysis it is easier to understand why the glass eel hand net is more likely to meet the objectives set out in Callum Robert’s Common-Sense Reforms and the Strategic Objectives of the European Fisheries fund to encourage environmentally sensitive fishing methods.  

Callum Robert’s Common-Sense Reforms

Reduce the present fishing capacity.

Eliminate risk prone decision making.

Eliminate Catch Quotas and instead implement controls on the amount of fishing

Require people to keep what they catch.

Require fishers to use gear modified to reduce by catch.

Ban or restrict the most damaging fishing gear.

Implement extensive network of marine reserves that are off limits to fishing.

Severn Hand Net

Unlike trawling there are a number of significant constraints on the use of the hand net.  The successful use of hand net requires a high degree of skill. There is only a very small window of opportunity of the hand net to be effective. It does  meet Callum Robert’s Common-Sense Reforms.

Key Principles for Glass Eel Fishing

The fishery should adopt environmentally sensitive  fishing methods.

The   catching method should be species specific.

The catching method should produce minimal by-catch

The fishery should have no impact on other larvae or marine life.

The fishing method  should not compromise the  survival rate or the welfare of the glass eels. (Glass eels are  sentient animals that require a high degree of husbandry  from their point capture to their point of release)

There should be minimal carbon foot print from  the fishing activity.

Harry Pope vs. French Trawler

Is the French  method of fishing sustainable?

Damaged glass eels from trawler.

French Trawler Gironde

On the Gironde the boats are of a much lower power and smaller. The size of the catch is not dissimilar. However the glass eels are much more vigorous.

Factors that impact on hand net fishing


No migration  temperatures less than 6°C

Optimal temperature 12°C for migration

Over 16°C the glass eel become so active that they start to escape from  the net.

Freshwater flows:

High and low freshwater flows impede the migration.

Photo period:

Day light has a negative impact on the migration.


This active migration behaviour is only imprinted on glass eels for a very short period (about three weeks).


A tide is needed to stimulate the glass eels to actively migrate. Due to physical constraints of the river only Spring tides are of sufficient size to over come these constraints, and a large enough, to stimulate the glass eels.