Eel Fisheries-Recruitment-Future

Decline of Eel Populations??? Outside safe Biological limits? How are we influencing change? Can we manage the population change? Will reducing fishing produce a predicable change in the eel population? No!

Glass Eel Recruitment Levels 1876 High 1930 Low 1950 High Company Low 1976 Company High % Stepped Reduction Then Progressive Slow Decline stabilising last 3 years

Glass Eel Recruitment Levels ICES - 1% of 1980 levels Industry - 15% - 20% of 1980 levels Back Calculation of recruitment 1980s based on average of last three years. –United Kingdom tonnes –France tonnes

Quantifiable Causes for Decline Industrial Revolution –Agriculture, Industry –Loss of migratory Pathways –Loss of Habitat Fishing??? Water Mill Circa 1900

Tide Assisted Migration Ratchet MechanismGlass Eels –1Y migration Spring –Passive Small Eels –2Y Migration Summer –Active

Loss of Migratory pathways Soft barriers –Migration possible some of the time –Dissipate tidal energy

Tidal Effect Effect of soft barriers on tidal flows Impact on assisted glass eel migration

Loss of Migratory pathways Hard barriers –Major civil engineering projects. Weirs, dams, locks, flood defences –Minor works. Valves, sluices. Pumped systems, and poor design.

Loss of Migratory pathways Hard barriers Weir-Tidal Flap-Submerged

Loss of Migratory pathways Hard barriers Tidal Flap- RaisedDrain-Raised

Water Management v. Migration Pumped BarrierNearly Every outlet Guarded Poor Design No management of migration Process of change unrecognised.

Loss of Migratory pathways Passes Ladders and Passes –for Glass eels Ineffective –for Small eels partially effective –Poorly managed and maintained Glass Eel/Eel Pass

Loss of Nursery Habitat Eutrophic - Still Water In area for assisted tidal migration Very little remains on River Severn Not accessible Mortality in River Nursery Habitat

Habitat Change SpringSummer

Loss of Habitat Wetlands Remaining –Year % –Year % –Year % Artificially Maintained Wetland Habitat –poor access. Summer

Habitat Change SpringSummer

Future of Eel Fisheries Recognise Environmental Change –Migration, Habitat, Engineering Not a Fishery Management Problem Choice between Economic Growth and the Environment. Problem pan European scale. Recovery of stock to previous historic levels not possible.