Kingston University Biodiversity Action Group

26-10-2015: Eels and river flies help shed light on the rivers of London

RMI volunteers at the end of Saturday's training
Warning – a longer then usual update on the Riverfly Monitoring Initiative training and the annual Eel Conference at ZSL.
Class room run through 
Two Saturdays ago, we ran the third of our Riverfly training sessions with ZSL. It was the best one yet, with everyone who signed up, turning up and getting stuck in on the day.

As usual the day was spilt into two halves. In the first half, Joe explained how three minute kick sampling worked and talked us through the identification of the species used in the methodology.

He explained how the simplified methodology was still robust enough to inform us of pollution incidents affecting the river, allowing subsequent reporting to the Environment Agency.

This past blog post tells you a little bit more about the project.

ID practice in the field
He then demonstrated how to do a kick sample in the field, allowing everyone to get practice identifying the species we were looking for.

The second half of the training event was spent with volunteers conducting their own kick sampling.

Tips on how to do the kick sampling effectively
Analysing their three minute sample

It got competitive with different groups trying to be the one to find case caddis larvae (the least frequently found of our typical Hogsmill species).
You can just see the front legs of the cased caddis...if you look hard enough!
Only two of the five groups present, found single cased caddis in their sampling.
Can you guess which groups found the cased caddis?
Due to the number of photos taken on the day, I thought I'd put together the collage above, in a bid to reduce the length of this post :)

Of our regular volunteers Bill was there, helping us train the new volunteers.

Bill has been instrumental in helping different groups get set up at the Hogsmill, sometimes moving equipment between groups etc.

He also helps out with lots of other ZSL projects which are one of the reasons why he won an “I Love Eels” award at the Eel conference last Tuesday at ZSL (more about that below).

Last Tuesday was the annual eel conference – this is our once a year catch-up on the eel project run by ZSL – reporting back results from all of the stations sampled in London, and where our efforts sit in the conservation efforts for this species.
Joe has a busy week swapping between different citizen science projects
This year it covered the usual review of the year’s data for all sites, how many silver eels are actually migrating out of our rivers back to the sea, and a Thames Water perspective on implementing the Eel Regulations.

I found this short video about the project on ZSL's website. The eel project has grown from 18 people in 2007 to over 100 people today including 14 partnership organisations.

Over 500 people have taken part in the programme and volunteered, that’s 0.006% of the population trained!

The main aim of the monitoring element of the project we look at the incoming journey of the glass eels into our rivers. We monitor the effects of barriers, and using this evidence, create a funding case for either modifications or removal to take place, effectively removing the barrier to fish migration.

Generally the higher up the catchment you go, the proportion of elver (baby eels) reduces in the total catch size. However, every eel that we get is important, even if they are older, as they move up the catchment in search of good habitat as the lower levels start to become full. 

Trends in recruitment: compared to 2013-2014 which were great years for recruitment, we’ve seen a drop in 2015, but we’re not sure why. 
Survey results for all of the sites
Our data for Middle Mill
The great news is that at the university we've continued to have an increase in numbers, unfortunately our site has followed the trend of other sites and had less elver this year then last year. Hopefully we'll continue to get more eels in 2016 with continual hopes for increases in elver numbers going forward. 

Next year we’ll have at least two new monitoring sites joining the existing ones so there are more locations and opportunities for people to monitor eels. 

If you are keen to find out if there is a site near you and if there is training that you can go on, please contact With your help, maybe we can get all of the rivers of London monitored and a bigger percentage of Londoners engaged with saving eels. 

Darryl Clifton-Dey from the Environment Agency (EA) filled us in about how the Environment Agency monitors the exodus of silver eels (adolescents) from our rivers, when they travel to the Sargasso Sea to breed. 

The target for eel conservation say that escapement (the number of silver eels leaving our rivers) needs to be 40% or the potential biomass before human impacts. 
Initial data in 2012 suggested that we were meeting targets
Initial reports in 2012 along with computer based modelling, seemed to suggest that we were meeting these targets, but something didn’t seem to quiet tally. There is a wide level of variation in the numbers; recent reanalysis of the 2015 data suggests that only 20% of the potential biomass of eels in our river is escaping!

The EA undertook measures to test the factors in the model, based on a small well monitored catchment. 

They tested the model on the Wandle, using technology to create sonar films of eels, the aim was to have footage which could be watched to identify the exact number of eels leaving the river at this point, and correlate it to various factors which are used in the model.

There was a slight hiccup in that the equipment kept failing, so data collection continues. Using the data that they were able to collect, they looked at three facts which are currently seen as being true of eel movements.

1. Eels move at night = Confirmed – most of the migration takes place between dusk and dawn.
2. Eels move under high flows = Disproved, they were seen during different flows.
3. Eels move out of rivers on the nights where the moon is dark = Disproved - a lot of the movement was observed during different phases of the moon. 

As a general rule, males are smaller when they leave the rivers (normally after seven years). Females seem to wait until they are at least 45-50cm long. If the growth rate of male and female eels are the same, this would suggest that they wait until they are older to return to the sea to breed. Maybe they have a better chance of surviving the journey to breed if they are larger. 

A lot more needs to be found out about eels and how they escape our rivers, as it may shed light on new ways of helping them. So studies continue. 

Matt Heart who is the Environment Engagement Lead (EEL!) for Thames Water talked about the different technologies they are employing at various works/abstraction points/sewage works etc. to stop eels from being pulled into these systems ranging from physical measures such as the Travelling Belt Screens to non-physical barriers such as strobe lighting scaring away animals. 

They use factors such as the fact that eels are rarely/not found above 150 m altitude and it’s rare to find eels over 100km from the tidal limit to establish where the eel regulations apply. And then look at the cost benefit analysis of how much the costs are to mitigate the issue, verses how much they have to spend on the system to provide water. 

Thames Water have plans for a lot of their London sites to put in mitigation for eels, mostly in the form of screens. Funding has just been secured for the first site, which will be used as a case study for subsequent sites. 

It was an interesting talk, as it shows how some companies feel forced to make these sorts of decisions between water supply and adding in needed mitigation immediately to ensure that they are not in breach of wildlife legislation. 

Its can be a tricky balance to maintain, especially if you consider how their actions can be perceived by media such as the tabloids, who often look for sensationalist angles to re-tell the story of rising bills. Past cases where the media manipulates mitigation costs for great crested newts and housing developments in one example of how they may try to vilifying these spends as prioritising a species over people. Rather than an  investigating our impacts on the environment and proper re-prioritising of funding to mitigate our impacts. 

Joe presents the Eel awards
The day was finished off with the presentation of the eel awards, and an opportunity for delegates to have a look around the zoo. I had a quick look around before I left.

If you have made it this far, I thought I'd leave you with the following mini quiz - can you name the animals pictured below?

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