Fisheries Monitoring of the Ribble Catchment 2013 By Gareth Jones. What next?
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Fisheries Monitoring of the Ribble Catchment 2013
By Gareth Jones
Areas with degraded habitat and poor salmonid fry returns are now being targeted using the results from 2013. More specifically, the River Loud and Park Brook are in the RRT’s immediate sights for 2014. The surveys have provided over ninety possible targets for improvement across the catchment and have connected with pro-active landowners that wish to see improvements to both their land and watercourse. The opportunities link together these individuals with those who can help practically or possibly even donate materials. Furthermore, those lesser opportunities can still make a cumulative difference with feeding into grant funding bids that aimed at tackling wider scale issues. With many areas of the lower catchment remaining to uncovered by our past geographical range our surveys will increasingly branch out to identify the continuing needs of our water courses and wildlife.
Results from 2013
For convenience we divide the results from our surveys in to separate sub-catchment areas. That is, the area of the Ribble catchment that is covered by the RRT is split into smaller areas defined by where water will drain into, either the river Calder, Ribble or Hodder. In the following sections we will refer to these…
The lowered water levels and prolonged dry spell have reduced the development of this year’s fry. Successful growth is measured using the length of the fry compared to that of the previous year(s). This was lower across all catchments in 2013 for trout and salmonwith the exception of trout upon the Hodder. Here, trout fry lengths were all but the same as the previous two years. In some exceptional circumstances some of our survey sites had even run dry! Main river temperatures exceeded 25 oCat West Bradford in mind July which is exceptional.
Motivation and methods
Each year, the Ribble Rivers Trust performs a series of fish surveys at locations across the Ribble catchment. The locations extend from just above the Brockholes reserve across to Colne and up to Ribblehead. Some 300 sites are visited and electrofished by our Fisheries Scientist and supported by volunteers, many of which are anglers or students. Electrofishing is the technique of adding an electrical current to water in order to aid capture and does not harm fish.
A sea trout captured on a mid-Hodder tributary, July, 2013.
Captures are collected in handnets, measured and then returned to the river afterwards. The number of trout and salmon fry are then counted and the site is assigned grades from A to F. The grades are mapped to help us quickly identify poor performing areas and assess particular features of interest. Many of these features correspond to places where the Trust can work to make improvements to the river. We can also use the results to see if our work is effective. Ultimately the RRT aims to improve the wild fish population to the benefit of anglers and the wider environment.
How did the surveying go last summer?
In stark contrast to 2012, the warm and dry summer aided and abetted the survey programme. Locations were surveyed for the first time across the Hyndburn catchment and we were able to access areas that had to be missed out in 2012 across the Lower Ribble. Aquatic algae and macrophytes benefitted and succulent growths were observed particularly throughout of the mid-Ribble area. Plant transpiration and a natural reduction in the solubility of oxygen with elevated temperature meant that river conditions became challenging. Lower oxygen levels also increase the susceptibility of wounded fish to secondary infection and increased predation risk.
Overall, the trout population of the Hodder demonstrated the greatest tolerance to the summer conditions based upon the proportion of sites with increased densities. Trout fry fared better in their development and survivability than the salmon.
The Hodder has continued to have a greater average number of salmon fry per site than the Calder and main Ribble. The discovery of salmon fry above Padiham has yet to manifest in the survey results obtained to date. This remains a disappointment whilst significant advancements to fish passage have been made.
The increased survey coverage of the Lower Ribble revealed greater number of juvenile eels than the previous year which have thrived off the back of a strong migratory run nationally. Their presence was greatest in the lower gradient and slowing flowing tributaries of the main river. …
(Above left) Continuing evidence of challenging barriers to fish migration, here Shoe Mill at Baxenden presents a significant obstruction. (Above right) More observations of otters have been made overthe past year than previous. Here, the RRT captured evidence of otters feeding at night throughout the mid-Ribble area.
Evidence of a quick win on Leagram Brook, near Chipping, where a pipe bridge was removed in summer 2013. In the electrofishing survey that followed later that summer salmon parr (inset) were discovered within a new habitat improvement scheme.
The Trust performed five fish rescues during the summer in the Colne water, Hyndburn, Langdenand Mid-Ribble sub-catchments and which have saved thousands of juvenile fish from being lost to in river works. With our catchment’s increasing population, more pressure will be exerted upon our local infrastructure and in turn, poses an increasing threat to our aquatic environment. The requirement for greater mitigation will grow and maintaining local interest in the condition of our ecosystem upheld through the Trust’s educational initiatives, research and practical work.
For more detailed reports from this and previous years please visit http://www.ribbletrust.org.uk/news/reports/ or contact [email protected]
The above charts show two different measures of salmon (left) and trout (right) fry grades for the whole Ribble catchment by scrutinising sites that have been repeated in each year from 2008 to 2013. The overall picture is that over the last six years, performance has not significantly changed. However, the pie-charts below show there has been an overall improvement on the number of trout (left) but fewer salmon were (right) captured compared to the previous year.
…More mature eels have also been found upriver with increased occurrence in amongst the towns of Accrington, Burnley, Colne and Clitheroe. This included an excellent result upon Great Harwood brook where the first fish of any kind was found amongst a past history of pollution incidents.
2013 was a good year for coarse species with more chub, lamprey, minnow and stickleback encountered than in the past three years. The presence of Chub were found as far up the catchment as Long Preston.
A total of 3672 trout and 1525 salmon fry were captured in all representing the increased geographical coverage over last year. In real terms the number of trout was up but salmon numbers down on the previous year. The number of trout fry is inflated by the coverage of the Lower Ribble and Hyndburn this year. However, there were better returns of trout fry in the lower Hodder catchment, an improvement on 2012. Salmon fry were absent in the surveys undertaken on Stock beck and the upper Hodder main stem below Stocks Reservoir. In both locations, salmon parr were still recorded but there was an absence of fry.
A eutrophied Ribble during low summer flows, 20th July 2013 (left). A low and very algal, Park Brook (right). It is hoped this once proud, sea trout spawning beck can be improved by preventing access for livestock and increasing tree cover over the brook.