A baseline survey of the River Triogue, Ballytegan,Portlaoise Co. Laois, focused on water quality, water chemistry, macroinvertebrate sampling and fish stock analysis by Pauric Byrne
This project was submitted as part of IT Sligo requirements of the award of Higher Certificate in Fisheries Management.October 2011 – Project Supervisor: Dr Frances Lucy, Institute of Technology Sligo.
The River Triogue is one of the main tributaries to the river Barrow. The river Barrow is the second longest main channel in the country with a total catchment size of approximately 3000 km² and the main channel length being approximately 192 km. The river Triogue influences the water quality of the river Barrow, due to the effluent outflow from the Portlaoise waste water discharge. 93 % of the catchment of the river Barrow is classed “at risk”, the remaining 7 % is classed “probably at risk”. This is mainly due to waste water treatment plant discharges and combined sewer overflows too many of the tributaries that flow into the river Barrow catchment.
Four sites were chosen for assessment and this survey consisted of water and macroinvertebrate sampling along with fish stock assessment. Relating to the results of the Q index and small stream risk score (SSRS) in this project site 1 was classified as class A and “at risk”, while sites 2, 3 and 4 were classified as class B and also at “risk”.
Five minutes electro fishing was carried out at each site, where no 0+ trout were caught, 1+ trout were caught at sites 1,2 and 3, while 2+ trout were caught at sites 1 and 3. Salmon parr were found at all sites except site 2 were the sewage treatment plant discharge is located. No eels were caught during this survey. From the results it shows it shows at is a spawning area and nursery area for salmon.
The River Triogue is a tributary of the river Barrow in County Laois. This is located in the South Eastern River District. The Triogue has a catchment size of 42.7 km² and is approximately 14.3 km in length. This river begins just outside a suburb of Portlaoise called Meelick and enters the river Barrow outside suburb called Clonterry, just outside Mountmellick in County Laois. Land use is mostly agriculture with some forestry in places and also some peat land bogs. The bedrock type is dinantian lower impure limestone’s at each site where samples were taking from and consists of cobble, gravel,fine gravel and silt in places.
Laois currently has a population equivalent of 26,000 which increased by over 20% between 2006 and 2011.
The River Triogue is managed by various agencies including Inland Fisheries Ireland and Laois County Council and they have done a lot in recent years to improve the catchment. A waste water treatment plant was upgraded in 2009 costing 54 million the council also got anglers from Portlaoise Angling Club and volunteers from the town to clean a stretch of the river in the town, were traffic cones, bicycles and even a cash register were removed from the river.
Pollution was first noted in the River Triogue in 1971, with Q values ranging from 1-3 , for 3 kilometres downstream of the waste water treatment plant, and has being known for series pollution up to 2009 due to the poor waste water treatment system, treating effluents from residential areas ,2 prisons, 1 hospital and small catering establishments. Now the fish population has increased dramatically with fair numbers of trout and salmon parr.
I decided to do this project on this river to examine its fishery potentials as it has not been electro fished for many years. Also to compare water quality parameters with recent years parameters (www.epa.ie) before the waste water treatment plant was upgraded to see how much of an improvement it is having on the rivers water quality. I am also sampling for benthic macroinvertebrates to see what is present in the River Triogue.
Materials & Methods
Sites for this survey were chosen by taking one sample, upstream from sewage treatment discharge, one at the discharge point and two sites downstream of the sewage discharge. The exact location was recorded at each site using a Garmin GPS model. These sites were used for sampling water quality, macroinvertebrates and fish stock assessment.
Site 1 – GPS S4661 9955, was located upstream of the sewage treatment plant discharge. The bank width was 5 meters and the wet width was approximately 4 meters. The average depth was 20 centimetres. The water had a slight colour on the day and the water velocity was moderate with a riffle/glide flow. The water clarity was clear. The substrate had a stony bottom which was loose and consisted of cobble, gravel and fine gravel. There was evidence of a human crossing point at this location and the litter was abundant. At this site the gradient was more pronounced and the channel was drained in spring 2010.
Site 2 – GPS S4661 9961, was located at the sewage treatment discharge point, 250 metres downstream from site 1(Table 2.1). The bank width was 7 meters but the wet width was approximately 5 meters on the day. The average depth was 35 cm. The water velocity was increased due to the outflow of effluent from the discharge. The water colour was slight but clarity was clear. The flow was a slow glide. The substrate was mixed containing cobble, gravel, fine gravel and had moderate siltation. There was no shading and litter was moderate. The water depth was much deeper here than site 1.
Site 3 – GPS S4649 9992, was located 310 metres downstream from site 2.
The bank width was 7 meters and the wet width was 6 meters. There was an average depth of 30 centimetres. The stream flow sequence was riffle and glide, the water velocity was moderate. The water had a slight colour but clear clarity. The substrate was loose and consisted of cobble, gravel and fine gravel. There was a slight build up of mud on both banks. The main land use was pasture.
Site 4 – GPS N4639 0062 was located further downstream approximately 900 metres from site 3. The bank width was 9 meters and the wet width was 7 meters. The average depth was 15 centimetres. There is a storm water discharge located at this site but there was no rain on the day, so had a moderate flow. The water clarity was clear and had a slight colour. The substrate was mixed and also loose containing cobble gravel, fine gravel and silt. The stream sequence was riffle/glide flow. This was an abraded channel and was very shallow. The bank was poached by cattle and there was no fencing in place.
Physical and chemical data was collected from the four sites on the 20th June 2011 and the 14th of July 2011. The physical and chemical data was collected and recorded by going to each site and observing the surrounding such as plants, trees and land use. River depth was recorded using a meter stick and river width was taking using a measuring tape. Disposable gloves were used for health and safety reasons due to the sewage treatment plant discharge. A kick sample was done using a net and 3 Stone washes were done using small brushes at each site and macroinvertebrates were obtained in buckets and identified at home using a microscope, then put in tubes preserved in 70% ethanol. The location of each site was recorded using a GPS. Water quality readings were taken using the following a Hach HQ30D (Dissolved oxygen meter), a Hach sension 5 (Conductivity meter) and a Hach sension 1 (pH meter).
Sampling for benthic (bottom) macroinvertebrate was carried out on the 20-06-11. The abundance and diversity of these organisms give us overall information on the productivity of the stretch of river sampled. Macroinvertebrate sampling is an effective method used in a range of fisheries applications. It gives information on the availability of food for fish and also the quality of the habitat. These are affected by a number of factors such as geology of the area, substrate type, dissolved oxygen tree growth in the riparian zone, land use in the surrounding area, time of year and also the presence of riffles, pools and glides and water levels. The most sensitive macroinvertebrates are always found in a riffle area so samples should be taking from here.
Two methods were used for sampling, which are:
(1) Standard two minute kick
(2) Stone wash
Two methods were used in order to asses the water quality of the stream. The first method used was the Environmental Protection Agency (EPA) biological quality rating system (Flanagen and Toner, An Foras Forbartha 1974). The second method was the small stream rick score (SSRS)(Walsh2005).
Biological Quality Rating System (Q rating /value)
This is an Irish River Quality scheme which was developed in the 1970‘s by Flanagan and Toner for the first national survey of Irish rivers. The Q index is a system in which the relationship between water quality and macroinvertebrates can be assessed. This is achieved by dividing invertebrate taxa into five different classified groups. These groups are as follows; group A, the sensitive forms, group B, the less sensitive forms, group C, the tolerant forms, group D, the very tolerant forms and group E the most tolerant. Once you assign your sample into these indicator groups, water quality can be determined by comparing the data with what might be expected from a polluted river.(www.EPA.ie/waterqualityreport) The EPA carry out Q index surveys as part of the monitoring programme for the EU Water Framework Directive(www.EPA.ie) (Water framework directive monitoring programme).
There is also intermediate categories such as Q3/4 that many rivers fall into due to organic pollution, this may happen due to agriculture when fertilisers enters the water through surface run off when it rains many sensitive macroinvertebrates move away from that part of the river and the less sensitive forms take over that area of the river.
Using this system has a number of advantages over other systems in that;
Macroinvertebrates can be easily acknowledged and put into categories according to their sensitivity to organic pollution.
Sampling is easy as it only requires a kick sample and a stone wash.
The system was introduced in Ireland with Irish species in mind.
This system will show any dramatic changes such as heavy pollution, from sampling the benthic macroinvertebrate from year to year.
Small Stream Risk Score (SSRS)
The SSRS is a risk assessment which is based on a biological monitoring programme. The Water Framework Directive monitoring surveys carry out this assessment as part of their biological classification of catchments. The system was developed based on the presence of indicator mayfly species, stonefly species, caddisfly larvae and the abundance of gastropods, oligochaetes, dipteran larvae and Asellus( water hog louse). An abundance category of 1-2 is given when the number of taxa is 1, this will give an index score of 4. When there are 2 + taxa there are 3 different abundance categories which have different index scores for different macroinvertebrates communities. The overall index score for the five groups is added up then divided by 5. The figure is then multiplied by 2 and this is your small stream risk score.(www.shannonrbd.com)
The stream can then be assessed by comparing the score against the following categories:
Macroinvertebrate field work
(1) Standard two minute kick sample – Walk into the river and place the net at the bottom of the river with the open side of the net facing the flow, time a two minute kick sample kicking vigorously at the bottom of the river towards the net. Put a small amount of water into your tray and empty contents of your kick sample into the tray. Water is added so macroinvertebrates will be easily seen as they will swim in the small amount of water. Pick macroinvertebrates from the tray and place in the bucket with a small amount of water.
(2) Stone wash – Carry an empty bucket into the river, pick up a stone and place it into the bucket. Add a small amount of water to the bucket then pick up the stone and brush of any macroinvertebrates present, look closely to see is there any cased caddis stuck to the rock. Repeat this procedure five times with each stone being small enough to pick up with one hand.
All macroinvertebrates were identified and counted. Samples of each were placed in tubes preserved in 70% ethanol and labelled.
Fish stock assessment
This river was last electro –fished many years ago, there is a massive improvement in the fish stock population throughout this river, all fish looked healthy and looked like they were feeding well this may be due to the new sewage treatment plant.
The electro – fishing of the 4 sites was carried out on the 14th of July 2011. All equipment was disinfected before any fishing was done. Conductivity was measured first of all. Conductivity readings were taken by walking into the river and placing the meter in the river until it stabilises then you have your reading. Conductivity in water means the ability of the water to pass an electrical current. This is a very important step that has to be carried out before electro-fishing as the voltage has to be set so the fish are just stunned and not killed. The fish are less conductive than the water and threshold response values from the fish are lower. Streams with low conductivity need high voltage. In general as fish get longer they are more easily caught this is because they get greater stimulation as they have longer nerves. Also larger fish are easier to see and therefore caught.
John Flynn and Michael Byron from Inland Fisheries Ireland supplied the gear for the fishing, because I did not have a licence to use the electric fishing set, so it was a team effort on the day, I measured the size of each fish caught.
Each site was fished for 5 minutes (Standard Method for WFD monitoring) covering 20 metres of the river, the area of each site approximately 130m². All fish types and lengths were recorded at each site.
Physical and chemical results
All sites were located on the river Triogue. The Bank widths and wets were similar at site 1, site 2 and site 3. Site 4 was a lot wider but shallower. The conductivity was recorded at all 4 sites twice, with the first being taken on the 20th June and the second was recorded 14th of July 2011. Water temperature was also recorded twice on the same dates and range from 13-16º.
From these results on the 14-07-11 of conductivity from site 2 you can see the sewage treatment plant discharge increases the conductivity enormously.
Site 2 Riparian zone plants
All riparian zone plants were the same at this site except for an invasive specie called Himalayan balsam (Impatiens glandulifera) this is an unwanted plant in Ireland, as it causes a threat for competition with our native plants. This plant’s flowering takes place from June- October. When the flower dries seed capsules emerge where the flower was on the plant and the slightest touch causes the seeds to disperse up to 20 feet from the parenting plant, seeds are capable of further dispersal by water and animals and human aid. Due to the plants nature it should be removed chemically rather than physically to stop it spreading any further.(www.invasivespeciesireland.com)
Site 2 in-stream plants
All in stream plants from previous site 1 were also the same at this site except for starwort. (Callitriche) and cladophora.
Site 3 Riparian zone plants
All other plants were the same in the riparian zone as at site 1 except there was no Himalayan balsam.
Site 3 In Stream plants
Site 3 had moderate vegetation in stream along with in-stream plants from site 1 and 2 it also had water cress present.
Site 4 Riparian zone plants
Site 4 had the same plants as previous sites along with nettles and white clover.
Site 4 in stream plants
At this site there was not as many plants in stream with only the algae cladophora and the plant Veronica.
In site 1, the total number of Ephemeropteras present in group 1 (3 tails) was 3 taxa with an abundance of 7 +, this gives a total index score of 8. There were no Plecoptera at any of the sites. There were 2 Trichopterans taxa present, with an abundance of 7+ this gives an index score of 4. From group 4 “Gold”, 5 taxa were present with an abundance of 7+ and an index score of 0. There were 8 Asellus found at this site giving an index score of 0 as. The total score for all 5 groups was 12, this is divided by 5 to give an average of 2.4 then multiplied by to get a SSR Score of 4.8 which categorised this site as “at risk”. When combining the Small Stream Risk Score with the Q rating, the river triogue has moderate Water Framework Directive status with slight pollution mostly being organic pollution due to the waste water treatment plant this being a point source so can be easily monitored. There is also non- point sources of pollution in this river due to agriculture, this is not as easily monitored as it may come from many places. These sources of pollution are surface run off from farms and fields due to heavy rainfall and also livestock waste entering the river due to no fencing in place. All these organic pollution sources have high levels of nitrogen and phosphorus this will lead to eutrophication which may deoxygenate the river, leading to fish kills. Organic pollution is the most widespread pollution source in Ireland , this occurs due to the excess of organic matter, such as manure or sewage enters the water, when organic matter increases decomposers also increase and will breakdown this organic matter and may cause oxygen depletion in the breakdown stage.
Site 2 Risk score combined with Q value
In site 2 the total numbers of Ephemeropteras were 2 taxa with an abundance of 7 +, giving an index score of 8. The total number of Trichopterans present in group 3 was 1 taxa with an abundance of 3 and an index score of 4. From group 4 “Gold” 5 taxa were present with an abundance of 7+ and a index score of 0. Asellus scored an index score of 0 again. The total score for 5 groups was 12 just as site 1 was with a final score of 4.8 which categorised this site as “at risk”. Combining this with a Q value of 3-4 classes the river as slightly polluted with a moderate Water Framework Directive status. Eutrophication has taken place at this site and it can be clearly seen due to the abundance of algae and green plants at this site, this is due to the nitrogen and phosphates coming from the discharge.
Site 3 Risk score combined with Q value
In site 3 the total number of Ephemeropteras present was 3 taxa with an abundance of 7+ and an index score of 8. There were 3 Trichopteran taxa present with an abundance of 7+ and an index score of 4. From the “Gold” group, 4 taxa were present with an abundance of 7+ giving an index score of 0. In group 5, only 3 Asellus were in my sample, this fits into the abundance 1 category with an index score of 2. The total score of all 5 groups was 14 and a average was then got just like the last site and then multiplied by 2 giving a final score of 5.6 which also categorises this site as “at risk”.
With a Q value of 3-4 and a “at risk” Small Stream Risk Score, again this has a moderate Water Framework Directive status and is slightly polluted, this is considered unsatisfactory as the game fish are at risk as oxygen depletion may occur in the summer months when flow levels are low and temperatures are elevated.
Site 4 Risk score combined with Q value
In site 4 , 2 taxa were present from Ephemeroptera, with an abundance of 7+ and an index of 8. There were 2 Trichopteran taxa present with an abundance of 6 and an index score of 8. In the “Gold” group 3 taxa were present with an abundance of 7+ and an index score of 0. Asellus scored an index score of 0. The total score of 5 groups was 12, giving an average of 2.4 and a final score of 4.8 which categorised the site as “at risk”. Combining this with Q value of 3-4 the game fish may be at risk in the River Triogue particularly in the summer months. This also has a moderate Water Framework Directive status with slight pollution.
Fish Stock Assessment
No eels or 0+ trout were caught on any of the 4 sites , site 1 had the most stone loach a 2+ trout, 1+ trout was the most common age with a total of 13 and, site 2 and 3 had the most 1+ trout, site 4 had the most salmon parr and the most minnow.
Site 1 had a total area of 100m² and produced a total of 5 trout ranging from 17.5 cm – 27cm, 3 trout were classed 1+ with the remaining 2 classed 2+. There was 3 salmon parr caught ranging from 5.5cm – 7cm .There were 6 stone loach captured ranging from 6.5cm – 7cm , there was also 2 minnow captured measuring 5cm and 2 stickleback measuring 3.5cm and 4.5cm. This gave a total of 18 fish at site 1.
Site 2 had a total area of 140m² producing a total of 5 trout all being 1+ ranging from 15cm – 18.5cm. There were no salmon parr captured at this site. 5 stone loach were caught ranging from 7.5cm – 9cm. Only 1 river lamprey was caught from all sites and it was at site 2, this lamprey looked like it had a tumour or a disease of some sort and it was 14.5cm in length. There was 2 minnow captured measuring 6cm and 1 stickleback was caught measuring 4 cm. This gave a total of 14 fish at site 2.
Site 3 also had a total area of 140m² producing a total of 6 trout ranging from 16.5cm – 20cm, 5 of these trout were classed as 1+ and 1 trout was 2+. There was 2 salmon parr captured measuring 5.5cm and 6 cm, there was also 2 stone loach captured being 1.5cm and 7cm. 7 minnow were caught ranging from 4.5cm – 6cm. Only 1 stickleback was caught at this site being 5.5cm. A total of 18 fish were caught at this site.
Site 4 had an area of 180m², no trout were caught at this site but 14 salmon parr were captured ranging from 4.5cm – 8cm. There were 2 stone loach caught being 7.5cm and 8.5cm, 9 minnow were caught between 4.5cm – 6cm and 4 stickleback were caught ranging from 1.5cm – 3.5cm. This site produced the most fish with a total of 28 and half of these fish caught were salmon parr, so this site also produced the most salmon parr mainly due to its very shallow water with a riffle/glide flow.
The River Triogue is a tributary of the river Barrow, it flows into the river Barrow just outside Mountmellick near a town called Clonterry. The substrate type at each site was mostly cobble, gravel and fine gravel, which is the type of substrate salmonids like to spawn in. The flow consisted of riffle/glide at site 1, 3 and 4 while there was a slow glide at site 2. None of the banks at any of the sites were fenced off, as a result livestock can enter the stream. Site 1, 2 and 3 looked like there were cattle in the field in recent years but there was none in the field at the time of sampling. Site 4 has cattle close by and they had access to the stream, this is not good for the river as the cows waste has high nitrogen and phosphorus levels which cause excessive plant growth which may lead to eutrophication and oxygen depletion and also has high BOD levlels which has organic carbon this also causes oxygen depletion in the river the waste also has to be broke down by the decomposers which also causes oxygen depletion, none of this is good for the river, the banks were poached at this site by the cattle.
Temperature and dissolved Oxygen (DO)
The water temperature readings taken at each site ranged from 13ºC – 16°C permissible. The DO readings taken, ranged from between 9.76 mg/l and 10.43 mg/l with % saturation varying from between 94.5%- 106.8%. These readings are considered allowable under the Salmonid water regulations 1998 and the Fresh water Fish Directive (78/659/EEC).
The Freshwater Fish Directive(78/659/EEC) and the Salmonid water regulations 1998, both state a mandatory limit value between 6.0 and 9.0 for salmonid waters (EPA 2001). It is very unlikely that salmonid species cannot survive outside these pH levels. The readings for the 4 sites ranged from 7.8-7.9 and are considered to be in the neutral range for salmonids.
Conductivity indicates the amount of dissolved solids present in the water and also an indicator of the range in which alkalinity and hardness values are likely to fall. While the freshwater Fish Directive (78/659/EEC) and Salmonid water regulations 1998 do not set out any parameters for a mandatory limit value but the surface water regulations 1989 set a mandatory limit value of 1000 uS/cm. The values on these 4 sites were between 548uS/cm -1115uS/cm, all sites were below the limit except for site 2 where the discharge enters the river. This reading was only above the mandatory limit when taking the second reading ., conductivity levels are changing all the time from where the discharge enters the river (www.fivecreeks.org/monitor/cond.html) which is not good for the salmonids. (www.Epa/parametersofwaterquality.ie) This is probably why no salmonids were found at this site, due to salts in effluent discharge which will increase conductivity.
Riparian zone and in stream plants
Site 2 was the only site with a lot of in-stream plants and cladophora mostly around the waste water treatment discharge to the river triogue, such effluents may have high nutrient levels at times and are changing all the time this is probably why the plant growth was excessive at this site. All other sites had a small numbers of in-stream plants and site 4 was the only other site with cladophora.
Site 1 – Sampling at site 1 produced a total of 13 different species comprising of 87 individuals. From group A, the most sensitive, 2 taxa were recorded. The Ephemeroptera (mayflies) present were Ecdyonurus and Heptagenia, both from the heptageniidae family. Site 1 was the only site where Heptagenia was found, probably because this was the only site sampled upstream from the sewage treatment plant discharge to the river Triogue, Heptagenia are pollutant intolerant, whereas other species of Ephemeroptera can resist small amounts of pollution such as Caenis. Their was no Plecoptera found at any of the 4 sites. In group B the less sensitive, only 1 taxa was found. This was the cased caddis Limnephilidae , Limnephilidae build their case out off small minerals and particles of gravel from the stream bottom. The larva is able to cement the particles together with a sticky silken thread that lines the inside of the case (www.utahoutdoors.com/flyfishing/patterns/limnephilidae.htm) In group C the tolerable group, 5 different taxa were recorded, from the Ephemereroptera , Caenis, commonly known as the anglers cursewas found to be present. A Caseless caddis , Hydropsyche was scarce. The dipteran Chironomidae informally known as chironomids or non- biting midges were found to be scarce, the fresh water shrimp Gammarus was also scarce. Potamomophyrgus was present at this site, this also known as Jenkins spire shell or New Zealand mud snail. Simulidae and Asellus were found present from the very tolerable group D. From group E, Tubificidae were present these aquatic annelids are usually abundant in organically polluted waters.
As group A has 2 taxa present, group B has only 1 taxa present, group C has 5 taxa being scarce – present with none excessive and D and E are present in small numbers, this site was given a Q value of 4. Other qualifying factors that assigned this site to a Q value of 4 are sewage fungus and other slime growths were absent. Cladophora was absent and dissolved oxygen levels ranged from 80-120%.
Site 2 – Sampling in site 2 located at the sewage treatment plant discharge, produced a total of 10 different species comprising of 105 individuals. In group A, the most sensitive, only1 taxa was recorded, this was Ecdyonurus and was present in small numbers. In the less sensitive group B, only 1 taxa was present in small numbers again, this is probably due to the effluent outflow from the sewage treatment discharge. The tolerable group C, had a total of 4 taxa comprising of 48 individuals, Caenidae were common at this site which shows that they are a tolerant mayfly. The dipteran Chironomidae were found to be scarce. From the Hydracarina (water mites) Acari were present. The fresh water shrimp Gammarus was scarce with only 2 found. Jenkins spire shell was present in high numbers at this site. In group D, Simulidae were common, Asellus were present and Hirudinea were found to be scarce. From group E, Tubificidae were present in small numbers only, which I found surprising as I thought they would be abundant at this site, as they are commonly known to be found around sewage treatment plants discharge area and areas with poor water quality.
This site was assigned an intermediate Q value of 3-4 due to 1 group A taxon present in small numbers. Group B taxa were scarce. Group C had 4 taxa with 2 being present on high numbers and the others were common and scarce. Group D, had 3 taxa being scarce, present and common. Group E had one taxa present in small numbers.Other qualifying factors are, macrophytes and algal growth s were excessive, Cladophora was excessive. Substrate was silted and DO levels ranging from <80 – >120%.
Site 3 – Sampling in site 3 produced a total of 12 different species comprising of 129 individuals (Table 3.6) In group A, 2 taxa were recorded. Both Ecdyonurus and Rhitrogena were found to be scarce. In group B, 1 taxa was present, this was the cased caddis Limnephilidae. In the tolerant group C, 5 different taxa were recorded, Caenis were found to be present. Rhyacophila and Philopotamidae both Caseless caddis were scarce, there was also Chironomidae, Gammarus and Jenkins spire shell which were all found to be scarce. From group D, Simulidae were abundant while Asellus and Hirudinea were scarce. Tubificidae were scarce from group E.
This site was also given an intermediate Q value of 3-4, as group A had 2 taxa , group B had 1 taxa present, group C had 5 taxa being scarce – present. Group D is the only group that is not qualifying for the Q value of 3-4 as Simulidae are abundant and they should be common at maximum. Asellus and Hirudinea are scarce. Other qualifying criteria was substrate was slightly silted and DO ranging from <80 – >120% .
Site 4 – Sampling in site 4 produced 10 different species adding up to 82 individuals. In group A , 1 taxa was recorded, this was Ecdyonurus and was found to be present. The less sensitive group B only had 1 taxa , which was Limnephilidae and this was scarce. Group C had 6 taxa these being, Caenis was found to be present , Chironomidae was present in small numbers, while Acari, Gammarus and Planorbidae were all found to be scarce. Group D had 2 taxa, Asellus were found to be common and Pisciola were scarce and group E were absent.
As groups A and B had 1 taxa each, being present and scarce, group C had taxa that were present and scarce and group D had 2 taxa that were common and scarce while group E was absent. This site was also given an intermediate Q value of 3-4.
Site 1 achieved a Q value of 4, this is considered unpolluted and this water is classified as Class A according to the EPA Biotic Indices. It has a good game fisheries potential , fair water quality and satisfactory condition.
Sites 2,3 and 4 achieved an intermediate Q value of 3-4 which considered slightly polluted and this water is classified as Class B according to the EPA Biotic Indices. This has variable water quality, all game fish are at risk and the condition is transitionional.
Heptagenia was only found at site 1 which was the only site sampled upstream from the waste water discharge. Sites 2 and 3 had a small amount of silt on top the substrate while site 1 and 4 did not have any. The River Triogue’s Q values have not being consistent for the last 30 years, they have being changing all the time. The last time the River Triogue received a Q5 value was in 1971 and this was 1.6 km upstream of Portlaoise, the same year it received a Q value of 1 downstream of the discharge this shows how poor the sewage treatment was back then. In 1989 a Q value of 4 was graded upstream from Portlaoise and a Q value of 2-3 was given downstream from Portlaoise waste water discharge. In the 1997 a Q value of 4 was graded upstream from Portlaoise and again dropped due to the sewage treatment plant to Q 2 downstream of Portlaoise waste water discharge. In 2003 the Q value was 3 and this was upstream and downstream of Portlaoise waste water discharge.
Fish Stock Assessment
No 0+ trout were caught at any of the sites this suggests that they are spawning further upstream from where the samples were taken or that they are entering different tributaries from the river barrow to spawn. There was also no eels caught during electro fishing which I found surprising as I thought there would be many in the river, this may be due to decline in the eel population at this moment of time.
The River Triogue holds nice size 1+ and 2+ wild brown trout and stocks are good and fish are healthy. Portlaoise would not be the best place to fish due to sewage treatment plant and health and safety reasons, disposable gloves should be worn if fishing was to be carried in this area. The best places said for fishing is outside Mountmellick at Clonterry bridge this is where the Triogue meets the River Barrow and brown trout can be caught here, the odd salmon can also be caught at this location and all fishing methods work well here, however dry fly seems to catch the larger trout.
The River Triogue which flows through Portlaoise and Mountmellick before entering the River Barrow was listed as Ireland’s fifth most polluted waterway by the environmental Protection Agency in the year 2000. As Portlaoise town population grew rapidly during the late 90’s poorly treated sewage was entering the river and ruined the river on an almost annual basis.
In 1999 there was a fish kill of around 100 wild brown trout and that was the seventh fish kill there in 10 years, this fish kill occurred downstream of Portlaoise. The total fish kill is now up to 8 since 1989 and was almost an annual event during the summer months in the late 90’s. Mainly due to the waste water treatment plant poorly treated sewage of an overpopulated town. Mountmellick angling club said they would be prepared to restock the River Triogue, but the Eastern Regional Fisheries Board had stated that it was not policy to re – stock a river that had the potential to re- stock from indigenous sources. Re-stocking the river would not help it at all, stocked fish particularly if stocked in numbers can be one of the biggest threats to the wild fish. The stocking of a fish from a non indigenous source might over a period of time dilute the wild gene pool.
The larger stocked fish tend to displace the smaller wild fish. The fishery and its wild fish should be preserved and improved where possible, habitat can be improved and pollution can be prevented just these few things would be better for the river, instead of artificial stocking which would be a waste of money.
The last fish kill in the River Triogue was in 2007 and was not due to pollution. Killeen Civil Engineering were prosecuted by the Southern Regional Fisheries Board, Mr David Mc Inerney, Senior Fisheries Environmental Officer investigated a building site adjacent to the River Triogue, just upstream of Portlaoise, when he saw heavy machinery alongside the river. The river had been dried out by over pumping for a 55 metre stretch leaving dead and stranded trout, juvenile Salmon, Lamprey, Crayfish Minnow and Eels in the dried out river section.
With the new and improved sewage treatment plant in place, the Triogue river system will improve as time progresses. There is high numbers of trout in the river and all looked healthy so this suggests the river is not at serious risk but maybe recovering from serious pollution. Looking at laois county council results the dissolved oxygen levels are over 8 mg/l since the waste water treatment plant was upgraded and dissolved oxygen levels are now better downstream according to their results. There was a very high reading for ammonia in May 2008 downstream which was 9 mg/l this is very dangerous for fish as it can cause stress and damage their gills, which may lead to fish kills. The physical aspects of the river triogue stream indicate it has potential as a spawning area for salmonids with suitable substrate such as gravel and fine gravel, and is also a nursery area as many salmon parr were captured during electro fishing. Relating to Q values from the past which were very inconsistent and changing due to the old sewage treatment plant, the river was one of Ireland’s most polluted rivers with many fish kills. Today the water quality has improved enormously thanks to the new waste water treatment plant, the river is at a recovery stage and the river should keep improving as time goes on having better water quality every year.
Fencing should be put in place at all 4 sites to prevent livestock entering the stream, banks from being poached and to prevent the introduction of fine sediments to spawning gravels.
Himalayan balsam should be chemically removed rather than physically, as it will keep spreading and spreading and will take over the banks leaving no space for other plants.
Water quality should be monitored routinely especially in the summer months as dissolved oxygen is at its lowest and in- stream plants/algae should be kept under control, if the fences were put in place this would help as livestock could not enter the stream and deposit their waste, farmers should also add water to their manure before spreading as this reduces it nutrient value so would not be as harmful to a river, if surface run off did occur. Farmers should have a proper storage facility for manure to ensure no rainwater will flood the area containing the manure, as this could contaminate any near by ground and surface waters, manure has high nutrients content particularly phosphates and nitrates, these nutrients can cause rapid in- stream plant/algae growth if a water body is contaminated with high levels of these nutrients, this may lead to eutrophication , due to this, high fish kills may occur in the summer months if there is to much in-stream plants/algae as this oxygen depletion this usually occurs at dawn, if a pollution incident happened at the same time the results may be devastating.
Environmental Protection Agency (2011) Available from www.epa.ie
EPD (2010), Available from www.gaepd.org
Greenhalgh, M and Ovenden, D, (2007) Freshwater Life Britain and Northern Europe, Pocket Guide. Collins
Iascach Intire (2011) Available from www.fisheriesireland.ie
Shannon RBD Project (2011) Available www.shannonrbd.com
I wish to express my sincere thanks to all the following people who assisted me with this project:
Dr Frances Lucy, Institute of Technology Sligo
John Flynn, Inland Fisheries Ireland
Michael Byron, Inland Fisheries Ireland
Oonagh Murphy, Laois County Council, Environmental Section
Colette O Rourke, Senior Staff Officer, Laois County Council, Environmental Section
William Walsh, Director of Eastern River Basin District Inland Fisheries Ireland