River Barrow Survey 2015
Inland Fisheries Ireland undertook a catchment wide electrofishing River Barrow Survey
during the summer of 2015. The study surveyed 35 sites on the River Barrow main channel and
canal cuts and 118 sites in 21 sub-catchments. The main aim of the River Barrow survey was to determine the
current status of fish stocks within the catchment. This is the first large scale catchment wide survey
undertaken in the River Barrow catchment to assess the status of all fish species present.
The River Barrow is Ireland’s second longest river after the River Shannon. It is approximately 192km in length from source to sea and drains a large catchment area (3010km2). The river is navigable from Athy, Co. Kildare to the tide at St. Mullin’s, Co. Carlow (approximately 65km of navigable waterways).
Electrofishing was the method used to obtain a representative sample of the fish assemblage in each
site. The methods used were in compliance with European standards for fish stock assessment. All
fish captured were identified to species level and counted. Fish lengths and weights were taken and
scales were removed from a subsample of species from each site. After processing all fish were
returned to the river. Subsequently fish were aged and growth was determined in the IFI laboratory.
Information collected during the course of this survey provided information (e.g. distribution and
abundance) on the different life stages of brown trout, Atlantic salmon, coarse fish species and pike.
A total of 12 fish species and one hybrid were recorded in the River Barrow Survey main channel sites, with
a total of 4070 fish being captured. Dace and roach were widely distributed throughout the main
channel being recorded at 91% and 80% of the sites surveyed respectively. Dace ranged in length
from 2 cm to 26 cm and were aged from 0+ to 7+ years, while roach ranged in length from 1.5 cm to
29.8 cm and ranged in age from 0+ to 9+. Atlantic salmon were present at 57% of the sites surveyed
on the main channel. The abundance of juvenile Atlantic salmon numbers was generally low in the
main channel. A small number of adult salmon were also recorded between Athy and St. Mullin’s.
These fish ranged in length from 49 to 73 cm and were age 2.1 or 2.2 (i.e. fish that that had spent
either one winter at sea (grilse salmon) or two winters (spring salmon) at sea). Brown trout were
only recorded at 46% of the main channel sites surveyed. While not present in large numbers at any
site surveyed the overall population appeared balanced.
The largest brown trout recorded was aged 3+, 36.8cm in length and weighed 575g. Perch were well distributed (74%) throughout the River Barrow main channel though their numbers were generally low. Pike were present at 54% of sites surveyed on the main channel and in general their abundance was low. They ranged in length from
8 cm to 92 cm and were aged from 0+ to 6+. Other fish species recorded during the survey were
minnow, gudgeon, European eel, stone loach, 3 spined stickleback and flounder. Roach x bream
hybrids were also recorded. Minnow and gudgeon were widely distributed throughout the sites
surveyed, while European eel were only recorded at 15 sites. Simple linear modelling revealed that
there was a degree of spatial segregation amongst the four main fish species (dace, roach, juvenile
salmon and brown trout) captured in the river during the survey. This has resulted in brown trout
and juvenile salmon being largely confined to the faster flowing, non-navigable river sections
downstream of the weirs. While the situation is less clear cut for roach and dace, the former species
was more prevalent in the canal cuts.
Bream were not recorded in the current survey. The reason for this is unclear; however a small
number of roach x bream hybrids were recorded, therefore the presence of juvenile hybrids
throughout the main channel suggests that spawning populations of bream are still present. More
extensive sampling within localised areas might provide further information into the status of this
important coarse angling species in the River Barrow.
A total of 6631 fish and fifteen fish species were recorded across the 83 sites surveyed in the River Barrow Survey. Brown trout and Atlantic salmon were the most common fish species recorded; brown
trout were well distributed while salmon were less so. Key sub-catchments for brown trout
spawning would appear to be the Pollmounty, lerr, Owenass and Douglas (Laois), but notable
spawning was also observed at sites in the Greese and Madlin rivers. Important brown trout nursery
waters, as highlighted by a relatively high density of 1+ and older fish, include the Dinin, Mountain
and Stradbally rivers but there was also a notable site on the Owenass River. The most productive
systems for Atlantic salmon spawning, as highlighted by the presence of salmon fry (0+), were the
Monefelim, Burren, Douglas (Laois), Greese and lower reaches of the Pollmounty rivers. Salmon
nursery waters included the Duiske, Aughavaud and Monefelim rivers. The most unproductive rivers
for brown trout and salmon were the Figile and Philipstown rivers. Poor water quality, poor habitat
and possibly competition from coarse fish species, particularly dace are the main reasons for this.
Dace were mainly present in the lower river reaches of rivers in the upper catchment such as the
Triogue, Cushina, Slate, Figile, Owenass and Tully. Coarse fish species, pike and perch were also
poorly represented in the sub-catchments. Lamprey sp. were recorded in 18 sub-catchments, while
eel was recorded within 17 of the 21 sub-catchments. Minnow and 3 spined stickleback were also
present at some sites.
The current study is the first large scale catchment wide survey undertaken in the River Barrow
catchment to assess the status of all fish species. However, there are still some knowledge gaps in
relation to certain species in the River Barrow catchment. For example, what contribution does each
tributary catchment make to the over-all brown trout population of the River Barrow main channel.
It is also not known how many tributaries contribute sea trout to the river. In addition the
interactions between brown trout and the invasive dace are not fully understood and it is unclear
about the status of bream in the catchment.
READ THE FULL SURVEY HERE >>>>>