Download - Institute of Fisheries Management

Fishing for a future- Studies of
Coregonus autumnalis (Pallas) in Lough
Neagh, Northern Ireland
Warren Campbell
Chris Harrod (QUB) Derek Evans (AFBI)
IFM Rare & Protected Species Conference 28 th March 2012

Lough Neagh
• Large (383 km 2 )
• Shallow (mean depth 8.9 m)
• Highly eutrophic
– Total P ca. 180 µg.l -1
• Long standing fishery (largely eel)
– 350 employed in 2010
– Co-operative owns fishing rights
• Unusual fish community
– Species of conservation concern
[coldwater]
• Pollan (Red list- vulnerable)
• River lamprey
• Brown trout
• Eels (Red list- critically endangered)
– Invasive & naturalised species [cool and
warmwater]
• Perch
• Roach
• Bream
• Gudgeon

Pollan (Coregonus autumnalis)
• Salmonid
• Glacial relict species
• Ireland supports only sub-Arctic population
– Known as the Arctic cisco
– Populations in Russia, Canada and Alaska
• Short lived (c.5yrs)
• Rapid growth rate
• Early maturing (2yrs)
– Consequently special case in fisheries management

Conservation value of Irish pollan
• IUCN red listed
– “Globally endangered”
• The only European vertebrate found uniquely in
Ireland
– All 5 European populations are Irish
• Lough Neagh described as having the last viable
population (Harrod et al, 2002)
• Irish populations have unique life history
strategy cf. rest of the world
– Wholly lacustrine, non-anadromous

Lough Neagh commercial fisheries
• Rights owned by Lough Neagh Fisherman’s
Cooperative Society Ltd.
– Created in 1965
• Perch
– Potential re-emergence with population
recovery, post crash due to overfishing
• Roach and bream
– Low value (31.5p/Kg) incidental fishery
• Pollan
– Medium value (£1.10/Kg)
– Most important fishery during 1 st half of 20 th
Century
– Last records kept suggest yield of 100-400
tonnes 1893-1914

PhD Aims- “An assessment of the fisheries potential
of Lough Neagh, Northern Ireland”
1. Characterise the
current status of the
fish community of
Lough Neagh to:
• Develop long-term
monitoring methodology
• Allow science-informed
management
• Investigate current and
future status of fisheries
2. Identify alternative
fisheries to that of the
declining eel fishery
• Inform diversification to
support rural economy and a
traditional way of life

PhD Research questions
• Fish community structure
– What is there? Is it consistent over time?
• Fisheries assessment
– What species are being harvested? How much?
– Provision of management advice under restricted eel
fishery, climate change
• Development of a standardised sampling
methodology for Lough Neagh
• Status of key species
– Pollan

Methodology
7 areas sampled every 7weeks
• Gill netting- European CEN
standard multimesh
• Draft netting- encircling of fish
with a net of known size - a
semi quantitative method
Parameters measured:
• Length & Mass
• Sex- Gonadosomatic Index of
maturity
• Age & growth-scales
operculae otoliths
• Diet- Gut contents
Lough Neagh sampling sites
BR - Ballyronan Bay
AR – Ardboe
WB – Washing Bay
CR –CranfieldBay
FL – Flats;
BA – Bartins Bay
LM– Lennymore Bay.

What is the current status of Lough Neagh
pollan?
Percentage composition
0 20 40 60 80 100
Perch Pollan Eel Brown Trout Roach Gudgeon Bream 3 spined stickleback River lamprey
Species

Population decline?
Comparison of draft netting catches
2006 (Inger et al) 2011 (present study)
Species Mean n ha ‐1 + 95% CI Mean biomass
(kg h ‐1 ) + 95% CI
Mean n ha ‐1 + 95% CI
Mean biomass
(kg h ‐1 ) + 95% CI
C. autumnalis 409.7 + 83.1 35.7 + 7.2 78.4 + 21.6 4.52 + 1.8
P. fluviatilis 76.7 + 14.4 2.9 + 0.5 136.7 + 34.3 2.9 + 0.7
R. rutilus 473.4 + 316.9 54.4 + 36.4 3.3 + 2.0 0.1 + 0.1
S. trutta 16.4 + 4.9 4.4 + 1.3 12.8 + 4.0 2.1 + 0.7
G. gobio 13.8 + 4.5 0.2 + 0.1 4.0 + 3.5 0
A. brama 20.8 + 10.9 21.2 + 11.1 1.1 + 1.1 3.9 + 6.2
A. anguilla 127.4 + 23.1 7.6 + 1.4 12.3 + 6 2.2 + 1.1
L. fluviatilis 3.3 + 1.5 0 0.2 + 0.4 0
G. aculeatus 8.8 + 7.8 0 0.6 + 0.7 0
Roach‐Bream
hybrid 1.2 + 1.1 0
0 0
• 81% decline in abundance within 5 years

Population decline?
Fork Length (mm)
50 100 150 200 250 300
1998 1999 2006 2011
Year
Temporal changes in pollan L F
• Pollan L F has declined (median values: 1999 – 231 mm;
2011 – 164mm).
• Cannot rule out overfishing of larger pollan.

Development of a monitoring programme for Lough
Neagh
Why?
• European CEN standard sampling
protocol using gill nets unsuitable for
Lough Neagh
– Too productive
– Too large
• Draft netting provides a quick estimate
of fish abundance, allowing sampling
on a larger scale than with gill nets
• Draft netting requires 1 day of suitable
weather conditions, gill netting requires
2 consecutive days
– Can occur infrequently on such a large
water body

Methods for a long term monitoring programme?
Draft and gill net comparisons
• Gill netting effort hampered by weather this season
– Not enough pollan samples to complete comparisons
• Harrod (2001) described no significant difference between pollan length frequency
distributions of multi-mesh gill vs draft net captured fish
– However, draft netting captured some small (

Methods for a long term monitoring programme?
Pollan larvae surveys
Pollan larva post-hatching
L T
=10.1mm (2/3/2012)
Pollan larva c. 20 days old
L T
=14.9mm(21/3/2012)
• Pollan are short lived
– Stock size dependant on strength of incoming year classes

Methods for a long term monitoring programme?
Pollan larvae surveys
• Towed Icthyoplankton net
– 1.5m x .5m mouth
– 1.5mm mesh size
– 3 tows/site each 1 min
– Flow meter attached, allowing
calculation of water volume sampled
and thus larval density
• Completed at 3 known spawning sites
– Weekly, during March/April Lough Neagh pollan larvae sampling sites
BR -Ballyronan Bay
CR – Cranfield Bay
LM– Lennymore Bay.

What is the growth rate of pollan larvae in Lough
Neagh?
Length (mm)
8 10 12 14
Density no./m 3
0.5 1.0 1.5 2.0
1 2 3 4
visit
Temporal changes in pollan larvae L T
1 2 3 4
visit
Temporal changes in pollan larvae density
• Hoped to use observed lengths, but mean length is being
suppressed by later hatching larvae
• Observation of just hatched larvae during all visits, and unexpected
increases in density with time confirm this
• Daily rings on otoliths instead?

Are there any differences in recruitment
levels between years?
• Early indications suggest
larger larval densities in 2012
than 2011
• Further sampling needed
• Tracking of cohorts postrecruitment
0 2 4 6 8 10 12
m3
Density
no./m 3
2011 2012
Year
20 day old pollan larvae densities at Ballyronan

Future status of pollan?
• Experiment to examine effects of temperature upon
survival to hatching of pollan eggs?
– Inform upon climate change effects
– Help describe factors impacting recruitment
• Decline in or restriction upon eel fishing
– Further fishing pressure on pollan
– Decline in illegal fishing of 0+ pollan for long line bait?
• More encouraging recruitment figures this year
– Addition of a strong year class?

Implications for management so far -1
• Data gained already influencing management
– Discussions with Lough Neagh Fisherman’s Cooperative Society Ltd.,
• Need a proper legislative framework tailored to inland fisheries in NI
– Limits on number of licences issued
– Current legal gill net mesh size 44mm
• Unenforced because too large for pollan capture
• Wilson (1973) caught no pollan in 45mm mesh nets
– Simply enforce existing legislation
• 230mm size limit- unenforced

Implications for management so far -2
• Further crack-down on illegal fishing
– Becoming a greater problem with increased
unemployment
• LNFCS needs to take control of scale fish fisheries
– Own rights, yet no interest in pollan harvest
– Fish merchants are currently allowed to buy fish
from fishermen
• Fishery anarchy!
• Means that we cannot quantify pollan catch
– Fish could realise a better price = less fish taken for
the same value
• Sold to fish merchant at £1.10/Kg
• Sold as pike deadbait, c. £5.50/Kg
• Uncontrolled fishery- threat
• Sustainably managed fishery- conservation benefit

Pollan- a special case in fisheries
management
• Fluctuating recruitment figures
• Stock size heavily dependant upon
recruitment
• May need a fluid management
strategy, so that fishing effort can
be controlled in relation to year
class strength
• Thankfully now a “hot topic”
– Inland fisheries, including that of
pollan, were discussed in a
Stormont session (21/2/12)
– Minister stressed need for study
and informed management plans

Acknowledgements
Funding from:
Department for Agriculture and Rural Development.
AFBI NI
Thanks go to:
Dr. Robert Rosell, Eugene O’Kane, Kevin Gallagher, Kenny Bodles, Dr.
Dennis Ensing, Peter Irvine, Sarah McLean, Lough Neagh Fisherman’s
Co-operative Society Ltd.