Warren Campbell

9 downloads 0 Views 1MB Size Report
Fishing for a future- Studies of. Coregonus autumnalis (Pallas) in Lough. Neagh, Northern Ireland. Warren Campbell. Supervisors: Dr. Chris Harrod (QUB).
Fishing for a future- Studies of Coregonus autumnalis (Pallas) in Lough Neagh, Northern Ireland

Warren Campbell Supervisors: Dr. Chris Harrod (QUB) Dr. Derek Evans (AFBI) IFM Rare & protected species conference 28th March 2012

Lough Neagh • Large (383 km2) • 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

• 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)

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 scale fish 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 1st half of 20th 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 is being taken? How much? – Management advice under loss of eel fishery, climate change • Development of a standardised sampling methodology for LN • 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 – Cranfield Bay FL – Flats; BA – Bartins Bay LM– Lennymore Bay.

60 40 20 0

Percentage composition

80

100

What is the current status of Lough Neagh pollan?

Perch

Pollan

Eel

Brown Trout

Roach

Species

Gudgeon

Bream

3 spined stickleback River lamprey

Population decline? Comparison of draft netting catches 2006 (Inger et al)

Species

Mean n ha-1 + 95% CI

2011 (present study)

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

0

0

Roach-Bream hybrid

1.2 + 1.1

0

• 81% decline in abundance within 5 years

200 150 50

100

Fork Length (mm)

250

300

Population decline?

1998

1999

2006

2011

Year

Temporal changes in pollan LF

• Pollan LF 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 –

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 (