INSTITUTE : MARINE INSTITUTE OF IRELAND
AUTHOR: N. Ó Maoiléidigh
Name of experiment (English):National Microtagging and Tag Recovery Programme
ID code: A02, Marine Institute
Financial source: Exchequer
Annual cost (ECUs): 150,000
Year experiment began (begins):1980
Year experiment ends (ended): Ongoing
Geographic distribution: 4
Stock assessment (input to models): 1
Harvesting (e.g. exploitation):3
Avoidance behaviour (e.g. water quality, disturbance):8
Behaviour at obstacles (e.g. dams, barrages etc.):6
Monitoring (of what ?): exploitation rates 9
SPECIES (Latin): Salmo salar
MAX_SIZE: 25 cm
AVR_SIZE: 14 cm (total length)
type of (primary) tag/mark: Code Wire tag
type of secondary tag/mark (double tagging): Finclip
Site of attachment of (primary) tag: Nose cartilage
Site of attachment secondary tag (in double tagging): Adipose fin
Method of attachment of (primary) tag: Microtag injector
Method of attachment secondary tag (in double tagging):
MS 222: 1
Faroes, Greenland, Irish Coast, Irish lakes/Rivers
NUMBER OF TAGS RELEASED (mean_year, primary tag): 300,000
GENERAL_TAG_RECOVERY RATE(%/year): 3%
REWARD_CURRENCY: IR P
METHOD NAME(Name of the method used in experiment): Coded Wire Tagging
Materials and methods
CWT tagging and recovery of tags - Up to 300,000 hatchery smolts are coded wire tagged annually between September and February in seven Irish rivers(CWT11) and subsequently released in April. Wild smolts are tagged in the River Corrib in the West of Ireland while migrating to sea in May. A 1 mm long magnetised tag etched with a specific batch code is injected into the nose cartilage of the juvenile fish. The code identifies the origin and release circumstances of any fish subsequently recaptured. All fish are anaesthetised when tagged. The adipose fin is removed to facilitate the identification of these fish in the recovery programme. A quality control check is made on the tagged fish to ensure that the tag has been correctly magnetised. Tagging mortality and tag loss is also estimated and subsequent analyses are based on the numbers of fish migrating rather than the number of fish tagged. Fish can be transported and released by truck or in some instances using helecopters.
International co-operative scanning programmes are carried out to identify tagged fish in the highs seas fisheries of West Greenland and Faroes. Catches from homewater fisheries (drift nets, draft nets, angling etc.) are monitored at 15 major salmon landing ports in Ireland each summer. Tagged fish are identified from the missing adipose fin. The tag is removed by coring the nose of the fish. The presence of the tag in the core is verified using a magnetic tag detector. Declared salmon landings in each of the corresponding areas are collected by the seven regional fisheries boards and compiled into a national date set by the Dept. of the Marine. Salmon landings are also provided by the Foyle Fisheries Commission and tag recovery information is supplied by the Dept. of Agriculture for Northern Ireland.
The number of tagged fish taken in these fisheries is estimated by multiplying the number of tags recovered in each fishery area by the ratio (raising factor) of the reported commercial catch in these areas to the sample size examined. There is also a substantial non-catch fishing mortality (NCFM) associated with these fisheries which includes all sources of losses from nets, natural mortality and non-reporting of catches. An estimate of NCFM is derived annually from local knowledge and experience. This can then be used to adjust the actual number of recovered tags to indicate the total stock available at the time. The percentage of the declared catch examined in this programme generally exceeds 50% and has been as high as 70%. For the purposes of this analysis it is assumed that the tags are randomly distributed throughout the fishery and that non-recognition or non-detection of tags is minimal. Exploitation is estimated by dividing the number of fish caught in a fishery by the number available to the fishery.
25. REFERENCES(only one or two):
Ó Maoiléidigh N., Browne J., Cullen A., McDermott T. and Keatinge M. (1994). Exploitation and survival of reared salmon released into the Burrishoole River system. Fishery Leaflet 161, Dept. of the Marine, Dublin.
Ó Maoiléidigh N., Browne J., McDermott T., Cullen A., Bond N., McEvoy B., O' Farrell M. and O' Connor, W (1995). Exploitation and survival of River Shannon Reared salmon. Fishery Leaflet No. 164, Dept. of the Marine, Dublin.
Ó Maoiléidigh N., Browne J., Cullen A., McDermott T. and Keatinge M. (1994) Exploitation of reared salmon released into the Burrishoole River system. ICES CM 1994/M:9.
Browne J., Ó Maoiléidigh N., McDermott T., Cullen A., Bond N., McEvoy B., O' Farrell M., and O' Connor W. (1994) High seas and homewater exploitation of an Irish reared salmon stock. ICES CM 1994 M:10.
Ó Maoiléidigh N., Browne J., McDermot T., Cullen A., Bond N., O’ Farrell M. and G. Rogan (1996) Marine Survival and Exploitation of Irish Salmon Stocks. Irish Marine Science Symposiam (eds. Keegan B. F. and O’ Connor R.), Galway University Press, University College Galway Ireland..
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