Marine Institute Open Access Repository >
Marine Institute Community of Research Publications >
Irish Fisheries Investigations >
Irish Fisheries Investigations >

Please use this identifier to cite or link to this item: http://hdl.handle.net/10793/799

Title: A second assessment of the whelk fishery Buccinum undatum in the southwest Irish Sea with particular reference to its history of management by size limit
Authors: Fahy, E.
Masterson, E.
Swords, D.
Forrest, N.
Keywords: Whelk Buccinum undatum
Issue Date: 2000
Publisher: Marine Institute
Citation: Fahy, E., Masterson, E., Swords, D. & Forrest, N., “A second assessment of the whelk fishery Buccinum undatum in the southwest Irish Sea with particular reference to its history of management by size limit”, Irish Fisheries Investigations No. 6, Marine Institute 2000
Series/Report no.: Irish Fisheries Investigations;6
Abstract: Whelk landings in the southwest Irish Sea increased from 56 t in 1990 to 6,575 t in 1996 after which they stabilized between 3,600 and 4,600 t annually. At its peak the fishery supported approximately 80 vessels but this number has halved since. In 1994 a size limit of 50 mm was introduced for conservation purposes. Age based assessments of the landings were carried out in 1994, 1996, 1997 and 1999, for which purpose the fishery, ranging from 52º10’ to 53º30’, is divided into four sectors. Landings to the four sectors display biological characteristics which indicate the occurrence of a number of stocklets rather than a single stock unit. Whelk in the south west Irish Sea are relatively thin shelled and the fishery has a low density of large crustacean predators. There is no evidence of contamination by TBT. The northern and southern ends of the fishery have relatively lower densities of larger/older animals; the centre sectors have smaller whelk of shorter life span at higher densities, some of them showing symptoms of a Lee phenomenon and slower growth. A survey of cpue places heaviest densities on the Codling and Rusk Banks, in strong tidal currents, at depths of < 20 m. Growth and maturation rates vary among stocklets. L∞ ranges from 102 to 116 mm. Length at 50% male maturation is usually within the range of 63 – 68 mm and ages of 6.1-7.2 years although landings to one sector have a 50% male maturation rate of 83 mm and 8.5 years of age. The existing size limit of 50 mm would, at best, afford protection to 40% of spawning males. Compliance with the size limit has been poor. From 20 to 33% of total landings in any of the assessed years have been less than the legal limit and in 1994 51% of landings in one sector were below the acceptable size. Trends in cpue have been monitored since 1990 and some areas do not show any marked tendency. On the contrary, some fishermen in the centre sectors improved their yield between 1994 and 1998. There are two explanations for this: the movement of pots onto virgin ground and the fact that fewer fishermen are competing for landings in the same areas. Whelk have responded to a reduction in fishing effort since 1996 immediately following which mortality coefficients (Z) were highest (0.79); they declined to an average 0.61 in 1999. In terms of yield per recruit however they remain high. The southern sector of the fishery is regarded as being most depleted although very few subsize limit whelks were caught there. The survival of the whelk fishery in the southwest Irish Sea is attributed to the instability of the market which is dominated by a single customer, South Korea. A more effective size limit for this fishery would be 68mm (83 mm in the northern sector) and this is considered unrealistic, suggesting that alternative management measures will have to be considered.
URI: http://hdl.handle.net/10793/799
ISSN: 1649-0037
Appears in Collections:Irish Fisheries Investigations

Files in This Item:

File Description SizeFormat
Irish Fish Invest No.6 Assesment Whelk Fishery.pdf1.25 MBAdobe PDFView/Open
Use License

Items in the Marine Institute Open Access Repository are protected by copyright, with all rights reserved, unless otherwise indicated.

 

Valid XHTML 1.0! Marine Institute Copyright © 2011  - Feedback