Definition, dynamics and stability of métiers in the Irish otter trawl fleet
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AbstractThe Irish otter trawl fleet operates in a complex multi-species multi-gear fishery, spanning a wide geographic area, and involving around 275 trawlers. Factorial and clustering methods were applied to 2003 fishing trip data to define thirty-three métiers. Definitions were based on six trip characteristics taken from logbooks, namely: fishing gear, mesh size, vessel length, species composition, area, and month. Métiers exploiting demersal species or species groups are characterised by single vessel bottom otter trawls, typically with mesh sizes of 70 mm or more, operating year round. This includes nine Nephrops dominated métiers highlighting the importance of this species to the fleet. Many demersal métiers are characterised by groups of species, such as mixed whitefish or slope species. Métiers exploiting pelagic species are often focussed on single species, and are typically seasonal, mid-water trawling (often paired) with mesh sizes less than 70 mm. Pelagic métiers account for the majority of landings by over an order of magnitude in several cases. Demersal métiers account for the majority of fishing trips and effort, (primarily Nephrops métiers), and vessels (primarily mixed species métiers). The new métier definitions were found to be appropriate remained relevant despite declining fleet landings and effort between 2003 and 2006. Species compositions within these métiers have generally remained similar to the proportions defined in 2003. These robust métier definitions present opportunities to improve fisheries sampling, assessment and management. Although métiers pose complexity challenge for such applications they can be used the building blocks for appropriate management units.
DescriptionNOTICE: this is the author’s version of a work that was accepted for publication in Fisheries Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Fisheries Research, [Volume 111, Issue 3, (November 2011)] doi: 10.1016/j.fishres.2011.07.005 http://www.sciencedirect.com/science/article/pii/S0165783611002505