Protocol for the Use of an Objective Mesh Gauge for Scientific Purposes

A mesh gauge developed by C. J. W. Westhoff under the auspices of the ICES Comparative Fishing Committee became the standard gauge for research activities in ICES countries in 1962 (ICES, 1962). In 1998/1999 the ICES Working Group on Fishing Technology and Fish Behaviour (WGFTFB) identified the need to refine mesh measurement methodologies to take account of the wider range of twines and netting types used in the netting industry since 1962. To deal with this request ICES adopted Council Resolution 1999/2B02 and established the Study Group on Mesh Measurement Methodology (SGMESH) under the Fisheries Technology Committee.

SGMESH was active from 2000 until 2003 and reported its findings and recommendations in ICES Cooperative Research Report No. 266 (Fonteyne and Galbraith, 2004). The Study Group recommended that all parties concerned should adhere to the specifications defined in the report, whether they are scientists, fisheries inspectors, netting manufacturers, or fishers. As advice derived from selectivity data determines mesh size regulations, it is logical that all stakeholders should use the same system of mesh measurement. The principle of using a longitudinal measuring force to stretch the meshes (as in the ICES Mesh Gauge) was maintained but the measuring force was changed from 4 kgf to 40 N or 100 N, depending on whether the mesh opening is smaller than 55 mm or equal to or larger than 55 mm. Until an instrument capable of making objective measurements, not subject to human influence, with the new measuring forces became available, SGMESH recommended that for scientific purposes the existing ICES gauge with 4 kgf measuring force was to be used and that a conversion formula should be applied to deliver a mesh opening equivalent to that obtained using a force of 100 N.

The development and testing of an objective mesh gauge was the objective of the European R&D and Demonstration Project “Development and testing of an objective mesh gauge”, known as the OMEGA project (Anon., 2005). Scientists, fisheries inspectors, and netting manufacturers took part in extensive laboratory and field tests. As a result of these tests the measuring forces proposed by SGMESH were to some extent modified to correspond better to current mesh measurements practices by fisheries inspectors and netting manufacturers. Information on the project’s progress and results was presented to WGFTFB to consider the new mesh gauge as a possible new standard. At its 2005 meeting WGFTFB recommended that the OMEGA mesh gauge be used as the new standard mesh measurement tool for scientific studies (ICES, 2005). This recommendation was confirmed by the Fisheries Technology Committee (FTC) at the ICES Annual Science Conference held in Aberdeen, Scotland, UK, from 20–24 September 2005. FTC also recommended that the “Protocol for the use of an objective mesh gauge” be published in the ICES Cooperative Research Report series and strongly recommended the use of the OMEGA gauge by the other stakeholders, in particular organisations responsible for control and enforcement in the Northeast Atlantic. ICES adopted these recommendations (C.Res. 2005/1/FTC08, 2005/4/FTC01, and 2005/4/FTC02).
An objective mesh gauge measures the opening of a mesh by stretching it between two jaws until a set force is reached. The key feature of such a gauge is that manual force is not used to stretch the meshes. Force is applied by an internal mechanism. Thus the measurement made of the opening of a mesh is independent of the operator. Extensive trials of such a gauge showed it to be suitable for use on both active and passive fishing gears by:
a ) fishery inspectors to enforce the conservation regulations;
b ) scientists to study mesh selection;
c ) net makers to check mesh sizes during the manufacture of sheet netting;
d ) fishers to check that their nets conform to the regulations.
An objective mesh gauge, suitable for use in all branches of the fishing industry, provides a common standard of measurement and assists the integration of the scientific, industrial, and enforcement aspects of fishery management. It should ensure that all inspectors will obtain the same values of mesh size and that netting supplied to fishers will not subsequently be found to be undersized. It will also be possible to manufacture netting with exactly the mesh sizes requested by customers. Fishers will be able to check mesh sizes before and during fishing operations using the same objective method as the inspectors.
Detailed background information on the technical aspects of objective mesh gauges is given in Annexes 1 to 5.