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REPORT OF THE WORKING GROUP ON MACKEREL AND HORSE MACKEREL EGG SURVEYS (WGMEGS)

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posted on 2006-01-01, 00:00 authored by ICESICES
• The 2007 egg survey in Portuguese waters in January/February will now be configured as a DEPM survey, rather than AEPM as is the case for all other individual surveys. This is targeted on the southern horse mackerel. The samples will still be useable for the NEA Mackerel AEPM, but means that this area will have one coverage, albeit more intense, rather than the tow in previous years. The remainder of the area will be covered in five periods from March to July, in a pattern similar to previous surveys.• CEFAS have withdrawn from the survey. This entails the loss of one complete survey, and the loss of considerable experience in histological analysis. In addition CEFAS will no longer be able to provide adult mackerel at the start of the spawning season for fecundity estimation. The WG regret this decision, and hope that CEFAS may be able to review this at some point and return to the survey. The impact will be to decrease the accuracy of the survey and make it more vulnerable to operational exigencies.• The group identified clear evidence of declining fecundity in horse mackerel over the last 25 years based on samples taken at the start of the spawning season. Samples taken during the spawning season since 1995 confirm this trend. This may be linked to the low levels of recruitment in this species and to the mismatch between landings based assessments and the surveys.• The egg surveys in the North Sea in 2005 indicate a biomass for NS mackerel of 223,000 tonnes. This is equal to the highest in the time series (which was in 1983). It also confirms the increase seen in 2002. The distribution of spawning in recent years has concentrated along the UK coast, in contrast to the historical situation of spawning in the central part of the North Sea, west of Denmark. Combination of the NS with the main surveys in the west and south was examined and considered feasible.

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