Workshop on Adult Egg Production Methods Parameters estimation in Mackerel and Horse Mackerel (WKAEPM)

The Workshop on Adult Egg Production Methods Parameters estimation in Mackerel and Horse Mackerel (WKAEPM) looked at the imprecision between institutes when processing survey samples. A number of protocol improvements were proposed, and these will be in place prior to the adult parameter analysis in 2022.

A calibration exercise was carried out prior to the workshop using standard mackerel and horse mackerel egg survey (MEGS) protocols. A second exercise was conducted during the workshop using a newly developed SmartDots module. Subgroups dealt with issues regarding annual egg production method (AEPM) and daily egg production method (DEPM) and added their recommendations to the manuals.

Descriptions for spent and massive atresia terms used during the screening process were redefined by adding further text and higher quality images into the ICES Survey Protocol Manual for the AEPM and DEPM estimation of fecundity in mackerel and horse mackerel (SISP- 5). Differences were noted in post ovulatory follicle (POF) and early alpha atresia identification, showing the difficulty associated with this work. In fecundity samples, there was high variance when identifying small oocytes close to the 185µm size threshold. It was recommended to have all fecundity samples analysed by two readers, and new criteria for the measurement of small oocytes were agreed. In atresia analysis, high variance was observed in both point and profile counting. High-resolution images are essential for this work, thus in 2022 slide scanner pictures will be taken for atresia analysis and will be sent around to all labs. There is still poor consensus on POF staging. Misclassifications between recent POFs and artefacts have now been clarified. Recent POF stages are used in spawning fraction estimation thus it is vital to be clear about them. A reference catalogue of images of early alpha atresia and POFs will be compiled and stored in SmartDots.

The desired number of gonad samples to be collected during the egg surveys, including North Sea samples, was defined. WGMEGS has requested that additional mackerel and horse mackerel female gonad samples would be collected by the Blue whiting survey, the Irish WESPAS survey and the Dutch Pelagic Fisherman’s Association, PFA. An updated version of the ICES Fecundity and Atresia database will be ready for testing at the beginning of 2022 and the survey protocol manual will be updated in 2024.