Workshop on Mackerel, Horse Mackerel and Hake Eggs Identification and Staging (WKMACHIS)

The Workshop on Mackerel, Horse Mackerel and Hake Egg Identification and Staging (WKMACHIS) is part of a series of workshops (WKMHMES, WKFATHOM) that aim to standardise the process of fish egg identification and staging. Since 2000, this workshop is held in autumn of each year prior to the triennial mackerel and horse mackerel egg survey. In 2021, however, the workshop had to be held online for the first time due to the continuing SARS-CoV2 pandemic. All egg identification and staging during the workshop were undertaken using images on the SmartDots WebApp, as opposed to real samples under microscopes. In advance of the workshop eggs were, however, sent to participants to be identified and staged under the microscope.

The majority of the time at the workshop was spent completing 2 rounds of identifying and staging mackerel, horse mackerel, hake and similar looking eggs. The results promoted discussion and highlighted specific problem areas. These discussions enabled further development of standard protocols, and enhancements to the species and stage descriptions. The results were reassuring and improved from the first to the second round of the exercises. However, and particularly in horse mackerel, bias in correctly identifying stage 1 eggs was higher than in previous workshops for both, experts and non-experts. These results can almost exclusively be explained by the change in workshop methodology that saw a move from a live view of the fish eggs to images.

As the mackerel and horse mackerel egg surveys are carried out once every three years, the workshop functions as a refresher for expert survey participants and as an introduction for new participants in egg analyses. It should however be realised that one week of workshop for egg identification and staging, particularly if carried out online and based on images, is not sufficient to train new participants. Institutes should ensure newcomers receive a thorough training while also allowing more experienced participants to refresh their knowledge ahead of the survey.

Again, as all previous workshops, the meeting demonstrated the importance of conducting the workshop a few months ahead of the mackerel and horse mackerel egg survey. For several valuable fish stocks in the Northeast Atlantic, the survey delivers the only fishery-independent SSB indices based on correctly identified and staged fish eggs. Ongoing discussion and training for consistency is, therefore, imperative. While many participants had problems working with images only, the use of image-based systems for (egg) analysis will become a central part of future workshops.