Mackerel and Horse Mackerel Egg & Larval Surveys

 

Gulf Sampler, used to collect fish eggs

Purpose of the survey

The aim of the international mackerel and horse mackerel egg survey program is to estimate the spawning stock biomass (the total weight of all sexually mature fish in the population) of the North-east Atlantic mackerel and horse mackerel stocks. This data feeds into stock assessments as fisheries independent information. In addition, the data provides important information on the timing and location of spawning for mackerel and horse mackerel. The survey has been carried out every three years since its inception in 1977 and can therefore provide important information about the distribution and timing of spawning in relation to climate change.

How is the survey carried out

The international mackerel and horse mackerel egg surveys take place every 3 years and cover the spawning grounds for both species in the NE Atlantic. Currently the survey area extends from southern Portugal to the Faroes, to the coast of Norway and the North Sea. Surveys take place between February and the end of July. A plankton sampler called a GULF VII is deployed from a survey vessel on a V-shaped tow. The tows take place to a maximum depth of 200m. The GULFs use a net with a mesh size of 250µ. Scientists extract, identify, count and stage the number of fish eggs from these plankton samples, and relate these to the number of eggs produced per female fish to obtain an estimate of the size of the spawning stock.

To find out more about: Where fish eggs are found? How species are identified? etc.. please download 'Fish Egg & Larval Surveys' (1.1 Mb pdf).

2022 Mackerel Egg Survey

2022 is a Mackerel Egg Survey year, involving eleven research institutes from nine countries, Germany, the Netherlands, Spain, Norway, Portugal, Ireland, Faroes, UK and Denmark (see map). Nineteen surveys in total are divided into six sampling periods, from February to July. Portugal started the survey off the Portuguese coast towards the end of January. Ireland started its first survey on March 2nd to the west of Ireland, with Scotland finishing the programme at the end of July to the west of Scotland. 2022 is the first time the North Sea egg survey is taking place in the same year as the western and southern surveys. Historically the North Sea would have been surveyed the year after the Atlantic survey, however the recent addition of new countries to the MEGS group has ensured there is sufficient effort to carry out all surveys in the same year.

Historically peak spawning of mackerel would take place between April and June in the Celtic sea and west of Ireland. In 2010 and 2013 peak spawning was found to have taken place much earlier in the year, February / March, and was concentrated in the Bay of Biscay. In 2016 and 2019 peak spawning once again took place between April and June, but occurred in more northern waters to the west of Scotland.

Horse mackerel egg production was very low in 2016 and 2019, with 2019 being the lowest in the time series.

   

Mackerel egg survey coverage

Provisional results from recent surveys

In each survey year egg numbers and preliminary fecundity results from all the surveys are compiled by the survey coordinator. For mackerel the data are worked up to calculate a spawning stock biomass, SSB, while for horse mackerel the data are presented as total egg production. These provisional results are presented to WGWIDE, the Working Group on Widely Distributed Stocks, for its meeting each August. WGWIDE carries out the stock assessments for both mackerel and horse mackerel. Finalised fecundity results are produced for the WGMEGS meeting the year following each survey. WGMEGS then produces a final survey SSB for mackerel for use by WGWIDE.  

Survey Funding

Ireland's Mackerel Egg Survey is part of Ireland's Data Collection Scheme which is carried out under Ireland's Operational Programme (OP), co-funded by the European Maritime and Fisheries Fund (EMFF) and by the Irish Government.