By Dr Steven Mackinson, Chief Scientific Officer, Scottish Pelagic Fishermen’s Association

The importance of scientific sampling to assess the composition of fish stocks and their status has been underlined by the results of an international five-year study on Western herring, in which Scottish fishermen played a key role.

One of the aims of the sampling surveys carried out by Scottish and other nationality fishing vessels working in partnership with government marine science institutes, was to determine whether the herring stock off the west coast of Scotland comprised of one stock, or different stocks split between the north and south.

The study on the genetic make-up of herring revealed that there are indeed different stocks, with those spawning in the northern sector off Cape Wrath and adjacent areas being genetically identical to North Sea herring, while those spawning further south around Ireland are a discrete, separate stock. Such knowledge is important because it greatly aids decision-making in fisheries management to ensure stocks are harvested sustainably.

For the last few years, no commercial fishing has been permitted for Western herring because, for undetermined reasons, levels of the various stock components are low.  Later this year, the results from this new five-year data set will be considered for the first time by the International Council for the Exploration of the Sea (ICES) to assist in a full ‘stock-take’ of the information available to assess the status of Western herring, which will aid the development of an effective rebuilding plan.

This is a ground-breaking development as it shows how fishermen working collaboratively with scientists can play a crucial role in survey work, which can then be fed into the official assessment process, thus helping ensure that the best available information is applied to addressing issues of shared concern. Industry’s support for scientific data collection means that there has been a higher intensity of monitoring than would otherwise have been possible, which is providing information to help make the stock assessment more robust.

Due to constraints on financial resources, there is often a shortfall in information from marine scientific surveys carried out by national governments. It therefore makes good sense for the fishing industry to contribute to the scientific process. The scope of the activities of our fishing boats, and the wide sea area they cover, offers the ideal platform for collecting relevant marine data.

With regards to the ongoing Western herring survey, and once ICES reaches its conclusions from the benchmark meeting in early 2022, it is uncertain whether this will result in commercial fishing being able to resume in the short-term by Scottish boats. There are, however, grounds for optimism over the longer period, with the most recent survey last September finding an abundance of one and two-year old herring on the spawning grounds to the West of Cape Wrath. These fish were not mature enough to spawn, but they will be able to do so this year and in subsequent years, so our hope is that these fish will return and give a sign that the stock will begin to increase.

Indeed, previous experience has shown that it takes just one good year-class of herring to boost stock levels for several years afterwards.

After all the tremendous effort by a variety of stakeholders in producing this dataset, we believe in advance of the ICES ‘stock-take’ meeting in 2022, it is more important than ever that this survey work continues to monitor the stock this year, looking for signs of new spawners and confirming the results from the genetic study.

The more we understand the complicated population dynamics of our fish stocks, the better our management response and ability to implement recovery programmes. Scottish fishermen are now at the heart of that process, and this is something we should all welcome.