SCIENCE TAKES A BROAD VIEW
GETTING the science right that underpins decisions about whether or not fish stocks are healthy, is becoming ever more crucial. One of the long-standing grievances Scotland’s fishing community has had against the EU and its quota system for fishing has been the perceived mismatch between what the EU’S scientists say about the poor health of some fish stocks and what the trawler skippers actually find when they are out at sea.
Having boats tied up at the quayside because quotas have been withdrawn on the grounds that stocks of some types of fish are dangerously low, is hugely dispiriting for the communities affected. This is particularly so when all the anecdotal evidence from trawler skippers is that they are seeing plenty of those particular fish types when they are out at sea, and stocks look back to sound levels.
In part this mismatch between what the EU scientists think about fish stock levels, and what fishermen see, is caused by the natural lag between analytical investigations in the lab, and the experience of fishing crews at the sharp end of coastal and pelagic fishing. In part, however, a contributing factor is that our understanding of the manifold factors that influence or inhibit the growth of plankton in the UK’S coastal shelf, and the natural processes that occur on the shelf, is still developing.
A recent report, entitled: Shelf Seas, the Engine of Productivity and prepared by the Centre for Environment, Fisheries and Aquaculture Science (Cefas), set out to shed some light on these processes. The report was based on results from the fiveyear NERC-DEFRA Shelf Sea Biogeochemistry programme, with the first three years spent gathering evidence and the last two years going on interpreting and analysing the data collected.
Phil Williamson, the project manager at the University of East Anglia School of Environmental Sciences says that the main authors of the report have a meeting scheduled with Marine Scotland in February 2019 to discuss its findings and to explore the implications for Scotland’s fishing sector. “What we were concerned about, when we started this project, were whether we were measuring the right things around the coast of Britain. Are we keeping sufficient track of changes in this ecosystem? How does the marine ecosystem respond to climate change?”
He points out that while there is masses of data on fish stocks, the data is much thinner and more poorly understood when it comes to looking at plankton levels in Britain’s sea shelf. “This is going back to the basic building blocks, starting with the basics of the carbon cycle and trying to understand why the seas behave as they do,” he notes.
He points out that it is already clear that climate change is having an impact on
UK shelf seas, and the impacts will intensify over time. “UK shelf seas provide many economic benefits. They act as a carbon sink, but we are still unsure about how much carbon is permanently removed from the climate system. One of our more surprising discoveries was finding a lack of dissolved iron, which is necessary for healthy plankton growth, in summer in the Celtic Sea and in Atlantic waters off Scotland. Our findings suggest that there could be other reasons, besides over-fishing, to account for the depletion of fish stocks, or which can account for sudden surges in fish stocks.”
He points out that once you get below the cycle of big fish eating smaller fish which eat smaller fish, and so on, you get to what supports the whole cycle, which is whether there are sufficient levels of phytoplankton and zooplankton in particular areas. “Plankton levels depend hugely on the levels of nutrients in the seas. Too much is bad, because it uses up oxygen in the water, and too little limits fish stocks. It is a complicated, interlocking set of processes that we are working to understand,” he concludes.