World Oceans Day is celebrated on 8th June each year and is a chance to celebrate our connections with the ocean and its importance to our lives. Food by the ocean is at the heart of some of my most treasured memories. Lobster with black beans and mash by a hut in Honduras, after a day watching parrot fish. Mackerel baps from the kiosk at the top of Freshwater West beach in Pembrokeshire, windswept, with the view of the glorious sands to myself. Blackened mahi mahi and fries served on a beer tray by the harbour in Nassau, laughing with fellow teachers on a Friday night. But can we continue to eat fish or seafood when we know that a third of our oceans are overfished, and that some fishing methods have a negative impact on our oceans? Ocean sustainability is still a hot topic, thanks to the awe-inspiring stories in Blue Planet II and videos on social media showing country-sized plastic drifts, we are becoming much more aware of the intricate balance of the ocean ecosystem, and of the power of people to both damage and protect our planet. The programme might have revealed the most incredible animal behaviours, but the UK seems to have taken away one thing from the series, and that’s the huge impact that we can have on the health of our oceans. From classrooms to supermarkets to government departments, everyone is focusing on our oceans: plastics, pollution and the urgent need for ocean sustainability. Blue Planet II arguably created a ‘teachable moment’ across society – an opportunity to raise interest, insight and create positive behaviour change for individuals, corporations and government, that will have an impact on our oceans for generations to come. Talking to teaching professionals, I often come away with the sense that sustainability, while included in several curriculum areas, is a concept young people can struggle with. At best it’s a slightly un-intuitive word than demands some unpicking. It can feel like a buzz word - associated simply with specific activities such as recycling - or a word they hear a lot about, but never get to delve into or really understand. In my personal and professional life, I’ve often struggled with it myself, and get disheartened when it appears that sustainability is all about “don’t” – don’t fly, don’t eat meat, don’t use plastic bags. And of course many of us do all these things and constantly feel like we’re not able to live the ideals of a sustainable world. Teaching the concept of sustainability in a way that encourages young people to see a positive future, where they can make a real impact, can be a challenge. So imagine my excitement when I discovered that seafood certified by the Marine Stewardship Council (MSC) uses a scientific calculation called Maximum Sustainable Yield to work out how much fish we can take from any fishery around the world, while making sure that there will be enough left so that they can reproduce – and crucially, so that fishing can continue indefinitely. Finally, a sustainable “do”! Do eat sustainably sourced fish! It was this concept I wanted to take to young people in my work developing the MSC’s education programme. In a blog from 2016, the MSC explains Maximum Sustainable Yield: “When a ‘virgin’, or previously unfished population is first harvested, its biomass will initially decline as a result of fishing. But there is a point where a roughly constant harvest can be maintained indefinitely without causing decline in the population, and where the productivity of the population is at its maximum. The dynamic equilibrium between fishing and replenishment is what we consider a sustainable fishing level.” 
The Maximum Sustainable Yield, or MSY, of a fish population is worked out using the biomass of the fish population, and the fishing pressure (the number and scale of fishing boats catching the fish). While MSY has a reasonably straightforward premise, of course the calculation is based on a number of complexities, not least that fish swim across the vast ocean with no regard to the scientists above it, trying to assess their numbers. Some see the concept of MSY as contentious, arguing that it’s hard to be sure exactly what’s going on beneath the ocean’s surface. The number of predators, availability of food, environmental variability, disruption of climate cycles and the ability of responsible institutions to manage the fishing pressure, all have to be taken into consideration. Modelling and forecasting, estimates of fishing biomass, knowledge of species biology, measurements by fishing boats, scientific surveys and multi-government quota negotiations, all help paint a picture of a wild world, out of sight, helping us to manage it in a way that conserves it for the future, while providing billions of us with our last large-scale wild-caught protein source. The MSC’s learning resources including the film “My dad the fisherman” aim to explain the need for ocean sustainability and break down some of the concepts behind it, in a way that supports the science curriculum and engages young people. They look at what sustainability really means, focuses on food webs, and on how improving the scientific knowledge base about our oceans can help the industry adopt sustainable fishing methods. The film tells the story of a teenage girl whose dad is a herring fisherman, using animation to bring the learning points to life for a teenage audience. Why might teachers want to focus on oceans and ocean sustainability? For a start, capitalising on the inspirational content they’ve watched on TV could help young people explore food chains and webs, as well as biodiversity and interdependencies in ecosystems in biology. Film can be a great stimulus tool to open up discussion and build critical thinking skills. By focusing in on sustainable oceans and fishing, and our reliance on the ocean, young people can also examine positive and negative human interactions with ecosystems in biology, through topical science that’s got everyone talking. I’ll be eating sustainable fish – and chips – on Saturday 8th June. Without a plastic fork. Happy World Oceans Day to everyone. Kate Jones is an education professional specialising in sustainability programmes and resources, and directs the global education programme at the MSC. Try out the resources here: https://20.msc.org/learn-about-ocean-sustainability Blog from the MSC – “What does sustainable fishing really mean?” Catherine Longo, 2016 http://blog.msc.org/blog/2016/05/25/sustainable-fishing-really-mean/ This blog is based on an article that originally appeared in Issue 369 / June 2018 edition of the Association for Science Education’s School Science Review
