I love the sea It's so wild and vast. It's ever changing from choppy and stormy to calm and still. I've lived by the sea all my life, because my dad is a fisherman. Like me, dad loves the sea. The salty, tangy smell hits his nose when he walks down to his boat, refreshing him before he prepares to go out to sea. I try to imagine what it'd be like to work out there in the wild with nothing but space around you. Working with nature, dependent on the weather. For most fishers including my dad it's a livelihood passed down from generation to generation. They inherit the skills and a love of the sea. I can hear the engine running, the ropes are loosening, the boat is leaving and as I wish him goodbye, I think about the challenge of searching for the fish he and his crew need to find in the vast ocean before he returns home. My dad and the crew are getting ready to catch herring - a small, silvery fish. Herring swim in huge numbers and come near to the surface at night making it easier to catch them, but will my dad and his crew find a gigantic shoal of herring tonight? Even though herring can group in huge numbers the fishery my dad operates in covers an even bigger area. So what is a fishery? A fishery is an area where fish are caught for commercial purposes. It can be a defined area of the sea or a collection of fishing boats that's been agreed by countries and fishers. You often have different fisheries for each fish so my dad's boat is part of herring fishery. My dad has described trying to find the fish they need can be a bit like looking for a needle in a haystack. In comparison to the sea their boat is a tiny dot in the ocean. Because of this, the captain of the boat like my dad needs to rely on the knowledge they've gained through years of experience to find the right fish, as well as use the right technology. Dad's bridge deck makes me feel like I'm on a spaceship. All these screens tell him everything he needs to know to catch the right amount of fish from informing him about the weather to picking up where the shoals of fish are. Tonight the herring are so plentiful that it doesn't take long to find them. Fishing is one of the oldest jobs on earth, making it both an exciting and dangerous livelihood to have. As well as the freedom and closeness to nature fishing brings, there's also the risk fishers can be lost at sea or have accidents on the boat itself. Because of this lots of careful planning and safety rules have to be followed to make sure the fishers stay safe while they work. Catching fish for a living is an essential part of many people's lives, but my dad says fish aren't always plentiful and earning from fishing can be unpredictable. Fishers rely on certain species of fish being available at the right time of year, but some fish species are now under threat. This can have a huge impact. A billion people around the world rely on fish as their main source of animal protein, while around one in ten people depends on fishing for their livelihood. I think fish is delicious and it's healthy too. It's one of the most ancient wild protein sources that everyone can enjoy and fishing is a big industry. Two hundred million people are employed in fishing and seafood production across the globe. Fish is the most traded food in the world above tea, coffee, bananas and sugar. For thousands of years people have fished in a balanced way, but they didn't catch beyond what they needed to eat or sell. But the increase in scale of fishing and more global demand for fish mean that fishing can result in the decline of fish stocks. Fishing itself isn't the problem, as there are fisheries that fish responsibly and sustainably, but without good management fishing can be destructive. When a certain species of fish, usually one which people like to eat most are fished too much they are unable to reproduce their numbers back to a healthy number and begin to decline. This is called 'overfishing'. Now almost a third of global fish stocks are overfished. That's a lot of fish for us to lose! If nothing is done to be prevent this decline there's a risk that some species will be gone, forever. Overfishing is not the only reason for this decline, another problem is bycatch. Bycatch is when fishing boats accidentally catch fish and animals that they don't really want or shouldn't take. It can be other species of marine life like sea birds and other marine creatures like sharks and turtles. Bycatch can also include young or undersized fish that are not really big enough to eat so should be left in the sea to grow. So what happens to marine animals when species of fish decline or disappear? All sea life is connected in a food web of prey and predator, each reliant on the other to survive. If predators such as cod, seals, sharks and dolphins lose one of their main sources of food then they too will begin to disappear. I wonder what would a world be like without fish and animals like seals, sharks and turtles, and what about the many people from countries around the world who rely on fishing as their main source of food as well us to earn a living? What's the solution to overfishing? I know my dad's fishery makes sure they don't overfish the species they catch and take care of the ecosystem. My dad says they fish 'sustainably', but what does this mean? Sustainable fishing means fishing in a responsible way, making sure fish populations do not drop below levels where they cannot reproduce and grow faster than they are caught. It's also important to make sure fishing doesn't damage marine life and their ecosystem, but how do they do this? Firstly, fishers need to know as much as they can about the fish and shellfish they catch and the ecosystem they live in. Fisheries work with scientists to understand how the fish and shellfish population grows and shrinks over time. This is controlled by births, migrations in and out of the fishery and deaths. This information can show them how much fish they can catch without overfishing. This scientific calculation is called the 'Maximum Sustainable Yield'. Fishers can use this information to choose a particular type of fish to catch, each fish has a role in this ecosystem and they vary in how plentiful they are at a given time. Taking this into account can help fishers decide if fishing is sustainable or not sustainable. My dad fishes for herring because they are plentiful in the ocean where he fishes, and they only fish for a certain number of fish or a 'quota' every year. Working with nature and not against it helps prevent unnecessary impact on marine life. Choosing the time of day or night to fish can avoid bycatch as different fish species come up close to the surface or swim down to the ocean depths at different times of the day, so sometimes you can find a time and place where you will only catch the fish you want. Fisheries can also use nets that ensure smaller fish and sea creatures can escape. Some boats use bright coloured flags on their fishing lines to scare seabirds away, but what about other fisheries across the world? The sustainability of our fish is a global issue. Half the world's trade of seafood comes from fisheries across Africa, Asia and Latin America. Many of them are working towards or are already fishing sustainably. The more people that fish in a balanced, sustainable way the more fish stocks can return to a healthy level so the ocean will be able to sustain more livelihoods in the future. Fishing sustainably is a global challenge that many fishers are tackling. No matter how far away seafood is caught it ends up in our shops, restaurants and supermarkets for us to buy and eat. That makes us part of this challenge too. So how do we know which products in the shops are sustainable and which are not? My dad's fishery is certified sustainable by an independent organisation which checks a few things - whether the fishery is catching fish at a healthy level, whether marine life and their habitats are being damaged and whether fishers are working together to safeguard life in the ocean. Once all these checks are done, fish and seafood products get a little blue label on so everyone knows. It's a new day. The crew are getting ready and the sea awaits them. My dad is a fisherman, like many across the world because he fishes sustainably he knows there will be fish to catch day after day, year after year and generation after generation. What can we all do to make sure our oceans are sustainable?