Silla’s guide to sustainable fish

How to source sustainable fish can be a minefield and if not your professional calling it may seem confusing and misleading at times. There is no universal consensus on what are the most pressing issues in terms of over fishing as different NGO’s and support organizations approach the issue of overfishing, fishing and farming’s impact the environment differently. However, it is a known fact that our fish stocks are depleting and it is up to us to ensure that there will be fish for future generations. Here I will share how I over time have navigated thestormy waters. Do keep in mind this is based on my knowledge and experience of working with fish, this is in no way definitive, but good 7guidelines from humble chef: 

Is it local? 

Is it seasonal? Is it fresh? 

How did it get here? 

Is it an engendered species? 

If it is farmed how is it farmed? 

Local: in the UK we are blessed with around 49 commercial species of fish and shellfish. We have some fantastic coastal fish markets like Brixham, Newlyn and Grimsby were good quality fish is landed daily and sold on to wholesalers, restaurants and distributors. Some is exported, unfortunately, and it is a known fact that the wider a repertoire of fish we eat in the UK will determine how much will remain here for our own consumption, it is a simple matter of supply and demand. It is important to think beyond the most popular species of salmon, tuna, prawn and cod and start tucking into great species like: MSC West Coast Hake, Devon Crab, Cromer Crab, MSC Hasting Herring, Mackerel from Scotland and the West Coast, hand dived scallops, razor claims, wild seabass, cuttlefish, lemon sole, coley, MSC cod, Cornish lobster – just to name a few, the world of fish is literary at your oyster. The best way to ensure that you eat good local fish is to build up rapport with your local fishmonger or fish counter, asking questions and being inquisitive will get your far on the fish front. I also recommend reading up on the information out there and good reference point would be Good Catch guide to buying seafood which can be found here.


Seasonality: it may come at as big surprise that some species should only be eaten seasonally as we have come so accustomed to all food being available all year around. The 2 main factors to consider are when does the fish migrate into UK waters and is the spawning period therefore best to avoid to eat all together. To give a few examples, most shellfish is available all year around, like rope farmed mussels, but Cornish crab is only available from May through to November when their breeding season is over and meat tender and sweet. On the contrary I prefer the hand dived scallops in the winter months when the waters are colder and these are dense, sweet and safer to eat. 

For the pelagic fish like mackerel, herring and sardines they have very specific season all subject the currents and weather fronts. The Hasting Herring is typically available from October and December when the swim along the coast to take refuge for spawning and then again swim further out to sea. Mackerel is available all year around, however should be avoided from January through to March when it is their spawning season. Mackerel is an absolutely fantastic eat in September and October when they are bursting with omega3 oils as they are fattening up for the colder winter months. Pilchards, or Cornish Sardines are fished on the Cornish coast an available from Mevagissey from June to September and the season move on to Penzanne from August through to February. We have some excellent oily fish in UK waters, let’s eat them more often instead of depending on tuna imports. 

Fresh fish and shell fish will always beat frozen fish and to ensure it is fact fresh and not defrosted I look at gills, skin, eyes, flesh and firmness. 

The gills should be bright and by that I don’t necessarily mean bright in color, but that there are no discolorations or traces of slime on the gills; they should be spongy with absolutely no odor – fresh fish does not have a “fishy” smell. The fishy smell we associate with fish is actually from fish which has already started to spoil as the enzymes in its gut has started to break down. 

Not all fish has scales, like mackerel, so check the scales or skin. The fish have a natural layer of slim, this should be none smelly, but if the skin is slimy and sticky then this fish has been in the counter for a day or two too long and it is a sign the fish has started to spoil. 

Examine the eyes, the eyes need to be open, clear and dark, almost like glass, and intact; sunken eyes are a giveaway that the fish is no longer very fresh. 

The fish should be firm to the touch, but just firm and not rigid. Fish flesh is naturally softer than meats like chicken or steak. Fish live a weightless existence, their body weight supported by water. Their muscles are much softer than their mammal counterparts because they are mainly used for swimming and quick burst of movements. Red fish tend to be slightly heavier than the water they subside in and are also hunters, like tuna, therefore they expand energy for both staying afloat and accelerate quickly. The red color steam from myosin which is the protein bringing oxygen to the mussels, not red in its own right, but when bound to oxygen it make the appearance of the flesh red. In contrast white fish is literary weightless and therefore just using energy to swim to find food. The pink color found in wild salmon is caused by it feeding on crustaceans like small grill and prawns, in the case of farm salmon the fishmeal will consist of oily fish from the sardine family, fish oil and a binder like maize or soy and it is common to add pigment to the feed as consumer prefer the salmon pink. There is some debate about the Omega3 content of wild versus farmed salmon as, the former have concentrated Omega3 from the concentrate of shellfish in their diet. Some good quality farmed salmon have proved that the rich oily fish diet in fact comes up with a similar result. 

Fish for sashimi is consumed post rigor mortis and depending on the species, but on average 6 hours after death. By freezing fish on catch the rigor mortis can be delayed and keeping the fish on ice will slow the process down, it is therefore so essential that fish is covered in ice when caught or harvest. 

There are many examples of responsible farmed or sustainable wild caught good quality shellfish used for sushi. Shellfish is rarely used raw in sushi but fresh hand dived scallops can be consumed raw are they no more than a day old and can be absolutely delicious. Often prawns will be frozen at source and best defrosted in cold running water over a 20 minute period providing they still are in there shell. Most shellfish for sushi need to be blanched or cured in either vinegar, mirin and/or citrus, so the acidity, sugar and/or alcohol makes the protein safe to eat raw. For everything else shellfish should just be cooked for a few minutes to keep tender and sweet. The same for mussels, whelks and claims, however oysters can of course be eaten raw and are best through the winter months when our waters are colder. 

Food miles: how did the fish get onto your plate? The carbon footprint matters, not only for fish, but for everything we ship across the globe. We of course live in global economy benefitting from development and technology, however when it comes to food we can really do our bit to reverse the impact our way of life has on the planet we inhabit. One absolutely golden rule I always adhere to is: if it is available from UK waters avoid the same species imported. Few examples: Scottish instead of Alaskan or Norwegian salmon, herring from Hasting or the Irish Sea instead of North Sea, MSC West Coats hake instead of imported MSC hake from South Africa, I think you get my drift. Popular species like tiger prawns, soft shell crab and tuna will of course be imported as they simply do not live in UK waters, in that case I would recommend frozen as this often mean they have been shipped instead of very damaging food miles by air. The plight of the endangered Bluefin tuna is that it on occasion will have been shipped from the Mediterranean Sea to Tsukiji market in Tokyo, sold on auction and then flown across the globe again to is destination in a metropolitan city, so when tucking into toro at a high end sushi bar in Hollywood the fish may have journeyed one and half time across the globe for its end destination. 


Endangered fish: talking of Bluefin tuna that is a fine example of a fish which has been fished near to its extinction, with the advances of fishing technology and the global explosion of sushi the demand for particular Atlantic tuna has far outdone what this stunning species of tuna can cope with. Bluefin tuna is a truly fascinating species of fish, torpedo shaped silver fish with blue fins, the tuna migrates across oceans, can dive as deep as 4000 feet and has an acceleration as fast as Ferrari – like a speeding bullets. They are a predatory fish feeding on oily fish like herring and mackerel from when they are born, it will take the Bluefin tuna 4 years to mature and they can live up to 40 years. In terms of biology one of the strongest species of our oceans, but being overfished for the enormous profit they create. The Bluefin tuna fishing fleet is so advanced in its technology from deep sea radar systems, spotter planes to nitrogen freezing champers onboard of ships. Bluefin tuna is fished by purse line literary scooping tons of fish up in one go including bycatch of marine mammals like dolphins. To date the record at Tsukiji is 1.75 million dollars for just one single fish – does this make the bite of melting toro taste better? If you like to learn more about Bluefin tuna and the preservation work which is being done to recover the species I recommend reading up on the following websites WWF and Greenpeace.

Bluefin tuna being so expensive most sushi operators in the UK use yellowfin tuna. There are some well managed yellowfin tuna fisheries in Korea, Maldives, Indonesia and Sri Lanka. Yellowfin tuna is caught by short long lining, a method which target tuna specifically to minimize bycatch. An even more sustainable method is hook and line providing the tuna swims near to the surf as is the case for the Maldivian tuna fishery. The yellowfin tuna fisheries are not without issues, but lots of work is being done in ensuring to support local fishing communities to fish to a sustainable method, to preserve the livelihood of the fishermen and their communities including the future supply. I would tread with caution nonetheless as more consumers turn to yellowfin tuna for their sushi fix we need to monitor closely as growing demand could take its tool. 

Marine Conservation Society has a very useful traffic light system classifying the sustainability of common species we consumes in the UK. Another useful source is Marine Stewardship Council certification scheme, this is a charitable organization who access individual fisheries sustainability by focusing on scientific available data on a particular species stock levels to ensure the fish being caught within its biological safe limit and to ensure the species are being fished to the best sustainable method with least impact on the environment. MSC has successfully accessed upwards to 15% of all fisheries and the little blue MSC logo is the strongest and most recognisable eco label for fish. Both MCS and MSC are great tools, however for inshore small fisheries local knowledge and recommendation are always relevant and in particular supporting smaller fisheries which may not have the means to enter the MSC scheme. 

Farmed fish: there is an undercurrent in the chef community that wild species of fish are of better quality and better for the environment than farmed, I am personally not 100% in agreement with this stand on fish sourcing. UK sourced wild fish with the MSC logo is obviously the best option, like West Coast Hake, Hasting Herring and Dover Sole, but many species are yet to be certified. The reality is that we like to eat fish, it is not only delicious it is also a very healthy source of good protein. For 1000s of years we have successfully farmed the land pushing our world population to the 7million+. Part of the solution to future food security is no doubt eating less protein and a more plant based diet, but a diet rich in good quality protein is healthy and enjoyable. The aqua culture in Europe is heavily regulated and it is paramount that any fish farm gets all the key aspect of farming fish right. Over the years I have devised 7 key factors I think is important when assessing a farmed fishery. The following is in no way definitive and hopefully serves to challenge our perception of farmed fish. Please bare with me whilst we dive into the technicalities: 

1. One key question would be: how is the brute stock sourced? One of the reason salmon is so successful is the fact that the lava, salmon eggs, can be stripped from a few breeding females, fertilised and then hatched all by human hand. The salmon, sea bass and sea bream farms does not depend on the wild juvenile stock. A contended topic is ranched Bluefin tuna which relies on wild juveniles and thereafter are being feet on fish fit for human consumption like mackerel, herring and sardines. This is putting even further pressure on wild stock. 

2. Density of the fish pen, does the fish have plenty of space to swim and exercise to simulate their natural habitat? For example, for Loch Duart Scottish farmed salmon the ratio will typically be less than 2% of fish to 98% of water 

3. For sea farmed fish I would question if there is a system in place for fallowing, that means are the farming done to a cycle allowing breaks in between generation of fish to ensure the seabed and the local habitat recover from any impact naturally. For tanked system I would question what energy source is powering the pumped and circulated water system? How is and how much of the water is being recycled? How is any waste water treated before discharged? 

4. Is there a system in place to ensure that algae build up on the nets are removed naturally to prevent the use of chemicals in the seawater which would impact on the bio-diversity and other species of fish and sea mammals. One good preventative measure is having a system in place to move fish, like a ‘swim through’ from one pen to another, lifting the algae soiled nets out of the water to dry naturally in the sun and wind and also returning valuable nutrients to the sea bio-diversity. 

5. How is often and many fish mortality and escapes? How is this monitored and prevented? 

6. How is the fish harvested and is this done to the standards set by RSPCA to assure this is done in the most humane way possible? The Royal Society for the Prevention of Cruelty to Animals how done some good work for farmed Atlantic salmon to support the welfare of the fish through its life cycle to its cull. 

7. What are the farmed fish feeding on? Fish meal are typically made of wild fish, fish oil and a binder like soy or maize. Is the soy or maize from a sustainable source ensuring no rainforest deforestation or/and intensively farmed? Is the fish and fish oil from a sustainable source and not overfished impacting on the bio-diversity of the waters it is fished from? What species of fish is used in the fishmeal? One popular species for fish meal is capelin, a small forage smelt fish fit for human consumption, but with little uptake. Many species of fish in the Northern Hemisphere feed on capelin, therefore important to the fish bio-diversity and it is paramount that capelin are not fished beyond their biological save limit. 

Farmed fish is complicated and not without issues, but like for chicken and pigs there is good and bad husbandry. When fish farms are well run and regulated they are very much a contender for some of the fish we will consume in the future. For a good guide to how to asses responsible farmed fish the Sustainable Seafood Coalition, SSC, has put together a voluntary code and on page 13 there is a very useful chart to assess whether a farm fishery is in fact responsible. 

Sourcing fish is a minefield, hopefully over time we will broaden our understanding and all collectively be able to do our bit to secure future supplies.