How to Keep Fish: A Complete Guide for British Waters

How to Keep Fish in Modern Day Agriculture

The equipment you’ll need depends entirely on whether you’re keeping fish alive for later release, transporting them home, or preparing them immediately. From my experience fishing various British waters, having the right kit makes all the difference.

Keeping Fish In your Fields

If you’re planning to keep fish alive temporarily, particularly for match fishing or to ensure freshness before dispatch, you’ll need specific equipment. A proper keepnet is essential for coarse fishing, though I should mention that keepnets are banned in certain fisheries and for specific species. Always check local bylaws before using one.

Look for keepnets with fine mesh (4mm or less), at least 2.5 metres long, and metal rings to keep them open in the water. The mesh must be knotless to prevent damage to the fish’s protective slime coating. I’ve found that longer keepnets work better as they give fish more space and allow better water flow.

For specimen fish or shorter holds, a proper retention sling or carp sack works brilliantly. These should be positioned in shaded, well-oxygenated water. Never use these for more than a few hours, and certainly not overnight in warm weather. Water temperature above 15°C significantly reduces oxygen levels.

How to Transport Your Fish

A high-quality cool box or ice box is absolutely vital if you’re keeping fish to eat. I always bring plenty of ice packs or crushed ice, as fish need to be chilled to below 4°C within hours of dispatch to prevent bacterial growth. The cool box should be large enough that fish aren’t cramped, which can damage the flesh.

You’ll also need a priest (a weighted club for humane dispatch), a sharp filleting knife, and clean cloths or kitchen paper. For sea fishing trips, I pack heavy-duty plastic bags or vacuum seal bags to prevent cross-contamination and keep everything clean.

Step-by-Step Instructions

Assessing Whether to Keep Fish

Before you even consider keeping a fish, you need to check several things. First, is it legal? Many waters have size limits, closed seasons, and bag limits. Coarse fish in England and Wales generally have a closed season from 15th March to 15th June on rivers, streams, and drains. Sea bass have strict minimum sizes (42cm) and bag limits. Salmon and sea trout require specific licences and have varying seasons depending on region.

I always carry a measuring mat and weigh sling because guessing sizes leads to problems. If a fish is undersized or you’ve reached your limit, it goes back immediately. Second, consider the fish’s condition. If it’s deeply hooked, bleeding, or unlikely to survive release, keeping it (if legal) is often more ethical than releasing it to die.

Think about sustainability too. Pike, for example, are slow-growing apex predators. Taking one removes years of growth from the ecosystem. I personally only keep fast-breeding species like mackerel, pollock, or roach from well-stocked waters.

Keeping Fish Alive in a Keepnet

If you’re using a keepnet, set it up before you start fishing. I secure mine with proper bank sticks, ensuring the net extends into water at least 1.5 metres deep with good flow. Stagnant water quickly becomes oxygen-depleted, especially on warm days.

When adding fish to the keepnet, wet your hands first to protect their slime coating. Lower the fish in gently, never drop them. Don’t overcrowd the net. As a rule, I never put more than 10-15 pounds of fish in a standard keepnet, and I reduce this in warm weather.

Check the keepnet every hour. If fish are at the surface gasping or showing signs of stress, release them immediately. I’ve learnt that keepnets work acceptably well in cold weather but become problematic above 18°C water temperature. Some fisheries around the Midlands now ban keepnets entirely during summer months, which I think is sensible.

Dispatching Fish Humanely

If you’re keeping fish to eat, humane dispatch is legally and morally required. The method varies by species, but the principle remains the same: cause instant loss of consciousness and death.

For most fish, I use a priest, striking firmly once on top of the head between the eyes. The blow should be hard enough to be instantly fatal. It’s unpleasant but necessary. Some anglers prefer the iki jime method, which involves inserting a spike into the brain (just behind the eyes) and then running it down the spine. This Japanese technique works brilliantly for larger fish like bass or pollack and results in superior flesh quality because it prevents stress chemicals from flooding the meat.

After dispatch, many fish benefit from bleeding. I cut the gills or throat and hold the fish head-down to drain. This is particularly important for oily fish like mackerel. The flesh stays cleaner and keeps longer.

Chilling and Storing

Immediately after dispatch and bleeding, fish must be chilled. I gut fish straight away, particularly in warm weather, as the stomach contents accelerate decomposition. Keep the liver from cod or other whitefish if you fancy it, but discard all other innards responsibly.

Pat the fish dry inside and out with clean cloths, then pack them in your cool box surrounded by ice. Don’t let fish sit directly in meltwater, as this damages the flesh. I create a layer of ice, then put fish in sealed bags, then more ice on top. Properly iced fish will keep for 2-3 days, but fresher is always better.

If you’re fishing somewhere remote like the Scottish Highlands, plan your ice supplies carefully. I’ve had trips where the ice melted faster than expected, so now I always bring extra and use good-quality cool boxes with thick insulation.

Common Mistakes to Avoid

Temperature Management Failures

The biggest mistake I see anglers make is underestimating how quickly fish deteriorate in warm conditions. I’ve watched people leave fish in keepnets during hot summer days on venues like the Norfolk Broads, only to find stressed or dead fish hours later. Water temperature is critical. Above 20°C, keepnets become inhumane for most species.

Similarly, failing to ice fish properly after dispatch ruins countless catches. Fish are made of protein that breaks down rapidly once enzymatic processes start. Without proper chilling, you’ll notice the flesh becomes soft and develops off-odours within hours. I’ve made this mistake myself on early fishing trips, and it taught me to always prioritise cooling.

Overcrowding and Stress

Cramming too many fish into keepnets, carp sacks, or storage containers causes stress, injury, and death. Fish need space and oxygenated water. I’ve seen match anglers with keepnets so full that fish at the bottom were being crushed. That’s not acceptable by any standard.

The same applies to cool boxes. Piling fish on top of each other damages the flesh, causing bruising and allowing bacteria to spread. Keep fish separated, chilled, and in single layers where possible.

Ignoring Regulations

Every water body has different rules. Some commercial fisheries around Lancashire and Yorkshire operate strict catch-and-release policies. Taking fish from these venues isn’t just frowned upon, it’s theft. Similarly, taking undersized sea bass or exceeding bag limits carries proper penalties, including fines up to £50,000 for serious offences.

I always check the Environment Agency regulations and specific fishery rules before keeping any fish. It’s your responsibility to know what’s legal, and ignorance isn’t a defence.

Expert Tips

Species-Specific Considerations

Different fish require different handling. Pike, for instance, should almost never be kept in keepnets. They’re too large, too stressed by confinement, and too valuable to the ecosystem. If you must retain one briefly, use a proper sling in deep, cool water for no more than an hour.

Flatfish like plaice or flounder handle being kept alive quite well if you create a cool, sandy-bottomed container with circulating seawater. I’ve kept them alive for several hours on beach fishing sessions in Devon, which ensures they’re incredibly fresh when cooked.

Mackerel deteriorate faster than almost any other British species. Their flesh begins breaking down within hours even when iced. If you’re keeping mackerel from a fishing trip off the south coast, gut and bleed them immediately, ice them thoroughly, and eat them that same evening if possible. The difference in quality is remarkable.

Seasonal and Weather Awareness

I’ve found that keeping fish alive works best from autumn through early spring when water temperatures stay below 12°C. During British summer heatwaves, I now practise catch-and-release exclusively for coarse fish because the mortality rate in keepnets becomes unacceptable.

Stormy weather and low pressure can reduce oxygen levels in water, making fish more stressed when retained. If I notice fish behaving lethargically, I cut my session short and release everything, even if I’d planned to keep some.

Improving Flesh Quality

The way you treat fish from the moment they’re caught affects how they taste. Stressed fish produce lactic acid and stress hormones that negatively impact flavour and texture. This is why the Japanese iki jime method produces superior results for species like bass or bream.

Bleeding fish thoroughly makes an enormous difference, particularly with species like mackerel, herring, or salmon. The flesh stays lighter in colour, tastes cleaner, and keeps longer. I always carry a sharp knife specifically for this purpose.

Speed matters too. The faster you dispatch, bleed, gut, and chill a fish, the better it will taste. I aim to have fish iced within 30 minutes of landing them when I’m keeping them for the table.

Frequently Asked Questions

Can I keep fish in a bucket of water?

You can temporarily hold small fish in a bucket with regular water changes, but it’s far from ideal. Buckets provide minimal space and oxygen quickly depletes. I’ve used buckets for transporting live bait or holding a single fish for 20-30 minutes maximum, but anything longer risks injuring or killing the fish. If you’re using a bucket, keep it in the shade, change the water every 10-15 minutes, and never overcrowd it. For anything more than brief temporary holding, use proper equipment like keepnets or retention slings.

How long can fish stay in a keepnet safely?

This depends entirely on water temperature, species, and keepnet quality. In cold water (below 10°C), most coarse fish can survive several hours in a good keepnet without major stress. However, in water above 15°C, I wouldn’t keep fish for more than two hours, and above 18°C, keepnets become unsuitable. I’ve seen experienced match anglers who won’t use keepnets at all during warm months because the risk of mortality becomes too high. Always check fish regularly for signs of stress like gasping at the surface or loss of balance.

Do I need to kill fish immediately after catching them?

No, you don’t need to kill fish immediately unless they’re badly injured. Many anglers, including myself, practise catch and release for most species. However, if you’ve decided to keep a fish for eating, dispatching it humanely as soon as possible is better practice. The exception is if you’re in a match or need to retain fish for weighing, in which case proper keepnet use is acceptable in suitable conditions. Never leave fish to suffocate slowly, which is both cruel and produces poor-quality flesh.

What’s the best way to transport fish home for eating?

The best method I’ve found is to dispatch, bleed, and gut fish immediately, then pack them in a cool box with plenty of ice. Layer ice on the bottom, place gutted fish in sealed plastic bags or wrapped in clean cloths to prevent direct ice contact, then add more ice on top. Keep the cool box closed and out of direct sunlight during transport. I drain meltwater periodically as fish sitting in water becomes waterlogged and loses quality. Properly transported this way, fish should reach home in excellent condition even after several hours of travel from places like Cornwall or Scotland.

Are there fish I should never put in keepnets?

Yes, absolutely. Pike should never be kept in standard keepnets as they’re too large and become extremely stressed. I also avoid keeping barbel in keepnets during warm weather because they’re particularly sensitive to low oxygen. Trout and salmon should never go in keepnets, they require immediate release or dispatch. Some fisheries have specific bans on keeping certain species like tench or carp in nets due to their value. Always check local rules, and when in doubt, use retention slings for specimen fish or practise immediate release. I’ve adopted a personal policy of only using keepnets for small silver fish like roach or skimmers during cold months.

How do I know if fish are still fresh enough to eat?

Fresh fish have several clear indicators. The eyes should be bright and clear, not cloudy or sunken. Gills should be bright red or pink, not brown or grey. The flesh should be firm and spring back when pressed, not leave an indentation. Fresh fish smell clean, like the sea or fresh water, never fishy or ammonia-like. I also check that scales are intact and the skin has a natural shine. If fish have been properly iced and stored, they’ll maintain these qualities for 2-3 days. When I’m unsure, I trust my nose. Any off smell means the fish goes in the bin, no exceptions.

Looking After Your Catch Responsibly

The key principles I’ve covered here apply across different fishing disciplines and species. Keep fish alive only in suitable conditions with proper equipment, dispatch humanely when keeping fish to eat, and chill them immediately. Understand the regulations for your specific location and species. Above all, make decisions that prioritise fish welfare and sustainability over convenience.

British waters offer brilliant fishing opportunities, from reservoir trout to coastal bass and everything between. By keeping fish properly, you’re contributing to conservation efforts, maintaining healthy fish populations, and ensuring this sport remains viable for future generations. That’s something worth taking seriously.

Author: Jack Bennett

Jack writes about practical farming, smallholding, and the realities of producing food in the British countryside. Having spent years around livestock, growers, and rural businesses, his articles focus on the honest side of agriculture. From keeping animals and growing crops to understanding the challenges farmers face, Jack’s work is grounded in real world knowledge and respect for the people who produce our food