Maximizing Your Catch: An In-Depth Guide on Using Saltwater and Chilled Environments to Preserve Freshly Caught Fish

When it comes to looking after your caught fish, you can quickly find reading some old wives tails and some 'well, just because' - so I thought I would do some research and detail some of the science behind what is happening, hopefully revealing some best practices along the way.


Whether you get your kicks from the thrill of catch and release or are a seasoned fisherman looking to bring home dinner, properly handling your catch is crucial. Here, though, we are discussing the harvesting and storing fish destined for the table. While it may seem complex, it all comes down to some simple yet important factors like temperature control, careful handling, and, above all, the use of saltwater.

Beyond the Rod and Reel: Essential Post-Catch Care for Your Fish

This article is intended to discuss what to do with your catch post retrieve and post Iki-Jimi and bleeding – separate but equally essential steps in optimising your catch. Understanding that some of the biggest challenges come after the catch is the first step to maximising your yield and preserving the quality of your fish.

Hauling up a gleaming prize from the abyss below, you know that feeling. The thrill of the fight, the satisfaction of success, that salty, primal connection to nature’s raw and ruthless beauty. But here’s a wrinkle: that exhilarating catch doesn’t end when the fish leaves the water. The most crucial journey of your prized catch is only just beginning. 

Catching a fish is one thing. Preparing it in a mouth-watering prime condition for the plate requires a different skill set. You might think, “Hold on, I’m a fisherman, not a marine biologist!” Fear not, good reader. While the world of post-catch fish care can seem complex and bewildering, underneath it all, the principles break down into common sense, respect for your catch, and a bit of basic science. And the first lesson in that science? Temperature matters. 

Keeping It Cool: How Temperature Affects Your Catch

Take a moment and imagine a beautiful warm day out on the water; think of how the blazing sun bears down on you, the constant lap of the waves against your boat, and the tension in the fishing line as a fight ensues between you and a particularly relentless fish. You prevail in the end, hauling in your catch with a triumphant grin. But amidst the joy and triumph, it’s essential to remember one cog in this wheel of recreational or professional angling – the relentless heat of the sun, which, believe it or not, poses quite a threat to your victorious catch. 

Why this is the case? Simply put, higher temperatures speed up the metabolic processes within fish, causing them to decompose faster. Even if the bite is a long way off, remember the hesitating heat and how quickly it can ruin the spoils of a good day’s work. 

This is where chilling comes into play, taming the infernal heat of a sunny day and maintaining the quality of your fish. Superior to simply tossing your prize catch into a cooler, maintaining the right temperature slows down any unwanted microbial action and enzymatic reactions in your fish. When adequately reduced, the heat gives way to a slower, more measured pace of decomposition, helping to maintain the freshness of your catch even hours after it is removed from its natural habitat. 

And what’s more, there is no one-size-fits-all approach to cooling your fish. It might be an icebox filled with crushed or flaked ice or an ice slurry that further slows down bacterial action, rendering high temperatures moot and preserving your catch in pristine condition.

Getting the best out of your fish is a race against the clock – and knowing how to cool it correctly could well mean the difference between a triumph tinged with regret and a fresh, flavoursome catch that’s sure to be the highlight of your next meal. So whichever method you choose, remember – with the right amount of knowledge, preparation and care, that triumph can be yours for the taking.

The Cold, Hard Facts: Direct Cold vs Ice Slurry in Fish Preservation

Retaining the freshness and integrity of your catch demands speed and mastery of temperature management. As fish are cold-blooded creatures, they originate from an environment with constant temperature regulations. However, fishing throws them into a new world with drastically different temperatures. You might be open to the temptation of dunking your prized catch on the ice, but let’s pause the instinctive reaction momentarily. Direct cold is only sometimes the answer.

The effects of an immediate temperature shock from an excessive direct cold temperature can be rather destructive. Exposing your catch to an abrupt cold snap may cause the flesh to contract sharply. This disruption to its structure can cause it to become rigid and lose some of its succulent characteristics. And that, dear friends, is the last thing we want.

The answer to avoiding shocking our piscatorial prizes lies in a single intriguing term – you may already know it – the ice slurry. But what makes the ice slurry so unique, you ask?

Comprising a mixture of crushed ice and seawater or saltwater, an ice slurry ensures a slower and gentler reduction in temperature while holding at an ideal constant cold environment that’s simply perfect for slowing metabolism and bacterial growth.

A direct cold application can shock a fish, while an ice slurry provides a gradual and controlled cold transition. An ice slurry also gives a full-body coverage that direct cold can’t, thereby ensuring an even spread of optimal temperature throughout your catch, preventing ‘hot’ spots where bacteria might thrive.

Cooling MethodsMaterials NeededProsCons
Direct ColdIce, coolerEasy to manage, quickly lowers temperatureDoesn’t chill the fish evenly
Ice SlurryIce, water, sea salt, containerChills fish faster and more evenlyRequires more materials, slightly more complex
Bottles of SaltwaterSaltwater, bottles, freezerConvenient, portable, reusableMore time-consuming to prepare
Flaked IceFlaked ice machineHighly effective cooling preserves fish qualityRequires a specialised machine, potentially expensive

Creating Your Own Arctic Ocean: The Benefits of Bottled Saltwater and Ice

A handy trick that savvy anglers swear by involves the preparation of ice. It hinges on the fact that a brine solution – water with salt dissolved in it – has a freezing point below zero degrees Celsius. 

Firstly, find out the temperature of your freezer. Then, prepare a saltwater solution with a freezing point that’s 5 degrees higher. Pour this solution into your containers, leaving about a fifth of the volume as buffer space to avoid an explosive situation during freezing. Cap off those containers and place them in your freezer. The beauty of this is that as the salt-infused ice thaws, it maintains a sub-zero temperature and, in turn, keeps your ice box cooler for longer. 

Let us dive deeper into the ‘icy’ heart of the matter. To calculate the freezing point of a brine solution, you need to take the initial freezing point of the water, typically 0 degrees Celsius, and subtract the product of the molality of the salt solution, the freezing point depression constant for water, and the number of ions formed when salt dissolves. Boiling it down to a formula, you’re sailing along these lines: 

∆TF = iKTm 

In that equation, ∆TF is the change in the freezing point, i represents the number of ions per formula unit, K is the freezing point depression constant (a mighty 1.86°C for water), and Tm is the molality of the solution.

Yup. I can see us all working that one out – here are a couple of quick ‘rough’ working examples –

  • If your freezer’s temperature is -20 degrees Celsius, aim for a brine with a freezing point of -15. For 100ml of water, you’ll need 22g of salt.
  • For a freezer temperature of -15 degrees Celsius, your brine should freeze at -10. In this case, 100ml of water will require 15g of salt.
  • If your freezer cools to -10 degrees Celsius, aim for a brine freezing point of -5. Here, 8g of salt should be mixed into every 100ml of water.

Don’t Spoil the Spoils: Why Fresh Tap Water is a Fish’s Foe

If fresh water is essential to humans, why wouldn’t it be the same for our precious cargo, the fish? Ironically, fresh tap water can be more damaging to your bounty than helpful, and it’s all down to the hidden organisms that inhabit its depths. 

When you turn that tap, unknowingly, you’re releasing much more than just water – you’re releasing a microscopic melange of microbes, a hidden universe of bacteria, fungi, and waterborne parasites. And while these are mostly harmless to us (largely thanks to our immune systems and water treatment processes), it’s a different story for your catch of the day. 

Remember, fish, especially those from salt environments, have evolved to thrive in conditions broadly absent of such microbial fauna. Their systems haven’t had to deal with the same microbial challenges as ours, and thus, a sudden microbe influx can lead to fast spoilage and unwanted health implications when consumed. 

Is it translating all this scientific jargon into layperson’s terms? Putting your fish under tap water is akin to dousing them with a foul potion, one that hastens decay and impacts the quality of the meat. It’s like offering a banquet, inviting many bacteria and enzymes to feast upon this aquatic treasure. It’s the most effective way to ruin your day’s hard work. 

Unlocking the Secrets of Salt: Why It’s a Fisherman’s Best Friend 

This brings us to salt, a simple compound that’s been used for centuries for seasoning and food preservation. Unlike freshwater, saltwater and salty environments present a harsh terrain for those unwanted microbes. 

Consider it, if you will, like a guardian angel for your catch. Imbued with protective qualities, it works tirelessly to fight off microbial invaders, slowing decay and maintaining freshness. And surprisingly, it does this in the most unassuming way: by pulling water out of bacterial cells through osmosis, effectively sucking the life out of them, thus halting their proliferation. 

In contrast to tap water, a nice bath in saltwater can significantly extend the shelf life of your catch, ensuring optimal quality when it finally graces your dinner table.

Seawater vs Saltwater: Choosing the Right Brine for Your Catch

I recently read an online debate about freshwater vs saltwater vs seawater – with many people simply repeating what they have previously heard, without any actual substance about their justification that seawater is flat-out better for your fish.

Let’s recap what we have already learned, though – fresh water is a no-go because of the potential microbes that it carries – it’s not simply just because it’s ‘freshwater’. Seawater, due to its salt content, doesn’t generally have this problem – though it could still carry contaminants that you don’t want near your (inner Harbour Auckland anyone?) – so – logically, purified water, with a measured amount of salt added back in, and nothing else would be the best option yet, would it not? Well – what is salt ice made out of?

Water TypeMicrobe LevelContaminant LevelSuitability for Fish
Fresh WaterHighVariesPoor
SeawaterLowCan be highModerate
Saltwater (made with purified water)MinimalLowBest

Your Catch, Your Kitchen: Preparing Your Fish for the Culinary Spotlight

  • Cooling your fish properly slows down the bacterial and enzymatic decomposition processes that can ruin the taste and texture of your catch.
  • An ice slurry is an effective method for chilling fish. It consists of a mixture of ice and water and can reduce the core temperature of your catch more quickly than direct cold.
  • Bottles of salt water can also be used to cool fish. Stored in the freezer, these can provide a quick and easy cooling solution in the heat of the moment.
  • Flaked ice is excellent for cooling fish rapidly, as its high surface-area-to-volume ratio allows quick heat transfer. As such, it is a good solution for larger catches.
  • Saltwater is far more beneficial for your catch than fresh water. The latter, especially from a tap, can contain harmful microbes that could negatively affect your catch.
  • Sea salt possesses hypotonic properties that help to combat bacteria on your caught fish, making it an advantageous option for preserving your catch.
  • Direct cold (as exerted by putting your fresh catch directly into a cooler or fridge) does offer effective initial cooling. Still, it should be supplemented with other adequate, long-term temperature maintenance methods.