Most people have never thought about what happens between a fish being pulled from the water and a tin landing on their counter. The assumption, if there is one, is that the fish goes in, the lid goes on, and that's more or less it. The reality is a more complicated series of deliberate steps: sourcing decisions made months before production begins, a pre-cooking stage, packers positioning fish by hand one at a time, and a pressurized sterilization process that makes shelf stability possible. In the case of our anchovies, a salt cure that runs for the better part of a year. 

From catch to can, each step exists for a reason, and understanding those steps changes how you see what's inside a tin of the world’s tastiest tinned fish!

Which Fish, Which Fishery, Which Season

Every tin starts with a sourcing decision.  Quality defines Fishwife's products, so this decision is taken seriously.

Species selection begins with where a fish lives and what it eats. Fish in colder, deeper water tend to accumulate more fat, which translates directly into flavor and richness in the tin. Fish from warmer, shallower water tend to be leaner and milder. Neither is better in an absolute sense.  Take our sardines: because we want a fatty, supple tin rather than a lean, dry one, water temperature is one of the first things we weigh when we choose where to source them. 

Fishery selection follows from there. Our cannery partners fish on specific, managed grounds where catch is regulated, and populations are monitored. Our sardines, anchovies, albacore tuna, and mackerel all carry MSC (Marine Stewardship Council) certification, which means an independent third party has verified that the fishery is operating sustainably. For farmed products like salmon and trout, the equivalent standard is ASC (Aquaculture Stewardship Council) certification.

Season matters too. UK sardines run in late spring and early summer, and the Iberian season follows a little later in the summer. The canneries we work with schedule production around these windows, not the other way around. 

Why Freshness Is Non-Negotiable

Once a catch arrives at port, the clock starts, but the urgency varies dramatically by species.

Sardines and anchovies are among the most fragile fish in commercial fishing. They're small, thin-skinned, and high in fat, meaning they deteriorate quickly. If they aren't cooled immediately after being caught, the fish begin to rupture due to their own gut enzymes. The skin tears, the flesh softens, and the quality degrades beyond the point of recovery, not just in terms of flavor but also in what can actually survive the canning process intact.

For sardines specifically, purse seine nets (large circular nets that encircle an entire school) bring the fish up fast. From there, they immediately go into the ice slurry. The journey from boat to cannery, whether via an auction house or direct delivery, happens as quickly as possible.

Larger, denser fish like albacore tuna are more forgiving. They can be handled over a longer timeline without the same risk of degradation. However, quality-focused canneries still move quickly, and the handling standards at the facilities we partner with reflect that.

Inside the Cannery: The Pre-Cooking Step Most People Don't Know About

Ask most people to describe how tinned fish is made, and they'll describe fish going into a tin and getting cooked. That's not wrong, but it skips a step that makes a significant difference.

Before packing, the fish is pre-cooked.

For sardines, the method is a steam tunnel: the fish pass through on a conveyor belt, exposed to controlled steam heat. For tuna, the loins are poached in salted water before any packing.

Why? Several reasons. The pre-cook stabilizes the fish's moisture level, which affects how it behaves after the tin is sealed. It also helps preserve flavor. Fish that skips the pre-cook and goes straight into the retort (more on that below) is cooking in a closed, pressurized environment with less control over the outcome. The pre-cook also eliminates the white, chalky globules of denatured protein that show up when fish is cooked poorly or too aggressively. You've probably seen this on a badly cooked fillet at home. In a tin, it's the equivalent signal that something went wrong upstream.

This is one of the things that separates commodity tinned fish from the kind of product that actually tastes good.

Hand-Packing: Why People, Not Machines, Position the Fish

In the case of sardines, after the pre-cook and head/tail removal, they go into a salty water bath, and the packing line begins.

On either side of the conveyor, packers pull each fish from the bath by hand, position it in the tin, and add the flavoring: a slice of preserved lemon, a whole hot pepper, a small measure of olive oil. The process repeats, fish by fish, tin by tin, across a full production run.

This is hand-packing, and it matters more than it might sound.

Machines can fill tins. They can deposit fish in bulk. What they cannot do is orient every fish correctly, account for size variation within a batch, or position a whole hot pepper so that it's actually in contact with the fish rather than just sitting on top of it. The artisanship visible when you open a well-packed tin is because someone cared and did it by hand.

The sauces in Fishwife tins follow different paths depending on the product. Some are made on-site in the cannery's own commercial kitchen. Others, like the pesto for our mussels, are produced off-site following Fishwife’s proprietary recipe and shipped to the cannery for packing.

This is what distinguishes the cannery partners we work with from commodity production. Our partners are multi-generational, family-owned operations where packers have been doing this work for years, sometimes decades. The average employee tenure at one of our sardine canneries is over ten years; that consistency shows in our tins.

The Retort: How a Sealed Can Becomes Shelf-Stable

Once the tin is filled, a seamer closes it, forming an airtight seal. At that point, the tin goes into the retort.

The retort is essentially a large industrial pressure cooker. It subjects sealed tins to precisely controlled heat and pressure, reaching temperatures above those achievable by a standard boil. The goal is commercial sterility: the elimination of any microorganisms that could cause spoilage or illness.

This is why a properly processed tin of sardines or tuna can sit on a shelf for years without refrigeration. It's not the salt, it's not the olive oil, it's the heat treatment. Commercial sterility, achieved through the retort, is what makes the product safe.

The retort also creates one of the most interesting R&D challenges in tinned fish development. When a sauce or marinade goes through the retort, it doesn't come out the same way it went in. High sugar content can caramelize or burn. Delicate flavors can be muted. Textures can shift. That means developing a new Fishwife SKU isn't just about getting the sauce right in a test kitchen; it's about understanding how that sauce will behave after it's been sealed in a tin and subjected to industrial heat. The formula that works before the retort may be completely different from the formula that survives it. Iteration is built into the process.

The Exception: Anchovies and the Months-Long Cure

Everything described above applies to sardines, tuna, mackerel, and most tinned fish. Anchovies work entirely differently.

Anchovies are not commercially sterile. They are cured.

The process begins immediately after the catch. The fish are cleaned, sorted by size, all by hand, then placed in large barrels layered with coarse rock salt. Each barrel holds hundreds of kilograms of fish. There they remain for a minimum of six months, sometimes up to a year.

During that time, the salt draws moisture out of the fish while enzymes within the fish break down proteins and cell structures. This is what produces the flavor anchovies are known for: the deep, savory, umami richness that distinguishes them from any other tinned fish. It's not added. It's made, slowly, from the inside out. The fish will turn reddish and develop a firmer, more compact texture.

After the maturation period, the fish are washed, briefly scalded to loosen the skin, and then cleaned entirely by hand: the skin is removed with a cloth, the spine is extracted, and the remaining innards are trimmed. The fillets are then dried to remove excess moisture, hand-packed in olive oil, and sealed. 

There's one important thing to know about storing anchovies at home: while they’re shelf-stable, they’re best kept cold. The curing process doesn't stop when the tin is sealed. It continues, slowly, at ambient temperature. An anchovy tin stored at 75 to 80°F for an extended period can become soft and mushy inside. The fish remains safe to eat, but the texture continues to evolve beyond what left the cannery.

Your Fishwife Anchovies are completely safe to store in the pantry, so don't worry if that's where you've kept them. But if you're planning to hold onto them for a while, we recommend storing them in the refrigerator. Cooler temperatures slow the curing process and help preserve the texture and flavor exactly as our producers intended. Once you've opened a tin, refrigerate any leftovers. 

The Fishwife Cantabrian anchovies come from Santoña, a town on Spain's northern coast where the craft of salt-curing anchovies has shaped local life for generations. 

Smoking: An Entirely Different Production Line

Smoked tinned fish, salmon, trout, and mackerel require a different process from the ground up.

Smoking typically happens in a separate facility from conventional canning, because the equipment required is fundamentally different. First, the fish is brined in a salt-and-sugar cure, sometimes with additional spices that vary by product, then cold- or hot-smoked over wood.

The canneries and smokehouses we partner with use actual wood. For our salmon and trout products, that means beech, maple, and birch in small batches. For the mackerel, beech wood. No liquid smoke, no shortcuts. The type of wood, the temperature, and the duration of exposure are tightly controlled because they determine the flavor.

Smoking reduces the moisture content of the fish considerably, which is part of why the texture of smoked tinned fish is firmer and more layered than its fresh-packed equivalents. It's also one of the more proprietary parts of the process. The specific brining formulas and smoking profiles are closely guarded.

After smoking, the fish is packed and processed through a retort, achieving commercial sterility just like the non-smoked products.

Why All of This Matters

Most tinned fish is not made this way. Commodity production uses high-volume lines optimized for capacity, not precision. Fish is machine-packed, so every tin looks fairly similar. Unlike hand-packed fish, producers aren’t making adjustments based on how the fish is arranged or how the flavoring is distributed.

The process described above for our Cantabrian anchovies - careful sourcing, cold-chain handling from boat to cannery, pre-cooking, hand-packing, and the months-long curing process - is what artisanal tinned fish production actually looks like. 

It's what justifies the term "conservas," the European tradition of treating tinned seafood as a finished, quality food product rather than a commodity.

Shop the Fishwife Collection!

Understanding the process helps you understand what you're buying when you open a Fishwife tin. Every tin in the Fishwife line is the result of sourcing decisions, hand-packing, months in salt, and careful iteration through the retort. Browse the full collection.