The Candidates

Two introduced species are ideal candidates for this recipe: redfin perch (Perca fluviatilis) and common carp (Cyprinus carpio). Both are invasive species with no size or bag limits in most Australian states — catching and using them is encouraged by fisheries authorities. Redfin in particular is excellent eating fish when handled correctly; its reputation suffers because most people who catch them do not know how to prepare them. Carp requires this pickling preparation to be palatable — it has a soft texture and strong flavour that the acid cure transforms.

Why Pickling Works

The acid in the pickling solution continues the denaturation process that cooking performs with heat — it firms the flesh, kills parasites, and preserves the fish without refrigeration for an extended period. The additional flavourings penetrate the fish over the curing time and produce a final product that has very little resemblance to the raw fish you started with. While different from traditional cold-smoking and curing methods, pickling offers an accessible preservation technique that requires minimal equipment.

Ingredients (for 500g fish fillets)

• 500g redfin or carp fillets, skin off, pin-boned, cut into 3cm pieces
• 300ml white wine vinegar
• 150ml water
• 60g white sugar
• 1.5 tablespoons salt
• 1 tablespoon yellow mustard seeds
• 1 teaspoon white peppercorns
• 4 bay leaves
• 1 brown onion, thinly sliced
• 1 lemon, sliced

Method

1. Initial salt cure: Toss fish pieces with 1 tablespoon of the salt. Cover and refrigerate for 4 hours. Rinse thoroughly and dry. This firms the flesh before the acid cure.
2. Combine vinegar, water, sugar, remaining salt, mustard seeds, peppercorns, and bay leaves in a saucepan and bring to a boil. Stir until sugar dissolves. Cool to room temperature.
3. Layer the fish, onion slices, and lemon in a sterilised jar. Pour the cooled brine over to cover completely. Seal.
4. Refrigerate for at least 48 hours before eating. Improves over 5–7 days. Keeps refrigerated for three weeks.

Serve on rye bread with cream cheese and dill, or as part of a cold platter. The result has nothing of the invasive pest about it.

The fundamental principle behind pickling freshwater fish lies in the transformative power of acid. When fish flesh is exposed to a solution with pH levels between 3.0 and 4.5, the acid denatures the proteins in much the same way heat does during cooking. This process breaks down tough fibres, firms up the texture, and creates an environment hostile to harmful bacteria while preserving the fish's nutritional value.

The acetic acid in vinegar penetrates the fish tissue, lowering the water activity (aw) to levels below 0.95, where most pathogenic bacteria cannot survive. Simultaneously, the salt component draws out moisture through osmosis, further concentrating flavours and creating an inhospitable environment for spoilage organisms. This dual action of acid and salt creates a preserved product that can last weeks when properly stored.

Essential Equipment for Fish Pickling

Success in fish pickling starts with proper equipment. You'll need non-reactive containers — glass or food-grade plastic only. Metal containers, particularly aluminium, will react with the acid and impart off-flavours to your fish. A quality set of glass mason jars from Ball or Kilner ($25-40 for a pack of six) provides the perfect storage solution, allowing you to monitor the pickling process and portion your preserved fish appropriately.

Sharp, flexible filleting knives are crucial for preparing your fish properly. The Rapala 7.5-inch Fillet Knife ($35-50) remains the gold standard among Australian anglers, maintaining its edge through countless filleting sessions. For removing pin bones from redfin, invest in quality fish tweezers or needle-nose pliers specifically designed for kitchen use.

A reliable kitchen scale ensures consistent results when measuring salt and sugar ratios. Digital scales accurate to one gram make the difference between perfectly balanced pickles and disappointing failures. Temperature control matters too — a refrigerator thermometer helps maintain the ideal 2-4°C range during the curing process.

The Perfect Pickling Solution

Creating the ideal pickling brine requires balancing acidity, salinity, and sweetness. Start with a base ratio of 3:2:1 — three parts quality white vinegar (5% acidity minimum), two parts water, and one part white sugar. For every litre of this base solution, add 60 grams of non-iodised salt. Iodised table salt can cloud the brine and affect flavour development.

White vinegar works well for neutral-flavoured pickles, but apple cider vinegar adds complexity and depth. Rice wine vinegar produces particularly delicate results with redfin. Avoid cheap, synthetic vinegars — their harsh acidity overwhelms the fish's natural flavours. Quality vinegar costs more upfront but transforms your pickled fish from acceptable to exceptional.

Species-Specific Preparation Techniques

Redfin Perch Preparation

Redfin perch responds beautifully to pickling when prepared correctly. Start by scaling thoroughly — redfin scales are particularly stubborn and require patience. Fillet along the backbone, then remove the rib bones carefully. The key challenge with redfin lies in the pin bones running through the fillet's centre.

For smaller redfin (under 25cm), score the fillet at 5mm intervals perpendicular to the pin bone line. This cuts through the bones, making them undetectable in the final product. Larger redfin allow for pin bone removal using tweezers — time-consuming but worthwhile for presentation. Cut fillets into portion-sized pieces, typically 3-4cm strips for optimal acid penetration.

Carp Processing

Carp requires more aggressive preparation due to its muddy flavour and soft texture. Immediately after landing, bleed the fish by cutting behind the gills and placing in cool water. This technique applies whether you're processing carp from your local dam or utilising the results from catching quality Murray cod fishing sessions where carp are common bycatch. Unlike the selective nature of wild trout fishing, carp removal benefits our waterways while providing excellent pickling material.