Proteins

Climbing Perch (Koi)

The Bengali 'koi' fish — climbing perch braised in mustard-oil curries for festive meals.

Koi, the Bengali name for climbing perch, is a small, hardy freshwater fish with firm flesh and a distinctive flavor. It is treated as a delicacy in Bengali cuisine, braised in mustard-oil curries (koi macher jhol) and served at celebrations. Despite its bones, it is prized for its rich taste and is traditionally cooked whole.

Climbing perch, called koi in Bengali, is a small freshwater fish (Anabas testudineus) native to the wetlands and ponds of South and Southeast Asia. Its name comes from a remarkable ability — it can survive out of water for extended periods and even climb inclines by wriggling and using its gill covers as hooks, which made it historically accessible to rural populations far from waterways. In Bengali kitchens, koi holds a place that transcends its modest size and low price: it is one of the few fish considered auspicious for specific rituals and appears on mandatory menus at weddings and festivals. The flesh is sweet and delicate, with a pronounced fishiness that Bengali cooks embrace rather than mask, and the bones — though small and numerous — soften during long cooking, making every part of the fish edible. This reflects a deep culinary philosophy of minimal waste, where the head, fins, and frame are prized contributors of body and flavour in braised dishes.

Koi's small scale (typically 15–25 cm) and firm flesh make it extraordinarily versatile — it stands up to heavy mustard-oil braises, surrenders to gentle steaming, and crisps beautifully when fried whole. The fish spoils quickly after death, more so than most freshwater species, which is why traditional markets sell it alive or freshly killed and why cooks treat it within hours of purchase. The flavour peaks in winter months (November–February), when the flesh is firmest and the sweetness most pronounced. In rural Bengal, surplus catches are salted and sun-dried for preservation, reconstituted in dal and torkari dishes throughout the lean season — a practice that also concentrates the fish's umami character into something deeply savoury.

Understanding koi means understanding Bengali fish cookery's core tension: the fish is delicate enough to ruin with overcooking, yet robust enough in flavour to anchor rich, spiced gravies. Master that balance and you have access to a fish that is simultaneously an everyday staple and a festive centrepiece — the same small creature appearing in humble weeknight jhol and on the platters of wedding feasts.

Measured in: piece
Storage: Fridge

Allergens

Fish

Types & varieties

Koi machh (whole small)

Most common market form; sold alive or freshly killed by fishmongers; used in most preparations

Koi bhuna style

Slightly larger specimens preferred for thick, slow-cooked bhuna gravies where the fish holds its shape through long simmering

Dried/salted koi

Sun-dried and salt-cured; reconstituted in dal or torkari; shelf-stable for months; soaking in warm water for 30 minutes reduces excess saltiness

Buying and Selecting Koi

In Bengali markets, koi is sold alive or freshly killed — this is the single most important indicator of quality. If buying from a fishmonger who has already cleaned the fish, check that the gills are bright red or pink, not brown or grey. The eyes should be clear and slightly bulging. Press the flesh with a finger: it should spring back immediately and feel firm, not leave an indentation. A mild sweet, ocean-like scent confirms freshness; any ammonia or sour smell is disqualifying. Because koi spoils rapidly after death, buy it last on your market visit and cook it within 24 hours. In winter months, slightly longer storage (up to 36 hours in the coldest part of the refrigerator) may be acceptable, but the flavour will have dulled. If the fish is for a special occasion, ask your fishmonger to save live koi and kill it just before you cook.

Buy live or freshly killed — avoid pre-cleaned koi whose provenance you cannot verify
Look for clear, bulging eyes and bright red gills
Press-test the flesh: it should spring back firmly
Smell for ammonia or sour notes — never cook fish that smells off
Purchase last on market visits and cook the same day

The Bengali Philosophy of Whole-Fish Cookery

Koi teaches a fundamental principle of Bengali fish cookery: no part of the fish is wasted. The head, fins, and frame are not removed and discarded as in some culinary traditions — they are left on and cooked through, contributing body, gelatin, and flavour to the gravy. The small bones soften during braising to the point where they are edible, a texture Bengali cooks call khara — slightly firm but not threatening. This approach is both cultural and practical: in a cuisine built around the subtle flavour of freshwater fish, the head and bones carry significant umami that defines the finished dish. When a Bengali cook prepares koi dalna, the gravy is partly built from the dissolved collagen and minerals released from the fish frame during slow cooking. Treating koi as a fillet to be deboned is not wrong, but it loses the essence of how this fish belongs in Bengali cooking.

Cook koi whole — head, fins, and frame included
The bones soften during braising and become edible
The head and frame enrich gravies with body and umami
Deboning strips koi of its cultural and culinary identity

Common uses

Mustard-oil braises (koi muithya, koi kalia) — the hallmark festive preparation with turmeric, green chilli, and kasundi mustard pasteShallow-fried whole (koi bhaja) — crisp exterior, flaky interior; served with rice and dal as a snack or sideSteamed in banana leaf (koi pathuri or koi chhopti) — with gram flour, coconut, and spices; a festive Bengali delicacyDalna — thin, tart gravy with tomatoes, brinjal, or potato; the standard everyday preparationJhol — light soupy curry with turai or lau vegetables; weeknight cookingBhuna — thick, slow-cooked gravy where larger koi absorb a concentrated spice base over 30–40 minutes of gentle simmeringDried koi in dal — reconstituted salted koi added to masoor or toor dal; the dal becomes the vehicle for intense umami

Tips & pitfalls

Never overcook — koi flesh turns chalky and loses its subtle sweetness if boiled aggressively; maintain a gentle simmer or use high heat only for frying
Salt the fish lightly before frying to draw surface moisture and achieve even, crisp browning without splattering
For curries, marinate in turmeric and salt for 15 minutes before cooking to firm the flesh and reduce perceived fishiness
When using mustard-based gravies, bloom the mustard paste in hot oil before adding liquid — this eliminates raw bitterness and develops the characteristic kasundi aroma
The head and bones are edible and prized in Bengali cooking — do not discard; they contribute body and richness to braised dishes
For banana-leaf steaming (pathuri), secure the parcel tightly with twine and steam over medium heat for 15–20 minutes; opening too early causes the fish to tear
If using dried koi, soak in warm water for 30 minutes before cooking; taste and adjust salt before adding to dal as curing salt levels vary
Common mistake: buying stale koi — it spoils faster than most fish; always press the flesh and smell it; ammonia or sour notes mean it is past use
Avoid heavy tomato-based gravies with small koi — the acidity overwhelms the delicate sweetness; save tomato for dalna with larger specimens

Nutrition

124kcal

Energy

519 kJ · per 100 g

Where the calories come from

Protein 68%Carbs 0%Fat 32%

Protein

20g

40% DV

Carbs

0% DV

Fat

4.2g

5% DV

Fiber

0% DV

Sodium

60mg

3% DV

Notable micronutrients

Vitamin B12225% DV

Selenium66% DV

Niacin (B3)37% DV

Vitamin B624% DV

Phosphorus18% DV

Vitamin A13% DV

Source · USDA FoodData Central · approx. Fish, bluefish, raw

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In the shops

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Good to know

Origin: South and Southeast Asia; widely available in Bengal (Bangladesh and West Bengal, India)
Scientific Name: Anabas testudineus
Common Names: Koi (Bengali), Climbing Perch, Vietnamese: cá rô, Thai: pla kee tua
Size: Small fish, typically 15–25 cm; market weight rarely exceeds 200g
Flavour: Sweet, delicate white flesh with pronounced fishiness; bones are small but numerous and soften during cooking
Season: Available year-round; peak quality in winter (November–February)
Freshness Test: Clear, bulging eyes; bright red or pink gills; firm flesh that springs back when pressed; mild sweet scent, not ammonia
Storage: Use within 24 hours of purchase; can be salted and dried for months (common in rural Bengal)
Price: Inexpensive staple; not a luxury fish
Preparation: Scales are small and firmly attached — thorough scaling is essential. Gut quickly as the innards spoil fast.

Substitutes

Puti (Indian barb) — Smaller and bonier, but shares a similar texture and fishiness; use 1:1 in curries and bhajas
Mola (Hilsa minnow) — Comparable size and oil content; good for frying; slightly milder flavour; a close second in Bengali markets
Small tilapia — Less fishy and bonier, but acceptable in bhuna and jhol preparations when koi is unavailable
Snakehead (murrel/channa) — Firmer flesh, less bony; use smaller specimens; not traditional for koi dishes but works in kalia and bhuna

Pairs with

Mustard oilTurmericGreen chilliKasundi (Bengali mustard paste)Posto (poppy seed paste)Brinjal (baingan)CoconutBrinjal and potato together

Also called

Climbing Perch · Koi Mach · Anabas