Blue Swimmer Crab (Nela Kekra)

Introduction

The Blue Swimmer Crab, scientifically known as Portunus pelagicus, is a coastal crab species highly prized for its sweet, succulent meat and tender texture. Known as Nila Kekra (نیلا کیکڑا) in Pakistan, this crab is found along the Arabian Sea coast, particularly in Karachi, Balochistan, and other parts of Southern Pakistan.

The Blue Swimmer Crab gets its name from its vibrant blue claws, which contrast beautifully with its olive or dark green body. This crab is highly sought after in the seafood market due to its delicate, sweet meat that remains tender after cooking. The Blue Swimmer Crab is popular in various culinary applications, including grilling, steaming, and adding to rich seafood curries. Despite having a relatively moderate meat yield compared to other crabs, its rich taste and versatility in the kitchen make it a highly favored delicacy.

Deep Dive: Habitat, Diet & Growth

Habitat

The Blue Swimmer Crab is predominantly found in shallow coastal waters, including estuaries, mangroves, and mudflats. These habitats provide the crabs with access to abundant food sources and protection from predators. In Pakistan, they are often harvested from Karachi, Balochistan, and other coastal regions along the Arabian Sea, where the water is typically brackish and rich in nutrients.

These crabs prefer the sandy or muddy substrates of the intertidal zones, where they can easily burrow to find shelter and food. The crabs are capable of swimming in open waters as well, which is why they are often referred to as swimmer crabs. Their presence in mangrove forests, where salt and fresh water meet, ensures that they can thrive and reproduce in an environment that supports their rapid growth.

The habitat also plays a vital role in the development of the crabs, as it provides them with a natural balance of food sources and environmental conditions that promote healthy growth.

Diet

The diet of the Blue Swimmer Crab is diverse, as it is an opportunistic feeder. These crabs primarily consume small fish, mollusks, polychaetes (marine worms), and other crustaceans that live in their environment. Blue Swimmer Crabs are particularly adept at scavenging, using their strong claws to capture and break down their prey.

Their diet heavily influences the texture and flavor of the meat, contributing to the sweetness and moisture that make Blue Swimmer Crab meat so desirable. Studies have shown that during the warmer months, their diet consists mainly of benthic organisms and mollusks, which are abundant in their coastal habitats. However, their opportunistic nature means that they will feed on whatever is available, making them highly adaptable to changing food sources.

Growth

Blue Swimmer Crabs exhibit rapid growth during their early life stages. In optimal conditions, they can grow up to 25 cm in carapace width, and their growth rate is influenced by factors such as water temperature, salinity, and available food. The crabs molt (shed their exoskeleton) several times during their life, with the size of their carapace increasing after each molt.

They reach maturity in about 12-18 months, depending on environmental conditions and food availability. This fast growth rate is one of the reasons why Blue Swimmer Crabs are so popular in commercial fishing, as they can be harvested within a short amount of time. The crabs are capable of reproducing multiple times per year, with females releasing millions of eggs into the water during the spawning season.

Concise Addition: Spawning & Conservation

The Blue Swimmer Crab spawns during the warmer months, with females releasing eggs that are fertilized externally. The larvae then develop into juvenile crabs through several stages, growing rapidly in the rich coastal habitats. The crabs play an important ecological role, as they help control populations of other marine species.

Although the Blue Swimmer Crab is not listed as endangered by the IUCN, conservation efforts are important to prevent overfishing, which could lead to population declines. Efforts focus on sustainable harvesting, protecting their natural habitats, and ensuring responsible fishing practices. Maintaining the health of mangrove forests and estuarine ecosystems is vital for the continued survival of this species.

Names & Taxonomy

• Common Name: Blue Swimmer Crab

• Local Name in Pakistan: Nila Kekra (نیلا کیکڑا)

• Scientific Name: Portunus pelagicus

• Family: Portunidae

• Order: Decapoda

• Class: Malacostraca

The Blue Swimmer Crab belongs to the family Portunidae, which is known for its swimming crabs. Its unique ability to swim sets it apart from other crabs that are primarily burrowers. The blue coloration of its claws is one of the defining characteristics that makes it easily recognizable.

Sourcing & Catching Method

Blue Swimmer Crabs are wild-caught using traditional fishing methods such as crab pots, trap fishing, and gill nets. Local fishermen employ sustainable practices to catch the crabs, minimizing harm to the surrounding environment and ensuring the crabs’ populations remain healthy.

Fishing for Blue Swimmer Crabs is typically done in mangrove forests and shallow coastal waters, where the crabs are most abundant. Once caught, the crabs are handled with care to maintain freshness and are delivered to local seafood markets and distributors. Sustainable practices, including size limits and controlled harvest periods, are essential to prevent overfishing.

Physical Traits & Texture

• Shell Color: The Blue Swimmer Crab has a dark green to olive-colored carapace with blue-tipped claws, giving it its distinctive name.

• Claws: These crabs have large, strong claws that are used for grasping and crushing their prey. The claws are typically blue in color, making them stand out visually.

• Meat Texture: The meat is firm, succulent, and moist, with a slightly sweet flavor. It is highly regarded for its tenderness and delicate texture, particularly in the claws and legs.

• Size: Blue Swimmer Crabs can grow to a carapace width of around 25 cm. The size and weight vary depending on environmental factors such as food availability and water quality.

Cutting Options & Yields

Cooking Ideas – Versatile, Rich & Crowd-Friendly

• Crab Karahi: Blue Swimmer Crab can be prepared in a spicy green masala, simmered with tomatoes, onions, and whole spices for an aromatic, flavorful dish.

• Crab Yakhni: This traditional dish involves simmering Blue Swimmer Crab in a rich broth made with whole spices, resulting in a fragrant, comforting soup.

• Spicy Garlic Butter Crab: A simple yet delicious preparation where Blue Swimmer Crabs are sautéed in butter, garlic, and chili for a mouthwatering treat.

• Crab Noodles: Stir-fry Blue Swimmer Crab with soy sauce, chili, and noodles for a delightful Asian-style meal.

• Crab Sashimi: For those who love raw seafood, Blue Swimmer Crab can be enjoyed as sashimi, with fresh crab meat and a touch of wasabi.

Tips for Selecting Fresh Blue Swimmer Crab (Nila Kekra)

• Shell: Look for a hard, intact shell with no cracks or chips.

• Claws: The blue claws should be full and unbroken.

• Eyes: The crab should have bright, clear eyes, which indicate its freshness.

• Smell: Fresh Blue Swimmer Crabs have a mild ocean scent, while a strong fishy odor is a sign of poor quality.

• Movement: The crabs should be active and responsive to touch. If they appear sluggish, they may not be fresh.

Tips for Storing Blue Swimmer Crab

• Refrigeration: Store live Blue Swimmer Crabs in the refrigerator at a temperature of 0–4°C and consume within 1–2 days for the best taste.

• Freezing: For longer storage, you can freeze the crabs in airtight containers. They are best used within 1–2 months when frozen.

• Avoid Thawing and Refreezing: Thawing and refreezing crabs can degrade the quality of the meat and impact its texture and flavor.

Nutrition Highlights (per 100 g raw meat)

• Calories: ~87 kcal

• Protein: ~18 g

• Fat: ~1.1 g

• Carbohydrates: 0 g

• Sodium: ~293 mg

• Calcium: ~89 mg

• Iron: ~0.74 mg

• Potassium: ~329 mg

Blue Swimmer Crabs are an excellent source of high-quality protein and are low in calories and fat, making them a great choice for a nutritious meal. The crabs also provide omega-3 fatty acids, vitamins, and minerals such as calcium, iron, and potassium.

Need Something Similar?

• Mud Crab: For a firmer texture and stronger flavor.

• Three Spot Crab: Delicate flavor, perfect for soups.