Say Aloha to the Pacific Threadfin (Moi). Meet the Polydactylus sexfilis, a fascinating species of marine ray-finned fish, commonly known as the Pacific threadfin or Hawaiian moi. This unique fish belongs to the Polynemidae family and is native to the expansive Indian and Pacific Oceans. Growing up to a maximum length of 61 cm and a weight of 3.2 kg, it’s no wonder why this fish is such a popular catch!
7 Amazing Moi Fish Fun Facts
- Ancient Ponds: Moi were farmed in cleverly designed, centuries-old Hawaiian ponds called “loko ia.”
- Moonlit Spawners: These fish prefer spawning during moonlit nights, near the third lunar quarter.
- Changing Genders: The Pacific threadfin switches from male to female during its lifetime – a rare and fascinating trait.
- Prehistoric Fish: Moi’s family, Polynemidae, has a 50-million-year-old history, dating back to the Eocene epoch.
- Cultural Significance: In ancient Hawaii, only male royalty could eat moi, making it a truly royal delicacy.
- Conservation Success: Moi returned to Hawaii’s Kiholo Pond after a decade-long absence, thanks to habitat restoration efforts.
- Aquaculture Innovations: Researchers have developed a genetically-enhanced moi line with a 25% increase in growth performance.
|Scientific Name||Polydactylus sexfilis|
|Common Names||Moi, Pacific Threadfin, Sixfinger Threadfin|
|Description and Appearance||Moi is a medium-sized marine fish with a compressed body, silver-gray color, and a distinctive dorsal fin divided into two sections. It has six long, thread-like pectoral filaments that extend from the pectoral fin, which are sensory organs used to detect prey.|
|Size||Moi typically grow to a length of 30-40 cm (12-16 inches) and can weigh up to 2.3 kg (5 pounds).|
|Habitat||Moi inhabit shallow coastal waters, estuaries, and lagoons, usually over sandy or muddy bottoms. They can also be found in areas with seagrass beds and coral reefs.|
|Distribution||Moi are distributed throughout the tropical and subtropical waters of the Indo-Pacific region, from the eastern coast of Africa to the Hawaiian Islands, and from Japan to Australia.|
|Diet||Moi are omnivorous, feeding on a variety of prey items, including small fish, crustaceans, and mollusks. They also consume algae and detritus.|
|Reproduction||Moi spawn multiple times throughout the year, with peak spawning typically occurring during the summer months. They are broadcast spawners, releasing their eggs and sperm into the water column for fertilization. The eggs and larvae are then dispersed by ocean currents.|
|Lifespan||Moi can live for up to 5-7 years in the wild.|
|Ecological Role||As a mid-level predator, the moi plays an important role in maintaining the balance of marine ecosystems by controlling the population of smaller prey species. It is also prey for larger predators, such as sharks and larger fish.|
|Predators||Larger fish, sharks, and marine mammals are known predators of the moi.|
|Conservation Status||Moi is not considered to be threatened globally and is listed as Least Concern by the IUCN Red List. However, local populations may be affected by overfishing and habitat degradation.|
|Economic Importance||Moi is a popular food fish and an important component of commercial and artisanal fisheries in many parts of its range. It is also a popular recreational sportfish in some areas.|
|Human Interaction||Moi has been a culturally significant fish for many Pacific Island communities, particularly in Hawaii, where it was historically reserved for royalty. Today, it is a popular food fish and recreational sportfish.|
|Evolution||The genus Polydactylus, to which moi belongs, is part of the Polynemidae family, which has a fossil record dating back to the Eocene epoch (56-33.9 million years ago). Moi’s specific evolutionary history is not well understood.|
|Adaptations||Moi’s long, thread-like pectoral filaments are a unique adaptation that allows them to detect prey in their environment. Their compressed body shape and silver-gray coloration help them blend in with their surroundings, providing camouflage from both predators and prey.|
|Research and Discoveries||Research on moi has focused on their biology, ecology, and population dynamics, as well as their potential for aquaculture. In recent years, there has been interest in developing sustainable aquaculture production for moi to reduce pressure on wild populations and meet increasing demand for this highly prized fish.|
|Captivity and Aquarium Trade||Moi is not commonly kept in home aquariums due to its size and specific habitat requirements. However, they are sometimes displayed in public aquariums and research facilities.|
Get to Know the Physical Features of the Moi (Pacific Threadfin)
The Pacific threadfin sports a pointed snout and an almost-horizontal profile. It has two separate dorsal fins, with the first dorsal fin featuring 8 spines and the second with a single spine accompanied by 12 or 13 soft rays. The anal fin is equipped with 3 spines and 11 or 12 soft rays, while the pectoral fin has 15 or 16 rays.
The caudal fin of the moi is deeply forked and comes with non-filamentous lobes. The lateral line, which has 60 to 67 pored scales, runs from the upper end of the gill slit to the upper end of the lower lobe of the caudal fin. These distinctive features make the Pacific threadfin easily identifiable among other fish species.
Where in the World is the Pacific Threadfin?
The Pacific threadfin has a widespread Indo-Pacific distribution. Adult moi prefer inhabiting turbid waters and can often be found in sandy holes along rocky shores. They thrive in the near-shore environment and are known to form large schools, making them a popular sight for divers and fishermen alike.
Munching on Crustaceans: The Moi’s Diet
When it comes to food, the Pacific threadfin is quite the fan of crustaceans and small fish. These benthic feeders have a particular preference for penaeid and caridean shrimps. Both juvenile and adult moi feed throughout the day, ensuring they consume enough energy to maintain their active lifestyles.
A Fascinating Lifecycle: From Males to Females
One of the most interesting aspects of the Pacific threadfin is its reproductive process. These fish are protandrous hermaphrodites, meaning they change from male to female during their lifetimes. The spawning season for the moi occurs between June and September, with peak spawning happening in the summer months.
Moi eggs are quite small, averaging at 0.75mm in diameter. Spawning typically takes place inshore, while the eggs hatch offshore. This unique reproductive process ensures the continued survival and growth of the Pacific threadfin population.
The Royal Fish: Moi and Hawaiian Culture
In Hawaii, the Pacific threadfin, or moi, holds a special place in history and culture. Moi was considered a delicacy reserved exclusively for male royalty, making it a highly sought-after fish in ancient times. However, with the arrival of Westernization, the prohibition on moi was lifted, allowing more people to enjoy this delicious fish.
Throughout the 1990s, stock-enhancement programs were implemented to rebuild the sport fishery for moi, due to the depletion of its wild stock. While commercial fishing for moi remains virtually nonexistent, aquaculture operations now provide stock for moi farmers across Hawaii. In pre-colonial Hawaii, moi was even farmed in specially-created ponds, showcasing the long-standing relationship between Hawaiians and this beloved fish.
Market Name and Popularity: Moi, the Tasty Catch
Moi is the market name for the Pacific threadfin and is highly regarded for its excellent flesh quality. It is typically sold whole or whole-gutted in limited quantities, due to its scarcity. With a shelf-life of 14 days, the moi remains fresh for a considerable period. In case you can’t get your hands on this scrumptious fish, market substitutes include black sea bass and hybrid striped bass.
Nutritious and Delicious: Moi’s Product Profile
The flesh of the Pacific threadfin is white to light gray and cooks up white, making it a visually appealing dish. The rich, mild-flavored meat is moist, tender, and flaky, providing a delectable culinary experience. Moi’s relatively high oil content helps keep the meat moist and enhances its taste.
Per serving, moi provides 122 calories, 4.1 grams of total fat, 1.4 grams of saturated fat, 69 mg of cholesterol, 73 mg of sodium, and 21.1 grams of protein. It’s a nutritious and delicious option for seafood lovers.
Cooking Tips: Savoring the Flavor of Moi
There are various ways to prepare and enjoy the Pacific threadfin. You can steam or bake the whole fish or sear fillets, depending on your preference. Moi can also be grilled, broiled, pan-fried, or even served raw as sashimi. Its oil content makes smoking a viable option as well, adding a unique twist to this versatile fish.
Conservation and Restoration Efforts: Protecting the Moi’s Habitat
Organizations such as The Nature Conservancy, Hui Aloha Kiholo, and volunteers are actively working to improve the habitat of moi in Kiholo Pond. This project is part of nine NOAA-funded projects aimed at protecting and restoring Hawaii’s coastal areas. Kiholo Pond is also included within the West Hawaii Habitat Focus Area under NOAA’s Habitat Blueprint.
These shoreline restoration efforts are benefiting the ecosystem within the pond, contributing to the conservation of the Pacific threadfin. Since 2011, both adult and juvenile moi have been observed in the pond, indicating a positive impact of the ongoing conservation and restoration work.