Fresh and frozen mahi-mahi is available year-round, although prices fluctuate dramatically. Fresh mahi-mahi is sold as skin-on fillets as well as H&G, while frozen fish is available as skin-on or skinless boneless fillets. The fish is low in saturated fat and a good source of vitamins B12 and B6, phosphorus, potassium, niacin, and selenium. When buying fresh mahi, for maximum shelf life, buying H&G mahi-mahi is the best product form. Look for bright skin colors and firm, pinkish meat to identify the highest quality of skin-on mahi fillets. Mahi-mahi has a mild sweet taste, making it popular in American restaurants. It is most abundant in January and February, when the catches off Ecuador and Peru are at their peak. Ecuador, Peru and Taiwan are the leading suppliers of mahi-mahi to the U.S. market.
Mahi-mahi live up to seven years and grow extremely fast, reaching up to seven feet (210 cm) in length and can weigh over 80 pounds. Most that are caught are about three feet (one meter) in length and weigh an average of 33 pounds. They typically live up to five years old. Mahi-mahi that school together often do not weigh more than 20 pounds. Larger individuals live alone or in pairs. They reach maturity in four to five months in the wild, and three months in captivity. They are considered dimorphic, meaning males and females differ in appearance. Males develop a large bony crest on their forehead, which is square. Females have a rounded head that does not develop a bony crest, and are smaller than males.
Spawning occurs year-round, peaking from April to July. In the Atlantic, they spawn under floating patches of brown algae called sargassum. Depending on their size, females release between 40,000 and one million eggs at each spawning event, which occurs every two to three days during peak season. Eggs and larvae are pelagic. Juveniles are recognizable due to alternating dark and light stripes along their body, which fade as they grow. Their brilliant blue-green and yellow colors fade to silver soon after they die.
Larval and juvenile mahi-mahi feed primarily on crustaceans. Adults eat a variety of prey but prefer a diet of invertebrates and fish. They rely heavily on sight to hunt, and therefore do so during the day in pairs or schools. Seabirds and fish, such as tunas, marlins, sharks, and swordfish, prey on mahi-mahi.
Mahi-mahi are widely distributed and can be found in tropical and subtropical waters throughout the Atlantic, Indian, and Pacific Oceans as well as the Mediterranean and the Caribbean. In the eastern Atlantic, mahi-mahi occur from the Bay of Biscay to as far south as South Africa. Along the US Atlantic and Gulf of Mexico they occur from Massachusetts to Texas. In the eastern Pacific Ocean they can be found from Oregon and California south to Hawaii, the Galapagos Islands, and Peru. In the western Pacific, they have been reported in the Philippines, Sea of Japan, Taiwan, and the Sea of Okhotsk. Mahi-mahi are a highly migratory species and are generally found near the surface at depths between 0 and 277 feet (0-85 meters) in offshore waters. Juveniles will form schools while older fish tend to be solitary. Females and small males can be found near natural and artificial floating objects including algae called sargassum. Larger males prefer open ocean habitat. They are most common in waters between 70 and 86°F (21 and 30°C).
Science & Management
The Dolphin and Wahoo Fishery Management Plan identifies several knowledge deficits regarding the biology and stock status of mahi-mahi and wahoo in the Atlantic EEZ and makes the following recommendations for future research:
Collect data to improve estimates of life history characteristics like growth and fecundity
Identify essential habitat
•Implement observer programs and studies of post-release mortality to examine the efficacy of minimum size requirements
As of yet it is unclear whether any there are any research programs underway to address these deficits.
2016 trials done by RECOVER (Relationships of Effects of Cardiac Outcomes in fish for Validation of Ecological Risk) at the University of Miami Rosenstiel School of Marine and Atmospheric Science expand upon existing research studying the effects of oil on fish, and their ability to recover after exposure. The team is currently evaluating the effects of oil exposure, like that from the 2010 Deepwater Horizon spill, on the genetic responses of mahi-mahi embryos and larvae. They found that heart development and functioning as well as sensory functions of the nervous system such as eyes, and neurological functions were impaired after exposure to oil at an early age. Sensory function is important for prey detection and predator avoidance.
Fishermen are working together with scientists from the Dolphinfish Research Program and Cooperative Science Services to study the migration patterns of mahi-mahi by tagging and releasing their catch. The results from 2002-2012 show that mahi-mahi migrate around the Atlantic Ocean. This information is important to track where mahi-mahi may be caught along their migration route, and suggests future international conservation efforts.
NOAA Fisheries and the South Atlantic Fishery Management Council – in cooperation with the Mid-Atlantic and New England Fishery Management Councils – manage the US Atlantic mahi-mahi fishery under the Dolphin and Wahoo Fishery Management Plan (FMP). Effective as of 2004, the FMP and its amendments provide a precautionary and risk-averse approach to management by ensuring no new fisheries develop for mahi-mahi and wahoo. The intended effects of the FMP are to conserve and manage US Atlantic stocks of mahi-mahi and wahoo by setting harvest restrictions for both the commercial and recreational sectors (with the recreational sector receiving a significant majority of catch allocation). Among measures the plan establishes are:
A permit system for commercial and charter vessels as well as dealers
Longline restrictions to comply with sea turtle and highly migratory species protection measures
Additional gear restrictions
A 1.5 million pound (or 13 percent of the total harvest) cap on commercial landings
Recreational bag limits (10 mahi-mahi per person per day with a limit of 60 mahi-mahi per boat per day (headboats are excluded from this boat limit))
Prohibiting the sale of recreational catches (unless the seller holds commercial permits)
Designating areas as Essential Fish Habitat and Habitat Areas of Particular Concern
A 20-inch fork length minimum size limit for mahi-mahi caught off the coast of South Carolina, Georgia, and Florida (there are no size restrictions elsewhere)
Scientists do not formally assess the US Atlantic mahi-mahi population; however, they did conduct an exploratory assessment of mahi-mahi in 2000 and determined that the stock was not overfished. Given their life history (highly productive, widely distributed) it is believed they are abundant and relatively resistant to high fishing rates. Atlantic mahi-mahi are not subject to overfishing.
NOAA Fisheries and the Western Pacific Fishery Management Council manage the Pacific mahi-mahi fishery in the western Pacific under the Fishery Ecosystem Plan for Pacific Pelagic Fisheries of the Western Pacific Region (FEP). The majority of the US mahi-mahi harvest occurs in the Pacific, mainly Hawaii, and is covered under the 2009 FEP. The FEP and its amendments do not establish specific management measures for mahi-mahi as current trends indicate that regulations are not necessary. Instead, the FEP establishes measures that apply to all troll and longline fisheries operating in the region. Among these measures are:
A permitting and logbook system
Area closures where longlining is prohibited to protect endangered Hawaiian monk seals, reduce gear conflicts, and avoid local stock depletions
Additional time-area closures
A vessel monitoring system for longline vessel to track vessel movements and enforce regulations
Carrying an onboard observer (when requested by NOAA) for longline vessels
Requirements for longline vessels owners to attend annual protected species workshops
NOAA Fisheries and the Pacific Coast Fishery Management Council manage the mahi-mahi fishery off the US West Coast under the FMP for US West Coast Fisheries for Highly Migratory Species. The FMP intends to ensure conservation as well as the promotion of the optimum yield of highly migratory species both within and outside the US Exclusive Economic Zone. The FMP establishes a permitting system and sets gear restrictions and operational requirements for commercial fishermen operating in the fishery.
Scientists do not formally assess the US Pacific mahi-mahi population; however, the population is assumed to be stable given their life history (highly productive, widely distributed). Even though they are resistant to high fishing rates, precautionary management measures are in place to maintain current mahi-mahi harvest levels. As of 2016, Pacific mahi-mahi’s overfishing status is unknown.
Mahi-mahi, aka "dolphinfish," are found worldwide in tropical and subtropical waters. They are prolific spawners and have extremely rapid growth, which helps them remain moderately resilient to fishing pressure. The stock status of mahi-mahi in the Atlantic Ocean is stable although a full assessment had not been conducted, according to a 2016 Seafood Watch report. Mahi-mahi are also assumed to be stable in the U.S. Pacific. Population data for the Western Atlantic and Gulf of Mexico are outdated. Stock status is also lacking for mahi-mahi caught in the Indian Ocean and throughout the Pacific Ocean.
Habitat impacts ( Wild)
Hook and line gear is mainly used to target mahi-mahi in the U.S. Atlantic, which has minimal contact with the ocean floor. In the U.S. Pacific, mahi-mahi are primarily caught using troll and handlines that do not adversely affect the seafloor substrate, according to Seafood Watch. The surface-set pelagic longline and purse seine gear used to target the fish around the world also has a minimal impact on the ocean habitat. Free-floating algae in the Atlantic called sargassum is an essential mahi-mahi habitat that became protected by fishery managers in 2003.
Bycatch is a major issue with mahi-mahi. The pelagic longline fisheries targeting the fish throughout the world are known to incidentally catch sharks, sea birds, and sea turtles. Some bycatch mitigation measures have been applied to fisheries in the United States, Canada, and Ecuador. Longline mahi-mahi fisheries in Guatemala, Costa Rica, Peru, Indonesia, Panama, and Taiwan catch sensitive species, but lack measures to address bycatch, prompting Seafood Watch to give them red ratings for that criterion. In the South Atlantic, longlines are known to interact with white-chinned petrel, leatherback turtles, loggerhead turtles, yellow-nosed albatross, and wandering albatross, which all have critical fishing mortality. A 2016 Seafood Watch report pointed to concern over bycatch that included sea turtles, silky and oceanic white tip sharks in the Atlantic Ocean floating object purse seine fisheries targeting mahi-mahi. Handline and troll gear is more selective and allows fishermen to release incidental catches quickly.
Mahi-mahi fishery management varies widely by country and region. The U.S. Atlantic mahi-mahi stock is managed by NOAA Fisheries and the South Atlantic Fishery Management Council in cooperation with the Mid-Atlantic and New England Fishery Management Councils. Measures include permit requirements, and size limits set on the fish in Florida, Georgia and South Carolina.
On the U.S. West Coast, mahi-mahi are managed by NOAA Fisheries and the Pacific Fishery Management Council under a fishery management plan for highly migratory species. Although there are no measures specific to mahi-mahi, fishermen in the longline fishery there must have permits, log books, carry a vessel monitoring system, and allow onboard observers from NOAA. Owners and operators are required to attend annual workshops about protected species. Seafood Watch called mahi-mahi management in the United States moderately effective overall.
In Canada, the stocks are managed by Fisheries and Oceans Canada. A 2016 Seafood Watch report called Canadian management for bycatch species insufficient compared to the United States. Although the mahi-mahi longline fishery in Ecuador has infrequent bycatch, Seafood Watch gave the country a good alternative rating for having a management framework in place to address the impact on mahi-mahi stocks and species of concern.
Other mahi-mahi fisheries lack effective management. Panama has some bycatch measures in place, such as voluntary circle hooks and a national plan for shark preservation, but Seafood Watch called them inefficient to protect vulnerable species. In addition, as of 2016, there were no harvest control rules. Indonesia lacks bycatch management measures for mahi-mahi, and Seafood Watch expressed concern over compliance with other management measures in place there. In Taiwan, although mahi-mahi is managed by the Fisheries Authority of the Council of Agriculture, there are currently no measures. Costa Rica, Guatemala and Peru are engaged in a fishery improvement project, but lack fishery management plans for mahi-mahi.