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Mahi Mahi is a highly migratory tropical and subtropical species that straddles multiple domestic and international jurisdictions. It is classified as undefined stock in Australian waters.

There are two species of Mahi Mahi in Australian waters; Common Mahi Mahi (Coryphaena hippurus) and Pompano Mahi Mahi (Coryphaena equiselis). Commercial and recreational catch is thought to be almost exclusively common Mahi Mahi and consequently it is the only species assessed here.

Common Mahi Mahi are a highly migratory tropical and subtropical species that straddle multiple domestic and international jurisdictions. Stock structure is not well resolved [e.g. Díaz-Jaimes et al. 2010] and for practical purposes, Mahi Mahi in the Indian Ocean and the Western and Central Pacific Ocean are considered to constitute two distinct management units which are managed by separate regional fisheries management organisations: the Indian Ocean Tuna Commission and the Western and Central Pacific Fisheries Commission. The boundaries of these units occur at the longitude of the Western Australia-Northern Territory border in northern Australia, and at the South Australia-Victoria border in southern Australia, reflecting the jurisdictional boundaries of these two RFMOs. The distribution of Mahi Mahi does not extend south of the Australian land mass.

Here, assessment of stock status is presented at the management unit level—Western and Central Pacific Ocean and Indian Ocean.

Indian Ocean

This cross-jurisdictional management unit has components in the Commonwealth, Western Australia and international and foreign waters. The status presented here for the entire management unit has been established using evidence from all jurisdictions.

Total reported commercial catch for the Indian Ocean (FAO areas 51 and 57) has increased progressively from 2,700 t in the year 2000 to a peak of 22,205 t in 2019, with an average of 18,222 t from 2016 to 2020 [FAO 2020]. Most of this reported catch, and most of the increase, has come from the western Indian Ocean (FAO area 51, west of 80 degrees E). 

In the Indian Ocean, the majority of Mahi Mahi are thought to be taken using a variety of artisanal fishing methods (such as troll and gillnet). In the industrial fisheries, catches are taken by all the major sectors including gillnet (for Indian Ocean), longline, purse seine (particularly floating object sets) and pole-and-line. 

For the Commonwealth part of the management unit, annual commercial landings are negligible and have not exceeded 2.1 t.

For the Western Australian part of the management unit, commercial and recreational landings are negligible with the stock generally not being subject to targeted fishing. The Western Australian commercial and charter catches from 2008–21 each averaged less than 0.25 t per annum. Mahi Mahi is not a major component of recreational landings, comprising less than 500 fish in the 2020–21 state-wide survey of boat based recreational fishing [Ryan et al. 2022].

Catches in South Australia are rare.

There has been no formal stock assessment of Mahi Mahi for the Indian Ocean area encompassing the Australian Fishing Zone. Benjamin and Karup [2012] undertook a virtual population analysis stock assessment using the software FAO-ICLARM Stock Assessment Tools (FiSAT) that was confined to the southwest coast of India and used data to 2009. They estimated fishing mortality at 0.37 which, in the context of natural mortality assumed to be 1.0 [Aires-da-Silva et al. 2016] indicates a relatively light level of exploitation in that region at that time. Australian catches form a small component of the total international Indian Ocean catch and no other indicators of biomass level are available. There is therefore insufficient information available to confidently classify the status of this stock.

On the basis of the evidence provided above, the Indian Ocean management unit is classified as an undefined stock.

Mahi Mahi biology [Uchiyama et al. 1986; Massuti and Morales-Nin 1997; Castro et al. 1999; Massuti and Morales-Nin 1999; Uchiyama and Boggs 2006]

Commonwealth – Recreational. The Australian Government does not manage recreational fishing in Commonwealth waters. Recreational fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters, under its management regulations. 

Commonwealth – Indigenous. The Australian Government does not manage non-commercial Indigenous fishing in Commonwealth waters, with the exception of the Torres Strait. In general, non-commercial Indigenous fishing in Commonwealth waters is managed by the state or territory immediately adjacent to those waters.

Commonwealth – Commercial (Catch). Catches reported for the Eastern Tuna and Billfish Fishery and Western Billfish and Tuna Fishery are for 2021–22, the most recent year available.

Western Australia – Recreational (Catch). Statewide survey of boat-based recreational fishing in Western Australia 2020–21 [Ryan et al. 2022]. Shore- based catch (if any) largely unknown.

Western Australia – Recreational (Management Methods). Boat-based recreational fishing licence required.

Western Australia – Charter (Catch). The charter catch is an estimate based on numbers of fish caught multiplied by an average weight.

Queensland – Indigenous (Management Methods). For more information see https://www.daf.qld.gov.au/business-priorities/fisheries/traditional-fishing  

Queensland – Recreational Fishing (Catch). Data are based at the whole of Queensland level and derived from statewide recreational fishing surveys. Where possible, estimates have been converted to weight (tonnes) using best known conversion multipliers. Conversion factors may display regional or temporal variability. In the absence of an adequate conversion factor, data presented as number of fish. 

Queensland – Commercial (Catch). Queensland commercial and charter data have been sourced from the commercial fisheries logbook program. Further information available through the Queensland Fisheries Summary Report https://www.daf.qld.gov.au/business-priorities/fisheries/monitoring-research/data/queensland-fisheries-summary-report 

New South Wales - Recreational Catch. The most recent estimate of the recreational harvest of Mahi Mahi in NSW was approximately 25,400 fish during 2017–18 [Murphy et al. 2022].  This estimate was based on a survey of Recreational Fishing Licence (RFL) households.  RFL households were comprised of at least one member who possessed a long-term (1 and 3 years duration) fishing licence and included other fishers resident within their households. Catch from exempt fishers and short-term licence holders is unknown but for Mahi Mahi long-term licence holders are estimated to be responsible for most  of the catch.

Northern Territory – Charter (Management Methods). In the Northern Territory, charter operators are regulated through the same management methods as the recreational sector but are subject to additional limits on licence and passenger numbers. 

Australian commercial catch of Mahi Mahi - note confidential catch not shown

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