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MAHI MAHIS (2023)

Coryphaena spp.

  • Heather Patterson (Australian Bureau of Agricultural and Resource Economics and Sciences)
  • Amy Kirke (Department of Industry, Tourism and Trade, Northern Territory)
  • Daniel Smith (Department of Agriculture and Fisheries, Queensland)
  • Jeff Murphy (New South Wales Department of Primary Industries)
  • Paul Lewis (Department of Primary Industries and Regional Development, Western Australia)

Date Published: June 2023

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Summary

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.

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Stock Status Overview

Stock status determination
Jurisdiction Stock Stock status Indicators
New South Wales Western and Central Pacific Ocean Undefined Catch
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Stock Structure

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.

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Stock Status

Western and Central Pacific Ocean

This cross-jurisdictional management unit has components in the Commonwealth, New South Wales, Queensland, the Northern Territory, and international and foreign waters. The status presented here for the entire management unit has been established using evidence from all jurisdictions.

In the western central Pacific, the majority of Mahi Mahi are taken using hook methods such as pelagic longline and troll, as well as significant bycatches by tuna purse-seine fishing using fish aggregating devices (FADs).

Total reported commercial catch for the Western and Central Pacific Ocean (FAO areas 61, 71 and 81) peaked at over 30,000 tonnes (t) on a number of occasions during the 1980s and 1990s [FAO 2022]. Catch in 2020 was 19,614 t with an average of 22,291 t from 2016 to 2020. Recent reported catches have been predominantly from the northwest Pacific (FAO area 61, north of 20 degrees N) and the western central Pacific (FAO area 71, 20 degrees N to 25 degrees S), with minor commercial catches reported in the southwest Pacific (FAO area 81, south of 25 degrees S).

There are likely to be significant artisanal, and to a lesser extent recreational, landings of Mahi Mahi throughout south east Asia and Oceania that are not included in the estimates above. In addition, Mahi Mahi may be discarded in some fisheries, although discard mortality levels are unknown.

In the Australian context, Mahi Mahi are not highly targeted by the Australian commercial sector, recreational catches are low and Australian catches form a small component of the total international Pacific Ocean catch. 

For the Commonwealth part of the management unit, commercial landings over the period 2013 to 2022 peaked in 2016 at 268 t and have averaged about 116 t over the most recent five years. Pelagic tuna longline is the primary gear used to catch this species.

For the New South Wales part of the management unit, commercial landings are relatively minor, at about 2.3 t for 2021–22 and averaging 4.9 t over the 5 year period 2017–18 to 2021–22. The most recent recreational estimate was from a survey done in 2019–20 with less than 100 fish being harvested [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 these 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 the vast majority of the catch.  Mahi Mahi are also targeted by the offshore charter fishery, primarily around a series of fish attracting devices deployed by NSWDPI. The offshore charter fishery reported a landed catch of 1.6 t for 2021–22 and an average of 0.9 t for the 5 year period 2017–18 to 2021–22. 

Queensland annual commercial landings have averaged around 2.3 t over the previous decade to 2021–22 while approximately 37 t were harvested recreationally in 2019–20 [Teixeira et al. 2021].  

For the Northern Territory part of the biological stock landings have been very low (< 100 kg). Landings only relate to charter operators fishing offshore. The last recorded catch in this jurisdiction was of one individual Mahi Mahi in 2019.

Catches in Victoria and Tasmania are rare. 

There has been no formal stock assessment of Mahi Mahi for the western central Pacific. A sustainability “overview” by Gilman et al. [2013] highlighted the lack of management of this species and information on management and stock status in the western and central Pacific Ocean (WCPO), but concluded that there was a “medium risk” relating to current biomass and fishing mortality due to the highly productive life history characteristics of Mahi Mahi.

Other studies have examined standardised CPUE trends [Campbell 2016], size trends [Campbell 2016], ecological risk status [Sporcic et al. 2019] and depletion [Kindong et al. 2020] in the WCPO region. However, each of these studies assessed data at a very localised subregional scale and as such have limited applicability to assessing status, noting the uncertainty over stock structure and movement/mixing for this species in the WCPO region. 

In the Australian region, Campbell [2016] standardised Eastern Tuna and Billfish Fishery (ETBF) pelagic longline catch rates to develop an index of abundance for Mahi Mahi within the Australian area of operations. For the period 1998–2014 the abundance index showed moderately high year-to-year variability and little, if any, overall trend through this period. The same study found strong seasonal changes in the mean weights of Mahi Mahi caught in the ETBF but no long-term trend over the same period. Sporcic et al. [2019] undertook ecological risk assessment of the ETBF and found Mahi Mahi to be a low-risk species in the context of ETBF interactions and within its operating area. 

Overall, however, there is therefore insufficient information available to confidently classify the status of this stock.

On the basis of the evidence provided above, the Western and Central Pacific Ocean management unit is classified as an undefined stock.

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Biology

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]

Biology
Species Longevity / Maximum Size Maturity (50 per cent)
MAHI MAHIS

4 years, > 1,490 mm

Females 550 mm FL Males 620 mm FL

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Distributions

Distribution of reported Australian commercial catch of Mahi Mahi
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Tables

Fishing methods
New South Wales
Commercial
Hook and Line
Trolling
Various
Recreational
Spearfishing
Hook and Line
Charter
Hook and Line
Management methods
Method New South Wales
Charter
Bag limits
Limited entry
Possession limit
Size limits
Spatial closures
Commercial
Spatial closures
Recreational
Bag limits
License
Possession limit
Size limit
Spatial closures
Catch
New South Wales
Commercial 1.68t
Recreational 25,400 (numbers-2017–18)

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. 

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Catch Chart

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

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References

  1. Aires-da-Silva, A, Valero, JL, Maunde, MN, Minte-Vera, CV, Lennert-Cody, C, Román, MH, Martínez-Ortiz, J, Torrejón-Magallanes, EJ and Carranza MN 2016, Exploratory stock assessment of dorado (Coryphaena hippurus) in the Southeastern Pacific Ocean, Inter-American Tropical Tuna Commission Scientific Advisory Committee, 7th Meeting, Document SAC-07-06a(i)
  2. Benjamin, D and Kurup, M 2012, Stock assessment of dolphinfish Coryphaena hippurus (Linnaeus, 1758) off southwest coast of India. Marine Biological Association of India doi:10.6024/jmbai.2012.54.1.01675-12.
  3. Campbell, R 2016, Catch of mahi mahi in the Eastern Tuna and Billfish Fishery–summary of AFMA data and construction of an annual abundance index. Background paper to the Tropical Tuna Resource Assessment Group, CSIRO Oceans and Atmosphere Flagship and AFMA, March 2016.
  4. Castro, JJ, Santiago, JA, Hernandez-Garcia, V and Pla, C 1999, Growth and reproduction of the dolphinfish (Coryphaena equiselis and Coryphaena hippurus) in the Canary Islands, Central-East Atlantic (preliminary results), Scientia Marina, 63(3-4): 317–325
  5. Díaz-Jaimes, P, Uribe-Alcocer, M, Rocha-Olivares, A, GarcÍa-de-León, Nortmoon, P and Durand, JD 2010, Global phylogeography of the dolphinfish (Coryphaena hippurs): The influence of large effective population size and recent dispersal on the divergence of a marine pelagic cosmopolitan species, Molecular Phylogenetics and Evolution, 57: 1209–1218.
  6. FAO 2022, Fisheries and aquaculture software. FishStatJ - software for fishery statistical time series .v4.02.08 (May 2022), In: FAO Fisheries and Aquaculture Department [online]. Rome. [Cited 23 March 2023]. http://www.fao.org/fishery/
  7. Gilman, E, Veiga, P, Spear, B, Schmidt, C, and Sousa, P 2013, SFP Global Sustainability Overview of Pacific Ocean Fisheries that Supply Mahi Mahi. Sustainable Fisheries Partnership Foundation. 6 p.
  8. Kindong, R, Gao, C, Pandong, NA, Ma, Q, Tian, S, Wu, F and Sarr, O 2020, Stock status assessments of five small pelagic species in the Atlantic and Pacific Oceans using the length-based Bayesian estimation (LBB) method, Frontiers in Marine Science, 7: 592082.
  9. Massuti, E and Morales-Nin, B 1997, Reproductive biology of dolphin-fish (Coryphaena hippurus L.) off the island of Majorca (western Mediterranean), Fisheries Research, 30: 57-65.
  10. Massuti, E and Morales-Nin, B 1999, Otolith microstructure, age, and growth patterns of dolphin, Coryphaena hippurus, in the western Mediterranean, Fishery Bulletin 97: 891–899.
  11. Murphy, J.J, Ocwada-Doyle, FA, West, LD, Stark, KE, Hughes, JM and Taylor, MD 2022, Survey of recreational fishing in NSW, 2019/20 - key results. NSWDPI - Fisheries Final Report Series No. 161
  12. Ryan, KL, Lai, EK, and Smallwood, CB. 2022, Boat-based recreational fishing in Western Australia 2020/21. Fisheries Research Report No. 327, Department of Primary Industries and Regional Development, Western Australia. 221pp.
  13. Sporcic, M, Hobday, A, Bulman, C, Hartog, J and Fuller, M 2019, Ecological Risk Assessment for the Effects of Fishing: Report for the Eastern Tuna and Billfish Fishery: Longline sub-fishery, data to 2015. Report for the Australian Fisheries Management Authority. 234p.
  14. Teixeira, D, Janes, R. and Webley, J 2021, 2019/20 Statewide Recreational Fishing Survey Key Results. Project Report. State of Queensland, Brisbane.
  15. Uchiyama, JH and Boggs, CH 2006, Length-weight relationships of dolphinfish, Coryphaena hippurus, and wahoo, Acanthocybium solandri: seasonal effects of spawning and possible migration in the central North Pacific. Marine Fisheries Review 68 (1–4): 19–29.
  16. Uchiyama, JH, Burch, RK and Kraul, S 1988, Growth of the dolphins, Coryphaena hippurus and C. equiselis in Hawaiian waters, as determined by daily increments on otoliths. Fisheries Bulletin 84:186– 191.
  17. Valero JL, Aires-da-Silva, A, Maunder, MN, Minte-Vera, C, Martinez-Ortiz, J, Torrenjon-Magallanes, EJ and Carranza, MN 2016, Exploratory management strategy evaluation (MSE) of dorado (Coryphaena hippurus) in the Southeastern Pacific Ocean, Inter-American Tropical Tuna Commission Scientific Advisory Committee, 7th Meeting, Document SAC-07-06a(ii),

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