Mola mola 

Scope: Gulf of Mexico
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Actinopterygii Tetraodontiformes Molidae

Scientific Name: Mola mola (Linnaeus, 1758)
Regional Assessments:
Common Name(s):
English Ocean Sunfish, Giant Sunfish, Headfish, Mola Ocean Sunfish, Moonfish, Sunfish, Sun-fish
French Môle, Môle Commun, Poisson-lune, Poisson Lune
Spanish Mola, Peixe Lua, Pez Cabeza, Pez Luna, Pez Sol
Tetraodon mola Linnaeus, 1758
Taxonomic Source(s): Eschmeyer, W.N. and Fricke, R. (eds). 2015. Catalog of Fishes: genera, species, references. Updated 2 September 2015. Available at: http://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp. (Accessed: 2 September 2015).
Taxonomic Notes: Recent investigations of M. mola mitochondrial sequences showed evidence that the genus Mola contains two species: M. mola and the southern sunfish, M. ramsayi (Bass et al. 2005). Report from Yoshita et al. (2009) concluded that the genus Mola contained three species.

Assessment Information [top]

Red List Category & Criteria: Least Concern (Regional assessment) ver 3.1
Year Published: 2015
Date Assessed: 2015-04-20
Assessor(s): Tyler, J., Perez-Espana, H., Robertson, R. & Vega-Cendejas, M.
Reviewer(s): Linardich, C.
Facilitator/Compiler(s): Gorman, C.

In the Gulf of Mexico, this pelagic species is widely distributed. There is little or no fishing effort likely to affect this species in the Gulf of Mexico. There are no known major threats; therefore, it is listed as Least Concern in the Gulf. 

Geographic Range [top]

Range Description:Mola mola is circumglobally distributed throughout warm and temperate zones of all oceans. In the eastern Pacific it is known from Canada (British Columbia), south to Peru and Chile (Chirichigno 1974, Eschmeyer et al. 1983). In the Indo-Pacific it is known throughout the Indian Ocean including the Red Sea, from Russia and Japan to Australia and New Zealand, and the Hawaiian Islands (Muus 1964, Smith 1965, Ayling and Cox 1982, Sims and Southall 2002, Cartamil and Lowe 2004, Houghton et al. 2006, Konow et al. 2006, Todd and Grove 2010). It is considered a waif in the Persian Gulf. In the eastern Atlantic it is known from Scandinavia to South Africa, (occasionally in the western Baltic, North, and Mediterranean Seas). In the western Atlantic it is known from Canada (Newfoundland) south to Argentina including the Gulf of Mexico and Caribbean Sea (Robins and Ray 1986, Figueiredo and Menezes 2000). Its depth range is 0-400 m (Cartamil and Lowe 2004).
Countries occurrence:
Cuba; Mexico; United States
FAO Marine Fishing Areas:
Atlantic – western central
Additional data:
Lower depth limit (metres):644
Range Map:190422-25

Population [top]

Population:This species is a common resident of the offshore waters of the northwestern Atlantic during the spring and summer months, with an estimated summer abundance of 18,000 (Kenney 1996 in Potter et al. 2011). Large aggregations of small (<1 m TL) Mola mola have been observed in coastal waters (Pope et al. 2010, Syväranta et al. 2012). In Irish and Celtic Seas, a total of 68 were spotted from 2003-2005, or an overall density of 0.98 sunfish per 100 km2 (Houghton et al. 2006). According to reports from the National Marine Fisheries Service (NMFS) Southwest Region, between 1990 and 1998, 26.1% of the drift net catch consisted of M. mola. This translates to a catch of more than 26,000 individuals (Rand Rasmussen, NMFS Southwest Fisheries Science Center, pers. comm. in Dewar et al. 2010). Off the coast of South Africa, M. mola bycatch rates from the tuna and swordfish longline fishery are estimated at 340,000 sunfish annually (Petersen 2005, Sims et al. 2009). 

Although estimates of population size are generally lacking, there is evidence of local population declines over short time scales. In Namibia, Mola mola showed a peak of catch landings in 2006 (40 metric tonnes), then decreased with only 7 metric tonnes in 2007 (FAO 2014); while CPUE was not available, this represents a decline of 82.5%. Landings have recently been reported from Argentina and are likely to increase (FAO 2014). In Ireland, there was been a decline of about 100% (13 to 0 metric tonnes) in 2 years (2000-2002). There was also a decline in Portugal from 12 metric tonnes in 1999 to about 0 in 2009 (FAO 2014).

Based on localized declines that exceed 80% and the likelihood that this species is experiencing high rates of bycatch throughout most of its range, we suspect this species is declining globally by at least 30% over 3 generation lengths (24-30 years) that includes both the past and the future.
Current Population Trend:Decreasing
Additional data:

Habitat and Ecology [top]

Habitat and Ecology:Mola mola is an oceanodromous, pelagic-oceanic species that occurs in subtropical waters between depths of 30 and 480 m, but is usually between 30 and 70 m (Powell 2001, Riede 2004, Allen and Erdmann 2012). Adults are found on slopes adjacent to deep water where they come in for shelter and to seek out cleaner fishes (Kuiter and Tonozuka 2001). It is an active swimmer capable of highly directional movements and horizontal movements independent of the current (Cartamil and Lowe 2004); it uses its anal and dorsal fins as a pair of wings (Pope et al. 2010). It feeds on fishes, mollusks, zooplankton, jellyfish, crustaceans, and brittle stars (Clemens and Wilby 1961, Scott and Scott 1988, Kuiter and Tonozuka 2001). Cartamil and Lowe (2004) observed a diel pattern in depth utilization, with fish residing in the warmer mixed layer above or within the thermocline at night and repeatedly diving beneath the thermocline into cooler water during the day (Californian waters, July-September 2001). Hays et al. (2009) also noted that although individual sunfish showed a range of preferred depth that altered over time, they were still moving up and down the water column and regularly returning to close to the surface. Although its exact function has yet to be resolved, Cartamil and Lowe (2004) proposed that periodic returns to the surface in M. mola may imply some form of behavioral thermo-regulation i.e. prolonged time in cold waters necessitates time spent at the surface to re-warm. This may explain the frequent observations of ocean sunfish observed 'basking' or swimming on their sides at the surface during the day (Cartamil and Lowe 2004). Conversely, Sims et al. (2009a) argued that extensive vertical movements may simply reflect a crepuscular searching strategy when prey are descending or ascending, with sunfish attempting to locate maximum prey abundances at this time. It has been also been suggested more generally that large amplitude dives or ascents of large pelagic fish and other vertebrates during prey tracking may represent prey searching behaviour (Shepard et al. 2006) characterized by extensive movements to new locations (Sims et al. 2008). It exhibits sexual dimorphism; females are larger than males (Pope et al. 2010). 
Maximum total length is 333 cm (Claro 1994); maximum published weight is 2.3 t (Roach 2003); all animals larger than 250 cm TL are female (Nakatsubo 2008). Very few studies have been conducted on the reproductive biology of ocean sunfish (Pope et al. 2010). In Japan,the spawning period is estimated between August and October and the same study also identified asynchronous egg development, suggesting it is a multiple spawner (Nakatsubo et al. 2007). The lifespan or reproductive age of M. mola under natural conditions is unknown, although captive animals have been maintained for more than 8 years (Nakatsubo et al. 2007). A growth curve derived from repeated measurements of captive specimens estimated an individual with a total length of 3 m would be about 20 years old (Nakatsubo 2008). Recent work used growth band pairs in vertebrae to age the closely related sharptail mola M. lanceolatus caught in the eastern Taiwan fishery (Liu et al. 2009). The age estimates ranged between >2 and >23 years for females and >1 and >16 years for males (Liu et al. 2009).  Mola mola is famously the most fecund of all vertebrates (Carwardine 1995) with a 137 cm female containing an estimated 300 million eggs (Schmidt 1921). By necessity, these eggs are very small (mean diameter 0.13 cm; Gudger 1936) and so M. mola growth is staggering. For the 0.25 cm larva to grow to a 3 m adult requires an increase in mass of 60 million times (Gudger 1936). A more atypical captive growth rates have been found to be between 0.02 and 0.49 kg/day in weight (M. Howard and T. Nakatsubo pers. comm. in Pope et al. 2010) and on average 0.1 cm/day TL (Nakatsubo and Hirose 2007). 
Longevity is estimated at between 20 and 23 years old; using a maximum age based estimator with low prediction error (M = 4.899t−0.916: Then and Hoenig 2014), the estimated adult natural mortality rate is 0.28-0.32. Age at first maturity is unknown, but inferred to be between 5 and 7 years (based on the smallest reported ripe female of 137 cm and assuming a linear growth rate to 3 m at 22 years old). Using the estimator for generation length of 1/adult mortality + age at first reproduction results in a generation length of 8-10 years, and thus a time window for calculating population declines of 24-30 years.
Generation Length (years):8-10

Use and Trade [top]

Use and Trade: Mola mola is not a commercially important fish (Fulling et al. 2007, Silvani et al. 1999), although there is some market for it in Japan (Sagara and Ozawa 2002, Watanabe and Sato 2008) and Taiwan (20.8-49.4 tonnes per annum, Liu et al. 2009). It is targeted by fishers in the western Pacific and south Atlantic. This species is also captured in large numbers as bycatch in long line, drift gillnet and midwater trawl fisheries. For example, the South African longline fishery for tuna and swordfish was estimated to have annually caught between 0.08 and 0.29 sunfish for every 1,000 hooks set (1.6-2.7 million hooks per year) in the 4 years between 2000 and 2003 (Petersen 2005). Furthermore, it was by far the most common bycatch species in the Cape horse mackerel (Trachurus trachurus capensis) midwater trawl fishery in the same region (Petersen and McDonell 2007), representing 51% of the total bycatch between 2002 and 2005 (Petersen and McDonell 2007). Similarly, M. mola comprised between 70 and 93% of the total fish catch in Spanish drift gillnet fisheries within the Mediterranean between 1992 and 1994 (Silvani et al. 1999); bycatch estimates from the Californian swordfish fishery suggest ocean sunfish make up 29% of all bycatch, far outnumbering the target species (Cartamil and Lowe 2004). A crude calculation using values from a recent study of the Moroccan fleet (Tudela et al. 2005) suggests an annual bycatch of 36,450 ocean sunfish. Whilst the majority of M. mola are returned to the water alive (Silvani et al. 1999), they often show varying levels of trauma (Cartamil and Lowe 2004) and post-catch survival data are lacking. 
There is little or no fishing effort likely to affect this species in the Gulf of Mexico (H. Perez-España and M. Vega-Cendejas pers. comm. 2015).

Threats [top]

Major Threat(s): Ocean sunfish populations may be vulnerable to fishing activity because of the high levels of bycatch observed in many fisheries, including long lines, drift gillnets and midwater trawls (Silvani et al. 1999, Cartamil and Lowe 2004, Fulling et al. 2007, Petersen and McDonell 2007). In South Africa, mid-water trawl fishery of the Cape horse mackerel  (Trachurus trachurus capensis) caught predominantly large individuals and observed a significant decline in ocean sunfish catch rates between 2000 to 2003, with other bycatch species remaining comparatively stable (Petersen and McDonell 2007). Bycatch estimates from the Californian swordfish fishery suggest ocean sunfish make up 29% of all bycatch; far outnumbering the target species (Cartamil and Lowe 2004). Mola mola is targeted by fishers in the western Pacific and south Atlantic. Mola mola is also captured in large numbers as bycatch in a number of widely distributed fisheries. However, in the Gulf of Mexico, there is little or no fishing effort likely to affect this species.

Conservation Actions [top]

Conservation Actions: The Moroccan government passed a law in 2007 to phase out the use of driftnets in which Mola mola are often caught as bycatch. Basic biological research and population monitoring of M. mola are recommended.

Citation: Tyler, J., Perez-Espana, H., Robertson, R. & Vega-Cendejas, M. 2015. Mola mola. The IUCN Red List of Threatened Species 2015: e.T190422A77281263. . Downloaded on 21 September 2017.
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