|Scientific Name:||Anguilla mossambica|
|Species Authority:||(Peters, 1852)|
Anguilla capensis Castelnau, 1861
Anguilla capensis Kaup, 1860
Anguilla delalandi Kaup, 1856
Muraena mossambica Peters, 1852
Tribranchus anguillaris Peters, 1846
Anguilla mossambica is olive to greyish black dorsally and lighter ventrally, with the caudal fin confluent with the dorsal and anal fin (Froese and Pauly 2011). This species has been described as the oldest, most basal species of the genus Anguilla (Minegishi et al. 2005).
|Red List Category & Criteria:||Least Concern ver 3.1|
|Assessor(s):||Jacoby, D. & Gollock, M.|
|Reviewer(s):||Harrison, I.J., Tsukamoto, K. & Weyl, O.|
|Contributor(s):||Ahn, H., Bennett, L., Casselman, J., Crook, V., DeLucia, M., Kaifu, k., Kurwie, T., Sasal, P., Silfvergrip, A., Turnock, S., Uchida, K. & Walker, M|
The African Longfin Eel, Anguilla mossambica, is endemic to the Malagasy area and is relatively common in the freshwater habitats of East Africa, Madagascar and other West Indian Ocean island chains. Currently, little is known about the population dynamics of this species although growing exploitation and a reduction in available maturing habitat implies that further research is necessary and important in determining local and global population trends. Anguilla mossambica is assessed as Least Concern owing to its relatively broad distribution and lack of real evidence of any negative impact by current threats to the population. It is advised, however, that monitoring is required to better estimate population size particularly in light of growing demand for tropical species of eels as a direct result of population declines and regulation on the trade of temperate species of eels. There is burgeoning evidence of increased trade of this species particularly from Madagascar so it is strongly recommended that A. mossambica is reassessed within the next five years (2019).
Assessment of this species was carried out during a workshop held at the Zoological Society of London from July 1st-5th, 2013.
This species is endemic to the South Western Indian Ocean (SWIO). Along the east coast of Africa, A. mossambica is found in rivers from Kenya south to Cape Agulhas, also found on Madagascar and other western Indian Ocean islands (Mascarene: Réunion and Mauritius Islands, Comoros: Mayotte Island and the Seychelles: Mahé and Praslin Islands). Anguilla mossambica, endemic to the Malagasy area, is also the most common anguillid species in the Eastern Cape, South Africa and in eastern Madagascar (Robinet et al. 2008).An extensive list of the described range of A. mossambica is given as: Comoros; Kenya; Madagascar; Mauritius; Mayotte; Mozambique; Réunion; South Africa; Swaziland; Tanzania; Zimbabwe. Across these regions, the species is present in most of the east flowing river drainages (Froese and Pauly 2011).
Native:Comoros; Kenya; Madagascar; Mauritius; Mayotte; Mozambique; Réunion; Seychelles; South Africa; Swaziland; Tanzania, United Republic of; Zimbabwe
|FAO Marine Fishing Areas:||
Atlantic – southeast; Indian Ocean – western
|Range Map:||Click here to open the map viewer and explore range.|
It has been suggested that spawning in this species occurs continuously between June and November in an area north-east of Madagascar and west of the Mascerene Ridge in the Indian Ocean (Robinet et al. 2008). This area in the westward-flowing South Equatorial Current (SEC) is thought to share similar conditions to the spawning sites of other anguillid eels such as A. japonica and A. marmorata (Réveillac et al. 2009). With virtually no monitoring and little fisheries data, however, there are currently huge knowledge gaps in our understanding of the population dynamics of this species.
|Habitat and Ecology:||
Anguilla mossambica is a demersal, catadromous eel. Spending the majority of its life in both quiet and fast flowing freshwater, brackish and coastal habitat, this eel makes one spawning migration to the open ocean where it is then thought to die (Réveillac et al. 2009). Arriving at the coast as transparent glass eels, these eels begin to gain pigment becoming elvers that ascend rivers mainly at night and overcome waterfalls and walls of small dams in order to migrate upstream towards suitable growth habitat. Like other anguillids, however, there is likely to be a portion of the population that remain almost exclusively in coastal habitat without making prolonged ascents into freshwater habitat (Tsukamoto 1998). The behavioural strategies of these non-migrant sea eels (sea residents) are explained by a latitudinal cline in the difference in food availability between marine and freshwater habitats (Tsukamoto and Arai 2001). Elvers in the Eastern Cape, South Africa arrive in considerably higher numbers in the summer than during the winter or spring months (Wasserman et al. 2012). Although the adults are usually fairly sedentary, otolith microchemistry suggests that some individuals are inter-habitat migrants that move between freshwater and saltwater habitats (Lin et al. 2012). Females can attain lengths of up to 120 cm and are generally longer and heavier than males (Froese and Pauly 2011). This eel is carnivorous, eating dead and/or living prey but especially aquatic insects, crabs and fish. After feeding in freshwater for ten years or more (McEwan and Hecht 1984), adults assume a silver ventral colouration, the eyes become enlarged and they return to sea to breed.This species is considered to breed east of Madagascar but moves southwest on its way to the Mozambique coast and South African rivers. The age of leptocephali - the larval form of the species - increases as they are found further south from the proposed spawning area and therefore it is suggested that individuals are transported southwards by the South Equatorial Current (SEC); the migration pathways in this species are estimated to be in the order of 1,000 to 2,000 km long (Réveillac et al. 2009). Of the three species that inhabit the Malagasy area (A. mossambica, A. marmorata and A. bicolor), A. mossambica have the slowest otolith growth rate due to its most southern distribution (Robinet et al. 2008).
|Use and Trade:||
The various life stages, ranging from juvenile to adult, of all anguillid species are harvested and traded on a global scale for consumption, with current demand predominantly driven by East Asian markets, in particular Japan and mainland China. A concerning pattern of exploitation is already apparent – when one Anguilla species or population becomes over-exploited, industry moves to the next in order to fulfil demand (Crook and Nakamura 2013).
Species of Anguilla are traded internationally as live eels for farming and consumption, as fresh, frozen and smoked/prepared eels for consumption and as skins and leather products for fashion accessories. Global trade data collated by the FAO for live, fresh, frozen and smoked/prepared anguillid species (non species-specific) are available for the period 1976-2009. According to FAO data, global annual Anguilla exports averaged around 20,000 tonnes in the late 1970s (valued annually at 55-95 million US dollars), after which annual exports showed a steady increase to a maximum of over 130,000 tonnes in 2000 (valued at over 1000 million US dollars). Since then annual exports have been declining, to just over 80,000 tonnes in 2008 and 2009 (valued at over 800 million US dollars). By weight, China and Taiwan are responsible for nearly 75% of these exports and Japan for over 75% of all imports (FAO 2013).
There are no FAO catch data for A. mossambica, however according to FAO trade data from the early 1990s, annual exports of frozen eels from Madagascar have averaged 10 tonnes and there are also some intermittent exports of this commodity from South Africa. Exports of live eels commenced in 1998, with regular yearly exports from Madagascar since then, averaging approx. 5 tonnes per year and reaching 9 tonnes in 2009. There are also records of live eel exports from Mozambique and Tanzania (FAO 2013). These exports include all life stages and could include a number of other species of Anguilla with overlapping ranges (including A. marmorata and A. bicolor), however it is known that there has been a recent increase in demand for A. mossambica glass eels to be exported to East Asia for farming.
Eel farming, which is responsible for over 90% of all Anguilla production worldwide (averaging at 280,000 tonnes per year since 2007, (FAO 2013), is reliant on wild-caught juvenile eels or glass eels, as raising eel larvae to the glass eel stage in captivity has only had limited success to date. The first known records of imports of live glass eel into Asia from Madagascar are from 2005, and since then they have been fluctuating from 20 kg to nearly 4,000 kg per year (in 2012), with the majority being imported into Hong Kong. Investment into sustainable fisheries and farming of eels in Madagascar and Mauritius, in particular of A. mossambica, has been reported in recent years (FIS 2010) and various Malagasy companies are now offering live eels for sale via B2B marketplaces/trade platforms such as Alibaba. In 2012, the press reported the intentions of a Japanese company to import one tonne of live A. mossambica from Madagascar every week for half the price of eels cultivated in Japan, in order to help the industry fulfil consumer demand (Anon. 2012).
Note: double-counting, under-reporting and misreporting must be taken into consideration when interpreting all available catch and trade data. See Crook (2010) for explanations of data issues.
The fragmentation of rivers caused by various barriers (weirs, dams, causeways etc) prevent the migration of glass eels upstream and silver eels downstream threatening the year on year recruitment of A. mossambica to freshwater habitat. In the warm temperate Sundays River, Eastern Cape, South Africa, this African Longfin Eel was found furthest upstream of all marine spawning fishes in a survey by Wasserman et al. (2011). The study suggests that A. mossambica is the only catadromous species that is able to traverse the 4 m high Cleveland Weir, although it does not discuss whether those captured were potentially trapped silver eels unable to migrate back to the ocean. According to the Federation of South African Flyfishers (FOSAF), barriers in some river systems, have led to A. mossambica becoming locally extinct such as in the Crocodile River catchment in Bloubankspruit, South Africa. Additionally, climate change has been proposed to play a role in fluctuations of abundance in anguillid species – particularly larval transport and glass eel recruitment – however, our understanding of these processes, and the scale of their influence, if any, is very limited.In recent years there has been increased investment into the sustainable fisheries and farming of A. mossambica particularly in Madagascar and Mauritius (Crook and Nakamura 2013). Furthermore, in the Eastern Cape of South Africa this species is particularly vulnerable to a parasitic gill worm (Pseudodactylogyrus anguillae), an alien species that appears to favour A. mossambica over A. marmorata, although the range of the parasite is somewhat restricted, largely being found in the Great Fish River System (Parker et al. 2011). Eels in the Southwest Indian Ocean are facing growing interest from international fisheries based in Madagascar and South Africa (Robinet et al. 2008) and glass eels are now being exported directly from Madagascar to Eastern Asian. It should also be noted that A. mossambica has a rich parasite fauna assosciated with it. Weyl et al. (2013) caution that the trade of live A. mossambica may result in the introduction of novel parasites into naïve eel hosts in other regions.
There is little information available regarding the conservation efforts throughout the range of the African Longfin Eel. In South Africa, however, there are plans to try and increase upstream and downstream river connectivity by linking adjoining sub-catchments in an attempt to aid migration (Rivers-Moore et al. 2011).
|Citation:||Jacoby, D. & Gollock, M. 2014. Anguilla mossambica. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 01 September 2015.|
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