Throughout its distribution, the Longtail Butterfly Ray is caught in coastal fisheries by demersal trawl, tangle nets, set nets, gill nets, droplines, longlines, and Danish seine (White et al. 2006, Blaber et al. 2009). It is taken as retained bycatch in industrial and artisanal fisheries for human consumption or fishmeal. In China, the number of powered fishing vessels increased from ~10,000 in the late 1960s to ~200,000 in the mid-1990s, along with an increase in vessel size and more modern fishing gear. Since 1989, the catch-per-unit effort of fish stocks has steadily decreased and large, highly valued species have been replaced by small, less valuable species, with most of the catch now used as feed in aquaculture (MacKinnon et al. 2012). The demand for seafood in China is high and increasing, with China among the largest consumers of seafood products globally; a 6 % annual increase per capita fish consumption was evident from 1990–2010 (Fabinyi and Liu 2014).
Taiwan ranks among the top 20 shark fishing nations globally and is a major global shark fin and shark meat trading nation (Oakes and Sant 2019). However, since the 1970s, most of the Taiwan global shark catch is from Taiwan fishing vessels operating in distant waters outside Taiwan exclusive economic zone (EEZ) (H. Hsu Taiwan National Fisheries Statistics pers. comm. 28/08/2019). By the 1950s, the Taiwan coastal fisheries were considered overfished, and fisheries expanded into offshore waters. The fisheries catch within the Taiwan Exclusive Economic Zone (EEZ) continued to rise from the 1950s until 1980, after which it steadily declined (Kuo and Booth 2011). The number of powered vessels operating in Taiwan’s EEZ significantly increased from the 1950s (3,215 vessels) to the late 1980s (peaked in 1989s at 15,900), and then slowly decreased to 11,200 vessels in 2017 (Huang and Chuang 2010, Liao et al. 2019, H. Hsu Taiwan National Fisheries Statistics pers. comm. 28/08/2019). The artisanal fishing effort has steadily and markedly declined for non-powered sampans (8,283–239 from 1956–2004), but remains steady for fishing rafts (14,273–12,984 from 1956–2004) (H. Hsu Taiwan National Fisheries Statistics pers. comm. 28/08/2019). In Taiwan, the demand for seafood has always been high with per capita fish consumption at 31.2 kg per capita in 2013 (Fabinyi and Liu 2014,Helgil 2019).
There is intense fishing pressure within Viet Nam. Most marine stocks have been declining since the 1990s and are now considered fully or over-exploited with a lack of adequate enforcement leading to essentially unregulated fisheries (Teh et al. 2014, FAO 2020). The motorized fishing fleet has been increasing since the 1950s and rapidly expanded in the mid-1980s to 2000s when Viet Nam moved towards a market-oriented economy (Teh et al. 2014). The fleet is dominated by small-scale artisanal and subsistence fisheries that have accounted for 60–85% of the fleet since the 1950s (Teh et al. 2014, Pauly et al. 2020). The artisanal and subsistence motorized fleet has tripled from 1950 (24,280 vessels) to 2014 ( 78,000 vessels) but has also substantially increased in effort in terms of engine power, particularly over the last two decades (Pauly et al. 2020). This fleet tends to operate in inshore waters at depths less than 50 m, and within 4–5 nautical miles from shore (Teh et al. 2014, FAO 2020). The demand for seafood is also high in Viet Nam, with per capita fish consumption steeply increasing over the last two decades to 36.3 kg per capita in 2017 (FAO 2020, Helgil 2020a). Viet Nam is among the top 20 importers of shark meat for 2008–2017 (Oakes and Sant 2019).
In the Philippines, the fishing fleet rapidly expanded in the 1960s and 1970s as small-scale artisanal fisheries became motorized and evolved into commercial fisheries. By the 1980s, overfishing was apparent throughout the Philippines, but government and foreign aid continued to subsidize motorizing of artisanal vessels into the late 1990s (Palomares et al. 2014). The commercial fleet operating in the Philippine EEZ tripled from the 1960s (2,100 vessels) to 2014 (6,400 vessels) (Palomares et al. 2014). Fishing shifted from mainly inshore demersal to offshore pelagic species during the late 1980s (Palomares and Pauly 2014). ‘Baby trawlers’ operate intensively in inshore waters and in waters less than 13 m deep, waters traditionally reserved for small-scale artisanal fishers (Palomares et al. 2014). The small-scale fleet increased ten-fold from 1950 (30,500 vessels) to the mid-1990s ( 338,700 vessels) and while the fleet size has since remained relatively stable, the effort in terms of engine power has continued to rise, as has the number of subsistence vessels (Pauly et al. 2020). All incidental catch in Philippines appears to be retained as discards are virtually non-existent (Palomares and Pauly 2014). In the Philippines, the demand for seafood has always been high with per capita fish consumption increasing over the last two decades to 34.1 kg per capita in 2013 (Helgil 2020b).
In Singapore, this species makes up ~2% of the rays landed (N. Clark-Shen pers. comm. 06/05/2020). In Malaysia, fisheries significantly contribute to the national economy through employment opportunities, and protein supply (A. Bin Ali unpubl. data 2020). This species is commonly landed, particularly during the monsoon season (A. Bin Ali unpubl. data 2020). Fishing effort in Malaysia has been increasing since 1950 across subsistence, artisanal, and industrial fisheries (Pauly et al. 2020). The number of vessels across all sectors has more than doubled from 22,800 vessels in 1950 to 50,150 vessels in 2014 (Zeller and Pauly 2016). However, the substantial increase over this period has been in engine power which has dramatically increased by ~30 fold (Pauly et al. 2020). Consequently, fisheries were fully exploited by the late 1970s (Teh and Teh 2014). Nevertheless, fish consumption continues to rise and most (~85%) comes from the Malaysian EEZ (Fowler et al. 2002, A. Bin Ali unpubl. data 2020). Small-scale inshore fisheries provide the main supply for local consumption. Fisheries operating within 30 nm from the coast contribute 85% to the total marine fish landings with vessels <70 GT. In waters beyond 30 nm from the coast, trawls and purse seines are the main fishing gears, deployed form large vessels >70 GT. These fisheries have contributed significantly to habitat destruction and reduced abundances of all commercially important fishes in the area (Teh et al. 2009).
In Indonesia, these small-scale fisheries comprise most (~90%) of fisheries production (Tull 2014). In some regions, effort by these small-scale fisheries has tripled when taking population growth into account (Ramenzoni 2017). Sharks and rays are an important resource in Indonesia and are the main livelihood for some communities (Sadili et al. 2015). Indonesia catches the highest number of chondrichthyans in the world with the catch of rays rising as shark fisheries collapse. In 2003, rays comprise over 50% of chondrichthyan landings, up from 32% in 1981 (White et al. 2006). Stingrays contribute the most (more than 95%) to elasmobranch catch by danish seines (cantrang) operating in the Java Sea (Fahmi et al. 2008). In 2009, it was reported that 680 trawlers operated in the Arafura Sea and that catches in inshore waters had declined with vessels travelling further south to maintain catches (Blaber et al. 2009). Although the numbers of trawlers currently operating is unclear, this intensive fishing pressure still continues; high levels of Indonesian trawl fishing in the Arafura Sea adjacent to the Australian Fishing Zone has been reported (Heazle and Butcher 2007, Northern Territory Government 2009), in addition to intensive longline and gillnetting throughout the Malacca Strait, with some mini-trawl operations and Danish seines operating throughout Kalimantan and the Java Sea (Fahmi unpubl. data 2020). Thus, the actual level of exploitation of this species could be extremely high throughout the Indonesian portion of its range.
In Thailand, the gulf coast is considered one of the most overfished regions of the world due to the rapid industrialization of their fishing fleet (Sylwester 2014). The number of Thai trawlers peaked in 1989 at ~13,100 boats (Poonnachit-Korsieporn 2000), which was reflected in the catch-per-unit-effort (CPUE) which declined from >300 kg per hour in 1963 to 20–30 kg per hour in the 1990s (Poonnachit-Korsieporn 2000). Fisheries in Thailand have been moving to deeper water for decades due to the overexploitation of the coastal region (Sylwester 2014).
Sharks and rays are captured by a wide range of gears in Myanmar. Since 2004, sharks and rays are largely taken as incidental catch in coastal gillnets, trawls (for fish or shrimp), longlines targeting mackerels, and hookah divers spearing at night (mostly catching rays and carpet sharks) (Howard et al. 2015, Mizrahi et al. 2020). These inshore fisheries are relatively small-scale and include many subsistence level fishers. At times since 1950, significant numbers of foreign vessels have operated in Myanmar waters targeting fish and shrimp. These vessels have operated in both inshore and offshore areas. Offshore fishing that incidentally catches sharks and rays is carried out by a large commercial fleet of mostly trawlers, purse seiners, and longliners. International Labour Organisation (2015) estimated of the number of vessels participating in the small-scale inshore fishery to be about 26,000 in 2013, with about 50% of them unpowered. The number of locally operated larger offshore vessels numbered 2,846 in 2013, having increased nearly 30% since 2009. Foreign fishing vessels numbered 153 in 2013, but had historically been much higher. Foreign vessels were banned in 2014.
Bangladesh has a substantial artisanal fishing fleet that operates throughout the coastal regions. In 2017–2018 there were 67,669 vessels reported to be operating (DoF 2018). All benthic rays in Bangladesh are targeted with non-baited demersal longlines (1–10 km) with 10,000–30,000 hooks that operate in 5–40 m depth (A.B. Haque unpubl. data 2020). Anecdotal reports indicate a steep decline in rays over the past 10 years (Ullah et al. 2014, A.B. Haque unpubl. data 2020). This decline is concurrent with steep increases in artisanal and subsistence fisheries effort (Pauly et al. 2020). The artisanal fishing vessels land >90% of the total marine catch and generally operate inshore at depths of 0–40 m but can operate to 80 m (Hoq et al. 2014, A.B. Haque unpubl. data 2020). The marine capture fisheries of Bangladesh exploit a complex, multi-species resource, and can be subdivided into subsistence (small-scale, non-commercial), artisanal (small-scale, commercial), and industrial (large-scale, commercial) fisheries sectors. Among the commercial catch, more than 90% is landed by artisanal fishing vessels, while industrial fisheries contribute around 6% to the total landed catch (Ahmad 2004). Each trawling vessel is equipped with trawl gear as well as demersal set longline gear to target shark and rays. There has been an increase in fishing vessels over the past 10 years. Many fishing vessels in the southwest region of the country will go out to sea for 5–10 days and sometimes more than 15 days and return with greater landings of larger ray species (A.B. Haque unpubl. data 2020). It is believed that there may be a number of nursery areas around coastal Bangladesh. Sharks and rays landed in the pre-monsoon season are often pregnant and near term. This period overlaps with significant fishing pressure (A.B. Haque unpubl. data 2020).
In Sri Lanka, fishing takes place all around the coast, but primarily within the continental shelf. The potential yield from coastal fish resources has been estimated at 250,000 t per year with 170,000 t(per year) from coastal pelagic species and 80,000 t from demersal species (Blindheim and Foyn 1980). Coastal fisheries still account for about 67% of the marine fishes caught, but there are some uncertainties regarding further expansion of coastal fishing activities (Wijayaratne 2001). Survey catch rate of sharks and rays was 105 kg per hr in 1980 from the Fritjof Nansen survey (Table VI, Sivasubramaniam 1985). Approximately 28,000 fishing crafts are operating in Sri Lanka. Out of this, 87% of crafts operate in the coastal fishery which consists of traditional non-motorised crafts and fiberglass reinforced plastic boats with inboard engines. Both types of vessels are generally day boats, not venturing far from the coast (Wijayaratne 2001). Over 28,000 fishing crafts are now operating, including multi-day boats that remain at sea sometimes for 20–25 days (NARA 2003).
In India, the majority of the geographic distribution of this species in the region overlaps with intense coastal fisheries. There are approximately 24,554 trawl vessels operating in the Indian part of the range (CMFRI 2010). The shallow depth distribution means this species is unlikely to have a depth refuge. There has been a significant increase in coastal fishing effort and power over the past 30 years (two generation lengths). There were about 6,600 trawlers operating in the Indian state of Gujarat in the early 2000s (Zynudheen et al. 2004). This number increased to 11,582 trawlers in 2010 (CMFRI 2010). Furthermore, there are over 13,400 gill netters operating along the west coast, with many other types of net gear also deployed in coastal areas (CMFRI 2010). A ray fishery has recently began (2 years) in the Andaman and Nicobar islands and uses demersal set gillnets to catch up to 6 t of rays per trip (3–5 days). There are currently 20–40 boats operating in this fishery (K.K. Bineesh unpubl. data 2020). In Pakistan waters, about 2,000 trawlers operate in shelf waters, targeting shrimp in shallow waters and fish in outer shelf waters (M. Khan pers. comm. 06/02/2017). In Iran, there is increasing fishing effort with the number of fishermen increasing from 70,729 in 1993 to 109,601 in 2002 (Valinassab et al. 2006).
The Longtail Butterfly Ray is reported in small numbers (< 1% of total elasmobranch landings) from Kuwait, Qatar and Bahrain (Moore et al. 2012, Moore and Peirce 2013). In the United Arab Emirates, this species was commonly caught in research demersal trawl surveys but also represented less than 1% of landed batoids by number observed during intensive landing site and market surveys (R. W. Jabado pers. comm. 20/04/2017). In the Red Sea, information on this species are limited to one report with no details of catch numbers (Bonfil 2003). No records have been confirmed in more recent market surveys from Sudan and the Saudi Arabian Red Sea (Spaet and Berumen 2015), although this could be due to high levels of discards of rays in the Red Sea region (e.g., Sudan and Eritrea (I. Elhassan pers. comm. 07/02/2017))
In the Arabian Sea portion of its range, fishing pressure in places is intense and increasing. For example, in the Indian state of Gujarat, the number of trawlers increased from ~6,600 in 2004 to over 11,500 trawlers in 2010 (Zynudheen et al. 2004, CMFRI 2010). Similarly, gillnet fishing (including net length) is increasing in India (Bineesh K.K. unpubl. data 2017). In Pakistan waters, about 2,000 trawlers operate in shelf waters, targeting shrimp in shallow waters and fish in deeper shelf waters (M. Khan pers. comm. 06/02/2017). In Iran, there is increasing fishing effort with the number of fishermen increasing from 70,729 in 1993 to 109,601 in 2002 (Valinassab et al. 2006). In the Red Sea, the number of Saudi Arabian traditional vessels operating increased from about 3,100 to 10,000 between 1988 and 2006 (Bruckner et al. 2011), while in Eritrea catch and effort data showed that total fishing effort as well as total annual catch increased more than two-fold from 1996 to 2002 (Tsehaye et al. 2007). In Somalia, illegal and unregulated fishing by foreign trawlers and longliners is rife and impacting elasmobranch populations (Glaser et al. 2015). Butterfly rays are generally discarded in the Red Sea and the Gulf (due to undesirable meat), in contrast to the normal retention in India. Survivorship from released line catches would be higher than trawl where the species may suffer mortality even if released.
This species’ preference for inshore coastal waters means it is also threatened by extensive habitat degradation, including pollution and clearing, and destructive fishing practices. Large coastal areas, in particular mangroves, have been lost in Indonesia and Malaysia through land conversion for urban development, shrimp farms, and agriculture. Across Indonesia and Malaysia from 1980 to 2005, the area of mangroves was reduced by >30% (FAO 2007, Polidoro et al. 2010). In Viet Nam, dynamite and cyanide fishing, and sedimentation have caused widespread destruction of coral reefs (Jameson et al. 1995, FAO 2020). Large areas of the coast are used for brackish-water aquaculture, which may have contributed to the dramatic loss of 45% of mangroves in Viet Nam from 1945–1995 (Jameson et al. 1995). Marine habitats in the Arabian Gulf are experiencing high levels of disturbance and quickly deteriorating due to major impacts from development activities (including dredging and reclamation), desalination plants, industrial activities, habitat destruction through the removal of shallow productive areas and major shipping lanes (Sheppard et al. 2010) which is likely to impact this species.
