The Porcupine Ray is caught across its range as target and incidental catch by a wide range of coastal fisheries that include demersal trawl, Danish seine, gillnet, dropline and longline, and handline gears (White et al. 2006, Blaber et al. 2009). It is retained in some parts of its range for its meat and high-value skin. Its preference for inshore coastal waters increases its susceptibility to capture with much of its range outside of Australia intensively fished.
Marine fisheries catches reported to the Food and Agriculture Organization of the United Nations (FAO) in the Western Indian Ocean (FAO region 51), have increased over the past 30 years but have levelled off since 1999 suggesting stocks are fully fished. There is concern for serial depletion with the number of species landed near-doubling from only 85 in 1971 to 152 reported in 2000 (van der Elst et al. 2005). More than 60 million people reside within 100 km of the coast of the Western Indian Ocean and there is great dependence on marine resources for food and employment (Obura et al. 2017). In contrast to many other regions of the world, where industrial fisheries with high-technical gear predominate, fishers in the Western Indian Ocean operate primarily at the subsistence and artisanal level. For example, in Tanzania, no more than 5% of fishers are active in industrial fishing, the other 95% being artisanal (van der Elst et al. 2005). Artisanal catches are underreported and most small-scale, artisanal, and subsistence coastal fisheries within the Western Indian Ocean are considered to be fully- or overexploited, especially where they are found close to population centres. The number of underexploited fisheries in the coastal zone has tended to decline and such fisheries are now an exception (e.g., Pierce et al. 2008). Whiprays dominated the small-scale fisheries across Kenya, Zanzibar, and northern Madagascar from 2016–2017 and were captured by handline, longline, bottom-set, and drift gillnet gear (Temple et al. 2019).
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. 2017). Since 2011, there was an increase in fishing pressure on large stingrays, like this species, due to increased demand for export of frozen wings to Thailand and Malaysia (M. Khan pers. comm. 2023). In Iran, there is increasing fishing effort with the number of fishers increasing from 70,729 in 1993 to 109,601 in 2002 (Valinassab et al. 2006).
In India, juvenile rays are found in estuaries and high fishing effort, particularly with stake and doll nets, occurs in this habitat. The majority of the geographic distribution of this species in the region overlaps with intense coastal fisheries. 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. There were about 6,600 trawlers operating in the Indian state of Gujarat in the early 2000s that increased to 11,582 trawlers by 2010 (Zynudheen et al. 2004, CMFRI 2010). Furthermore, there were over 13,400 gill netters operating along the west coast (CMFRI 2010). Though the number of gill netters has decreased slightly to 6,548, the number of trawlers has almost tripled in 10 years to 30,772, in addition to other types of net gear deployed in coastal areas (CMFRI-FSI-DoF 2020).
In Sri Lanka, there are ~65,000 vessels operating, but fishing takes place mostly in the coast (~93%) (MFARD 2015). There is a heavy reliance on fisheries, both direct and indirect, through the employment of ~550,000 people and supply of ~67% of animal protein in the diet of Sri Lankans (Herath et al. 2019). Per capita fish consumption in Sri Lanka is increasing, and ranged from 12–15 kg per annum in 2016 (Herath et al. 2019).
In Bangladesh, the marine capture fisheries 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 trawlers 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 (Haque et al. 2022). 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 (Haque et al. 2022). Anecdotal reports indicate a steep decline in rays since 2004 (Ullah et al. 2014, Haque et al. 2022). This decline is concurrent with steep increases in artisanal and subsistence fisheries effort (Pauly et al. 2020).
In Myanmar, since 2004, sharks and rays are largely taken as incidental catch (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. International Labour Organisation (2015) estimated 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.
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 which declined from >300 kg per hour in 1963 to 20–30 kg per hour in the 1990s (Poonnachit-Korsieporn 2000). As of 2020, the number of trawlers operating in Thailand is 3,555 vessels, with ~4,000 net operators, >8,000 hook and line operators, and >4,000 other vessels (SEAFDEC 2023). In Malaysia, fishing effort has been increasing since 1950 (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 and fisheries were fully exploited by the late 1970s (Teh and Teh 2014, Zeller and Pauly 2016). Yet, the fleet in Malaysia remains large with almost 49,000 vessels operating in 2020 (SEAFDEC 2023). Small-scale inshore fisheries provide the main supply for local consumption (Teh et al. 2009).
In Indonesia, 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). There are over 1,150,000 fishing vessels operating in Indonesia, more than 1 million of which are powered vessels (SEAFDEC 2023). Sharks and rays are an important resource in Indonesia and are the main livelihood for some communities (Sadili et al. 2020). Indonesia catches the highest number of chondrichthyans in the world with the catch of rays rising as shark fisheries collapse. In 2003, rays comprised 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). These patterns of stingrays comprising higher numbers of chondrichthyan landings still persists (Fahmi pers. comm.15 May 2020). Intensive longline and gillnetting occurs throughout the Malacca Strait, with some mini-trawl operations and Danish seines operating throughout Kalimantan and the Java Sea (Fahmi pers. comm. 15 May 2020). Thus, the actual level of exploitation of this species could be extremely high throughout the Indonesian portion of its range.
In the Philippines, all incidental catch appears to be retained as discards are virtually non-existent (Palomares and Pauly 2014). The fishing fleet in the Philippines 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 Exclusive Economic Zone tripled from the 1960s (2,100 vessels) to 2014 (6,400 vessels) (Palomares et al. 2014), but has since been reduced to 5,557 vessels in 2020 (SEAFDEC 2023). ‘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).
In Papua New Guinea, this species is caught in the Gulf of Papua Prawn Fishery where it represented <1% of the total elasmobranch catch by number and was considered at medium risk from the fishery based on its susceptibility to capture and recovery potential (Baje et al. 2021). This species has some refuge from fishing pressure in northern Australia where fishing pressure is relatively limited and managed, and trawl fisheries mandate the use of bycatch reduction devices that have reduced the catch of whiprays by >95%, although juveniles may not be effectively excluded (Griffiths et al. 2006).
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). The Porcupine Ray is considered to be potentially one of the most vulnerable chondrichthyans to the impacts of climate change in northern Australia (Chin et al. 2010).
