The Silky Shark is the second most caught species of shark globally, after the Blue Shark (Prionace glauca) (Oliver et al. 2015). The Silky Shark is both targeted or caught as incidental (bycatch) by longline fisheries and purse seine fisheries (especially those using drifting fish aggregating devices [FADs]) as well as by artisanal fisheries. FADs are made of a floating object and nets that lie vertical in the water column to attract schools of fish. The Silky Shark, as well as other species, is easily entangled in the nets; and there have been large increases in the use of FADs since 1996 (Leroy et al. 2013). Whether they are targeted or an incidental catch, the Silky Shark is often either retained for its meat and fins where regulations allow, or released with high mortality rates apparent in the tropical purse seine fisheries (Hutchinson et al. 2015). Total catches of the Silky Shark reported to FAO are mainly from Sri Lanka (Western Indian Ocean) with the FAO catch less than 4,000 tonnes (t) from 2005-2009 before doubling in 2010 and 2011. Catches then decreased to ~5,000 t in 2012 and 2013 (FAO, 2015).

The Silky Shark was found to represent at least 3-4% of the fins auctioned in Hong Kong, the world's largest shark fin trading center - the third highest after Blue Shark and Hammerhead Shark (general) (Clarke et al. 2006a) - and Hong Kong is thought to make up more than half of the global shark fin trade (Clarke et al. 2004, 2006b). Silky Shark fins are valuable to the trade, although they are not one of the highest value fin types (S. Clarke, unpubl. data).

Eastern Central and Southeast Pacific Ocean
The Silky Shark is taken in pelagic commercial fisheries in the eastern central and southeast Pacific, as well as in coastal artisanal fisheries of the region. Fishing pressure from longline and purse seine fisheries targeting tunas and swordfish is high, and it is the main shark species caught in fisheries using FADs as well as longline fisheries in the eastern Pacific (Oliver et al. 2015). In addition to mortality, FADs may be influencing behaviour of the Silky Shark. In the eastern Pacific, Silky Shark diet contained high proportions of FAD-associated prey items, probably due to the increasing likelihood of an encounter with prey items at FADs (Duffy et al. 2015). If this behaviour continues, Silky Shark may be increasingly attracted to FADs and fishing mortality may be increased.

Mexico contributed the most to catch of the Silky Shark in the north and southeast Pacific, catching up to 40% of the total catch (12-16,000 t in the north and 11-16,000 t in the south per year) (IATTC 2013). The IATTC observer database from 1993-2005 showed that the Silky Shark was caught throughout the ocean west of central America, Colombia, Ecuador, and Peru out to about 170°W on purse seines set on FADs. The Silky Shark was the most commonly caught species of shark in the purse seine fishery for tunas in the eastern Pacific Ocean (IATTC 2007). The fishery has largely increased the use of FADs, which the Silky Shark is attracted to, increasing the catch rate of the Silky Shark in the fishery (Aires da Silva et al. 2014). Additionally, it is mainly juveniles caught North of the equator and caught in FAD sets.

Reported catches of the Silky Shark are approximately four times higher north of the equator in the purse seine fleets (IATTC 2013). In the north, 30-45,000 individuals were caught each year (2006-2010), while in the south, <10,000 individuals were caught each year (IATTC 2013). In the longline sector of the IATTC, annual catches of the Silky Shark ranged from 20-60,000 individuals in the north to 10-30,000 individuals in the south. Catches of the Silky Shark in waters around Mexico have been steadily increasing from the late 1970s, when over 3,000 t were caught to the 2000s, when 6-7,000 t of Silky Shark was caught (IATTC 2013). Central American unreported catch was estimated to be similar to the catch in Mexico of 6-7,000 sharks in recent years (IATTC 2013).

The Silky Shark are a major component of the shark catch in many fisheries along the Pacific coast of Central America. Observations made on a longline research vessel that sampled waters in the Exclusive Economic Zones (EEZs) of Panama, El Salvador, and Guatemala found that Silky Shark constituted 31%, 47% and 29% of the total catch respectively, and 80%, 63% and 44% of the shark catch respectively (Porras 1996). Off Chiapas, southern Mexico, Silky Shark (along with Scalloped Hammerhead Sphyrna lewini) form the large bulk of the shark catch (Soriano-Velásquez and Acal Sánchez 2008). In Tres Marías Islands, Mexico, Silky Shark is a major part of the catch constituting 27% of landed sharks in 1996 (Pérez-Jiménez et al. 2005). In San José and Buena Vista, Guatemala, Silky Shark constituted 73% of recorded catches landed, in a sample of 4,211 sharks, from 1996 to 1999 (Ruiz and Ixquiac 2000).

International longline vessels operating in the eastern central Pacific landed and exported over 8,000 t of shark carcasses and 900 t of shark fins from Costa Rica in 2002 (Costa Rica official INCOPESCA Fishery Statistics 2003), the large majority of which were recorded as the Silky Shark. However, these figures must be interpreted with caution as other sharks may have been misidentified as the Silky Shark. International vessels are known to transship shark products on the high seas, meaning these shipments are unreported. In 1991 in Costa Rica, sharks formed 27% of the total catch (Arauz et al. 2004). In 2000, only 8% of the total catch was sharks, 71% of which were Silky Shark. In 2003, the proportion of sharks in the total catch decreased further to 5% of the total catch, the Silky Shark made up 58% of the shark catch (Arauz et al. 2004). In the Costa Rican longline fishery, most of the Silky Shark catch is composed of juveniles. Since 2004, adults made up less than 15% of the Silky Shark catch (Dapp et al. 2013). Additionally, the total length of individuals caught decreased significantly from 2004 and 2007 to 2008-2010, indicating a decrease in spawning stock biomass (Dapp et al. 2013).

In Manta (the largest fishing port in Ecuador), artisanal fisheries data from September 2003 to the end of 2006 showed over 22,000 Silky Shark were caught (J. Martínez pers. comm. Feb. 2007). From 2008-2012, over 137, 000 individuals were caught throughout Ecuador which is six times the amount of the previous four years (Martínez-Ortiz et al. 2015). The landed females ranged in length from 61-309 cm TL, and the males ranged in length from 63-288 cm TL. In terms of landed weight of the Silky Shark, in Ecuador in the early 2000s, less than 400 t were landed annually, and from 2007-2011, 900-1,300 t per year were landed (IATTC 2013). Catch records from 2007-2008 for nine ports in Ecuador show that catches of Silky Shark was highest in the warmer summer months from March-August (IATTC 2011). Individuals landed were mainly 114-246 cm TL for females and 101-233 cm TL for males with a peak at 160 cm TL for both sexes (IATTC 2011). This peak corresponds to immature individuals, therefore, a majority of the Silky Shark landed in Ecuador is immature.

Western Central Pacific and Indian Ocean
The tropical waters of the Western and Central Pacific Ocean (WCPO) currently support the largest industrial tuna fishery in the world with an annual tuna catch approaching one million tonnes. The two main gear types, longline and purse seine, accounted for over 90% of the target tuna catch in this area in 1999 (Williams 1999). The most prevalent bycatch species found in the longline fishery are Silky Shark, Blue Shark, Pelagic Stingray (Pteroplatytrygon violacea), and the Oceanic Whitetip (Carcharhinus longimanus) (Williams 1999). The most prevalent bycatch species in the purse seine fishery is Silky Shark accounting for 95% of the elasmobranch bycatch in the FAD-associated purse seiners (Hutchinson et al. 2015). Due to the high rate of exploitation in the Indo-Pacific, the Silky Shark population is at risk of genetic diversity loss (Clarke et al. 2015b).

In the WCPO, the longline fishery catches the highest number of Silky Shark with the estimated catch (based on observer data) in 2009 of 189,000 individuals compared to 69,790 individual Silky Shark taken in the same year for the purse seine fishery (Lawson 2011). Once brailed from purse seines, Silky Shark have been shown to be deceased 72% of the time when brought on board (Poisson et al. 2014). They have also been shown in the WCPO purse seine fishery to have a high post-release mortality of greater than 84% (Hutchinson et al. 2015). In the WCPO, longlines and purse seines mainly catch juveniles (Rice and Harley 2013). In the western Pacific, a CPUE for Silky Shark of 1-25 kg per set was found on purse seine sets on tuna schools unassociated with FADs from 1998-2010 (Leroy et al. 2013). On purse seine sets on anchored FADs, the CPUE from 1998-2010 was between 5-50 kg per set and on drifting FADs, the CPUE was 25-60 kg per set (Leroy et al. 2013).

In pelagic longlines based off Hawaii, Silky Shark is caught mainly on deep sea sets. Most of the Silky Shark catch (62.5%) was taken above the equator (0° to 10°N), even though only 3% of fishing was observed above the equator (Walsh and Clarke 2011).

In Taiwan, reported catches of Silky Shark increased by 1,058 t from 2003-2011 (Davidson et al. 2016). This may be due to better reporting. Malaysia does not report catches but does list Silky Shark as a commercial species that is used for fins and meat. Silky Shark is sold locally in Malaysia and prices have been increasing (Lack and Sant 2012). Similarly, Vietnam has no data available on the amount of Silky Shark caught, but it is included in catch reports of sharks (Lack and Sant 2012). In Thailand, Silky Shark is noted as being caught at a “normal” amount, however, there is little training for fisheries officers in identification. This may account for an underestimation of Silky Shark catch (Krajangdara 2014).

Papua New Guinea had a coastal longline shark fishery in which Silky Shark made up >50% of the shark catch (Kumoru 2003). The fishery ceased in June 2014 due to the WCPFC requirement to not land or retain Silky Shark (see Conservation). Over 765 t of Silky Shark was caught in 2001. In 2011, 72% of sharks caught on longlines was Silky Shark (Lack and Sant 2012). The proportion of Silky Shark in the shark longline catch was >50% through 2013-mid 2014 (J. Smart pers. comm 2015). In the Solomon Islands, Silky Shark accounted for 23% of all longline bycatch and 84% of purse seine bycatch (in data collated in 2009; Lack and Meere 2009). The meat is kept for local subsistence and fins are exported. As of 2006, all fin exporters had to be licensed which increased the reliability of reported catches (McCoy 2006). In Fiji, Silky Shark accounted for 13% of longline bycatch and was caught in low levels in the purse seine fishery (2009 collated data; Lack and Meere 2009).

The Silky Shark is a very common component of shark and tuna longline and tuna gillnet fisheries in Indonesia (White et al. 2006). Indonesia’s reported shark catch represents 13% of the global total shark catch. Of this, 15% were reported as Silky Shark from 2001-2004. This represents an average annual catch of 15,943 t of Silky Shark (Lack and Sant 2012). Since 2009, a National Plan of Action-Sharks (NPOA) in Indonesia has been implemented and Silky Shark is listed as a commercial species in the Indonesian NPOA (Lack and Sant 2012). Silky Shark is fished over its entire size range with larger individuals caught on longlines at the beginning of the season and smaller individuals caught in gillnets once the catch rate on longlines decreases (Hall et al. 2012).

Pelagic fisheries have operated in the Indian Ocean for more than 50 years; Japanese long-liners in the eastern Indian Ocean since 1952 and in the western region since 1956. Russian, Taiwanese, and South Korean vessels have fished there since 1954-1966 (Gubanov and Paramonov 1993). Sharks are targeted in several areas, including off India where they are captured using hook and line and in large mesh gillnets, which are among the world’s largest (Anderson and Simpfendorfer 2005). Silky Shark was the most commonly caught shark at FADs in the Indian Ocean during a small pilot study of observers onboard French vessels - 61.5% of Silky Shark was discarded dead at sea, 30.5% partially alive kept onboard, ~7% discarded alive (Viera and Pianet 2006). In a more recent study of FADs in the Indian Ocean, it was estimated that 480,000-960,000 Silky Shark become entangled and subsequently die annually in Indian Ocean FADs (Filmalter et al. 2013). The number of Silky Shark that die by becoming entangled in the FADs was estimated as 5-10 times higher than the number estimated to be taken as bycatch in Indian Ocean FAD-associated purse seine sets (Filmalter et al. 2013). Sharks that were caught in FADs died and fell out within two days, therefore, there is the potential for very high levels of cryptic mortality on FADs (Filmalter et al. 2013). In the Indian Ocean, due to the high abundance of FADs, it was estimated a Silky Shark has a 29% chance of surviving to age one, 9% chance of survival to two years, and only a 3% chance of survival to three years old (Filmalter et al. 2013). On the Southwest coast of India, at Cochin, Silky Shark was recorded as a small portion of landed sharks through 2000-2002. In 2010, their contribution had increased to 16.3% of shark landings at Cochin (Kizhakudan et al. 2013); however, this increased contribution may partly be as a result of potential increase in reporting.

In the Maldives, it was estimated that some 85% of oceanic shark catch comprise Silky Shark (Anderson and Jauharee 2009). Although no specific data were available, Maldivian shark fishermen who specialize in longlining for oceanic sharks anecdotally reported declines in abundance and average size of Silky Shark; all fishers commented that Silky Shark numbers had decreased by >50% in the past 20 years (Anderson and Jauharee 2009). A fishery for Silky Shark has operated off Sri Lanka for many years and Sri Lanka are one of the only countries to report species-specific Silky Shark catch to FAO. The Silky Shark reported landings have decreased in Sri Lanka from 2003 to 2011 by 2,798 t (Davidson et al. 2016).

The Silky Shark is caught by Australian longline fisheries operating on both the east and west coasts (AFMA 2014). Due to management restrictions, total retained catch of sharks by these fisheries is low and Silky Shark is not a major of component of those that are retained. Overall effort on the west coast of Australia is low. Due to the spatial distribution of effort on the east coast (greatest between 25-30°S), few Silky Shark are captured. No assessment of Silky Shark has been undertaken by Australia (although the east coast fishery data was included in the WCPO Silky Shark stock assessment) (Rice and Harley 2013). Australia has a range of management measures in place to mitigate impacts on all sharks. These include trip limits of a maximum of 20 sharks, a ban on the use of wire traces and shark finning bans (Gilman et al. 2007).

Atlantic Ocean
The first longline fisheries in the Atlantic were begun by the Japanese fleet in 1956 in the western equatorial waters (Uozumi and Nakano 1996). The fleet expanded rapidly in the 1960s, and covered almost the entire Atlantic by the late 1960s (Bonfil 1994), including the areas currently fished by the American fleet. Fishing pressure in the Atlantic Ocean longline fisheries is high and ongoing. In the United States, Silky Shark is caught by the commercial shark bottom longline and the pelagic longline fishery, and in recreational shark fisheries. In the shark bottom longline fishery in Gulf of Mexico and Southern Atlantic, Silky Shark represent a major byproduct species (Enzenauer et al. 2015). Approximately 75% of individuals caught are retained, mainly comprising small individuals (<110 cm TL). The rest are discarded, of which one third are discarded dead (Enzenauer et al. 2015). Silky Shark is one of the five most captured shark species caught in the Cuban longline fishery (Espinosa 2004).

Silky Shark is taken in several longline fisheries in the Southwest Atlantic, including those off Santos, southern Brazil (Arfelli and Amorim 1994, Amorim et al. 1998), Natal, northeastern Brazil (Hazin et al. 1990) and Uruguay (Marín et al. 1998). The species is taken in artisanal gillnet fisheries off southern Paraná State (Costa and Chaves 2006). In Brazil, Silky Shark is generally retained and marketed (Arfelli and Amorim 1994, Marín et al. 1998). Silky Shark catch in the longline tuna fishery off Brazil increased from 2004-2008 and then declined from 2008-2010 (Fredou et al. 2015). The highest catch rates occurred near the coast, with two exceptions in the central Atlantic. Similar to most catch data of Silky Shark, a high proportion of individuals were immature (Fredou et al. 2015). In another part of the Atlantic, in Spain, the landings of Silky Shark plummeted in the early 2000s from 17 t in 2002 to ~1 t in 2011 (Eurostat 2013).