The Spinner Shark is caught globally as target and retained bycatch of industrial, small-scale, and recreational fisheries using a range of gears, including trawl, longline, and gillnet (Joung et al. 2005, McVean et al. 2006, Carlson and Bethea 2007, Geraghty et al. 2013, Jabado et al. 2015, Dharmadi et al. 2017). It is also taken in beach protection programs that target large sharks (Dudley and Simpfendorfer 2006, Roff et al. 2018). Under-reporting of the Spinner Shark is likely due to misidentification with the Blacktip Shark (C. limbatus) (Tillett et al. 2012, Ebert et al. 2013). At-vessel mortality (AVM) was estimated as 56% in a commercial prawn trawl fishery and 4–97% in commercial longline fisheries (Ellis et al. 2017, White et al. 2019). The longer soak times in the longline fisheries had a much higher AVM (Ellis et al. 2017).
In the Northwest Atlantic, the species is among a range of carcharhinids targeted by the commercial fishery along the southeast coast to the Gulf of Mexico. It is a common component of the commercial catch in the north-central Gulf of Mexico, but is less often caught in the fisheries along the eastern seaboard of the United States. It was ranked among the top seven coastal sharks at risk from the ICCAT longline fisheries based on productivity and susceptibility (Arrizabalaga et al. 2011). However, the species was only infrequently captured prior to 2010 with only 3 reported captures from 2010 to 2017 (ICCAT 2018). In the Mexican Atlantic, the Spinner Shark accounts for a small proportion of the total shark catch in the small-scale fishery catches. The small-scale fisheries in Mexico account for 97% of the country’s marine fleet and take most of the Mexican shark catch, which is substantial and places Mexico among the top 10 global shark catching countries (Pérez-Jiménez and Mendez-Loeza 2015, Oakes and Sant 2019). Spinner Shark represented 0.1–1.4% of the shark catch over three separate studies from 1993 to 2014, with the number of individuals captured in those studies varying from 808 in 1993–1994, to 30 in 2007–2010, and 37 in 2011–2014 (Castillo-Géniz et al. 1998, Castillo-Géniz 2001, Pérez-Jiménez and Mendez-Loeza 2015, Martínez-Candelas et al. 2020, Pérez-Jiménez et al. 2020). The species was reported as seasonally common in the early years of the fishery during 1980–1998 (Martínez-Candelas et al. 2020). Fishing effort on sharks peaked in 1980–1998 but a 35% reduction in shark catches from 1999 to 2008 led to a reduction in the shark fishing fleet and effort (Pérez-Jiménez and Mendez-Loeza 2015, Martínez-Candelas et al. 2020). It has been recorded as a small portion of small-scale fisheries catches in the Guatemala Caribbean (Hacohen-Domené et al. 2020).
In the Mediterranean Sea, this shark was a significant bycatch of the pelagic longline fishery operating from eastern Algerian ports (Fowler et al. 2005). In West Africa, the demand for shark fin in the 1980s drove the development of artisanal targeted shark fishing across the region (Diop and Dossa 2011, Set0 et al. 2017, Moore et al. 2019). Spinner Shark are among the reported shark catches of West Africa, with the species among those caught in the highest numbers in Guinea-Bissau (Diop and Dossa 2011). By 2010, there were an estimated 252,000 unregulated artisanal and 3,300 industrial vessels (that mostly take shark as bycatch) operating in West Africa (Diop and Dossa 2011, Belhabib et al. 2018). In the Arabian Seas region, fisheries have experienced increased demand for sharks since the 1970s due to the shark fin trade and as a result, effort is increasing in traditional shark fisheries in many areas and likely has increased fishing pressure on this species (Bonfil 2003, Henderson et al. 2007, Jabado et al. 2015). In South Africa, the Spinner Shark is caught incidentally by pelagic longline, commercial and recreational line, prawn trawl fisheries, and the beach protection program. The estimated average annual catch was 1–10 t from 2010 to 2012 (Best et al. 2013, da Silva et al. 2015). In Mozambique and Madagascar, mostly unregulated small-scale fisheries that target sharks, including the Spinner Shark, are intense with 45,805 and 78,787 vessels, respectively operating in these countries in 2013 and 2012, respectively (Cripps et al. 2015, Temple et al. 2018).
In Southeast Asia, the catches of this species vary spatially and temporally across the region. It was among the top 10 species landed at some major fishing ports, such as Cilicap, Indonesia and infrequently recorded elsewhere (SEAFDEC 2016). In Indonesia and Papua New Guinea, this species is caught by longline, with juveniles a common catch of inshore gillnet fisheries in Indonesia (White et al. 2006, White et al. 2017, White et al. 2019). It was one of the most abundant species landed in eastern Indonesia from 2001 to 2006 (White 2007). The extensive loss and degradation of habitats such as coastal mangroves are also an indirect threat to coastal and inshore habitats of this species; Southeast Asia has seen an estimated 30% reduction in mangrove area since 1980 (FAO 2007, Polidoro et al. 2010).
In Australia, the Spinner shark is caught in low levels as bycatch in Western Australian trawl fisheries, the Northern Prawn Fishery, and the Eastern Tuna and Billfish longline fishery (Patterson et al. 2018). It is also taken in east coast line fisheries, although it is frequently misidentified as either the Australian Blacktip Shark (C. tilstoni) or the Common Blacktip Shark (C. limbatus) (Harry et al. 2011, Sumpton et al. 2011, Tillet et al. 2012). In southeast Queensland, approximately 30% of the total catch is the Spinner Shark, all specimens of which were less than one year old (Gutteridge 2012). While this catch is considerable, the life history of the Spinner Shark indicates that it can sustain high levels of fishing mortality in the juvenile age classes as part of a gauntlet fishery, that is, a fishery that only catches sub-adults and minimizes mortality on the breeding stock (Simpfendorfer 1999, Prince 2005, Smart et al. 2020). Therefore, this level of fishing effort in southeast Queensland is suspected to be sustainable. However, heavy fishing pressure on the adult stock is suspected to lead to population declines (Simpfendorfer 1999, Prince 2005, Smart et al. 2020).
