Shortfin Mako Shark

Atlantic Ocean

Shortfin mako has a very low capacity to withstand fishing mortality, yet it is experiencing intense exploitation (Dulvy et al. 2008). For this species, regional variation in the intensity of fishing mortality is an important factor in determining their conservation status. They are sought for both their meat and fins; thus unlike many other oceanic pelagic sharks, they are frequently targeted by the large longline fleets in the Atlantic Ocean. The species comprises approximately 7% of total catch (weight) in the Atlantic Swordfish fishery and approximately 10% (weight) of all North Atlantic shark catch (Mejuto et al. 2006a,b; Hareide et al. 2007). It is also a highly prized recreational gamefish (Dulvy et al. 2008).

This mako is not only an important species for pelagic longline, but also driftnet, set gillnet and hook-and-line fisheries wherever it occurs, particularly from nations with high seas fleets (Holts et al. 1998). It is taken as a bycatch from tuna (Thunnus spp.) and billfish (Xiphiidae and Istiophoridae) longline fisheries worldwide, with carcasses and high value fins retained. Big-game sports angling for makos is widespread, and the International Game Fish Association lists this species as a record game fish. Fisheries for Shortfin Mako exist or existed in the Eastern Atlantic and the Mediterranean Sea (Compagno 2001).

In the Northeast Atlantic, the data provided on this mako is incomplete and very limited, which is currently confounding trend analyses and hampering calculations of bycatch levels. Shortfin Mako is of high value to both the finning and meat trade, and many European fisheries land specimens gutted, with the head attached. The practice of finning is likely to result in undocumented catches and mortality of the species in some fleets (ICES 2012). Using a novel method of filtering fishery logbooks to obtain CPUE data, and to deduce the levels of underreporting of shark species, Nakano and Clarke (2006) found that this shark was underreported by an average of 33% across all logbooks analysed, with the worst example revealing an underreporting of 65%.

The historical use of generic shark categories is problematic, although many European countries have begun to report more species-specific data in recent years (ICES 2012). There have been significant discrepancies between reported catch in databases from ICCAT, the Fisheries and Aquaculture Organisation (FAO) and the Statistical Office of the European Communities (EUROSTAT). The ICCAT Secretariat consolidated these three data-sources into a unique database, and currently progress is being made on its validation and the associated analysis of equivalent data series at various aggregation levels (Palma et al. 2012). FAO data have been revised in recent years, and historical catch figures have increased from those previously reported (ICES 2012).

In the Hong Kong shark fin market, some traders mentioned infrequent mixing with the less abundant Longfin Mako (I. paucus) (Clarke et al. 2006). Combining results of the genetic analyses from this study with the stochastic modelling of trade records allowed the contribution of individual species to the trade to be determined. Shortfin Mako fins showed an 85% concordance with the market category ‘qing lian’, which equates to a trade proportion for this species of approximately 2.7% (probability interval 2.3–3.1%). The actual percentage is likely to be somewhat higher, as the species was also present in the ‘wu yang’ (Silky Shark Carcharhinus falciformis) trade category.

This shark is highly susceptible to overexploitation by pelagic longline fisheries in the Atlantic Ocean, according to a productivity and susceptibility analysis carried out by Cortés et al. (2010), which revealed it to be amongst the most sensitive. The analysis also revealed that the species has a lower productivity than previously thought based on more recently acquired life history variables, and that post-capture mortality was 92%.

This species has been caught in large numbers particularly on the high seas in pelagic longline fisheries, but also in other commercial pelagic fisheries and recreational fisheries. The first longline fisheries were prosecuted by Japan in western equatorial waters beginning in 1956 (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. Throughout the Atlantic, the fleet landed mako sharks and fins (Nakano 1993). It has been estimated that in the early 1990s, the Spanish longline fleet caught approximately 750 tonnes per year of Shortfin Mako in the Atlantic Ocean and Mediterranean Sea (Bonfil 1994, Compagno 2001).

No complete data are available specifically for the Northeast Atlantic, but the species is taken as a bycatch of the pelagic fishery. The area around the Strait of Gibraltar is considered a nursery area for Eastern Central Atlantic Shortfin Mako and most specimens caught are juveniles. This area is heavily fished by the Swordfish longline fishery off the west coast of Africa and Iberian Peninsula. Shortfin Mako became increasingly targeted in the western Mediterranean Sea at the end of the 20th century. European Union (EU) vessels fishing for small pelagic teleost (bony fish) species off the western coast of Africa are also known to take significant elasmobranch (shark and ray) bycatch, including Shortfin Mako in unknown numbers.

In the US and Canadian pelagic longline fisheries, this shark is one of the most commonly caught species. The index of abundance in the commercial longline fishery off the Atlantic coast of US has shown a steady decline (Cramer 1996) and other reports on declines are now available (Baum et al. 2003, ICCAT 2005, Cortés 2012: see Population section for details). As for recreational fishing, Casey and Hoey (1985) stated that the recreational catch of this species along the US Atlantic coast and in the Gulf of Mexico in 1978 was 17,973 fish weighing some 1,223 tonnes.

Mediterranean Sea

Even though driftnetting is banned in Mediterranean waters, this practise has continued illegally (WWF 2005). The Moroccan Swordfish driftnet fleet in the Alboran Sea operates year round, resulting in high annual effort levels (Tudela et al. 2005). Even though sharks are a secondary target or bycatch of this fishery, some boats deploy driftnets one to two miles from the coast where the chance of capturing pelagic sharks is higher. The catch rate for Shortfin Mako is nearly three times higher in boats actively fishing for sharks (from 0.6 to 1.9 N/fishing operation and 0.06 to 0.14 catch per km net). Both annual catches and mean weights of Shortfin Mako have fallen as a result of fishing mortality in the Moroccan driftnet fishery, illustrating the likely effect of this illegal fishery on stocks in the Alboran Sea and adjacent Atlantic (Tudela et al. 2005).