Blue Shark Alive: A value of $9.71 million

The blue shark, Prionace glauca, is globally decreasing according to the IUCN (last updated in 2019). It is categorized as Endangered (North Atlantic), Near Threatened, Vulnerable (South Atlantic), and Least Concern on the Red List. The main threat is from the “fishing and harvesting” of aquatic resources, with its habitat being in the Oceanic and Neritic (near coastal) zones. Conservation actions that are needed include species management, research, and monitoring. This is due to the fact that, according to the IUCN, there is a probable median decline of 7.3% in the global population size.

With its long fins, the blue shark can travel far distances. Its large eyes allow the blue shark to hunt in the deep regions of the ocean where there is limited light. According to studies, these sharks can travel over 11,000km in between eight and nine months – which equates to around 43km per day. In another study, a large female juvenile shark swam in the region of 28,139km over 952 days. Blue sharks prefer the south in the winter, with the Azores being a popular mating and nursery area. Also, they have been recorded at a depth of up to 696m. They prefer the cooler and deeper waters, yet are found in tropical, subtropical, and temperate waters. Being curious, fast, and showing no fear, they are seen as being potentially dangerous to humans but there is minimal data about attacks.

It has been stated that the blue shark is not aggressive towards humans. They also prefer to stay in hierarchical groups – either male or female groups – with similar-sized sharks. Recently, in 2020, scientists identified that there are two main genetic groups of blue sharks - one in the Indo-Pacific region and the other in the North Atlantic/Mediterranean region. The possible mixing area is in the southeastern Atlantic region. There are varying reports regarding the blue shark catch. Some reports state that roughly 10m to 20m blue sharks are killed yearly through fishing as they are popular for the trade of shark fins, leather, and oil from the liver.

Blue Sharks in the Azores

The Azores is in the Mid-Atlantic Ridge and there are nine islands in the archipelago. These volcanic islands lie around 1,300km to the west of Portugal, and the islands, spread across 650km, are divided into three groups –Eastern, Central, and Western. The blue sharks congregate in the Azores islands in the North Atlantic Ocean during the summer months. The 180m deep Condor Banks is an area where fishing is prohibited, and blue sharks are often sighted there except apparently when the shortfin mako is present.

This is a popular freediving site. Since 1980 the Marine Protected Areas have been developed. These three areas have reached 110,00km2 with varying levels of protection for marine species and habitat. During the months between July and October, around the islands but especially Pico island in the Central Group, it is possible to see blue sharks on a regular basis. The north of the archipelago is an important area for breeding as a nursery as both the male and female blue sharks are found in this region of the Atlantic. Due to their small size, the mortality rate is high for the first year of their life. But, for the surviving young blue sharks, it is their main home for around two years before they start moving further afield.

Diving to view the blue shark is becoming extremely popular in the Azores with the season being early July to later in October. During this time the visibility can be up to 30m and the temperature of the water ranges between 21-25oC. It is advertised that there is more than a 90% shark viewing success rate. Many blue sharks and other species which use the topography and climate of the Azores are falling victim to longline fishing. This is a problem that needs urgent attention.

Even nearly a decade ago, in 2014, a study into migratory patterns of this pelagic shark identified the critical need for sustainable management of the "heavily exploited" blue shark in this North Atlantic region where important nursery grounds and seasonal migrations are exploited and result in significant fish mortality. This is particularly pertinent taking cognizance of the fact that the IUCN assessment of the blue shark (based on ICCAT 2015) indicates that the Northern Atlantic population is Endangered. The simulations estimate a median regional population decline of around 53.9%. Considering this, it is understandable why the blue shark being classified as a Priority Species according to the UK Post-2010 Biodiversity Framework.

Blue Sharks in Northern Spain

Spanish fishing for swordfish using surface longlines has been occurring for hundreds of years, with blue sharks being incidental bycatch. They made up 87% of shark landings in the ten years leading up to 2007. Since then the regulations concerning other species of sharks have resulted in the blue shark becoming the targeted species in Spanish coastal waters. In particular, catch rates have been greater when the temperatures are warmest.

There are several reasons which could account for the increase in the number of sharks along the coast of Spain – the Mediterranean Sea; the North East Atlantic; and the northern coasts of Spain in the Galicia region and the Bay of Biscay within the cold Atlantic Ocean. It could be due to climate change with the rising sea temperatures which means possible changes in migratory patterns or distribution, changes in pupping areas, recruitment events being unusually high, or overfishing which has resulted in a lower number of fish stocks and therefore sharks have to come closer to the shore while looking for prey. This overfishing affects the entire food web and the health of the oceans.

The sharks that have been sighted more frequently over the past ten years include, inter alia, white sharks, hammerhead sharks, and, more commonly, the blue shark. The blue sharks include young pups and juveniles up to around 0.5m in length – the latter of which are sometimes found on the beach – to full-grown sharks.

The pups feed on cephalopods and small fish, hence the reason for them needing to come close to shore due to food competition. They actually can travel from around 360km offshore in the deep ocean, past the Galician Shelf or sea bank which has a maximum width of 35km, to the coast in order to find food. It is also a survival strategy as larger blue sharks eat the smaller ones and the coast is safer until they are larger, at which time they return to the deeper waters. Many, however, do not survive due to the lack of food. The newborns and juveniles that have been caught by longliners close to the Galician coast more recently have averaged between 50cm to 150cm which could also suggest that the Galician shallow inshore waters could be a nursery area for blue sharks. This is a fairly recent phenomenon and increases the vulnerability of the blue shark species which brings into consideration their protection. Thanks to new surveillance networks that have been introduced by marine researchers, more accurate numbers can be determined. Also, these small blue sharks do not actually pose a threat to beachgoers, and the blue shark has always been found along the coast of Galicia. The total number of all recorded shark attacks in Galicia is one, which occurred in 1908.

Blue Shark Catches

A 2022 report by Poseidon stated that the live weight of catches in 2019 was estimated at over 189,000t. Averaged at 27kg a shark, that will then indicate over 7m blue sharks. But, this excludes the unreported catches so the number could be estimated at in excess of 10m. Further, according to the Poseidon report, in 2019 53% of the above catch was in the Pacific Ocean, 13% in the Indian Ocean, and 34% in the Atlantic Ocean. Almost 80% of the total blue shark landings were by five countries – including two European countries (Spain and Portugal), Taiwan, Indonesia, and Japan. Most of this shark catch was from longline fleets that target sharks.

The misconception is that sharks are strictly bycatch, but these fleets specifically target sharks. Other fish, such as tuna, is the bycatch, not vice versa. The blue shark fin trade volume of exported fins amounted to over 67,000t in 2019 and involved 177 countries. The meat of the blue shark reached 36% of the global shark volume that was traded in 2019 (ARTiS database) with the importing countries identified as China, Greece, Brazil (highest consumer), Singapore, and Italy. Blue shark meat is therefore mostly an export commodity. Sea Around Us estimates approximately 81,156t of the global blue shark catch, relative to 189,783t of legally landed blue sharks (the Sea Around Us indicative volume is around 9% less), were discarded presumably due to illegal finning. The case for the blue shark rests on the industry that has the stronger financial pull power. One argument is that the commercial blue shark fishing industry is too significant to ignore.

From one perspective, commercial shark fishing is valuable – according to Poseidon (2022), the ex-vessel value of the 189,783t of blue shark meat and fins landed equated to EUR 411m. However, this averages out at less than EUR 2.00/kg – significantly less than many other comparable farmgate prices. It is also important to acknowledge that this was generated from the landing of over 7m blue sharks removed from the ocean. Therefore, when taking the total ex-vessel and retail value of the sale of blue shark meat and fins into account, an average individual shark is selling for only EUR 150-160.

Furthermore, based on the total tonnes relative to total blue sharks, it is calculated that, on average, each landed shark weighed only 27kg. Considering that an adult male blue shark weighs 27-55kg and an adult female weighs 93-182kg (with the maximum reported weight being 391kg), it would suggest that the vast majority (as previously identified) are juveniles. Added to this, since there is no true idea of how many blue sharks are in the global oceans, the extraction of over 7m blue sharks per year (of which 91% are immature) poses a large risk to the survival of the species. This is particularly concerning considering that, based on Druon et al. (2022), the global abundance of blue sharks is 0.96 sharks/km2, which leads to an estimated global population of around 20m sharks. Without a sufficient stock of reproductive adults, eventually there will be insufficient genetic diversity to ensure the long-term viability of the population. Besides the implications for the oceans and climate change (taking cognisance of the fact that sharks contribute to carbon absorption), there is a health issue relating to commercial shark fishing. This is due the fact that shark meat can have a harmful effect on human health. Therefore, whilst the industry may create some value, this value is likewise negated by the healthcare burden that could be potentially created through the sale of sub-standard food.

For example, Krabbenhoft and Rickert (2016) state that methyl mercury is absorbed by humans through fish consumption. This, in turn, affects the central nervous system and, in more severe circumstances, it can result in irreversible damage to the brain. The implication of this, according to Trasand et al. (2005), is a global annual loss in productivity equal to USD 2.2bn to USD 43.8bn, based on prices in 2000. While there are multiple sources of methyl mercury poisoning, the provision of shark meat would be one contributing factor. This implies that commercial shark fishing does not only have implications for the blue shark population, but potentially also for human health and well-being, and ultimately global economic growth.

The baseline value of the blue shark population in the waters of Northern Spain and the Azores is $97.1 million. This value is comprised of the following:

• Conservation Value, Azores : $39.3 million

• Conservation Value, Northern Spain : $57.8 million

• Based on the midpoint estimated number of sharks in the region, the implied average value per individual over 30 years of $1726

While all of the numbers above are great arguments why we should protect our sharks as an investment, ultimately, the most important reason why sharks matter is the important role they play in keeping our ocean healthy. And that should be the overriding reason why we respect and protect sharks.

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SPECIAL THANKS

Endangered Wildlife OÜ and Shark Allies would like to thank Dr Gonzalo Araujo, Isaias Cruz Irujo, and Dr Maite Erauskin-Extramiana for their expert advice in preparing this report, and ElasmOcean e.V. and Stop-Finning Germany/EU for their financial support.