Cruise along with us on an open-ocean journey to learn more about the Blue Shark!
Dive in below to check out fun facts and ways to help save this amazing animal.
FAMILY: Carcharhinidae
SCIENTIFIC NAME: Prionace glauca
COMMON NAMES: Blue Shark, Blue Whaler Shark, Great Blue, Great Blue Shark
Their name comes from the blue color of their tough skins- yep, they're REALLY blue!
It's believed that this special counter-shading provides excellent camouflage,
and makes the Blue shark perfectly suited for life in the open ocean.
TYPE: Fish
IUCN Red List Status: NEAR THREATENED (assessed 2018)
SIZE:
Blue sharks can grow to ~13ft (380 cm) and weigh in at over 500lbs (226 kg)!
Males average between 6 - 9ft (182-282 cm) with females generally larger at 7-11ft (220 and 330 cm) in length. It is believed that males mature around 4-6 years old (between 6-7ft) and females around 5-7 years old (at 7ft and larger).
AVERAGE LIFE SPAN:
The average lifespan for this species is believed to be more than 20 years.
Females are known to mate with more than one male, meaning any given litter may have more than one father. After mating and a gestation period of 9-12 months pups are born in late spring & summer; litters can be 4 to over 100 pups, but average size is around 30 pups per litter.
Blue sharks are viviparous, which means they birth to live young that are nourished by a placental yolk sack internally until fully developed. Baby Blues are born at a length of ~12-21in (~35-50cm) in offshore nursery areas.
DID YOU KNOW:
Common predators of Blue Shark include: Orca whales (Orcinus orca), larger sharks like Shortfin Mako (Isurus oxyrinchus) and White sharks (Carcharodon carcharias)!
Video Via: Deep Marine Scenes
DISTRIBUTION:
Blue sharks inhabit surface waters - 1,148 ft (350 m) depths of temperate and tropical oceanic waters within latitude 60ºN to 50ºS. Blue sharks prefer the cooler temperature ranges between 53-68ºF (12-20°C).
Blue sharks are a highly migratory, pelagic species that rarely come close to shore, although they may frequent inshore areas around oceanic islands or locations where the continental shelf is narrow, occasionally swimming closer to inshore at night.
Blues often segregate by age, sex, and reproductive phase. Juveniles, sub-adults, mature sharks, and pregnant females are usually found in separate areas, with adults meeting up briefly to mate.
Experts believe that blue sharks use their iconically large pectoral fins to ride currents, conserving energy as they migrate; Migrations often follow major trans-oceanic currents and relate to prey availability and reproductive cycles.
The Blue is the most wide-ranging shark species, being recorded in all tropical and temperate seas. Interestingly, genetic results suggest there's one global blue shark population- meaning little to no differentiation within/between ocean basins to date.
DID YOU KNOW:
The Blue shark serves as chosen host to a variety of copepod parasites. Examples include: Pandarus satyrus- which attaches itself to pectoral fins, Kroeyerina elongata, which lives inside the shark's nose, Echthrogaleus coleoptratus, a body surface dweller and inhabitants of the gills both Kroyeria carchariaeglauci and Phyllothyreus cornutus. These loads can exceed 3,000 copepod individuals that can lead to sight impairments or even changes in gill structure!
DIET:
Despite their impressive size, Blue sharks specialize in relatively small prey items including: small fishes like herring or sardines, crab and shrimp, even small octopi, cuttlefish or squids in which they undertake regular dives into deeper pelagic waters to hunt.
Feeding mostly occurs mostly at night but living in the open ocean means that prey may be hard to come by so they can also hunt throughout the day. Additionally, Blue sharks will often aggregate to feed on shoaling events or around larger carrion in the water.
DID YOU KNOW:
Even though they are known for their slower, gentle glide through the water - Blue sharks can swim at bursts up to 25 mph, allowing it to catch up with prey.
NOW WATCHING:
CONSERVATION:
In some places, Blue Shark are an important species to drive local economy in marine tourism as divers, photographers, etc. all enjoy encountering it.
While not overtly aggressive, it is not a timid shark and should be approached with caution, especially if it has been circling since it may attempt an exploratory bite in test feeding.
According to ISAF, Blues are responsible for 13 unprovoked shark bites worldwide; notably, 3 of those documented attacks resulted from an air or sea disasters and several accounts refer to blue sharks attacking shipwrecked sailors floating in the open ocean.
The Blue Shark is one of the most prevelent species found within the shark fin trade as well as the most heavily fished shark species in the world. In fact, it is reported they comprises the majority of shark fins imported in Hong Kong- 17.3% in 1991–2001 and 49% in 2014. Even though its meat is often discarded, the demand seems to be increasing and is used in some regions where it's sold fresh locally, frozen, or dried for international trade.
Globally, Blue Sharks are caught as bycatch (annual reporting of about 20 million individuals caught) in commercial and small-scale pelagic longline, purse seine, and gillnet fisheries.
In the United States, Australia and Europe, Blues are considered a sport fish and such are highly valued by big-game recreational fishers and although many practice catch and release, recreational fishing poses a threat due to post-release mortality rates which has been reported 10–35% for Blue Sharks. Despite this research, there are very few national catch limits and no international catch limits in place to protect shark populations.
Alarmingly, recent reports indicates an approximately 60-80% decline in catch rates and reductions in sightings frequency, but data is still inadequate to assess a global population decline.
LEARN MORE:
Video via: NOAA
Check out more in-depth information about
this species with below source links and organizations!
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