Sleepy sharks are known for their quiet and sluggish nature deep beneath the ocean, which is how they earned this nickname.
Although they are one of the largest predatory fish in the ocean, living throughout the Pacific, Pacific sleeper sharks are relatively unknown to many.
A group of scientists has embarked on a mission to create a comprehensive database of information about this slow-moving shark species.
Pacific sleeper sharks are closely related to Greenland sharks. They share similar characteristics and can even interbreed.
Adult Pacific sleeper sharks are often found roaming the depths of the ocean (Photo: NOAA Ocean Exploration and Research).
They can grow up to 4.3 meters long. It is speculated that adults living in deeper ocean areas may even reach lengths of up to 7 meters.
There is also suspicion that sleeper sharks possess a lifespan that rivals their relatives (the Greenland shark is known to be the longest-lived vertebrate species, with an average lifespan of around 400 years).
However, unlike Greenland sharks, sleeper sharks are undervalued, possibly due to their lack of commercial value, the absolute difficulty of accessing their habitats, their low occurrence rate, and the stringent requirements for catching and handling these large animals.
Currently, sleeper sharks are listed as a species experiencing a decline in population and are threatened according to the IUCN Red List.
Now, one of the most significant findings from genetic studies shows that the actual number of Pacific sleeper sharks may be much larger than previously predicted.
Lead author Beth Matta noted: “We used to think that there were three major species in the genus: Pacific sleeper sharks, southern sleeper sharks, and Greenland sharks. Now we know that southern sleeper sharks do not have genetic differences from Pacific sleeper sharks.”
They also discovered a wealth of evidence supporting the potential longevity of these sharks, suggesting they can live for several hundred years.
For instance, a study using radiocarbon dating to analyze the eye lenses of this shark species revealed that they grow twice as fast as Greenland sharks, yet still grow significantly slower than many other fish species, resulting in a lifespan well above average.
The eye sample of a Pacific sleeper shark used to determine their age (Photo: NOAA Fisheries).
Many pieces of evidence also indicate that Pacific sleeper sharks exhibit slow growth rates, late maturation, and long lifespans. These factors may make them particularly susceptible to overfishing.
