Ocean Life in Alaska

  • Alaska Skate

    Skates 101

    Skates are closely related to sharks and have similar life cycles. They grow slowly, reproduce late in life, and donít produce many offspring which makes them vulnerable to overfishing. The health of the population is dependent on the survival of juveniles and mature adults. Fisheries management measures ensure that skates are minimally impacted by commercial fishery activities.

    Skates in Alaska

    Fifteen of the 280 species of skates found worldwide occur in Alaskan waters. Two skate species are only found (endemic) in the Aleutian Islands: the butterfly skate and leopard skate.
    The most common skates by region:
    Gulf of Alaska - Big skate, longnose skate, Aleutian skate, Alaska skate, and Bering skate.
    Aleutian Islands - Whiteblotched skate and Aleutian skate.
    Bering Sea shelf (< 200 m) - Alaska skate.
    Bering Sea slope (> 200 m) - Alaska skate and Aleutian skate.

    Why managing skates is important?

    "Directed fishing for skates, where fishers are deliberately trying to catch them, has been prohibited since 2005, but they can be retained as bycatch in some fisheries. Fishery managersí decisions are based partly on the biological vulnerability of skates, and partly on the high levels of incidental catches." Olav Ormseth, AFSC stock assessment scientist

  • Skate egg case

    Skate reproduction

    Skates are oviparous which means they lay an egg containing a developing embryo. The tough, seaweed looking, brownish-green colored egg cases, also called mermaids purses, are deposited directly onto the seafloor. The young continue to grow for months or even years in the egg case until they hatch. Big skates can lay up to seven embryos per egg case. Shortly after they hatch, juvenile skates are highly mobile, able to feed, and resemble adults.

    Where do baby skates come from? (brochure)

    Skate habitat

    Skates prefer to lay their egg cases in specific locations called nursery sites. Researchers at the Alaska Fisheries Science Center have identified eight nursery sites along the Bering Sea slope during summer bottom trawl surveys. Each of these sites cover an area of about 5 square nautical miles. During the summer, these nursery sites are busy with adult skates laying large numbers of egg cases. Each area is species-specific, meaning only one species lays eggs in a nursery site.

  • Alaska Skate

    Skate age and growth

    Some skates, like the whitebrow skate, have been observed to be as old as 37 years and reach lengths of over 5 feet. Scientists use vertebrae to determine a skateís age. Vertebrae were chosen as an ageing structure due to their growth zones which resemble tree rings. These rings are visible when viewing cross sections of the vertebra. In Alaska, it was found that the maximum age for big skate was 13 years at a total length (tip of snout to tip of tail) of 1.43 m. The longnose skate had a maximum age of 15 years at 1.14 m. For Aleutian skate the maximum age was 14 years for at 1.47 m, whereas, the Bering skate had a maximum age of 21 years. Maximum length of the Bering skate differed by region. In the Bering Sea it is 82.8 cm and in the Gulf of Alaska it is 86.94 cm. The Alaska skate has a maximum age of 15 years for males and 17 years for females.

    Check out some great images of skates!
    Print your own poster of skates in Alaska!