(Top to bottom: Raja binoculata,   Bathyraja parmifera )

The fish family Rajidae, commonly known as skates and rays, includes about 280 species of primarily benthic fishes found throughout the world’s oceans from tropical to cold temperate latitudes. At least 14 species of skates are known to occur in the Gulf of Alaska, Aleutian Islands, and Bering Sea from the 8 m to depths of over 1500 m. Many of these species are widely distributed, with ranges extending south along the coast of North America as well as into the western North Pacific, Sea of Okhotsk, and Sea of Japan.

Alaska’s skate fauna includes representatives of two genera: Raja and Bathyraja. The genus Raja, commonly known as the “stiff-snout” skates because they have a robust rostral cartilage, includes approximately 30 species worldwide and a North Pacific assemblage of 6 species ranging from the Gulf of California to the Bering Sea and into the western North Pacific. This North Pacific Assemblage is thought to be a cluster of closely related species and will probably be recognized as a separate genus in the future.

The genus Bathyraja, also known as the “soft-snout” skates due to their flexible rostral cartilage, includes over 40 species distributed throughout the world’s oceans. Bathyraja is the most broadly distributed and most diverse of all the skate genera, and the greatest diversity of Bathyraja occurs in the North Pacific. Most of Alaska’s skate species are included in this genus, although some authors include one or two of the species in the genus Rhinoraja. In general, members of the genus Bathyraja tend to be smaller and inhabit deeper waters than species of Raja.

The current level of interest in skate biology has provided impetus for a number of projects at the AFSC (see current research links below) including the report of a new species of skate from the Aleutian Islands (B. mariposa) and a review of species related to the Alaska skate (B. parmifera), as well as a report of the deepwater species B. abyssicola and Amblyraja badia new to Alaska. The AFSC’s Age and Growth Program began ageing Raja and Bathyraja species in 2003, and since then has produced a skate ageing manual as well as new techniques using vertebra for ageing skates in the Southern Alaska Peninsula. Research efforts also include the study of the reproductive behavior of the Alaska skate and Aleutian skate with focus on the characterization of skate nursery areas and approaches for nursery conservation in the southeastern Bering Sea. A molecular assay is being developed to use to identify skates on the basis of tissue samples. The AFSC is also collaborating on reproductive and life history studies on skates with the Pacific Shark Research Center at Moss Landing Marine Laboratory. Other AFSC research efforts include estimating capture probability of a survey bottom trawl for Bering Sea skates.

As we continue to refine and improve our ability to identify skates in the field, our ability to conduct scientifically rigorous investigations on the skate populations of Alaska improves dramatically. Ultimately, these studies augment the agency’s ability to provide effective stewardship of Alaska’s marine resources.


For more skate images see the "Skates of Alaska" poster by D. E. Stevenson, and J. W. ORR  (.pdf, 2.1 MB).
 

(left to right: Bathyraja minispinosa, B. violacea, B. mariposa)