Skates of Alaska Research
 |
(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.
- A nursery site of the Alaska skate (Bathyraja parmifera) in the eastern Bering Sea.
HOFF, G. R.
2008. A nursery site of the Alaska skate (Bathyraja parmifera) in the eastern Bering Sea. Fish. Bull., U.S. 106:233-244. (.pdf, 1.37MB) Online.
- Emerging patterns of species richness, diversity, population density, and distribution in the skates (Rajidae) of Alaska.
STEVENSON, D. E., J. W. ORR, G. R. HOFF, and J. D. McEACHRAN.
2008. Emerging patterns of species richness, diversity, population density, and distribution in the skates (Rajidae) of Alaska. Fish. Bull., U.S. 106:24-39. (.pdf, 2.92MB). Online.
- Food habits and diet overlap of seven skate species in the Aleutian Islands.
YANG, M-S.
2007. Food habits and diet overlap of seven skate species in the Aleutian Islands. U.S. Dep. Commer., NOAA Tech. Memo.NMFS-AFSC-177, 46 p. (.pdf, 853 KB). Online.
- Age and growth of big skate (Raja binoculata) and longnose skate (R. rhina) in the Gulf of Alaska.
GBURSKI, C. M., S. K. GAICHAS, and D. K. KIMURA.
2007. Age and growth of big skate (Raja binoculata) and longnose skate (R. rhina) in the Gulf of Alaska. Environ. Biol. Fishes 80:337-349.
- Skate Egg Predation in the Eastern Bering Sea
By: GERALD R. HOFF
Conference: Western Groundfish Conference (15th), Santa Cruz, CA., Feb 2008
(2008 poster, .pdf, 2.58MB) Online.
- Embryonic Development of the Alaska and Aleutian Skate
By: GERALD R. HOFF
Conference: Western Groundfish Conference (15th), Santa Cruz, CA., Feb 2008
(2008 poster, .pdf, 1.3MB) Online.
- Additional publications, posters, and reports.
|
 |
|
|
(left to right: Bathyraja minispinosa, B. violacea,
B. mariposa)
|
|
