examination of egg case variation in bathyraja interrupta · examination of egg case variation in...

Examination of Egg Case Variation in Bathyraja interrupta The Bering Skate, Bathyraja interrupta, shows considerable morphological variation across its range. Research biologists at the Alaska Fisheries Science Center recognize at least 4 distinct morpho-types in Alaskan waters. Currently it is unknown if this variation describes environmental, population or species level differences. Our approach is to examine the egg cases of the Bering skate from Alaskan waters for distributional variation congruent with the adult forms. Skate egg cases identified as those of the Bering Skate were collected in Alaska from 4 general areas: the Northern Eastern Bering Sea NEBS , Southern Eastern Bering Sea SEBS , the Central Gulf of Alaska CGOA , and Southeast Alaska SEA , these areas match the distribution of variation seen in adult Bering Skates. Morphological and meristic data were collected on large samples of egg cases from each area and tested for differences based on collection location. Statistical analysis showed differences amongst the variables, with the keel width and egg case width being the most sig- nificant characters defining the groups. The differences shown among egg case characters may add to the growing evi - dence of cryptic species of Bathyraja interrupta across its range. Bering Sea Gulf of Alaska Adult characters: Large size, anterior portion of disk mostly naked of dermal denticles except above orbits, interrupted dorsal thorns on mid-disk, golden color. Egg case characters: Large size with wide keels. Allison Linnell University of Washington School of Aquatic and Fishery Sciences Seattle, Washington 98195 Gerald Hoff Alaska Fisheries Science Center NMFS, NOAA 7600 Sand Point Way NE Seattle, Washington 98115 Grace Hutton Northeastern University 360 Huntington Avenue Boston, Massachusetts 02115 Adult characters: Large size, disk mostly covered with dermal denticles, interrupted dorsal thorns on mid-disk, dark brown sometimes with dark mottling. Egg case characters: Large size with moderate keels. Adult characters: Moderate size, disk mostly covered with dermal denticles, often complete dorsal thorns on mid-disk, dark brown sometimes with mottling. Egg case characters: Moderate size with narrow keels. Adult characters: Small size, disk mostly covered with dermal denticles, often complete dorsal thorns on mid-disk, dark brown sometimes with mottling. Egg case characters: small size with narrow keels. NEBS SEA CGOA SEBS Locaon Case Length Std Error Case + Keel Width Std Error Keel Width Std Error Case Width Std Error NEBS 82.07 0.47 68.16 0.43 16.35 0.33 51.73 0.39 SEBS 84.67 0.48 65.39 0.42 13.95 0.33 51.39 0.38 CGOA 83.21 0.5 58.98 0.42 10.47 0.27 48.39 0.42 SEA 73.74 4.35 46.42 3.11 6.35 1.09 40.07 2.52 Skate egg case is shown actual size Skate egg case is shown actual size e recommendations and general content presented in this poster do not necessarily represent the views or official position of the Department of Commerce, the National Oceanic and Atmospheric Administration, or the National Marine Fisheries Service. SEA CGOA SEBS NEBS Frequency Case width (mm) Keel width (mm) Frequency SEA CGOA SEBS NEBS Layout and Design by Rebecca White Graphics Unit — Alaska Fisheries Science Center Skate egg case is shown actual size Skate egg case is shown actual size

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Examination of Egg Case Variation in Bathyraja interrupta

The Bering Skate, Bathyraja interrupta, shows considerable morphological variation across its range. Research biologists at the Alaska Fisheries Science Center recognize at least 4 distinct morpho-types in Alaskan waters. Currently it is unknown if this variation describes environmental, population or species level differences. Our approach is to examine the egg cases of the Bering skate from Alaskan waters for distributional variation congruent with the adult forms. Skate egg cases identified as those of the Bering Skate were collected in Alaska from 4 general areas: the Northern Eastern Bering Sea NEBS , Southern Eastern Bering Sea SEBS , the Central Gulf of Alaska CGOA , and Southeast Alaska SEA , these areas match the distribution of variation seen in adult Bering Skates. Morphological and meristic data were collected on large samples of egg cases from each area and tested for differences based on collection location.

Statistical analysis showed differences amongst the variables, with the keel width and egg case width being the most sig-nificant characters defining the groups. The differences shown among egg case characters may add to the growing evi-dence of cryptic species of Bathyraja interrupta across its range.

Bering Sea

Gulf of Alaska

Adult characters: Large size, anterior portion of disk mostly naked of dermal denticles except above orbits, interrupted dorsal thorns on mid-disk, golden color.

Egg case characters: Large size with wide keels.

Allison LinnellUniversity of WashingtonSchool of Aquatic and Fishery SciencesSeattle, Washington 98195

Gerald HoffAlaska Fisheries Science CenterNMFS, NOAA7600 Sand Point Way NESeattle, Washington 98115

Grace HuttonNortheastern University360 Huntington AvenueBoston, Massachusetts 02115

Adult characters: Large size, disk mostly covered with dermal denticles, interrupted dorsal thorns on mid-disk, dark brown sometimes with dark mottling.

Egg case characters: Large size with moderate keels.

Adult characters: Moderate size, disk mostly covered with dermal denticles, often complete dorsal thorns on mid-disk, dark brown sometimes with mottling.

Egg case characters: Moderate size with narrow keels.

Adult characters: Small size, disk mostly covered with dermal denticles, often complete dorsal thorns on mid-disk, dark brown sometimes with mottling.

Egg case characters: small size with narrow keels.

NEBS

SEA

CGOA

SEBS

Location Case Length Std ErrorCase + Keel

Width Std Error Keel Width Std Error Case Width Std Error

NEBS 82.07 0.47 68.16 0.43 16.35 0.33 51.73 0.39

SEBS 84.67 0.48 65.39 0.42 13.95 0.33 51.39 0.38

CGOA 83.21 0.5 58.98 0.42 10.47 0.27 48.39 0.42

S E A 73.74 4.35 46.42 3.11 6.35 1.09 40.07 2.52

Skate egg case is shown actual size

The recommendations and general content presented in this poster do not necessarily represent the views or official position of the Department of Commerce, the National Oceanic and Atmospheric Administration, or the National Marine Fisheries Service.

SEA

CGOA

SEBS

NEBS

Freq

uenc

Case width (mm) Keel width (mm)

Freq

uenc

SEA

CGOA

SEBS