First Records of the Whiteblotched Skate (Bathyraja maculata) in the Eastern Gulf of Alaska

Abstract

The Whiteblotched Skate (Bathyraja maculata) is an elasmobranch species of the family Rajidae that was first described in 1977 from 21 specimens collected throughout the Bering Sea (Ishiyama and Ishihara 1977). Bathyraja maculata is distinctive, with a dorsal surface that varies from gray to dark brown and is punctuated with white to yellow blotches of various sizes. The ventral surface is white to light gray and often blotchy, darkening at the margins of the disc and on the uniformly dark tail, which has broad lateral folds. Nuchal and tail thorns are present and strongly developed, but middorsal, orbital, and scapular thorns are absent. The snout is short and flexible, and the interobital space is flat and wide (Ishiyama and Ishihara 1977; Mecklenburg and others 2002). Female B. maculata reach a maximum total length (TL) of 147 cm (Stevenson and others 2007), with males reported to a maximum size of 132 cm TL (JW Orr, National Marine Fisheries Service (NMFS), Alaska Fisheries Science Center (AFSC), Seattle, WA, pers. comm.). Bathyraja maculata ranges from the northern Sea of Japan and Sea of Okhotsk throughout the Bering Sea and Aleutian Islands (Mecklenburg and others 2002) at depths of 73 m (Fedorov 2000) to 1193 m (Stevenson and others 2007). Its easternmost record in the Aleutian Islands is off Umnak Island (53°24'N, 168041'W; Mecklenburg and others 2002). Bathyraja maculata has been commonly taken in trawl surveys of the western Bering Sea continental slope (Orlov 1998; Dolganov 1999), eastern Bering Sea continental slope (Hoff and Britt 2003, 2005) and Aleutian Islands (Zenger 2004). It also frequently occurs in shallower, continental shelf waters (ca. 100 to 200 m) of the western Bering Sea (Orlov 1998; Fedorov 2000) and Aleutian Islands (Zenger 2004), but appears to be scarce on the broad, eastern Bering Sea continental shelf (Lauth and Acuna 2007a, 2007b). Previous records of B. maculata from the Gulf of Alaska are few and restricted to the Gulf's western margin, where it has been reported at 3 locations during NMFS-AFSC bottom trawl surveys (Stevenson and others 2007, 2008; Fig. 1). The easternmost of these records represents a specimen collected approximately 163 km southwest of Kodiak Island (56°04.8'N, 156034.2'W, 191 m depth) during the summer of 1999 (DE Stevenson, NMFS-AFSC, Seattle, WA, pers. comm.). However, 3 B. maculata were recently collected from the Alexander Archipelago, southeastern Alaska, and are presented here. These records considerably extend the known distribution of B. maculata and suggest that it may be more widespread in the Gulf of Alaska than previously indicated. The Alaska Department of Fish and Game (ADFG) conducts annual longline surveys in Clarence Strait, including US waters of Dixon Entrance and Chatham Strait of the Alexander Archipelago, to assess the condition of Sablefish (Anoplopoma fimbria) stocks in these areas. Gear used during ADFG surveys consists of longlines containing forty-five 13/0 Mustad circle hooks per line, fastened at 2-m intervals and baited with squid. Twenty-five contiguous lines are deployed at established locations of 366 m depth, and gear is fished for 3 to 11 h prior to retrieval. All fishes caught during these surveys, including skates, are enumerated. Typically, only Longnose Skates (Raja rhina) are identified to species, but during the 2006 lower Clarence Strait survey, conducted from 17 to 22 May, skates of all species were distinguished. In addition, photos were taken of WINTER 2008 193