Macrourus berglax Lacepede 1801

Macrourus berglax Lacepède 1801

Macrourus berglax Lacepède, 1801: 169, 170, Pl. 10 (Fig. 1) (original description, no types known, Greenland, Iceland, North Atlantic). Iwamoto in Cohen et al., 1990: 234 –236 (description, key); Trunov & Konstantinov, 1990: 44 –54 (description, key, in Russian, English summary).

Diagnosis. Ventral surface of head almost entirely scaleless except for short longitudinal series of small scales on preopercle and occasional isolated scales above angle of mouth and rarely on posterior end of lower jaw. Pelvic fin with 8 (rarely 9) rays. Lower jaw laterally with 2–4 irregular rows of small teeth, reduced to one row at posterior end, and increased to about 5 teeth wide at symphysis. Upper jaw teeth about 4–5 rows wide, the outer series slightly enlarged. Body scales large, 13–17 diagonal rows from anal fin origin to lateral line. Pyloric caeca 14–23.

Specimens examined. Non-type specimens (18). BMNH 1890.11.1.4 (125 mm HL, 580+ mm TL), off Finnmark, Norway, received from Prof. Robert Collett, 1890; CAS 223416, ex. VIMS 12893 (4, 91.5–143.5 mm HL, 410–605 mm TL), Bear Seamount, 39° 56' N, 67° 25' W; 1132–1888 m; Delaware cruise 200304, sta. 23, 19 May 2003; ISH 67/55 (67 mm HL, 292+ mm TL), west of Greenland, 63° 13' N, 52° 40' W, 500 m Anton Dorn sta. 41/ 55, 25 Sep. 1955; ISH 243/63, (59 mm HL, 261 mm TL), southwest of Barents Is., 73° 33' N, 17° 20' E, Anton Dorn sta. 936/ 63, 410 m; 28 Nov. 1963; ISH 257/63 (2, 57– 58 mm HL, 247–258 mm TL), southeast of Barents Is., 75° 54' N, 21° 17 E, 450–460 m; 29 Nov 1963; VIMS 12892 (2, 97.3–142 mm HL, 444–615 mm TL), VIMS 12973 (2, 109.2– 144.3 mm HL, 485–613 mm TL), and VIMS 12987 (2, 92.4–99.6 mm HL, 400–420 mm TL), Bear Seamount, 39° 53' N, 67° 26' W, 1396–1430m, Delaware cruise 200304, sta. 26, 20 May 2003; VIMS 12972 (3, 88.1–102.4 mm HL, 400–480 mm TL), Bear Seamount, 39° 58' N, 67° 27' W, 1946–2022 m; Delaware cruise 200304, sta. 32, 22 May 2003.

Counts and measurements (Tables 1 –2).

Description (Figure 1, Tables 1 –2). A detailed description is not given here because this species is very similar in general form to Macrourus carinatus and M. holotrachys. The key identifying characters are listed above in the diagnosis and the differences between each species are listed in Comparisons and remarks and Table 3.

Size. Reported to reach more than 910 mm TL (Wheeler 1969), but most commonly 400–800 mm TL, with females attaining much larger sizes than males. In the Barents Sea, specimens larger than 700 mm TL were all females (Dolgov et al. 2008:351).

Distribution. Widely distributed in North Atlantic slope waters with temperatures from around 0 to about 4.5° C. Off the North American coasts it occurs from about latitude 37° N, northward to the Labrador Sea and Baffin Bay, and along the east coast of Greenland, north and east to Spitzbergen; in the eastern Atlantic, it is found from the British Isles north into the Norwegian and Barents Seas and into the Arctic slopes (82–83° N) off Spitsbergen. See Iwamoto (1990a, Fig. 535). Depth range recorded is 180 to 2740 m (Wheeler, 1969) but commonly between 200 and 2000 m (Murua 2003; Murua and de Cárdenas 2005).

Comparisons and remarks (Table 3). Macrourus berglax and M. holotrachys are distinguished from the other three species of Macrourus by lacking scales or having only small patches of scales on the underside of the head behind the mouth. M. berglax is very similar in morphology to M. holotrachys, and the two nominal species appeared similar based on mitochondrial COI sequences (Smith et al 2011). However, our study material showed the following differences for M. berglax compared with M. holotrachys: scales in a diagonal row from anus to lateral line 13– 17 v. 18–26, pyloric caeca 14– 23 v. 9–16, pelvic fin rays usually 8 (rarely 9) v. 8–9 respectively (Tables 1 & 2). Macrourus berglax is recorded only from the North Atlantic Ocean from about 37° N northward, and M. holotrachys is recorded only from the South Atlantic and South Pacific Oceans from about 37° S southward.

Additional mtDNA studies that used the non-coding and potentially faster evolving control region gave results that showed a species specific indel region in all 5 species of Macrourus. The shallow sequence divergences among all five species of Macrourus likely indicate either recent evolutionary divergence or slow nucleotide substitution at COI in this genus (Smith, unpublished data).

Macrourus berglax is a commercially important species in the North Atlantic and is taken mainly as by-catch in the deepwater trawl fishery for Greenland halibut (Reinhardtius hippoglossoides). Annual catches of the species peaked in 1998 and 1999 at more than 7000 tons, but declined to below 4000 tons between 2001 and 2003.