376 



A nearsurface, daytime occurrence 

 of two mesopelagic fish species 

 iStenobrachius leucopsarus and 

 Leuroglossus schmidti) in a glacial fjord 



Alisa A. Abookire 



Kodiak Laboratory 



National Marine Fisheries Service 



301 Research Court 



Kodiak, Alaska 99615 



E-mail address alisa abookireiiJ'noaa gov 



John F. Piatt 



Alaska Biological Science Center 

 U^ S^ Geological Survey 

 101 1 E. Tudor Road 

 Anchorage, Alaska 99503 



Suzann G. Speckman 



School of Aquatic and Fishery Sciences 

 University of Washington 

 1122 NE Boat Street 

 Seattle, Washington 98105 



the day to the epipelagic zone (0-200 

 m) after sunset (Sobolevsky et al., 

 1996). Larval northern smoothtongue 

 are abundant in the upper 50 m of 

 Alaskan coastal waters during daylight 

 (Haldorson et al., 1993; Norcross and 

 Frandsen, 1996), but after the post- 

 larval and early juvenile stages they 

 are typically found at depths greater 

 than 150 m (Taylor, 1968; Mason and 

 Phillips, 1985). Previous accounts of 

 adult northern smoothtongue at shal- 

 low depths were those of collections 

 made after sunset (Barraclough, 1967; 

 references in Hart, 1973), and in some 

 areas adults do not exhibit diel vertical 

 migration but remain at depths below 

 240 m (Mason and Phillips, 1985). 

 There has previously been no documen- 

 tation of either juvenile or adult north- 

 ern smoothtongue in the upper 50 m 

 of the water-column prior to sunset. 

 The purpose of our study was to doc- 

 ument the nearsurface (<15 m), day- 

 time occurrence of both juvenile and 

 adult northern lampfish and northern 

 smoothtongue in Glacier Bay, Alaska. 



The northern lampfish iStenobrachius 

 leucopsarus, family Myctophidae) and 

 northern smoothtongue (Leuroglossus 

 schmidti, family Bathylagidae ) are 

 mesopelagic fishes, defined by their ver- 

 tical distribution in the mesopelagic 

 zone (200-1000 m) during daylight 

 hours. Northern lampfish range from 

 the Bering Sea to southern California 

 (Shimada, 1948). where their abun- 

 dance is highest along the continental 

 slope and decreases over the continen- 

 tal shelf They are the most abundant 

 species in the mesopelagic zone of the 

 Bering Sea (Pearcy et al, 1977; Sobo- 

 levsky et al., 1996), the Gulf of Alaska 

 (Purcell, 1996), and the eastern North 

 Pacific Ocean off Oregon (Pearcy, 1964; 

 Pearcy et al, 1977). Northern smooth- 

 tongue also concentrate in areas bor- 

 dering the continental slope and are 

 widely distributed from southern Brit- 

 ish Columbia to the Bering Sea (Peden, 

 1981) and are very abundant in the 

 Okhotsk Sea (Sobolevsky et al., 1996). 



Although lai-val myctophids spend 

 day and night in nearsurface waters 

 (Frost and McCrone, 1979), juvenile 

 and adult northern lampfish typically 



inhabit depths of 300-600 m during 

 the day (Paxton, 1967; Pearcy et al., 

 1977; Frost and McCrone, 1979; So- 

 bolevsky et al., 1996; Watanabe et 

 al., 1999). Off the Oregon coast north- 

 ern lampfish exhibit seniimigrant be- 

 havior: a large portion of the popula- 

 tion migrates from a daytime depth of 

 300-600 m to about 50 m at night, and 

 a nonmigratory portion of the popula- 

 tion has both a day- and night-time 

 vertical distribution at about 500 m 

 depth (Pearcy et al, 1977). This semi- 

 migrant behavior also occurs in the 

 Gulf of Alaska (Frost and McCrone, 

 1979), in the western North Pacific off 

 Japan (Watanabe et al., 19991, and off 

 California in both the San Pedro Ba- 

 sin (Paxton, 1967) and Santa Barbara 

 Basin (Cailliet and Ebeling, 1990). Af- 

 ter sunset, migratory northern lamp- 

 fish have been collected at depths as 

 shallow as 20 m in the Bering Sea (Na- 

 gasawa et al., 1997). We are unaware 

 of any studies in which adult northern 

 lampfish were collected at depths of 

 less than 100 m prior to sunset. 



Northern smoothtongue migrate from 

 the mesopelagic zone (200-1000 m) in 



Materials and methods 



Glacier Bay is a fjord in Southeast 

 Alaska that extends northward and 

 bifurcates into a west arm and Muir 

 Inlet (Fig. 1). We conducted 48 mid- 

 water trawl tows at 34 stations from 

 10 to 23 June 1999. Fishes were lo- 

 cated with a Biosonics DT4000 digital 

 120-kHz echo sounder, and significant 

 targets were fished with a modified 

 herring mid-water trawl with a mouth 

 opening of 50 m-. Mesh sizes dimin- 

 ished stepwise from 5 cm in the wings 

 to 1 cm at the codend, which was 

 lined with 3-mm mesh. A plastic col- 

 lecting bucket with 1-mm mesh was 

 attached to the end of the codend, and 

 was detached and rinsed after each 

 tow. A Furuno net-sounding system 

 monitored the depth of the headrope 

 during fishing operations. A temper- 

 ature depth recorder (TDR, Wildlife 

 computers model MK7) was mounted 

 on the headrope to determine the exact 

 depth of the net during fishing oper- 



Manuscript accepted 12 September 2001. 

 Fish Bull. 100;376-380 (2002). 



