NOTE Abookire et a\ NearsLirface, daytime occurrence of two mesopelagic fishes in a glacial fiord 



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• Stations sampled 

 10 20 Kilometers 



A 



Figure 1 



Stations I • ) sampled by midwater trawl in Icy Strait and Glacier Bay. Alaska, during June 1999. 



ations. Mid-water trawls were considered failures if the 

 trawl doors crossed, the net mesh tore, or if the net-sound- 

 ing system failed to detect the headrope of the trawl. 

 These tows were omitted from data analysis. 



We fished from a 22-m stern trawler, the RV Pandalus. 

 The towing speed was about 2.5 kn. and the average tow 

 duration was 20 minutes. There was one deep tow at site 

 1. At site 2 there were four tows, beginning with three 

 shallow tows and ending with one deep tow to 100 m (Ta- 

 ble 1). All fishing was done prior to sunset between 0839 

 and 1933 h ADT (Alaska daylight time). After fishing at 

 a station, we deployed a CTD (Seabird Electronics Inc, 

 SBE-19 SEACAT profiler) to measure water temperature 

 (°C), salinity (ppti, density (kg/m'^l. turbidity (FTU, forma- 

 zine turbidity units), and chlorophyll concentration (pg/L). 

 CTD measurements were taken every second and we pres- 

 ent average values (n=3) of data collected in each 1-m 

 depth interval. If multiple fishing tows were made at a 

 station, only one CTD cast was made. 



All fishes were identified in the field to the lowest pos- 

 sible taxon, counted, and fork length (FL) was measured to 

 the nearest millimeter. Length-frequency histograms were 

 plotted for northern lampfish and northern smoothtongue, 

 and fish lengths were grouped in increments of 2 mm. 

 Ages were estimated from length-frequency histograms 

 based on previous studies of length-at-age and length- 

 at-maturity for northern lampfish (Smoker and Pearcy. 



1970; Nagasawa et al., 1997) and northern smoothtongue 

 (Mason and Phillips, 1985; Sobolevsky and Sokolovskaya, 

 1996). 



Results 



Both mesopelagic species were captured infrequently; 

 northern lampfish were present at only two of the 34 sta- 

 tions (?!=60) and northern smoothtongue at only one sta- 

 tion (7i=133, Table 1). Northern lampfish and northern 

 smoothtongue accounted for only 4% of the 5011 fish cap- 

 tured at all 34 stations; capelin (51'*. Mallotus villosus) 

 and walleye pollock (36'^t. Theragra chalcogramma) were 

 the most abundant species. Northern lampfish mature 

 at 4 years of age, and of the 60 individuals captured, 

 about 86 % were juveniles (31-59 mm FL) and 14'7f were 

 adults (65-83 mm FL). Northern smoothtongue mature at 

 2 years of age, and of the 133 individuals captured, about 

 64% were juveniles (35-53 mm FL) and 369f were adults 

 (54-85mmFL, Fig. 2). 



At site 1, two individual northern lampfish (sizes 31 

 and 37 mm) were captured at 90 m depth during day- 

 light (Fig. 1, Table 1). At site 2, next to Muir Glacier, we 

 fished during daylight hours from 1730 to 1930 h. In the 

 first tow (4.5 hours prior to sunset), we fished at 10-15 

 m depth and 12';( of the northern lampfish were adults 



