Brodeur et al.: Summer distribution of early life stages of Theragra chalcogramma 



613 



Ammodytes hexaptervs (14) — 



Bathyagonus infraspinatus (17) = 



W- 



ee 



Errex zachirus (16) 



Gadus macrocephalus (42)  



Theragra chalcogramma (57) • 



Hippoglossoides elassodon (60) 

 Liparis spp. (39) 



Atheresthes stomias (44) - 



Pleuronectes bilineatus (40) • 

 Icetinus spp. (45) 



Bathyagonus alascanus (42) - 

 Sebastes spp. (30) 



Lumpanus spp. (10) 



Zaprora silenus (22) 



Figure 9 



Results of the Recurrent Group Analysis showing the main grouping (within box) and associated taxa 

 (outside box) at an affinity level of 0.40. The numbers in parentheses are the occurrences of each taxon. 



Discussion 



Despite the relatively large biomass 

 of adult fishes that inhabit this re- 

 gion, the mid-summer abundance 

 and distribution patterns of ichthyo- 

 plankton have received little atten- 

 tion. The one previous study (Hinck- 

 ley et al., 1991), which used a Methot 

 trawl to sample the western Gulf of 

 Alaska in June and July 1987, exam- 

 ined only the distribution of late lar- 

 val and early juvenile T. chalco- 

 gramma. The highest densities of 

 this species were found east of the 

 Shumagin Islands, a finding that was 

 similar to what we found. The only 

 other surveys conducted during the 

 summer employed net gear with 

 small mouth openings (see Kendall 

 and Dunn [1985] and references 

 therein) and caught mainly eggs and 

 early larvae. Some of the differences 

 in species composition between the 

 most commonly used ichthyoplankton gear (e.g. 

 bongo nets) and that used in this study are likely 

 due to extrusion of smaller larvae through the meshes 

 of the Methot net. For example, one of the numeri- 

 cally dominant taxa collected during June and July 

 in small-mesh bongo-net gear is Bathymaster spp. 

 (Kendall and Dunn, 1985; Rugen 2 ) which did not, 

 however, occur in our Methot trawl collections. Since 

 Bathymaster spp. larvae average only around 10 mm 



Lumpenus spp. 

 G. macrocephalus (I) 



Z. silenus 



Sebastes spp. 

 Liparis spp. 

 B. alascanus 

 E. zachirus 



T. chalcogramma (l+l) *■ hexapterus 



G. macrocephalus (j) 



H. elassodon 



A. stomias 



I eel in us spp. 



P. bilineatus 



B. infraspinatus 



Figure 10 



Taxa groupings resulting from the Two-way Indicator Species Analysis. The 

 larval (Z) and juvenile (j) stages of Theragra chalcogramma and Gadus 

 macrocephalus are indicated separately. 



in length in early June (Rugen 2 ), they are probably 

 too small to be caught by the Methot trawl in July. 

 Conversely, some taxa (e.g. T. chalcogramma) that 



2 Rugen, W. C. 1990. Spatial and temporal distribution of lar- 

 val fish in the Western Gulf of Alaska, with emphasis on the 

 period of peak abundance of walleye pollock (Theragra 

 chalcogramma) larvae. NWAFC Proc. Rep. 90-01, 162 p. 

 Alaska Fish. Sci. Cent, Natl. Mar. Fish. Serv., NOAA, 7600 Sand 

 Point Way NE, Seattle, WA 98115-0070. 



