578 



Fishery Bulletin 100(3) 



1961 

 (n =555) 



1973-76 

 (n=310) 



1 984/87 

 n=1625) 



1 993/96 

 (n=1581) 



Figure 14 



Proportional biomass composition of Gulf of Alaska groundfish communi- 

 ties from the 1960s through the 1990s as estimated from bottom trawl 

 surveys. All surveys used similar gear, but sampling in 1961 and 1973-76 

 was limited to 0-400 m depth. Total number of hauls is indicated below 

 each time period. 



composition of the groundfish community on the shelf 

 and upper slope has changed substantially since the early 

 1960s. Resource assessment surveys were conducted in 

 1961 and 1973-76 with similar gear and covering much 

 of the same area that was sampled during the later sur- 

 veys. Survey data from the 1960s and 1970s have to be 

 interpreted carefully because the sampling design, gear, 

 and the spatial coverage of these sui-veys differ from the 

 surveys done in the 1980s and 1990s.'' In particular, no 

 stations below 400 m or east of 136°W were sampled in 

 the early surveys. In spite of these caveats, changes in 

 species composition among surveys are likely to reflect ac- 

 tual changes, at least for taxa that occur primarily above 

 400 m and west of 136°W. The data suggest a dramatic 

 decrease in the relative abundance of red king crab iPara- 

 lithodes camtschaticus) and Tanner crab iChionoecetes 

 spp. ), which together accounted for 22% of total CPUE in 

 1961, and for less than 1% after the 1970s (Fig. 14). The 

 data indicated that walleye pollock became the dominant 

 species in the mid-1970s, peaked in the early 1980s, and 



has declined in relative abundance since then. Arrow- 

 tooth flounder replaced walleye pollock as the dominant 

 groundfish species in the 1980s and 1990s. Pacific Ocean 

 perch and other rockfishes have increased substantially 

 in biomass since the 1970s. Sablefish and Pacific halibut, 

 two of the commercially most valuable species, made up a 

 substantially larger proportion of the total CPUE in the 

 1980s and 90s compared to earlier decades (Fig. 14). The 

 relative abundance of sculpins declined from about 8% in 

 the early 1960s to less than O.l'/r in the 1980s and 1990s. 

 The observed difference is likely to reflect a real decline in 

 sculpin abundance of several orders of magnitude between 

 the 1960s and 1980s. The decline appears to continue into 

 the 1990s, as suggested by a decrease in the frequency of 

 occurrence and biomass of two of the most abundant scul- 

 pin taxa (bigmouth sculpin and Myoxocephalus spp., see 

 Fig. 13, Table 2). 



The observed increase in overall groundfish biomass in 

 the GOA from the 1980s to the 1990s (Fig. 6) is consistent 

 with increases in the productivity of the northeast Pacific 



