FISHERY BULLETIN: VOL. 84, NO. 3 



5. 175 



— 4.425 



r- 

 X 



u 



Q 



LU 



H 3.675 

 < 



LU 



U 

 in 



> 



LU 



5 2.925 



2.175 



Y = -12. 18836 + 3. 16640 X 



N = 491 



_L 



l 



J L 



J L 



4.600 



4.800 



5.000 5.200 



LN BODY LENGTH (X) 



5.400 



Figure 4.— Relationship between body length and eviscerated body weight in fresh Pacific herring in the vicinity of 

 Auke Bay, AK, sexes combined. Variates transformed to their natural logarithms (LN). Points represent 1-9 specimens. 



Seasonal Cycles in Fat and Gonads 



Adult Pacific herring feed chiefly on zooplankton 

 and small fishes (Hart 1973). In the Auke Bay vicin- 

 ity, zooplankton peak in abundance in June or July 

 and are virtually absent from November to March 

 (Fig. 6; fig. 3 in Carlson 1980). In an unpublished 

 study of Auke Bay herring, stomachs were mostly 

 empty during late fall and winter (R. E. Haight, 

 cited in Carlson 1980). 



Pacific herring spawn in Auke Bay in late April 

 or May but may spawn as late as 4 June (Wing 2 ). 

 Eggs hatch 14-20 d after spawning, based on incu- 

 bation temperatures for herring in British Colum- 

 bia (Outram 1965 3 ) and temperatures for mid- 

 April and May in Auke Bay, which are similar to 



2 B. L. Wing, Northwest and Alaska Fisheries Center Auke Bay 

 Laboratory, National Marine Fisheries Service, NOAA, P.O. Box 

 210155, Auke Bay, AK 99821, pers. commun. November 1981. 



3 Outram, D. N. 1965. Canada's Pacific herring. Dep. Fish. 

 Can., Ottawa, Fish. Res. Board Can., Biol. Stn., Nanaimo, B.C., 

 23 p. 



those for British Columbia (Wing 4 ). The time of 

 spawning seems optimal to allow spawned fish and 

 their newly hatched larvae to feed during the 

 heaviest zooplankton concentrations of the year 

 (Fig. 6). 



Because the peak in zooplankton abundance is 

 relatively brief, the period immediately after spawn- 

 ing is critical for fattening of adults and for growth 

 and survival of newly hatched larvae. Feeding and 

 fattening of all life stages of Auke Bay herring may 

 also be aided by the submarine illumination afforded 

 by the longest days and highest levels of light, early 

 in the summer. 



Fat accumulated about the viscera during the 

 period of maximum zooplankton abundance and 

 reached highest indices shortly afterward, about 

 mid-July (Fig. 6). It then declined rapidly but slightly 

 differently in each sex. There is evidence, also, based 



4 B. L. Wing, Northwest and Alaska Fisheries Center Auke Bay 

 Laboratory, National Marine Fisheries Service, NOAA, P.O. Box 

 210155, Auke Bay, AK 99821, pers. commun. July 1983. 



712 



