Ageing and Back-Calculating Growth Rates of Pacific 

 Herring, Clupea pallasii. Larvae by Reading Daily 



Otolith Increments 



Erlend Moksness and Vidai- Wespestad 



ABSTRACT: Newly hatched Pacific herring, 

 Clupea pallasii, from eastern Bering Sea were re- 

 leased into an outdoor concrete basin and raised on 

 natural plankton. The larvae were sampled fre- 

 quently during the first two months, and a growth 

 cune for that period was established. Otoliths from 

 52 herring larvae, collected over the entire experi- 

 mental period, w ere examined for daily increments. 

 Increments were formed on a daily basis from the 

 end of the yolk-sac stage (age 8 days) and were 

 found to be independent of the growth rate of the 

 herring larvae. The increment widths, however, re- 

 flected the growth rate of the larvae. 



Otoliths have been used to estimate daily age 

 and gi-owth since Pannella (1971) reported that 

 the number of primary increments in otoliths 

 approximated daily deposition. Brothei's et al. 

 (1976) raised northern anchovy, Engraulis mor- 

 dax, and California gi'union, Leuresthes tenuis, 

 from eggs in the laboratory and verified that 

 increment formation occurred daily. Jones (1986) 

 found that daily increment analysis had been 

 applied to at least 29 species of larval fish to 

 estimate age, but validation of the technique was 

 based on laboratory observations that may be 

 invalid for wild populations. Atlantic herring, 

 Clupea harengus, have been investigated for 

 daily increment formation (Gjosaeter and 

 0iestad 1981; Geffen 1982; Lough et al. 1982; 

 Jones 1985; Messieh et al. 1987). Contradictory 

 findings by various authors have created contro- 

 versy concerning whether Atlantic hemng de- 

 posit growth increments on a daily basis. 

 Gj0saeter and 0iestad (1981) found 99 incre- 

 ments in 97 d herring gi'own in a large outdoor 

 enclosure; however, their sample size was too 

 small to be conclusive (Jones 1986). 



Erlend Moksness, Institute of Marine Research, Fl0devigen 

 Biological Station, N-4817 His, Norway. 

 Vidar Wespestad. Northwest and Alaska Fisheries Center, 

 National Marine Fisheries Service, NOAA, 7600 Sand Point 

 Way N.E., BIN C15700, Seattle, WA 98115. 



The early life history of Pacific herring, 

 Clupea pallasii. from the eastern Bering Sea 

 was studied in the same enclosure as Gj0saeter 

 and 0iestad's (1981). All the herring were 

 spawned on the same day, and larvae hatched 

 over a 3 d period. Otoliths were examined peri- 

 odically during the experiment and from surviv- 

 ing individuals at the termination of the experi- 

 ment. 



MATERIAL AND METHODS 



Pacific herring eggs were collected from the 

 spawning grounds in Bristol Bay, AK at low tide 

 on 24 May 1986. The eggs collected had been 

 deposited between 22 May and 23 May on inter- 

 tidal rockweed, Fucus sp. Water temperature at 

 the time of spawning was 4.5°C and salinity was 

 30%c. Further spawning did not occur (before or 

 after) in the area in which the eggs were col- 

 lected. Fucus fronds with light egg coverage 

 (1-2 egg layers) were collected at random within 

 the spawning area, packed into half liter plastic 

 bags, filled with seawater, and sealed. A total of 

 25 bags were filled with about 2,000 eggs/bag. 

 The bags were placed in insulated shipping con- 

 tainers with gel ice, which were shipped via air 

 to the Fl0devigen Biological Station in Arendal, 

 Norway. Upon arrival at Flodevigen the eggs 

 were unpacked and placed in hatching boxes, 

 which were supplied vrith flowing seawater at 

 7.7°C and at salinity of 327cf. 



The eggs began hatching on 10 June 1986 and 

 finished by 12 June 1986. Fifty percent hatching 

 (11 June) was defined as day (age = 0) in the 

 experiment. Newly hatched larvae were col- 

 lected from incubation boxes in white plastic 

 cups in gi-oups of 5-25, counted, and transferred 

 to 5 L cyhnders, which were placed in an 8.1°C 

 water bath. A total of 25,200 larvae hatched 

 from an estimated total of 50,000. The eggs were 

 not treated during incubation and a heavy fun- 

 gus growth developed. This caused most of the 

 egg mortality. 



Manuscript Accepted May 1989. 

 Fishery Bulletin, U.S. 8?": 509-513. 



509 



