319 



Abstract.— Juvenile pink salmon, Onco- 

 rhynchuti gorbuscha, from four consecu- 

 tive brood years were tagged as they emi- 

 grated to the estuarine waters of Auke 

 Bay, and information was obtained on 

 the relationships between early marine 

 growth, environmental conditions, and 

 survival to adulthood. Juveniles that 

 emigrated from Auke Creek later in the 

 spring spent significantly less time in 

 the estuary. Individual growth rates of 

 tagged fish recovered in Auke Bay ranged 

 from 3. 1'* to l.\'7c per day. In all study 

 years, juvenile pink salmon grew more 

 slowly in early April than in late April 

 and early May. Water temperature and 

 growth were significantly correlated in 

 all years, but growth did not consis- 

 tently correlate with the biomass of epi- 

 benthic prey or zooplankton available to 

 the fish. Comparisons of expected and 

 observed growth rates suggested that 

 low prey availability, as well as low tem- 

 peratures, may have limited growth for 

 early spring emigrants. Although early 

 emigrants encountered poorer growth 

 conditions, survivors were larger at a 

 given date than later emigrants, their 

 larger size possibly protecting them 

 from size-selective predation. Early 

 marine growth was significantly related 

 to intra-annual cohort survival to adults 

 (r-'=0.65, P<0.05). Larger fish con- 

 sistently survived better than their 

 smaller cohorts for all years. Although 

 early marine growth was an important 

 determinate of survival within a cohort 

 of pink salmon, other factors, such as 

 predator abundance, contributed to the 

 large interannual variability observed. 



The relation between early 

 marine growth of pink salmon, 

 Oncorhynchus gorbuscha, 

 and marine water temperature, 

 secondary production, and 

 survival to adulthood 



Donald Mortensen 

 Alex Wertheimer 

 Sidney Taylor 



Joyce Landingham 



Auke Bay Laboratory 



Alaska Fisheries Science Center 



National Marine Fisheries Service, NOAA 



11305 Glacier Highway 



Juneau, Alaska 99801-8626 



E-mail address (for D Mortensen): don mortensenainoaa gov 



Manuscript accepted 29 November 1999. 

 Fish. Bull. 98:319-335 (2000). 



Pink salmon, Oncorhynchus gorbus- 

 cha, are the most abundant Pacific 

 salmon species native to the west 

 coast of the United States and 

 Canada (Morrow, 1980). In south- 

 eastern Alaska pink salmon typi- 

 cally mature after 15 tol8 months 

 at sea and return to their native 

 streams to spawn in late summer 

 and early fall. Pink salmon usu- 

 ally spawn in the lower portions 

 of streams just above the inter- 

 tidal zone and in intertidal areas 

 at stream mouths (Bailey, 1969). 

 Eggs hatch in January or Febru- 

 ary and the embryos (alevins) con- 

 tinue to develop within the gravel 

 of the stream bed. In late March 

 or early April juvenile pink salmon 

 (fry) emerge from the gravel and 

 emigrate downstream to salt water 

 and begin feeding on epibenthic 

 organisms and small zooplankton. 

 They form schools and reside in 

 the nearshore marine habitat for 

 several weeks (Heard, 1991). This 

 early marine residency is evidently 

 a critical stage in the early life 

 history of salmon and can signif- 

 icantly affect year-class strength 



(Parker, 1968; Walters et al., 1978; 

 Bax, 1983; Nichelson, 1986). Rapid 

 growth during this early marine 

 period may be a mechanism by 

 which size-selective mortality is 

 reduced (Parker, 1971; Hargreaves 

 and LeBrasseur, 1985). 



Growth and mortality of juvenile 

 fish is thought to be coupled with 

 the magnitude and timing of pri- 

 mary and secondary production 

 (Gushing, 1976; Pitcher and Hart, 

 1982; D'Amours, 1987). Slight vari- 

 ations in migration timing and the 

 developmental rate of juvenile fish 

 in relation to secondary production 

 influence feeding success and may 

 in turn affect growth and survival. 

 Subarctic estuarine ecosystems are 

 characterized by high levels of pri- 

 mary and secondary production in 

 spring (Russell-Hunter, 1970; Lar- 

 rance, 1971; Goering et al., 1973). 

 Consequently, the timing of emigra- 

 tion of species such as juvenile pink 

 and chum, O. keta, salmon may have 

 evolved so that this highly productive 

 period maximizes growth and sur- 

 vival (Murphy et al., 1988; Holtby et 

 al., 1989). This concept is somewhat 



