FISHERY BULLETIN: VOL. 87, NO. 3, 1989 



both groups of marked hatchery fish, were esti- 

 mated about 800-980 kg in 1984, 250-280 kg in 

 1985, and 450-800 kg in 1986 (Table 2). Increases 

 in the biomass, indicative of accumulation of bio- 

 mass from growth exceeding loss of biomass 

 from migration or mortality, were not apparent 

 in any year. 



Total production or net growth of juvenile 

 chum salmon (a product of the cumulative bio- 

 mass over all days after the release of marked 

 fish times the instantaneous growth rate of 

 marked fish) measured 282 kg, 103 kg, and 235 

 kg in 1984, 1985, and 1986, respectively (Table 

 2). Total production is underestimated because 

 production before the release of marked fish is 

 not included. These production estimates are 

 only 32%, 38%, and 37% of the estimated aver- 

 age biomass of the first two collection periods 

 after releases in 1984, 1985, and 1986, respec- 

 tively. 



DISCUSSION 



Netarts Bay is an important nursery area for 

 juvenile chum salmon. Despite the small size and 

 high flushing rate of Netarts Bay, juvenile chum 

 salmon were captured during about a 2 mo dura- 

 tion in all three years. This is about the same 

 duration as reported for wild juvenile chum 

 salmon in Yaquina Bay, Oregon (Myers and Hor- 

 ton 1982), but is less than the three or more 

 months reported for Tillamook Bay, Oregon 

 (Henry 1953; Forsberg et al. 1977), Grays Har- 

 bor, Washington (Herrmann 1970), the Skagit 

 River salt marsh, Washington (Congelton et al. 

 1982), and the Nanaimo Estuary, British Colum- 

 bia (Healey 1979, 1982a). Juvenile chum salmon 

 were reported in Hood Canal from January 

 through July by Bax (1982). The mean residence 

 times (see Healey 1979 for equation) of marked 

 groups of hatchery-reared juvenile chum salmon 

 (0.75-2.2 g at release) ranged from 5 to 23 days 

 in Netarts Bay. These residence times are about 

 the same as those found by Healey (1979) in the 

 Nanaimo Estuary, but were more than the resi- 

 dence time of about 2 days in a small tidal chan- 

 nel reported by Congelton et al. (1982). Clearly, 

 juvenile chum actively maintain themselves in 

 many estuaries during early development. 



Catches of juvenile chum salmon in the bay 

 declined rapidly over time. The proportions lost 

 from emigration and mortahty are difficult to 

 separate. Healey (1982a) concluded that some 

 fish immediately emigrated from the Nanaimo 

 and Nitinat Estuaries. Bax (1982) reported 



initial dispersal of marked hatchery fish, and net 

 movements of 3-14 km/d for juvenile chum salm- 

 on in the elongated fjord of Hood Canal that 

 would rapidly remove chum salmon from a small 

 estuary. Lannan (1983) noted fish and bird 

 predation on juvenile chum salmon in Netarts 

 Bay. Most of the fish predation was caused by 

 cutthroat trout, Oncorhynchus clarki, during 

 downstream migration of chum fry and by Pa- 

 cific staghorn sculpin, Leptocottus armatus, as 

 fry entered the bay (J. Lannan, pers. comm.^). 

 We examined 57 large (> 100-215 mm FL) 

 staghorn sculpin, 34 cutthroat trout (95-365 mm 

 FL), and 28 coho salmon (95-156 mm FL) caught 

 in our beach seine collections in Netarts Bay and 

 found three juvenile chum salmon in staghorn 

 sculpin stomachs and one in a coho salmon 

 stomach. Gulls, mergansers, cormorants, and 

 herons were common in the bay, but we have no 

 data on their food habits. Harbor seals, Phoca 

 vitulina, were also common in Netarts Bay in 

 late spring; their scats were analyzed, but oto- 

 liths of juvenile salmon were not identified 

 (Brown and Mate 1983), perhaps because the 

 smallest sieve they used had a mesh size of 0.5 

 mm, a mesh that would retain otoliths of only 

 large juvenile chum. 



The distribution of juvenile chum salmon in 

 Netarts Bay, with higher catches generally in 

 the upper than lower bay early in the spring, and 

 the reverse later in the spring is similar to that 

 found by Healey (1979, 1982a) in the Nanaimo 

 Estuary, by Myers and Horton (1982) in Yaquina 

 Bay, and by Forsberg et al. (1977) in Tillamook 

 Bay; but in the Nitinat Estuary no evidence of 

 seaward progression was found (Healey 1982a). 

 In Netarts Bay, juvenile chum salmon moved 

 extensively over the tidal flats, aggi'egating in 

 shallow water during periods of both high and 

 low tide (cf. Mason 1974; Forsberg et al. 1977; 

 Healey 1979, 1982a). In late spring, fish cur- 

 tailed their movements into shallow warm 

 waters of the upper bay at high tide and were 

 concentrated instead in the lower estuary. 



Based on limited pelagic samphng, we found 

 no evidence for movement of fish into the deep 

 channel areas of the lower bay later in the 

 season. Juvenile chum salmon larger than 45-55 

 mm were caught in large numbers at some 

 shallow seine stations in the lower bay in May 

 and June. Some individuals were as large as 89 



''J. Lannan, Oregon State University, Hatfield Marine 

 Science Center, Newport, OR 97365, pers. eommun. 22 

 December 1988. 



564 



