Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

caspia) and cormorants (Phalacrocorax spp.) also take significant numbers of juvenile or
adult salmon. Stream-type juveniles, especially yearling smolts from spring-run
populations, are vulnerable to bird predation in the estuary. This vulnerability is due to
salmonid use of the deeper, less turbid water over the channel, which is located near
habitat preferred by piscivorous birds (Binelli, Ricciardi et al. 2005). Recent research
shows that subyearlings from the LCR Chinook salmon ESU are also subject to tern
predation. This may be due to the long estuarine residence time of the LCR Chinook
salmon (Ryan, Carper et al. 2006). Caspian terns and cormorants may be responsible for
the mortality of up to 6% of the outmigrating stream-type juveniles in the Columbia
River basin (Roby, Collis et al. 2006; Collis 2007).
Antolos et al. (2005) quantified predation on juvenile salmonids by Caspian terns nesting
on Crescent Island in the mid-Columbia reach. Between 1,000 and 1,300 adult terns
were associated with the colony during 2000 and 2001, respectively. These birds
consumed about 465,000 juvenile salmonids in the first and approximately 679,000
salmonids in the second year. However, caspian tern predation in the estuary was
reduced from a total of 13,790,000 smolts to 8,201,000 smolts after relocation of the
colony from Rice to East Sand Island in 1999. Based on PIT-tag recoveries at the colony,
these were primarily steelhead for Upper Columbia River stocks. Less than 0.1% of the
inriver migrating yearling Chinook salmon from the Snake River and less than 1% of the
yearling Chinook salmon from the Upper Columbia were consumed. PIT-tagged coho
smolts (originating above Bonnevile Dam) were second only to steelhead in predation
rates at the East Sand Island colony in 2007 (Roby, Colis et al. 2008). There are few
quantitative data on avian predation rates on Snake River sockeye salmon. Based on the
above, avian predators are assumed to have a minimal effect on the long-term survival of
Pacific salmon (FCRPS 2008).
Fish Predation
Pikeminnows (Ptychocheilus oregonensis) are significant predators of yearling juvenile
migrants (Friesen and Ward 1999). Chinook salmon were 29% of the prey of northern
pikeminnows in lower Columbia reservoirs, 49% in the lower Snake River, and 64%
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