. Bulletin - Southern California Academy of Sciences. Science. 1/14/2004 5/28/2005 10/10/2006 2/2272008 7/6/2009 11/18/2010 4/1/2012 Fig. 3. Average (mean) and maximum daily water temperatures in Topanga Creek, 2005-2010. Food availability The ability of O. mykiss in Topanga Creek to grow quickly and reach large size (>250 mm) raises questions about how these fish meet their bioenergetic demands. Once salmonids reach a size of about 270-300 mm, they tend to become piscivorous regardless of habitat type, and a piscivorous or even cannibalistic diet may be necessary to maintain growth beyond
. Bulletin - Southern California Academy of Sciences. Science. 1/14/2004 5/28/2005 10/10/2006 2/2272008 7/6/2009 11/18/2010 4/1/2012 Fig. 3. Average (mean) and maximum daily water temperatures in Topanga Creek, 2005-2010. Food availability The ability of O. mykiss in Topanga Creek to grow quickly and reach large size (>250 mm) raises questions about how these fish meet their bioenergetic demands. Once salmonids reach a size of about 270-300 mm, they tend to become piscivorous regardless of habitat type, and a piscivorous or even cannibalistic diet may be necessary to maintain growth beyond this size (Bannon and Ringler 1986; Huryn 1996; Keeley and Grant 2001). Although piscivory in lake-dwelling trout populations is common, stream-dwelling resident O. mykiss most often feed on invertebrates and evidence of piscivory or cannibalism is rarely observed (Frost 1939; Jonsson and Sandlund 1979; Haraldstad et al. 1987, all as cited in Vik et al. 2001). Certain conditions, however, may facilitate the adoption of a piscivorous diet. For example, rainbow trout are known to prey on sockeye and chum salmon fry or smolts where such prey are concentrated, such as in small coastal streams or the outlets of lakes (McCart 1967; Hartman et al. 1967; Ginetz and Larkin 1976; Ruggerone and Rogers 1984; Fresh and Schroder 1987). Table 2. Size of O. mykiss in Topanga Creek and other coastal southern California streams. Sampling period Fork Length ( mm) Stream Mean Range Age class Topanga Creek November 2008- 102 (n=89) 55-125 0 (this study) 2009 153 (n=79) 110-226 1 222(n=19) 170-291 2 Ventura River April 1995 250 (n=47) 190-395 unknown (Capelh 1997) Santa Paula Creek November 2007 (electrofishing) 98(n=173) 68-214 all ages. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Southern California Academy of Sciences. Los
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