tion of speckled sanddabs over its entire open coast 

 range. 



Biotic and abiotic factors, in addition to temper- 

 ature, must be considered when relating temper- 

 ature preference data to field situations. Factors 

 such as the presence of predators or prey, nutritive 

 condition, light levels and/or physical substrate 

 can influence the temperature selected under 

 natural conditions (Fleming and Laevastu 1956; 

 Brett 1970, 1971; Blackburn and Williams 1975; 

 Beitinger and Magnuson 1975). Stephens (in 

 press) reported that the speckled sanddab prefers 

 sand (outer stations in King Harbor) rather than 

 mud substrate (inner stations in King Harbor). 

 These types of parameters are probably particu- 

 larly responsible for the 22*%^ variation in field 

 occurrences that was not explained by tempera- 

 ture. In the laboratory where we controlled these 

 variables, we found a higher correlation (r^^j. = 

 -0.976) between fish occurrence and tempera- 

 tures, which accounted for 95% of the variation in 

 fish position. 



Based on the laboratory data, it appears that the 

 water in King Harbor is usually warmer than that 

 preferred by speckled sanddabs. This is particu- 

 larly true if one considers the modal selected 

 temperature (9°C). Reynolds (1977) suggested 

 that the mode is the best indicator of fish's thermal 

 preference. Occurrence of speckled sanddabs in 

 King Harbor, where their modal preferred tem- 

 perature was not observed on any of the surveys 

 indicates that this harbor (particularly the inner 

 part) may be a marginal area for this species. We 

 observed a high rate of parasitism by the isopod 

 Livonica vulgaris in King Harbor on speckled 

 sanddabs (virtually 100% infection i, compared 

 with the lower levels (approximately 25% infec- 

 tion) observed in this species collected in La Jolla, 

 Calif. (Ford 1965). This appears to support our 

 hypothesis that this area may be of marginal 

 value to speckled sanddabs and that they may be 

 under stress and more susceptible to infection. 

 Snieszko (1974) reported such a relationship be- 

 tween stress and infection for some fish species. 



Acknowledgments 



The authors thank Deirdre McDermott-Ehrlich 

 of the Lockheed Center for Marine Research for 

 editing the manuscript. Thanks is also given to 

 Douglas Johnson and Nancy Conrad of Occidental 

 College for their technical assistance. 



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