. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CRANGON FRANCISCOftUM PALAEHON UACRODACTYLUS. STATION NUMBER FIGURE 10. Abundance of Crangon franciscorum, Palacinon inacrodactylus, and Neomysis mcrccdis at stations 42-70, on selected dates, May, 1977-September, 1978. Arrow pointing upward marks \f/ce salinity, arrow pointing downward marks 18%f salinity. the photoperiod was above 12 hr light: 12 hr dark, March, and occurred repeatedly at 20°C under 16 hr photoperiod (Barclay, 1978). Laboratory bioassay indicates optimum salinity for adult C. franciscorum to be around
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. CRANGON FRANCISCOftUM PALAEHON UACRODACTYLUS. STATION NUMBER FIGURE 10. Abundance of Crangon franciscorum, Palacinon inacrodactylus, and Neomysis mcrccdis at stations 42-70, on selected dates, May, 1977-September, 1978. Arrow pointing upward marks \f/ce salinity, arrow pointing downward marks 18%f salinity. the photoperiod was above 12 hr light: 12 hr dark, March, and occurred repeatedly at 20°C under 16 hr photoperiod (Barclay, 1978). Laboratory bioassay indicates optimum salinity for adult C. franciscorum to be around 18-20%c (Khoram and Knight, 1977). In 1977 this salinity range was present in lower Suisan Bay (stations 42^-6) yet no specimens of C. franciscorum were collected from that area in 1977 (Fig. 9). During 1978 that salinity range was located downstream of the study area throughout the year. More recent salinity tolerance investigations indicate juvenile C. franciscorum to be more tolerant of low salinity, with \00% survival at 2%c (Shaner, unpublished). Although low salinity limits the upstream distribution of specimens of C. franciscorum, other factors are important in determining their downstream distribution. The distribution of C. francisconiin in the delta is influenced by the availability of its principal prey species, N. mercedis. Analysis of gastric mill contents of C. franciscorum indicates that not only is C. franciscorum density much higher in locations were N. mercedis density is high (Fig. 9), but those individuals of C. franciscorum in areas of high prey density take more prey than those from low prey density areas (Siegfried, in preparation). The dearth of other populations of suitable prey species in the delta region may be an important factor linking the distribution of the crangonid population to that of N. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appe
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