. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HERMIT CRABS AND THEIR SHELL SUPPLIES 131 60 40 • 1969-1970 o 1971-1972. J_ _L 0 SHELLS AVAILABLE PER CRAB-MONTH FIGURE 4. Observed changes in the crab population related to the number of Thais shells that became available during the period. The shell supply changed seasonally. Many new shells became available during the spring and summer, and few were available during the winter (Table VI). These seasonal pulses in shell availability were reflected in 1969 and 1970; the crab population increased duri
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. HERMIT CRABS AND THEIR SHELL SUPPLIES 131 60 40 • 1969-1970 o 1971-1972. J_ _L 0 SHELLS AVAILABLE PER CRAB-MONTH FIGURE 4. Observed changes in the crab population related to the number of Thais shells that became available during the period. The shell supply changed seasonally. Many new shells became available during the spring and summer, and few were available during the winter (Table VI). These seasonal pulses in shell availability were reflected in 1969 and 1970; the crab population increased during summer and fall and decreased during winter. Shell supplies also changed over the longer term. The snail populations at Shady Cove declined almost continuously during the period of study (Spight, 1972). Correspondingly, crab numbers also declined steadily after reaching a peak in 1969 (Fig. 2). These parallel courses in crab and snail populations are consistent with the hypothesis that crab numbers are affected by the shell supply. Crab population size was related more directly to shell availability by plotting the net change in the crab population (Nt + i -- Nt, from Table V) against the rate of shell availability (number of new shells per crab-month, from the crab population of Table V, and the number of snails seen for the last time, Table VI). When numbers were changing greatly (1969-1970), variations in shell supply accounted for 59% of the variations in crab numbers (r2 = ; Fig. 4). The correspondence is less for the whole period (1969-1972; r2 =; the crab population increased overwinter, 1970-1971, and decreased the following spring, while shell supplies should have fostered changes in the opposite direction). The data of Figure 4 indicate that under the conditions at Shady Cove, Pagurus. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustration
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
