Effects of Temperature on Length of Intermolt Periods in Juvenile Male Chionoecetes bairdi

Paul, A; Paul, J

The purpose of this study was to examine the effect of temperature on the intermolt duration of juvenile Tanner crabs Chionoecetes bairdi Rathbun. The average length of the intermolt period for Gulf of Alaska male Tanner crabs, with carapace widths (CW) of 24–26 mm, was ascertained for captives held at 3°, 6°, and 9°C. No test specimens died, and regardless of rearing temperature they fed avidly during captivity. Molting intervals were summarized in units of days and degree days. Increasing the rearing temperature from 3° to 6°C reduced the number of days between molts, but raising it to 9°C did not result in a similar reduction. The intermolt periods were 154 (SD =24), 78 (SD = 14), and 74 (SD = 8) days for juveniles held at 3°, 6°, and 9°C, respectively. The number of days between molts for the 3°C test group was significantly longer than the intermolt duration of juveniles reared at 6° and 9°C. There was no significant difference in the number of days between molts for the 6° and 9°C groups. In units of degree days, the mean intermolt periods at 3° and 6°C were nearly identical: 462 (SD = 74) and 467 (SD = 87) days, respectively. At 9°C molting occurred after an average of 665 (SD = 73) degree days. At 3° and 6°C, degree-day intermolt durations were not significantly different, but at 9°C the intermolt duration was significantly longer than those observed at 3° and 6°C. Thus, at 9°C, a temperature commonly encountered by Gulf of Alaska Tanner crabs during fall, a prolonging of the degree-day intermolt duration occurred. The degree-day method of describing intermolt durations worked adequately at 3° and 6°C, but above 6°C additional experiments are needed to better comprehend the influence of temperature on molting frequency. There was no obvious relationship between rearing temperature and growth. The average increase in carapace width for males held at 3°, 6°, and 9°C was 33% (SD = 4), 32% (SD = 6), and 32% (SD = 8) with no significant differences detected in gr

Effects of Temperature on Length of Intermolt Periods in Juvenile Male Chionoecetes bairdi

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