Temperature-dependent development, growth and mortality in larvae of the deep-water prawn Pandalus borealis reared in the laboratory

Abstract

As part of investigations on how increase in temperature affects development, growth and survival in crustaceans, larval blology of the deep-water prawn Pandalus borealjs from 2 northern Norwegian fjords was studied. Larvae were maintained in individual glass jars for 60 d in the laboratory with ad libitum food conditions under 4 different temperature regimes. Two cohorts of larvae from the Malangen fjord were introduced to 4.2OC; one ('Malacon') was kept at this temperature and the other ('Malainc') was subjected to a temperature increase of 0.03"C d-l. Two cohorts from Balsfjorden were introduced to 2.5"C; one ('Balscon') was kept at this temperature and the other ('Balsinc') was subjected to a temperature increase of 0.04"C d -' In Balscon, development was clearly arrested from the second zoeal stage (ZII), and only a few individuals moulted to ZIII around Day 50. ZVI occurred at Day 60 in Balsinc and Malainc. Stage durations varied in all groups, but stage duration tended to decrease from ZIII to ZV. There was no significant difference in dry weight between the groups before Day 30. Thereafter, growth was more rapid in the regimes with increasing temperature. There was a clear effect of temperature on mortality. Higher rnortalities occurred in the 2 groups held at constant temperatures; under increasing temperatures mortality was low during the entire period. Thus, a high rate of temperature increase favours survival in zoeal stages of P. borealis, more than a constant high temperature.