Seasonal Variation in Spawning by Preovigerous American Lobster (Homarus americanus) in Response to Temperature and Photoperiod Manipulation

Abstract

By manipulating temperature and photoperiod, we altered the incidence and timing of spawning in preovigerous American lobster (Homarus americanus), but the degree of alteration was affected by season. Females moved from natural conditions to unseasonably high temperatures (13–14 °C) and short daylengths (LD 8:16) beginning on 27 November did not spawn. Spawning rarely occurred (1%) when these conditions were started on 21 December (winter solstice), but after 8 January, there was a direct relationship between time spent at normal winter conditions and the incidence of spawning after environmental manipulation (8 January, 17%; 23 January, 45%; 8 February, 73%; 3 April, 82%; 12 May, 96%). Spawning occurred 26–42 d after photoperiod and temperature change, and the shortest times were associated with the longest periods of winter conditioning. Furthermore, a relatively brief exposure to normal winter environment enabled preovigerous lobster to disregard daylength and spawn in response to increasing spring temperature. This study indicates that spawning in response to environmental manipulation is altered by season, that duration of exposure to winter conditions influences the timing and incidence of spawning, and that different cues are utilized in different environmental regimes.