Temperature regulation of reproduction in female American lobsters (Homarus americanus)

Temperature is the dominant regulator of reproduction in inshore stocks of American lobsters (Homarus americanus). Seasonal temperature cycles coordinate the molt and reproductive cycles, maintain the characteristic alternate-year spawning cycle, and influence size and age at maturity, security of egg attachment, and time of hatching. Most reproductive events require a seasonally changing temperature cycle with low winter temperature (=£5°C) and moderate summer temperature (5=10°C). Under temperature regimes with relatively warm winters or summers, females may spawn twice between molts, molt and spawn in a single season, and molt twice in succession without an intervening spawning. If winter temperature remains above 6-8°C throughout the winter, the cyclic relationship between molting and spawning is disrupted, incidence of molting is increased, reproductive failure becomes common, and spawning is no longer synchronized within the population. Seawater temperature thus influences latitudinal distribution - at the northern limits of the range summer water temperatures are too low for most females to spawn, while at the southern end of the range warm winter temperatures reduce spawning incidence.