Incubation period for the lobster Homarus gammarus at various temperatures

For Homarus gammarus in the North Irish Sea, a notional spawning date of 15 August was selected on the basis of substantial commercial catch data. Berried females were exposed to fluctuating temperature regimes, with average temperatures between 10.0° and 18.3°C. Incubation periods ranged between 3.6 and 9.5 months. The relationship between incubation period and the sum of monthly average temperatures was approximately linear, and can be used to calculate the temperature regime required to cause hatching at a preselected time. At 10.4°C (the local annual average temperature), the estimated incubation period is 11 months. This is compared with data for H. americanus, which indicate an incubation period of 11.4 months at a local annual average temperature of about 8.1°C. The implications of this are discussed.