Growth at moult and intermoult period in the Norway lobsterNephrops norvegicusfrom Galician waters

Size increase at moult, duration of the intermoult period, and moulting seasonality of the Norway lobster Nephrops norvegicus off Galicia (NW Spain) were studied in the laboratory. At a mean pre-ecdysis carapace length, CL, of 35 mm the absolute moult size increment (MI) was 2.1±1.1 mm (mean±s.d.) in males and 1.7±0.7 mm in females. This corresponded to percentage moult increments (PMI) of 6.2 and 5.5% in males and females, respectively. There was a significant positive linear relation between MI and CL in males but not in females. Percentage moult increments in males were constant throughout the CL range examined (21–54 mm), but in females a significant negative linear relationship was detected between lnPMI and CL. In both sexes the growth at moult decreased with increasing holding time under laboratory conditions, especially in the case of ecdyses taking place after more than 1 year in captivity. In males, MI was lower in smaller holding tanks. Duration of the intermoult period was similar in both sexes (180±80 days in males and 174±65 days in females), and increased significantly with increasing CL. Moulting seasonality was not marked, but two moulting seasons in autumn–winter and spring–summer were recorded. The information obtained in the present study was compared with available data for the Norway lobster in other geographical areas in the NE Atlantic and Mediterranean.