Biology of Berried, Larval and Juvenile Homarus gammarus

European Lobsters (Linnaeus 1758) or Homarus gammarus are decapod crustaceans in the family of Nephropidae. Female lobsters reach maturity at 5 to 7 years of age while males reach maturity slightly earlier (Beard and McGregor 2004). Reproduction occurs after a female lobster has moulted and still lacking an exoskeleton. Females then carry fertilized eggs underneath their tail for 9 -11 months. The eggs which are first black when laid turn bright orange when ready to hatch (Agnalt et al. 2006). A female lobster or hen, can on average carry around 12,000 eggs although some large hens have been recorded carrying 40,000 eggs. A pregnant lobster is often referred to as berried (Holthuis 1991). Hatching occurs from May to September and takes 5 -10 days for each female to release all the larvae with an 80% chance of the eggs becoming larvae (Burton 2003). To grow, European Lobsters moult, this means the larval period can be identified as different stages are shown in figure 1 (Williamson 1969).

The European Lobster has a shortened larval stage compared to other decapods (Rötzer and Haug 2015). A newly hatched larvae will go through 3 moults, through which the larvae are pelagic and omnivorous (Templeman 1936). Once post-larvae stage 4 been reached, after 10 -15 days, the larvae settle to the benthos and begin the first juvenile stage (Brönmark and Hansson 2012). The juvenile stage lasts for about 1 month at an optimal temperature of 18 degrees Celsius (Rötzer and Haug 2015). Larvae hatch at about 7mm in length and measure 12mm in length by the 4 moults (Agnalt et al. 2004).

3 main lobster hatcheries exist in the UK, one in Orkney, Padstow Cornwall and one on Anglesey. The ideal environmental conditions proposed by Seafish for these hatcheries are shown in Figure 2 (Burton 2003). 

An adult lobster’s diets include fish, crabs and shellfish (Mente Eleni et al. 2001). While larvae can feed on algae, artemia, mysid shrimp and chopped up shellfish as well as dried and frozen foods. Fresh food with high fatty acid component led to the highest survival rates of larvae and juveniles (Kristiansen et al. 2004). Larvae are opportunistic feeders so if food is not provided in excess there will be high rates of cannibalism, also lack of food during each larval stage has been shown to lengthen each stage (Templeman 1936).