The effect of temperature on foraging activity and digestion in the American lobster Homarus americanus (Milne Edwards, 1837) (Decapoda: Nephropsidae) feeding on blue mussels Mytilus edulis (Linnaeus, 1758)

Abstract

The foraging activity and digestive processes of the American lobster Homarus americanus , feeding on blue mussels, Mytilus edulis were investigated over a temperature range of 5-15°C. Lobsters ate more food with increasing temperature, consuming maximal levels of approximately 5% of their body mass of mussel flesh in one sitting in 15°C water. When foraging behaviour was observed over 7 days, lobsters were more active outside of their shelter at 10 and 15°C and consumed more mussels at these two temperatures. Although lobsters were more active during the hours of darkness, they still exited shelters and fed during the light period if food was available. The lobsters consumed at least one mussel every 15.8, 7.8, and 4.7 h in temperatures of 5, 10, and 15°C, respectively. The passage of a mussel meal through the digestive system of lobsters was considerably slower compared with other decapod crustaceans. Transit rate decreased as the temperature was increased, with clearance times of 252, 133 and 69 h in temperatures of 5, 10, and 15°C. Although the time between feeding bouts decreased with increasing temperature, at the time of next feeding the amount of food that had been cleared from the foregut was the same in each temperature (approximately 20%), suggesting that this proportion of stomach emptying could be the cue for next feeding. Recent work has suggested that lobster numbers increase in the presence of mussel aquaculture operations. This work gives further insight into the feeding behaviour and activity around mussel farms, and suggests that lobsters could be an effective means of removing moribund mussels that could be lost during the harvesting process.