Describing lobster moulting patterns in the East Coast of Canada

Principal Investigator: Raphael Vanderstichel
Co-Investigators: Crawford Revie & Jean Lavallée

Since the early 2000s, there has been a significant increase in the proportion of soft-shelled lobsters caught in southwest Nova Scotia, up from 5-10%, historically, to 30-40% in recent years. Lobster shell hardness is directly related to moulting, so understanding factors associated with moult timing is vital to the sustainability of the industry. Soft-shelled lobsters have low meat yield and poor survivability during holding and transportation, and pose an economic challenge to the lobster industry.

The objectives of this study were to describe the moulting patterns of lobsters in Atlantic Canada and to identify factors associated with soft-shelled lobsters. We used data from the Atlantic Lobster Moult and Quality Monitoring project, collected from a number of locations in the two most productive lobster fishing areas in southwestern Nova Scotia.

Our analyses included more than 119,000 samples, from 2004 to 2014, and indicated that the monthly proportion of soft-shelled lobsters ranged from 9 to 38% during the study period. Our analyses demonstrated that the lobster sex and size, and average depth of the fishing locations were strongly associated with shell hardness. Our logistic model revealed that the shell quality was significantly influenced by the month of sampling and the fishing areas, which suggests seasonal and regional differences. Variability in shell quality between years indicates the possible impact of climatic variation over time.