Size at Maturity

From May to June 2025 data was collected in six Lobster Fishing Areas (LFAs) through a CLRN collaborative initiative involving over eight fishing organizations and Fisheries and Oceans Canada (DFO) scientists from the DFO Gulf and Maritimes regions to study the size at which female lobsters reach sexual maturity. The Size at Onset of Maturity, the size at which 50% of females reach maturity (SOM50), is a key measure for lobster stock assessment and helps guide management decisions like the minimum legal harvest size. Maturity varies by Lobster Fishing Area (LFA) and can change over time due to environmental shifts (e.g. temperature) and fishing pressure. Updated data are essential to support sustainable management. 
 
The project brought together fishermen’s associations, research organizations, scientists, and fish harvesters to investigate female lobster maturity in LFAs 23, 25, 26A, 31B, 32, and 34. Timing of sampling to evaluate SOM50 is critically important. It needs to happen in late spring when female lobsters are at distinct points of reproductive development. In most LFAs, sampling took place during active fishing seasons, where commercial fish harvesters provided opportunities to collect lobsters representing different size classes.  
 
In the lab, researchers examined each lobster’s ovaries and pleopods (swimmerettes) to assess reproductive development. Across the six LFAs, the teams processed over 1,500 ovaries and over 3,000 pleopods. The work contributes to better understanding of how maturity varies regionally and over time, key information for maintaining healthy lobster populations. By working together, this collaboration strengthened sampling capacity, reduced costs, and improved coordination among organizations.  
 
This project emerged from discussions at the first Canadian Lobster Research Network meeting in 2024, where partners identified maturity as a key knowledge gap. In recent decades, harvesters have been seeing more smaller egg-bearing females. This may be linked to climate change, with temperature playing a major role in declines in SOM50 in the US. There are still large gaps in SOM50 data across the species’ range, with many areas lacking estimates. Understanding SOM50 and the changes it’s undergoing is essential for assessing lobster populations and guiding effective management, making ongoing research critical.