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Does berried female American lobster exposure to an anti-sea lice drug in sediment affect subsequent egg and larvae development? 

St. Andrews, New Brunswick, Canada – October 8, 2024 

The American lobster fishery represents an important ocean economic sector in Atlantic Canada where berried (egg carrying) females may also geographically overlap with Atlantic salmon fish farms that may be using anti-sea lice drugs. This study investigated a novel exposure regime involving berried female lobsters living for a 10-day period on sediment that was spiked with varying concentrations of emamectin benzoate (EMB and marketed as SLICE®) to mimic the likely presence of these females in the vicinity of aquaculture sites.   “A 10-day exposure period was chosen for our study based on other published research following the movement patterns of adult American lobsters. This provides a reasonable duration of time that a moving lobster may spend near an aquaculture site whether they are treating for sea lice or not,” explains Dr. Davide Asnicar, a Post-doctoral Fellow at The Huntsman Marine Science Centre and lead author on the published study in the peer-reviewed journal Science of the Total Environment.

Technical staff collected berried female lobsters from the local fishing area and maintained them within the 
Huntsman Marine research facilities to complete the study. Four test concentrations of EMB were chosen, including concentrations measured near Canadian aquaculture sites and up to 30x higher than these environmentally relevant concentrations. Natural sediment was collected locally and mixed with EMB stock solution to acquire the tested target concentrations. Two replicate tanks were assigned to contain each sediment treatment scenario, including no, low, medium and high EMB concentrations plus two tanks with no sediment present, with each tank holding three berried female lobsters. Daily assessments were completed for lobster mortality and water quality. Water samples were taken at the start and end of the exposure period to confirm treatment concentrations of EMB and its main metabolite desmethyl EMB. 

Asnicar explains, “After the 10 day exposure period we had no mortality within the berried female population but this was just the beginning for this particular study.” Female lobsters were returned to common housing until molting, mortality, or egg hatching. Egg clutches were assessed weekly to monitor development then eventually hatched within a single lobster holding tank with a subset of collected larvae held through the first molt to become Stage II larvae. “Adults were again housed together after releasing all of their larvae as we waited to determine molting success and meat quality following their earlier sediment exposure to EMB,” adds Asnicar. 

Measured average EMB concentrations from the study tanks were close to the planned target concentrations with the highest EMB tested being 1061.23 ng g-1 dry weight (dw). In comparison, EMB concentrations were recently detected in sediment near Canadian aquaculture sites up to 37 ng g-1 dw. The study therefore tested sediment concentrations that were 29x the environmentally relevant concentrations at the end of the exposure. 

Study results showed that a single, 10-day exposure of berried female American lobsters to EMB concentrations nearly 29x greater than the highest measured Canadian concentration near aquaculture operations did not cause significant effect on all assessed endpoints for ovigerous (berried) females whether related to molting, meat index and/or intervals/timing for hatching and hatch success. These results were mirrored in lobster larvae post-hatching with no observed effect on molt interval duration or molting success and no other abnormalities noted.

“Our results suggest that adult lobsters are not at risk when exposed to EMB in the sediment and the next generation of lobsters are also protected if an exposure occurs while in the attached egg stage,” concludes Asnicar. 

The research publication was co-authored by Dr. Benjamin de Jourdan, also a Research Scientist with Huntsman Marine, and science staff at the adjacent Saint Andrews Biological Station. The study was funded by Fisheries and Oceans Canada. 

Research Publication: 

Asnicar, D., L. Jonah, B. de Jourdan, M. Kingsbury and D. Hamoutene. 2024. Exposure of female lobsters to sediments spiked with emamectin benzoate: Effects on eggs and larvae early development. Science of the Total Environment 948: 174840. https://doi.org/10.1016/j.scitotenv.2024.174840

Image 1: Graphical abstract highlighting the study methods and results.

Image 2: Containers set-up to incubate hatched larvae per individual female lobster to allow tracking and molting to Stage II.

Image 3: Sampling for blood protein levels from previously exposed adult female lobsters to complete the BRIX index as an established proxy for meat content and quality. 

Story by Bud Adams, The Huntsman Marine Science Centre.  

For additional information or images relating to this article, please email huntsman@huntsmanmarine.ca. 

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