Science Improves Understanding of Atlantic Halibut in Gulf of St. Lawrence
This article was originally published in the Winter 2020 edition of the Union Forum magazine.
Atlantic halibut abundance has been increasing in the Gulf of St. Lawrence. Fish harvesters have been saying that for years. But what do we really know about the Gulf of St. Lawrence Atlantic halibut? Until recently, understanding of population characteristics such as annual migrations and spawning behaviors was primarily based on limited local sampling data and estimates based on studies in other regions or related species; not much to go on.
However, an electronic tagging study implemented in 2013 is yielding interesting results that are already redefining the understanding of Gulf halibut distribution and behavior. Approximate migration tracks produced from the depth profiles recorded over the course of the electronic tag deployment are showing, as in this example (Figure 1), that halibut can migrate well beyond where they were tagged for large portions of the year. Additionally, several halibut have shown unique profiles of depth use suggestive of spawning behavior, extreme rises off the seafloor (Figure 2) uncharacteristic of depth uses seen at other times in the year.
The success of this project has been extremely dependent on collaboration with fish harvesters from the beginning, and their help is still valuable. New questions about halibut spawning behavior, seasonal migration, and habitat use have been raised by the findings from the electronic tags.
Masters student Rachel Marshall of the Memorial University of Newfoundland Marine Institute is looking to address those questions through interviews with fish harvesters who have long-term experience fishing for Atlantic halibut in the Gulf of St. Lawrence. The information collected during these interviews will be presented to stock assessment scientists and managers at the next Gulf halibut stock assessment.
Fish harvesters who are actively fishing for groundfish in NAFO divisions 3Pn and 4R, and who have been doing so for at least five years, who are interested in participating in this study, please contact Rachel Marshall (email: Rachel.Marshall@mi.mun.ca). In-person interviews are expected to take place on the West Coast of Newfoundland between February 15th and 23rd, 2020.
Figures from: Le Bris, A., Fisher, J.A.D., Murphy, H.M., Galbraith, P.S., Castonguay, M., Loher, T., and Robert, D., 2018. Migration Patterns and Putative Spawning Habitats of Atlantic Halibut (Hippoglossus hippoglossus) in the Gulf of St. Lawrence Revealed by Geolocation of Pop-up Satellite Archival Tags. ICES Journal of Marine Science 75:1, 135–47.