IJMS Editor’s Choice – Tracking Atlantic halibut migration

The latest Editor’s Choice article from the ICES Journal of Marine Science is now available. Here a unique academic-government-industry collaboration sheds new light on movement ecology of Atlantic halibut.

Published: 15 October 2020
​Knowledge of movements and migrations within exploited fish populations is key to understanding factors driving population dynamics. Over a seasonal cycle, adult fish often display complex migrations among spawning, feeding, and overwintering grounds that have major implications for fisheries management and in particular for the design of robust abundance surveys.
The movement patterns and migrations within a population can be identified through numerous approaches such as otolith microchemistry, mark-recapture experiments, or electronic tagging. Within this suite of potential methods, Pop-up Satellite Archival Tags (PSATs) have become a premier tool in the study of fish habitat use and movement ecology, as they may yield high-resolution temperature, depth and light data that can feed geolocation models to reconstruct fish movement tracks. PSATs are data storage tags externally mounted on fish that detach following a pre-programmed deployment duration, then transmit their position and a portion of archived data via Argos satellites. A major advantage of using this technology to detail a broad range of migration strategies is that some data are obtained independent of recapturing the animal.
However, in most PSAT studies to date, conclusions have been drawn using incomplete datasets transmitted by Argos satellites. Transmitted data constitute hourly to daily summaries generally representing less than 1% of the full archived datasets, which may conceal key short-lived behaviours such as spawning, and result in high confidence intervals for geolocation results. The only way to overcome this limitation is to physically-recover PSATs after they release from their host fish, which gives access to full archived datasets.
In this new study on the migration ecology of Atlantic halibut in the Gulf of St. Lawrence, Gatti et al. deployed a total of 114 PSATs over a period of 5 years. A unique partnership with government scientists and the fishing industry allowed them to carry out dedicated recovery operations across the stock range using direction-finding antennas (Argos goniometer) designed to detect active Argos transmitters. This strategy aboard fishing vessels allowed the team to access archived datasets from a total 62 physically-recovered PSATs.
PSAT detachment locations indicated almost-systematic summer site fidelity in halibut from all sectors of the Gulf. In contrast, the reconstructed movement tracks, using the high-resolution archived data, revealed that all tagged fish converged within the Gulf’s deep channels to overwinter and spawn. This suggests strong mixing during the spawning period and thus limited population structure within the Gulf of St. Lawrence. These results provide key information on spawning areas and migration patterns; valuable new inputs to the fisheries assessments of the stock.
This study clearly illustrates the power of collecting archived data from PSAT deployments for resolving key management issues at the scale of a given stock. The authors conclude their article by providing advice on strategies that can facilitate successful PSAT recoveries and make the best use of the high-resolution archived data, including the value of partnering with the fishing industry to maximise flexible ship time opportunities.

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Fish harvesters and scientists -beside the fishing vessel Jenny Dion- display their catch of six pop-off satellite archival tags (PSATs) recovered  offshore in the Gulf of St. Lawrence, Canada. Such at-sea collaborations facilitated the recovery of 62 PSATs, providing new insights into the migrations, spawning behaviour, and habitat use of Atlantic halibut within one of Canada's most lucrative fisheries.  Photo: Dominique Robert.


Stock-scale electronic tracking of Atlantic halibut reveals summer site fidelity and winter mixing on common spawning grounds


Paul Gatti, Dominique Robert, Jonathan A D Fisher, Rachel C Marshall, Arnault Le Bris
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IJMS Editor’s Choice – Tracking Atlantic halibut migration

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