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

Abstract

Knowledge of movement ecology, habitat use, and spatiotemporal distribution is critical to inform sustainable fisheries management and conservation. Atlantic halibut in the Gulf of St. Lawrence (GSL) is of great economic value, although little is known about its spatiotemporal distribution, seasonal migrations, and spawning areas. To investigate these aspects, 114 pop-up satellite archival tags (PSATs) were deployed on halibut from 2013 up to 2018 throughout the GSL. A total of 62 physically recovered PSATs provided complete archived datasets with high temporal resolution. PSAT detachment locations revealed specific summer site fidelity. In contrast, the reconstruction of movement tracks with a geolocation model revealed that all fish converged to the Gulf’s deep channels to overwinter and spawn. This suggests strong mixing during the spawning period and thus one reproductive population within the GSL. These findings illustrate the utility of large-scale PSAT tagging combined with dedicated PSAT-recovery surveys to reveal critical stock-scale information on movements and spawning locations. This information addresses important gaps in the movement ecology of this halibut stock, revealing that reported summer site fidelity, based on years of conventional tagging, also conceals important winter mixing that is only apparent through analyses of movement on the time scale of annual cycles.

Spatial Ecology of Atlantic Halibut across the Northwest Atlantic: A Recovering Species in an Era of Climate Change

“…Electronic tagging studies characterize detailed movement of individuals, and even more detailed if archival tags are retrieved and allow for analysis at higher temporal resolution (Fisher et al 2017), allowing insight into fine-scale behavior. Progress in the last decade in electronic tagging technologies has revealed a variety of migratory behaviors through the reconstruction of migration tracks using geolocation models (Seitz et al 2017;Le Bris et al 2018;Liu et al 2019;Gatti et al 2020;James et al 2020;Gatti et al 2021). Within the Gulf of St. Lawrence, 62 pop-up satellite archival tags (PSATs) placed on Atlantic halibut have been recaptured over multiple years, providing complete archived datasets with high temporal resolution (Gatti et al 2020).…”

“…Progress in the last decade in electronic tagging technologies has revealed a variety of migratory behaviors through the reconstruction of migration tracks using geolocation models (Seitz et al 2017;Le Bris et al 2018;Liu et al 2019;Gatti et al 2020;James et al 2020;Gatti et al 2021). Within the Gulf of St. Lawrence, 62 pop-up satellite archival tags (PSATs) placed on Atlantic halibut have been recaptured over multiple years, providing complete archived datasets with high temporal resolution (Gatti et al 2020). Groups of Atlantic halibut were tracked from five locations in the summer, to a common channel in the winter, where they exhibited spawning rises.…”

“…Contingent structure leads to a diversity of migration patterns within an area or population. Both long and short-distance migrations and year-long residency have been observed for Atlantic halibut both within the Gulf of Maine (Seitz et al 2016;Kersula and Seitz 2019;Liu et al 2019) and the Gulf of St. Lawrence (Le Bris et al 2018;Gatti et al 2020;James et al 2020). Migratory diversity is even observed at the scale of the tagging location.…”

“…Migratory diversity is even observed at the scale of the tagging location. For instance, there has been a year-round residency and an 800-km migration observed from Atlantic halibut tagged the same day at the same location in the north-east Gulf of St. Lawrence (Gatti et al 2020). Atlantic halibut tagged at the same location within a few days of each other in the southern Gulf of St. Lawrence have also demonstrated different migration routes and separate winter spawning areas (James et al 2020).…”

“…The commonality among tagging studies includes partial migration (Kerr and Secor 2012; Dingle 2014), in which seasonal migratory contingents overwinter on the continental slope and return to inshore foraging sites for summer, resident contingents that do not move significantly, and a small minority of fish that are recaptured at extreme distances from where they were conventionally tagged. The seasonal migrations have displayed variation in timing, likely influenced by fish size, maturity state, and the geographic distance between summer feeding areas and available wintering habitats, resulting in a diversity of migration patterns (Gatti et al 2020). Importantly, seasonal migrations are assumed, and in many instances shown, to be spawning migrations.…”