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

Abstract

Characterizing migratory behaviours contributes to the sustainable management of marine fishes by resolving stock structure and identifying the timing and locations of events within fish life cycles. The migratory behaviour of Atlantic halibut (Hippoglossus hippoglossus) in the Gulf of St. Lawrence (GSL), Canada was characterized over an annual cycle using pop-up satellite archival tags (n = 15). Daily probability density functions of individual halibut positions were estimated using a geolocation model specifically developed to track demersal fish species in the GSL. Reconstructed migration routes (n = 8) revealed that Atlantic halibut displayed seasonal migrations, moving from deeper offshore waters in the winter to shallower nearshore waters in the summer. Variability in migratory behaviours was observed among individuals tagged at the same location and time. One individual resided year round in the vicinity of the tagging site, three individuals displayed homing behaviour, and four individuals did not return to the tagging site. The identification of presumed spawning rises for two individuals suggested that spawning of Atlantic halibut occurred in the GSL. Although based on a limited number of individuals, these results suggest that Atlantic halibut in the GSL forms a philopatric population, supporting the current separate management of this stock from the adjacent Scotian Shelf and southern Grand Banks stock.

Strong relationship between commercial catch of adult Atlantic halibut (Hippoglossus hippoglossus) and availability of suitable habitat for juveniles in the Northwest Atlantic Ocean

“…2). These temperature windows are similar to those from GSL pop-up satellite archival tagging studies from Le Bris et al (2017) and Murphy et al (2017). Among regions, the environmental variable windows of occurrence of juveniles overlap with slight Table 4 Depth, slope, and bottom temperature (summer, winter, and range) were used as predictor variables to model the distribution and availability of suitable habitat for Atlantic halibut (Hippoglossus hippoglossus) by using data from trawl surveys conducted from 2001 to 2013 in the northwest Atlantic Ocean.…”

“…On a scale from 0 to 1, an AUC value greater than 0.9 is widely accepted as "excellent" or "high" accuracy, and less than 0.6 is generally considered a "fail" because 0.5 means probabilities are no better than random (Phillips and Dudik, 2008;Halvorsen, 2013). For the remainder of the analysis, we used the habitat-suitability layer from the strongest performing model, and we also excluded the GSL because tagging evidence supports the management of this area as that of a separate stock (McCracken, 1958;Neilson et al 5 ;Stobo et al, 1988;den Heyer et al, 2012;Le Bris et al, 2017).…”

“…Studies with electronic tags to elucidate northwest migration patterns and spawning locations of Atlantic halibut (e.g. Armsworthy et al, 2014;Seitz et al, 2016;Murphy et al, 2017;Le Bris et al, 2017) will ultimately improve our ability to define and manage halibut stocks. However, owing to growing commercial interests, there is an immediate need for scientific information to support management decisions.…”

“…If subpopulations exist, assessing distinct stocks as a single large stock often runs the risk of overestimating stock size; such a practice was likely responsible for the collapse of the stock of Atlantic cod (Gadus morhua) (e.g., Sterner, 2007). True spatial overlap between management units and actual underlying population structures supports accurate stock assessments, and therefore a mismatch between the two is reason to revisit respective management regimes (Lundy et al, 1999;Reiss et al, 2009). Here we do not show that subpopulation structures exist within the Scotian Shelf and Southern Grand Banks of Newfoundland Atlantic halibut management unit, but provide reasons to further investigate this possibility.…”

Pop-up satellite archival tag (PSAT) temporal data resolution affects interpretations of spawning behaviour of a commercially important teleost

“…This is due to an absence of information on spawning behaviour, timing and location. When spawning behaviour is accurately characterized and combined with modelling approaches that reconstruct movements over an annual cycle based on PSAT-recorded temperature and depth, and an understanding of the local temperature fields and bathymetry [35], high-resolution data recovered from PSATs provide new opportunities to identify spawning locations of Atlantic halibut in the Gulf of St. Lawrence [36].…”