We investigated the effect of environmental conditions on Atlantic mackerel spawning habitat in the southern Gulf of St. Lawrence (sGSL). Based on generalized additive models, we (i) modelled the optimal spawning habitat of mackerel in the sGSL using daily egg production (DEP) in June, (ii) predicted known and new potential present spawning habitats in the GSL and the northâwest Atlantic, and (iii) assessed how they respond to future climate change. Our findings showed that both mackerel presenceâabsence and givenâpresence DEP were associated with sea surface temperature (10â16.5°C), salinity above 31 and depth < 120 m. Adding zooplankton showed a marked effect on the DEP givenâpresence compared to the presenceâabsence. Predictions of spawning habitats under present (1999â2012) and future scenario (2066â2085) conditions were estimated from the presenceâabsence model without zooplankton, using physical conditions of the BNAM. Under present conditions, our model predicted well the main spawning habitat in the sGSL and other known secondary spawning habitats in the northern GSL (nGSL), the western and southern Newfoundland, and the northâwest Atlantic coast. Under future conditions, our study suggests that spawning habitats in the sGSL and the nGSL would expand. Our results, therefore, suggest that mackerel could benefit from a warmer GSL, minimizing the potential for a northward migration of the stock due to decreasing suitability of the sGSL as its main spawning ground, and a new but spatially limited potential habitat in Newfoundland coasts. These results can be used to inform stock management and develop adaptive management plans in the context of climate change.