Climate-driven poleward range shifts are creating new fishing opportunities at range margins, but it remains unclear which management approaches work best when populations at new sites depend on immigration from distant sources. Here, we developed a deterministic, size-structured, two-site fishery model linking a warm-temperate source population (Site A) with a cooler receiving site (Site B) through temperature-dependent dispersal. The model was parameterised for yellowtail kingfish (Seriola lalandi) under the SSP5-8.5 climate scenario for 2000-2100. We implemented the model in three steps: recreational fishing only, addition of a TAC-managed commercial sector, and activation of local recruitment at the receiving site. Six management scenarios were tested in each step. When recreational fishing was the only sector, unregulated effort rapidly depleted the emerging population in all but the weakest effort-response case, with biomass at the receiving site declining by more than 95% relative to the most conservative recreational-only scenario. Adding a TAC managed commercial sector raised biomass only when recreational removals were also constrained, increasing final biomass at Site B by an order of magnitude relative to no-management baselines. Local recruitment, activated by warming in the full model, amplified the benefits of protective management. Scenarios maintaining biomass above spawning threshold saw final biomass increases of 19–117% relative to the migration only step, whereas depleted populations gained very low recruitment. A sensitivity analysis increasing post-release mortality nearly sixfold (from 15% to 85%) showed that catch-and-release-intensive strategies were most vulnerable, with biomass reductions of up to 76%, while the TAC 50-50 strategy was most resilient (−25% change). Overall, the model suggests that early, precautionary management of range-extending fisheries, particularly hard catch caps rather than effort-based controls, may be more effective in supporting both biomass protection and catch during climate-driven colonisation.