<p>We examine whether the mobility of a transboundary stock can incentivize a bilateral marine reserve agreement, where one fishing country pays its neighbor to become a marine reserve. The key insight is that precisely because fish move across borders, non-cooperative extraction is likely to be excessive, which lowers fishery profits for both countries. Under our proposal, the payor benefits from the spillover and elimination of non-cooperative extraction, both of which raise fishing profits. The payee benefits from direct financial compensation in exchange for creating the marine reserve. We create a dynamic and spatial game between two countries sharing a transboundary stock. We determine the mobility conditions under which the payor is willing to pay and the payee is willing to accept the payment. We illuminate the biological and economic conditions under which an agreement is incentive-compatible for both countries and conditions under which one or both countries would oppose such an agreement. We find that larval dispersal plays little role in agreement acceptance if adult movement is high. However, if adult movement is low, high larval dispersal can promote agreement acceptance. We also find that this agreement can fully reproduce the conservation and economic benefits gained under a cooperative fishing agreement if adult movement from the fishing patch to the reserve patch is low (≤ 40%) and adult movement to the fishing patch is high (≥ 60%). We discuss the implementation challenges using four real-world transboundary stocks and highlight global issues that bilateral marine reserve agreements can help solve.</p>