The tropically associated black mangrove (Avicennia germinans) is experiencing a climate-induced range shift and expanding into salt marshes of northern Florida, southern Louisiana and most recently, Horn Island, MS. To date, little is known about how black mangroves function as nursery habitat for important fishery species such as shrimps or how their increase may affect survival of such species. The main objective of our study was to determine habitat preference and survival rates of common, economically important penaeid shrimps in the presence and absence of the increasingly abundant tropical predator, the gray snapper (Lutjanus griseus). We also examined the effects of habitat identity and structure on juvenile white shrimp (Litopenaeus setiferus) and brown shrimp (Farfantepenaeus aztecus) behavior, using preference experiments in indoor mesocosms both with and without the predatory gray snapper. Results showed that shrimp prefer Spartina over Avicennia with or without predation risk. Survival of shrimp was lowest in sand and highest in medium-density Spartina. Thus, a marsh-to-mangrove habitat conversion could ultimately result in decreased shrimp survival.