Habitat characteristics drive fish recruitment enhancement in threatened coastal nursery habitats

Abstract Structured coastal habitats serve as vital fish nurseries globally, yet the role of biotic and abiotic factors in shaping this function remains unclear. Understanding these relationships will allow more informed conservation and restoration decisions and effective communication of their anticipated effects on fish production. We conducted a meta‐analysis of 102 studies (2002 responses) to evaluate the potential drivers of fish recruitment enhancement (RE), defined as the relative increase in young‐of‐year fish abundance in structured vs. unstructured bottom, in North American salt marshes, oyster reefs and submerged aquatic vegetation (SAV). All three habitats significantly enhanced fish recruitment, with SAV and salt marshes exhibiting greater RE than oyster reefs. Restoration increased fish recruitment in all three habitats (130%–180%), but only restored marshes and oyster reefs—not SAV—achieved RE comparable to their natural counterparts. Habitat characteristics were consistently influential predictors of RE across habitat types. In SAV, shoot cover and biomass were positively associated with fish recruitment, with RE being 295% higher in SAV with dense (~80%) compared with sparse (~20%) shoot cover. Fish recruitment increased with oyster cover but declined at greater reef heights, with low (<0.2 m) and moderate (0.2–0.5 m) relief reefs each supporting 215% and 110% greater RE than high relief reefs (>0.5 m). Proximity to SAV and oyster reefs increased RE in salt marshes by 170%; however, this positive effect was not reciprocated in SAV and oyster reefs near marshes. RE remained consistent across temperature and salinity gradients, whereas it was strongly influenced by tidal regime in salt marshes and SAV. Synthesis and applications . Our findings underscore the importance of habitat attributes and physical settings as the key predictors of fish enhancement across threatened coastal nurseries of North America. Restoration and management efforts should aim to optimize these factors to maximize fish recruitment potential amid ecosystem degradation.