Habitat heterogeneity: importance of salt marsh pools and high marsh surfaces to fish production in two Gulf of Maine salt marshes

Both permanent high marsh pools and the intertidal surfaces of Spartina patens high marshes in southern Maine, USA, proved to be important habitat for resident mummichog Fundulus heteroclitus production. Manipulations of fish movement onto high marsh Surfaces revealed similar growth rates and production among fish that were (1) restricted to pools, (2) had access to known areas of marsh surface, or (3) had free access to the entire marsh, Smaller scale manipulations with marked fish revealed that males with access to the marsh surface accumulated significantly more biomass, often exhibited higher growth rates, and had a 1.6x greater production rate than males restricted to pools. Female production was only slightly higher for fish that could access the marsh compared to fish restricted to pools, While both pools and marsh surface appeared to support fish production, habitat partitioning also existed between sexes of mummichogs; males may rely more on the marsh surface for food while females rely more on pools. Growth and production of mummichogs in pools on the high marsh surface was lower than values reported from more southern, low marsh dominated systems. This was attributed to differences in (1) abiotic factors of salt marsh pools (this study) and tidal creeks and channels (other studies), (2) climate, and (3) tidal inundation and access time to the marsh surface. Fish production on the surface of Gulf of Maine high marsh ecosystems was equivalent to production in adjacent tidal creeks and channels. Thus, the high marsh surface proved to be an important habitat for supporting fish production in this region.