Comparisons of fauna among natural and transplanted eelgrass Zostera marIna meadows: criteria for mitigation

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Abstract
Numerical abundance, species composition and size of fish and shrimp were compared among (1) unvegetated, (2) transplanted, (3) recently seed-colonized, and (4) mature, natural eelgrass habitats to determine the equivalence of transplanted eelgrass beds to their natural counterparts. In general, fish and shrimp were most abundant in mature natural eelgrass habitats and least abundant in unvegetated habitats. We developed a vector-graphical analysis that shows epibenthic faunal abundance to be closely coupled with eelgrass bed development. In an area where transplants performed poorly, the fanual component had a different composition and significantly lower numerical abundance in comparison to natural beds. Faunal abundance and composition in a 1.9-yr.-old transplanted bed and a 6-mo-old seed-developed bed were indistiguishable from mature natural eelgrass beds. Our data indicate that recruitment of fish and shrimp to eelgrass habitats established through transplantation can occur in time, though not as rapidly as with naturally-seeded beds. Areal shoot density may serve as an inexpensive diagnostic parameter of functional equivalence for most resident macroepifauna. Abundance data need to be interpreted through functional mechanisms such as predation which act to produce the observed abundance in order to separate habitat function from dysfunction. Restored seagrass habitats have the potential to make substantial contributions to fish and shrimp production provided the habitats persist.