Article Title：δ15N isotope studies of life history and trophic position of Fundulus heteroclitus and Menidia menidia
Abstract：
We used delta N-15 isotopic signatures to follow the trophic position as well as the life history of 2 of the most abundant fish species of the Waquoit Bay estuarine system: common killifish Fundulus heteroclitus and Atlantic silverside Menidia menidia. Juvenile fish bore isotopic signatures specific to the estuary in which they had been growing. The fish changed in delta N-15 as they grew and had significant, estuary-specific differences in delta N-15 signatures. F, heteroclitus increased in length by 3 to 4 cm as they increased in delta N-15 by up to 4 parts per thousand. The magnitude of the shift in delta N-15 is consistent with movement of the fish similar to1 trophic step up the food web. E heteroclitus remained within their native estuaries year-round, and retained the isotopic signatures of,their prey in each estuary. M, menidia moving offshore during the winter months lose estuary-specific differences in delta N-15, and appear to feed at a higher trophic level than fish residing in the estuaries. Evidence from gut content analysis, coupled with results of the stable isotopic measurement, closely concurs with the life history characteristics of these 2 well-known fish species, and provides additional insight into life history habits and feeding.
Keywords: stable isotopes; food webs; trophic level; life history; migration; nitrogen loading
DOI: 10.3354/meps214299
Source：MARINE ECOLOGY PROGRESS SERIES
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