Survival and Density of a Dominant Fish Species Across a Gradient of Urbanization in North Carolina Tidal Creeks

摘要

Development in the southeastern US coastal plain generates the need for a better understanding of how survival and abundance of estuarine nekton respond to urbanization. Apparent survival and density of the dominant Atlantic coast salt marsh fish, the mummichog Fundulus heteroclitus, were estimated in four North Carolina tidal creeks using a model simultaneously fitted to mark-resight and mark-recapture data. Rates of weekly loss (mortality plus emigration) were high (similar to 10%). Sampling for tagged fish within and outside of study creeks showed high site fidelity to each creek, indicating that loss largely resulted from mortality rather than emigration. Estimated rates of apparent survival were lowest in the creek with the least instream- and watershed-level impacts. This creek has direct (non-culvert) access downstream to a larger waterbody, suggesting that enhanced access by predators and/or greater rates of permanent emigration may have contributed to lower apparent survival in this creek. There was a positive relation between minnow trap catch-per-unit-effort (CPUE) and density allowing the relationship between CPUE and habitat and urbanization to be examined in a total of six creeks. The largest CPUE estimates occurred early in each growing season and were associated with creeks possessing characteristics most representative of undisturbed salt marsh mosaics: high percentage of marsh coverage instream and downstream and high percentage of marsh edge. Given generally limited movement outside of creeks, differences in abundance among creeks likely result from different levels of recruitment that are related to salt marsh availability. Priority preservation of salt marsh habitats may be warranted by natural resource planners to maintain abundance levels of this trophically important species.