Ichthyofaunal utilization of newly-created versus natural salt marsh creeks in Mission Bay, CA

Abstract

Loss of wetland habitat has proceeded at an alarmingrate in southern California, and increasingly marshrestoration and creation are being used to mitigatethese losses. As part of an effort to evaluatefunctional equivalence of created systems, theichthyofaunal assemblages in a created and adjacentnatural marsh in Mission Bay, San Diego, Californiawere compared. Fishes trapped in both marshes includedFundulus parvipinnis, Gillichthysmirabilis, Acanthogobius flavimanus, Ctenogobius sagittula, Atherinops affinis, andMugil cephalus. Fundulus parvipinniswasnumerically dominant in both systems, representing onaverage 69% of all fishes trapped in the createdmarsh and 65% of all fishes trapped in the naturalmarsh. Gillichthys mirabiliswas the second-mostabundant species, representing on average 31% of allfishes trapped in the created marsh and 28% of allfishes trapped in the natural marsh. Species richnessand dominance measures were similar between the twosystems, while abundances were higher in the naturalrelative to the created marsh. The size-structure ofF. parvipinnisand G. mirabilisdifferedbetween the created and natural marsh creeks, with thecreated marsh populations being skewed towards largersize classes. These size differences are believed toarise from differences in creek morphology between thecreated and natural systems, and potentially affectboth predators and prey of these species in the marsh.Mark-release-recapture revealed considerable marshfidelity, with as many as 35% of the F.parvipinnistagged in a marsh being recovered one daylater in the same marsh. Stable isotope analyses ofF. parvipinnisrevealed similar δ15Nand δ34S values between marshes; howeverthere was a consistent enrichment in 13C (>3per mil) in tissues of F. parvipinnisfrom thecreated marsh, supporting the high marsh fidelitysuggested by tagging results. This first publisheddocumentation of the Mission Bay marsh resident fishessuggests that the created marsh ichthyofaunalassemblage was distinct in density and size structurefrom the adjacent natural marsh, and provides lessonsfor future restoration efforts.