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

Drew M. Talley

Abstract

Loss of wetland habitat has proceeded at an alarming rate in southern California, and increasinglymarsh restoration and creation are being used to mitigate these losses. As part of an effort to evaluate functional equivalence of created systems, the ichthyofaunal assemblages in a created and adjacent natural marsh in Mission Bay, San Diego, California were compared. Fishes trapped in both marshes included Fundulus parvipinnis, Gillichthys mirabilis, Acanthogobius flavimanus, Ctenogobius sagittula, Atherinops affinis, and Mugil cephalus. Fundulus parvipinnis was numerically dominant in both systems, representing on average 69% of all fishes trapped in the created marsh and 65% of all fishes trapped in the natural marsh. Gillichthys mirabilis was the second-most abundant species, representing on average 31% of all fishes trapped in the created marsh and 28% of all fishes trapped in the natural marsh. Species richness and dominance measures were similar between the two systems, while abundances were higher in the natural relative to the created marsh. The size-structure of F. parvipinnis and G. mirabilis differed between the created and natural marsh creeks, with the created marsh populations being skewed towards larger size classes. These size differences are believed to arise from differences in creek morphology between the created and natural systems, and potentially affect both predators and prey of these species in the marsh. Mark-releaserecapture revealed considerable marsh fidelity, with as many as 35% of the F. parvipinnis tagged in a marsh being recovered one day later in the same marsh. Stable isotope analyses of F. parvipinnis revealed similar ¹⁵N and ³⁴S values between marshes; however there was a consistent enrichment in ¹³C (>3 per mil) in tissues of F. parvipinnis from the created marsh, supporting the high marsh fidelity suggested by tagging results. This first published documentation of the Mission Bay marsh resident fishes suggests that the created marsh ichthyofaunal assemblage was distinct in density and size structure from the adjacent natural marsh, and provides lessons for future restoration efforts.