Linking habitat and life history for conservation of the rare saltmarsh topminnow Fundulus jenkinsi: morphometrics, reproduction, and trophic ecology

Abstract

Fundulus jenkinsi is a state and federally listed Species of Concern because it is rare and is threatened by human activities, and ecological information is lacking. Fish collected from Louisiana, Mississippi, Alabama, and Florida, USA, during winter, spring, and summer were evalu- ated for selected habitat-linked reproductive and trophic metrics. Mouth-gape-weight relationships increased with standard length (SL) but did not differ by gender. An exposed genital papilla, an anal sheath, and an elongated posterior anal ray separated mature males from females in 86.7% of the fish examined (year round), and adding vertical bars and dark dorsal pigmentation increased this per- centage to 96.7% (seasonal). There was a clear season-size spawning relationship, whereby fish <20 mm SL were immature, and ovary phases and oocyte stages suggested that spawning initiated in spring/early summer. Diet did not vary by size-class but did vary seasonally. Summer diets were most similar to each other compared to other seasons, with prey consisting of arachnids, crab zoea, dipterans, amphipods, hymenopterans, and hemipterans. Aquatic prey size classes shifted with increased fish size and mouth gape, which allowed for larger prey to be consumed. Smaller-bodied terrestrial prey were consistently consumed regardless of fish body size. Overall, reproduction and diet are strongly linked with mid- and high salt marsh access. These data highlight small, intercon- nected intertidal creeks embedded within salt marshes as access points for reproduction and forag- ing and suggest that 'dendritic' complexes of intertidal creeks should be a focus in conservation plan- ning efforts, and that efforts to restore tidal marsh habitat should attempt to mimic these naturally occurring complexes.