Key silverside

The Key silverside (Menidia conchorum) is a species of fish in the family Atherinopsidae: Menidiinae. It is endemic to the Florida Keys.

The American Fisheries Society (2023 in press) and Eschmeyer's Catalog of Fishes (2023) verified Menidia conchorum Hildebrand & Ginsburg 1927 as a valid species under the Atherinopsidae family and Menidiinae subfamily, relying on opinions of practicing authorities in fish taxonomy and systematics such as Robins and Ray (1986), Gilbert (1992), Conover et al. (2000) and Musik et al. (2000). This species is exclusive to the Florida Keys, where it inhabits both brackish and marine environments. Morphological and genetic studies have established its genetic and morphological distinction from nearby related species (O'Leary et al. 2016).

Since the 1980s, Menidia conchorum populations have faced a significant decline, predominantly due to the rapid disappearance of their habitat in the salt-ponded waters of the lower Florida Keys and, more importantly, due to the effect of rising sea levels the Florida Fish and Wildlife Conservation Commission recently cataloged the species as threatened. The U.S. National Marine Fisheries Service has also identified the species as a Species of Concern.

Species Description
Getter's 1981 survey, conducted in the late 1970s across the entire Florida Keys, established that the Key silverside exhibits a limited distribution, confined to the lagoonal and ponded waters of the Florida Keys. This unique and relatively rare habitat is home to a community of fishes, many of which are found exclusively in this location.

As the smallest known species in the genus Menidia, according to the Florida Fish and Wildlife Conservation Commission, female Key silversides can reach up to 58 mm in standard length, while males typically grow up to 50 mm. While it shares a close relationship (paraphyletic) with the Tidewater silverside (Menidia peninsulae), the Key silverside is distinguishable by its deeper body, yellow coloring, and habitat and range restrictions. Moreover, laboratory tests show it has a lower cold tolerance than its relatives.

Conservation
The sea level rise continues to inundate many of the larger salt ponds that have become lagoonal. These isolated, fragmented ponds serve as crucial lifelines for the survival of the species. In the past, many such salt ponds and lagoons have been filled for development purposes, significantly reducing available habitats. This has resulted in the loss of numerous ponds, previously occupied sites, and ponded and lagoonal habitats.

If proactive interventions are not undertaken, the extinction of an endemic Florida Keys fish species - the Key silversides - may be within the next decade (Getter, 2010).

Conservation Designations
According to the Florida Fish and Wildlife Conservation Commission, following the research findings from the Key silverside Biological Review Group and subsequent discussions with other FWC fish experts, the staff recommends that the Key silverside (Menidia conchorum) be listed as a Threatened species. This recommendation is based on the fact that the species fulfills the listing criteria as outlined in rule 68A-27.0012, F.A.C.

Status Reviews
Dr. Chuck Getter, who has been studying the species since the 1970s for his doctoral dissertation (Ecology and survival of the Key silverside, Menidia conchorum, an atherinid fish endemic to the Florida Keys, Ph.D., University of Miami, Rosenstiel School of Marine and Atmospheric Sciences), is currently conducting further research on this species (Getter 2009, 2010). This ongoing work involves updating his initial research with new data in preparation for publication.