Globally, riverine fishes are affected by degradation of habitat, stream alterations, lost stream connectivity and introduction of non-native species. The plains topminnow Fundulus sciadicus, a small stream-dwelling fish, currently does not have a federal conservation status in the USA; however, anecdotal reports have suggested its decline for the last 20 yr. Our goals were to evaluate the validity of its reported decline and to determine the current range-wide status of this species. We identified 927 historical sites (1889−1999) of occurrence and compiled recent records or re-visited 667 sites (2000−2010). We found plains topminnow at 189 (28.0%) of these sites. Although Nebraska represented the center of distribution and included 66.7% of all historical sites, plains topminnow were only found at 34.4% of historical sites, with the largest declines observed in the Platte and Republican River drainages. Current sampling efforts in Colorado, Missouri, Oklahoma, South Dakota and Wyoming found similar declines. In Iowa and Kansas, plains topminnow was not found, whereas potential increases in distribution were observed in a single drainage in Minnesota and Wyoming. In addition to our sampling efforts, we repeatedly sampled 40 sites within Nebraska to determine detection probability. Detection probabilities for plains topminnow were consistent at 0.76 ± 0.05 (mean ± SE) among sites that were sampled with a single visit. Further research is needed on the species and the potential threats to its occupation of sites, as no singular cause for decline seems plausible. Observed threats include degradation and loss of habitat and shifts in species assemblages towards generalist non-native species. 16: 235-247, 2012 ditionally, lotic systems are geographically expansive and can be influenced by multiple alterations and disturbances at the same time, which makes determining the primary causes for species decline and loss difficult (McCartney 2002). KEY WORDS: Fundulus sciadicus · Plains topminnow · Fundulidae · Endemic · Decline · Threat Resale or republication not permitted without written consent of the publisher Contribution to the Theme Section 'Endangered river fish: threats and conservation options' OPEN PEN ACCESS CCESSEndang Species ResThe plains topminnow Fundulus sciadicus is en demic to the central United States (Fig. 1) with 2 disjunct populations (Lee et al. 1980). The largest distribution is centered in Nebraska and extends to north eastern Colorado, southwestern Wyoming, southern South Dakota, southwestern Minnesota and Iowa (Baxter & Stone 1995, Weitzel 2002, Rahel & Thel 2004. The second population is centered in Missouri and ex tends from Kansas south to Oklahoma (Pflieger 1997) (Fig. 2). The plains topminnow is currently ranked as globally secure according to the Natural Heritage database (NatureServe 2011). However, all states in the native range, except Oklahoma, recognize some level of concern for plains topminnow. In Iowa and Kansas, plains topminnow is presumed extirpated (Harlan et al...
The plains topminnow Fundulus sciadicus appears to be experiencing reductions in geographic range and local abundance, which has led to regional protection throughout its native range. Conservation of this species may require introductions to reestablish populations at known historic locations. Therefore, a pond was constructed during September 2007 to house a refuge population of plains topminnow in Nebraska. A total of 123 plains topminnow were stocked into the pond in two stocking events during 2008. Plains topminnow populations were sampled throughout 2008 and mark-recapture population estimates were conducted after reproductive events during 2009 and 2010 resulting in estimates of 9,844 ± 1,698 (mean ± SD) and 3,974 ± 452 plains topminnow, respectively. Mean fish weight was used as an estimate of pond biomass, which was 28.4 kg/ha in 2009 and 44.9 kg/ha in 2010. Reproduction was first observed in 2008 and in each following year, and a strong year-class was produced in 2009, which suggested there were factors that limited reproduction in the other 2 years. Extensive culture may be an effective way to rear plains topminnow and related species. However, more research is needed to determine factors that affect year-class strength and production.
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