Individual study: Translocation of a freshwater fish, the fringed darter Etheostoma crossopterum, to a tributary of the Cache River, Illinois, USA
Poly W.J. (2003) Design and evaluation of a translocation strategy for the fringed darter (Etheostoma crossopterum) in Illinois. Biological Conservation, 113, 13-22
Captive breeding and reintroduction programmes are often pursued to create new, and maintain or bolster dwindling populations of uncommon or endangered species. In this study, a satellite population of the fringed darter Etheostoma crossopterum, a locally distributed fish confined to rocky streams in the states of Alabama, Tennessee, Kentucky and Illinois (USA) was established in a tributary of Cache River as a conservation measure.
Darter collection: On 25 March 2001, adult fringed darters Etheostoma crossopterum were collected with a seine net from Mill Creek (37°22'02”/89°14'55”; Miller road, 7 km W Dongola) and an unnamed tributary of Big Creek (37°21'53”/89°09'48”; old U.S. Rt. 51 bridge, Dongola) where the species was abundant. Captured darters were held in aerated coolers.
Darter releases: Darters were allowed to acclimate for 30 min in a mixture of water from the capture and release sites before being released into the stream (a tributary of the Cache River at U.S. Rt. 51 bridge, 3.5 km SSE of Cobden). Sixty darters were released: 13 males and 27 females from Mill Creek; and 7 males and 13 females from the unnamed tributary of Big Creek. Release was female biased because males can spawn with more than one female. The late March 2001 release coincided with the start of the two month breeding season.
Darter breeding: Visual searches for nesting males were made on six dates between 28 March and 27 May 2001 over 100 m of stream around the introduction site. In 2002, nest searches were made on five dates between 14 March and 15 May. During searches, rocks were also gently tilted to look for fish and eggs. When a nest was located, the number of males and females present was recorded, and in 2001 the egg clusters were photographed.
Darter censuses: A 3.0 x 1.8 m seine net was used to census a 150 m section of the stream on 14 October 2000, 15-16 September 2001 and 9-10 September 2002. All captured individuals were held in a cooler to prevent re-captures while a section was sampled, distinguished as adults or juveniles (from that year) by size, and returned to the stream after the census.
Darter breeding: Fringed darters bred increasingly successfully over the experimental period. Between March and May 2001, 1,424 rocks were examined and eleven nests were located containing a total of 4,216 eggs. This had increased to 44 nests located on 1,449 rocks examined between March and May 2002 (no egg counts were made).
Darter censuses: The population structure shifted over the study. In 2001, 107 juveniles and six adults were captured, which changed to 25 juveniles and 79 adults in 2002.
Conclusions: The introduction of fringed darters to the tributary of Cache River at the start of their breeding season appears to have been a successful strategy: nesting and autumn adults increased in numbers over the two years. Consequently, the authors suggest that this translocation protocol might be applicable to endangered species such as Barrens Etheostoma forbesi, relict E. chienense, and duskytail darters E. percnurum.
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