Individual study: Translocation of a freshwater fish, the fringed darter Etheostoma crossopterum, Bradshaw Creek, 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 as a conservation measure.
Darter collection: On 25 March 2001, adult fringed darter fish Etheostoma crossopterum were collected using a seine net from Mill Creek (37°22'02”/89°14'55”; Miller road, 7 km west of 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 release: Darters were allowed to acclimatise for 30 min in a mixture of water from the capture and release site before being released into Bradshaw Creek upstream of Winghill Road (9 km eat of Cobhen, Union County). Sixty darters were released: 13 males and 27 females from Mill Creek; and seven males and 13 females from a 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, 2,256 rocks were examined and a total of fourteen nests were located, with 4,498 eggs. This increased dramatically to 124 nests located under 3,050 rocks examined between March and May 2002 (no egg counts were made).
Darter censuses: Recruitment increased over the study. In 2001, 46 juveniles and two adults were captured, which rose to 115 juveniles and 28 adults in 2002.
Conclusions: The introduction of fringed darters to Bradshaw Creek at the start of their breeding season appears to have been a successful strategy: nesting and numbers of first autumn juveniles increased 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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