Fish Assemblages in Streams Subject to Anthropogenic Disturbances Along The Natchez Trace Parkway, Mississippi, USA

Abstract

A three-year study (July 2000 – June 2003) of fish assemblages was conducted in four tributaries of the Big Black River: Big Bywy, Little Bywy, Middle Bywy and McCurtain creeks that cross the Natchez Trace Parkway, Choctaw County, Mississippi, USA. Little Bywy and Middle Bywy creeks were within watersheds influenced by the lignite mining. Big Bywy and Middle Bywy creeks were historically impacted by channelisation. McCurtain Creek was chosen as a reference (control) stream. Fish were collected using a portable backpack electrofishing unit (Smith-Root Inc., Washington, USA). Insectivorous fish dominated all of the streams. There were no pronounced differences in relative abundances of fishes among the streams (P > 0.05) but fish assemblages fluctuated seasonally. Although there were some differences among streams with regard to individual species, channelisation and lignite mining had no discernable adverse effects on functional components of fish assemblages suggesting that fishes in these systems are euryceous fluvial generalist species adapted to the variable environments of small stream ecosystems.

Kajian terhadap komuniti ikan telah dijalankan selama tiga tahun (Julai 2000 – Jun 2003) di empat batang anak sungai iaitu Sungai Big Bywy, Little Bywy, Middle Bywy dan McCurtain. Sungai-sungai ini terletak di sepanjang Natchez Trace Parkway, di daerah Choctaw Mississippi, USA dan merupakan anak sungai kepada sungai Big Black. Perlombongan lignit dijangka memberikan kesan negatif kepada kualiti air sungai Little Bywy dan Middle Bywy manakala Sungai Big Bywy didapati mempunyai sejarah dalam pelurusan sungai. Sungai McCurtain dipilih sebagai sungai rujukan. Ikan disampel menggunakan unit electrofishing mudah-alih (Smith-Root Inc., Washington, USA). Secara relatifnya, kelimpahan ikan tidak menunjukkan perbezaan yang ketara antara kesemua anak sungai (P > 0.05), namun kelimpahan ikan pada setiap musim adalah berbeza. Ikan jenis insektivor didapati mendominasikan kesemua anak sungai yang dikaji. Walaupun hasil kajian menunjukkan terdapat perbezaan dari segi struktur spesies, tetapi perlurusan sungai dan perlombongan lignit tidak menunjukkan kesan negatif terhadap komponen fungsi komuniti ikan ini. Ini menujukkan spesies ikan di sungai tersebut bersifat euryceous fluvial generalist yang mampu beradaptasi dengan ekosistem anak sungai yang pelbagai.