Longitudinal patterns in flathead catfish relative abundance and length at age within a large river: effects of an urban gradient

Abstract

We investigated the spatial variation of flathead catfish (Pylodictis olivaris) relative abundance and growth in the 274 km long Kansas River to determine if population dynamics of catfish are related to urbanization. Electrofishing was conducted at 462 random sites throughout the river in summer, [2005][2006] to collect fish. Relative abundance of age 1 fish ( 200 mm), subadult (>200-400 mm) and adult fish (>400 mm) ranged from 0.34 to 14.67 fish h À1, mean length at age 1 was 165 (range: 128-195) mm total length (TL) and mean length at age 3 was 376 mm TL (range: 293-419 mm TL). The proportion of land use within 200 m of the river edge was between 0 and 0.54 urban. River reaches with high relative abundance of age 1 flathead catfish had high relative abundance of subadult and adult catfish. River reaches with fast flathead catfish growth to age 1 had fast growth to age 3. High urban land use and riprap in the riparian area were evident in river reaches near the heavily populated Kansas City and Topeka, Kansas, USA. Reaches with increased number of log jams and islands had decreased riparian agriculture. Areas of low urbanization had faster flathead catfish growth (r ¼ 0.67, p ¼ 0.005). Relative abundance of flathead catfish was higher in more agricultural areas (r ¼ À0.57, p ¼ 0.02). Changes in land use in riverine environments may alter population dynamics of a fish species within a river. Spatial differences in population dynamics need to be considered when evaluating riverine fish populations. Published in

Urbanization in a great plains river: Effects on fishes and food webs

“…Instream and riparian habitat differed throughout the river changing from a heterogeneous instream habitat areas to areas dominated by an urban riparian zone with homogeneous instream habitat. This corresponded to urban areas that were deeper and had fewer braided channels and islands, which is consistent with Paukert and Makinster (2009) who documented more variable habitat with areas of islands, log jams, rip rap and more channels in the heterogeneous reach of the Kansas River. The reduction of instream habitat in urban areas of the river indicates homogenization of these habitats (Lenat and Crawford, 1994;Yoder et al, 1999;Paukert and Makinster, 2009).…”

“…This corresponded to urban areas that were deeper and had fewer braided channels and islands, which is consistent with Paukert and Makinster (2009) who documented more variable habitat with areas of islands, log jams, rip rap and more channels in the heterogeneous reach of the Kansas River. The reduction of instream habitat in urban areas of the river indicates homogenization of these habitats (Lenat and Crawford, 1994;Yoder et al, 1999;Paukert and Makinster, 2009). Table I, and the numbers associated with each species represents the low urbanized (1) reach, the intermediate (2) Higher enrichment of 15N may occur with high nitrogen loading in streams from agriculture (e.g.…”

“…The river is a shallow (typically < 1.5 m) sand bed river with many shallow side channels, and sandy islands usually overgrown with willows and grasses (Eitzmann and Paukert, in press) particularly in upriver reaches. Mean depth is typically < 1.5 m throughout the river most of the year (Paukert and Makinster, 2009).…”

“…In the Illinois River Karr et al (1985) found all feeding guilds had declining abundance of species (except for omnivores) and related this to habitat modifications due to urbanization. Also, growth of flathead catfish Pylodictis olivaris was slower in areas with less instream habitat diversity and increased urbanization, which suggests less food available or an increase in intraspecific competition in these areas (Paukert and Makinster, 2009).…”

Response of endemicClariasspecies’ life-history biometrics to land use around the papyrus-dominated Mpologoma riverine wetland, Uganda

“…However, knowledge of the ecology of the small catfishes Clarias alluaudi (Boulenger, 1906) and C. liocephalus (Boulenger, 1898) is still limited. Some research has shown that fish assemblage structure is altered by land uses such as agriculture, but fewer studies have focused on population-level biometrics which include length, weight and condition of individual fish species (Paukert and Makinster 2009). Some studies have also demonstrated the relationship between fish assemblage and habitat structure (Kadye and Moyo 2007).…”