Fatty Acid Profiles Distinguish Channel Catfish from Three Reaches of the Lower Kaskaskia River and its Floodplain Lakes

Abstract

Running Title: Fatty acid biomarkers in riverine channel catfish KEY WORDS: fatty acids, catfish, Ictalurus punctatus, floodplain lakes, food webs 2 ABSTRACT Despite the increasing use of fatty acids (FAs) as biomarkers in aquatic food web analysis, little information is available regarding differences in FA profiles of fish among habitat types in riverfloodplain ecosystems. The objectives of this study were to 1) test whether the FA profiles of channel catfish (Ictalurus punctatus) differed among three reaches of the lower Kaskaskia River and its floodplain lakes, and 2) to compare FA profiles among muscle, liver, and adipose fin tissues collected from these fish. Profiles differed significantly among sites, especially between upper and lower river sites, and between river channel and oxbow lake sites, suggesting differences in FA availability for channel catfish occupying different habitats and river reaches in the Kaskaskia River system. Specifically, the essential FAs 18:2n-6 and 18:3n-3 increased in catfish tissues from upstream to downstream reaches, which could reflect increased floodplain connectivity and decreasing impoundment effects downstream. Ratios of n-3 to n-6 FAs were higher in fish from oxbow lakes, perhaps suggesting increased use of autochthonous production in the floodplain relative to the main river channel. Muscle and adipose fin FA profiles exhibited similar location-related trends, whereas liver FA profiles were markedly different from the other tissue types. These results suggest that adipose fin tissue samples may be a viable, less-invasive alternative to muscle tissue for analysis of FA profiles in channel catfish. Our study supports the use of tissue FA profiles in identifying habitat utilization by channel catfish, and perhaps habitatspecific energy contributions to riverine consumers. Furthermore, our work highlights floodplain habitat as a potential source of essential n-3 FA and the associated importance of maintaining river-floodplain connectivity to support aquatic food webs.

Polyunsaturated fatty acids in stream food webs – high dissimilarity among producers and consumers

“…DHA is selectively and highly retained over other PUFA in fish, consistent with all reviewed datasets. It is still not clear if the high retention of DHA in fish is mainly driven by dietary DHA (Dayhuff, ; Rude et al., ; Young et al., ) or by endogenous PUFA conversion (Henrotte et al., ; Hixson et al., ; Murray et al., ; Oboh, Betancor, Tocher, & Monroig, ; Tocher & Dick, ). Our results showed that DHA retention in fishes from subtropical rivers is greater than that from temperate rivers, suggesting fishes may spend extra energy to synthesise LC‐PUFA under high temperature leading to more energy loss (Farkas, Csengeri, Majoros, & Oláh, ).…”

“…Algal PUFA variations induced by river longitudinal gradients significantly affected fish PUFA composition (Dayhuff, ; Rude et al., ; Young et al., ). Interacted with light availability, nutrient inputs and temperature, river longitudinal gradients also determine fish distribution (Buisson, Blanc, & Grenouillet, ).…”

“…PUFA retention ratios between consumers (fish and invertebrates) and algae were calculated by dividing consumer PUFA% by algal PUFA% (i. (Dayhuff, 2004;Rude et al, 2016;Young et al, 2016) or by endogenous PUFA conversion (Henrotte et al, 2011;Hixson et al, 2014;Murray et al, 2014;Oboh, Betancor, Tocher, & Monroig, 2016;Tocher & Dick, 1999). Our results showed that DHA retention in fishes from subtropical rivers is greater than that from temperate rivers, suggesting fishes may spend extra energy to synthesise LC-PUFA under high temperature leading to more energy loss (Farkas, Csengeri, Majoros, & Ol ah, 1980).…”

“…EPA and ARA) (Niebylski & Salem Jr, 1994), even at very low temperatures (Stillwell & Wassall, 2003). (Dayhuff, 2004;Rude et al, 2016;Young et al, 2016). Interacted with light availability, nutrient inputs and temperature, river longitudinal gradients also determine fish distribution (Buisson, Blanc, & Grenouillet, 2008 Bunn, Davies, & Winning, 2003;Delong & Thorp, 2006;Lau, Leung, & Dudgeon, 2009).…”

“…In addition, LC-PUFA retention in some consumers is strongly affected by environmental changes. For example, LC-PUFA retention in stream invertebrates was less in river sections with greater water temperature (Gladyshev et al, 2016), and varied in channel catfish, carp and bluegill with longitudinal locations from upstream to downstream of rivers (Dayhuff, 2004;Rude, Trushenski, & Whitledge, 2016;Young, Whitledge, & Trushenski, 2016). It is important to determine which physiological factors cause the differences in LC-PUFA retention among fish and invertebrates to improve our understanding of trophic PUFA dynamics and production in stream ecosystems.…”