Applicability of gill raker filtrates and foregut contents in the diet assessment of filter-feeding Asian carps

Abstract

Reliable estimation of the diet composition of filter-feeding Asian carps is essential to evaluate their effects on ecosystem functioning. In previous studies, the diet composition of these fishes was primarily determined based on the analysis of foregut contents. To assess the reliability of foregut content analysis in diet assessments, these were compared with gill raker filtrate analyses. Gill raker filtrates were found to be more reliable than foregut contents for determining food composition due to higher amounts of sample, significantly higher numbers of identifiable taxa (including both phytoplankton and zooplankton), and considerably higher numbers of intact planktonic individuals. The present findings indicate that diet composition analyses based on foregut samples alone are likely to underestimate the number of individuals and the biomass of planktonic species which are less resistant to digestive processes.

Relationship between gill raker morphology and feeding habits of hybrid bigheaded carps (Hypophthalmichthysspp.)

“…Filtrate samples were collected with a flat stick directly from the inner grooves of the gill rakers, where the filtered material is compressed before ingestion. Further information on the methods of filtrate sample collection can be found in the study of Vitál et al, (2015). This study has demonstrated that filtrate samples are more appropriate for the determination of food composition of bigheaded carps, compared to foregut samples.…”

Trophic Patterns of Bighead Carp and Silver Carp Follow the Seasonality of Resource Availability

“…Foregut contents were collected immediately and fixed in Lugol's iodine for a few minutes and then preserved with 10% formaldehyde solution for further identification. Foregut contents [14] and gill raker filtrates [32] are two methods for microscopic identification of diet assessment, but the foregut content is used in this study as it is more general method and has been applied by our research team consistently [14,19,20,33]. The phytoplankton for stable isotopic analyses was collected from filter lake water samples on glass fiber filters (Waterman GF/C, New York, NY, USA), and we removed the zooplankton and particulates under a microscope, and then collected these on glass fiber filters (Waterman GF/C) and rinsed them with 0.01N HC1 and distilled water [34].…”