Potential of Ichthyological Collections for the Study of Trophic Ecology of Native Freshwater Fish Species ^†

Abstract

Our objective is to assess the potential of ichthyological material from scientific collections for contemporary trophic studies by determining whether stomach contents of freshwater fish preserved in museum collections are well conserved and therefore comparable to those of present-day specimens. Specifically, we examined whether stomach contents from four native species—Squalius alburnoides, Iberochondrostoma lemmingii, Pseudochondrostoma willkommii, and Anaecypris hispanica—housed in the Museo Nacional de Ciencias Naturales (MNCN, CSIC) are suitable for quantitative dietary analyses. Museum specimens were collected in the Guadiana and Guadalquivir basins during spring–summer prior to 1980. Contemporary specimens were captured by electrofishing during spring–summer 2025 in the Bembézar River (Guadalquivir basin). Stomach content from the anterior third of the stomach was identified under a stereomicroscope, and all prey items were categorized. To analyze diet composition and characterize interspecific trophic structure, we assessed multivariate homogeneity of dispersion (PERMDISP) and performed permutational multivariate analyses of variance (PERMANOVA) based on Bray–Curtis distances. SIMPER analyses were used to identify the dietary items contributing most to dissimilarities between historical and contemporary samples for each species. Potential preservation-related biases were further evaluated by comparing the frequency of larval prey categories in museum specimens versus contemporary specimens. Our results indicate: (i) the overall suitability of museum specimens for dietary studies in all species examined; (ii) no evidence of a systematic loss of larval prey items in collection material, suggesting the absence of a generalized degradation bias; (iii) significant dietary differences between contemporary (2025) specimens and historical specimens (pre-1980), which in P. willkommii and I. lemmingii may be attributable to data dispersion, whereas in S. alburnoides these differences may reflect changes in trophic ecology, potentially associated with the introduction of invasive exotic species; and (iv) no significant differences in diet between historical and contemporary specimens of Anaecypris hispanica.