Body-size Relations and Mouth Dimensions of Fresh and Preserved Freshwater Fish

The relations between fish total (TL) fork (FL) and standard (SL) lengths, between TL and maximum height (H-max) and horizontal (HMO) and vertical (VMO) mouth openings and mouth area (MA) of four freshwater fish species (Alburnoides thessalicus, Barbus strumicae, B. balcanicus and Squalius vardarunsis) are estimated for several rivers of northern Greece. The same relations for B. strumicae and S. vardarunsis are also provided based on preserved samples deposited in the fish collection of the Laboratory of Ichthyology (School of Biology, Aristotle University of Thessaloniki). The relations between different lengths are all linear. The relations between HMO - TL and VMO - TL are either linear or exponential depending on the species and on the water system, while MA is exponentially related to IL for all studied species. Mouth area (MA) increases faster with TL, for S. vardarunsis, which has a higher trophic level than for B. balcanicus and B. strumicae. Differences are also found for the slope (parameter b) of the above relations between fresh and preserved samples and between the same species from different river systems. Such relations are important for defining the ecological position of each species in the food web and, thus, are used in ecosystem-based models.