e determined regression relat ionships between head bone lengths and body size (standard length and weight) in chub Leuciscus cephalus and Eurasian perch Perca fluviatilis, two species taken frequently by the otter in the River Lee catchment. All relationships yielded significant linear equations, whereas those for bone vs. body weight were logarithmic. Regression slopes for head bones do not differ greatly within species but do across species of the same family.
Relationships between bone size and body length are reported for common Iberian barbel Barbus graellsii, Iberian nase Chondrostoma miegii and chub Leuciscus cephalus from the Ebro River basin. Linear regression was used to analyse possible relationships between bone and fish length and multiplicative regression to investigate relationships between bone size and body weight. All generated regressions were highly significant and displayed high coefficients of determination (> 0.89). No differences were found between the generated regressions and other relationships reported for similar species. Therefore, we suggest that our regressions might be used for other Mediterranean species belonging to these genera.