Length-weight relationshipsof fishes from tributaries of the Ebro River, Spain

Department of Zoology and Ecology, University of Navarra, Pamplona, Navarra, SpainIntroductionIn this study the parameters of the length–weight relationships(LWR) are reported for 12 freshwater fish species collectedfrom seven tributaries of the Ebro River (Spain). Three of thespecies are endemic to the Iberian Peninsula (Chondrostomamiegii, Barbus graellsii and Barbus haasi) whilst Alburnusalburnus, Rutilus rutilus, Silurus glanis, Cyprinus carpio andMicropterus salmoides are exotic introductions (Doadrio,2001). Until recently, the Iberian populations of gudgeon wereconsidered to be descendents of introduced populations ofGobio gobio (Linnaeus, 1758). However, recent studies (Do-adrio and Madeira, 2004) have assigned the Iberian andsouthern French populations of gudgeon to a new species,Gobio lozanoi, based on genetic and morphological characters.Material and methodsThe ichthyofauna was sampled by electrofishing during 2004and 2005. The sampling sites are distributed in three sub-basins of the Ebro River in Huesca Province (Spain). TheAtares River drains into the Arago´n River and was sampled inMay 2004. During June and August 2004 we surveyed theCaldares, Asabo´n, Susi´a and Irues rivers, from which the firsttwo drain into the Ga´llego River whilst the others drain intothe upper Cinca River. These specimens were identified andthen measured to the nearest 0.1 cm (total length, TL) andweighed in the field with a digital balance to an accuracy of0.01 g (total weight, W). The middle and lower Cinca Riverwere sampled in November 2004 whilst the middle Ga´llego wassurveyed in September 2005; collected specimens were trans-ported on ice, but not frozen, to the laboratory for identifi-cation, measuring and weighing.The LWR for the total body weight was calculated using theequation:W ¼ a TL