Modelling critical factors affecting the distribution of the vulnerable endemic Eastern Iberian barbel (Luciobarbus guiraonis) in Mediterranean rivers

Abstract

Luciobarbus guiraonis (Eastern Iberian barbel) is an endemic fish species restricted to Spain, mainly distributed in the Júcar River Basin District. Its study is important because there is little knowledge about its biology and ecology. To improve the knowledge about the species distribution and habitat requirements, nonlinear modelling was carried out to predict the presence/absence and density of the Eastern Iberian barbel, based on 155 sampling sites distributed throughout the Júcar River Basin District (Eastern Iberian Peninsula). We used multilayer feed-forward artificial neural networks (ANN) to represent nonlinear relationships between L. guiraonis descriptors and variables regarding the physical habitat and biological components (macroinvertebrates, fish, riparian forest). The gradient descent algorithm was implemented to find the optimal model parameters; the importance of the ANN’s input variables was determined by the partial derivatives method. The predictive power of the model was evaluated with the Cohen’s kappa (k), the correctly classified instances (CCI), and the area under the curve (AUC) of the receiver operator characteristic (ROC) plots. The best model predicted presence/absence with a high performance (k= 0.66, CCI= 87% and AUC= 0.85); the prediction of density was moderate (CCI = 62%, AUC=0.71 and k= 0.43). The fundamental variables describing the presence/absence were; solar radiation (the highest contribution was observed between 2000 and 4200 WH/m2), drainage area (with the strongest influence between 3000 and 5.000 km2), and the proportion of exotic fish species (with relevant contribution between 50 and 100%). In the density model, the most important variables were the coefficient of variation of mean annual flows (relative importance of 50.5%) and the proportion of exotic fish species (24.4%). The models provide important information about the relation of L. guiraonis with biotic and abiotic variables, this new knowledge can help develop future studies and management plans for the conservation of this species in the Júcar River Basin District and, potentially, for the conservation of other endemic fish species of Barbus and Luciobarbus in Mediterranean rivers.

Fish community responses to antecedent hydrological conditions based on long-term data in Mediterranean river basins (Iberian Peninsula)

“…Conceivably, other factors such as hydromorphology, water chemistry, biogeographical region, river size, or inhomogeneity between surveys could mask some existing relationships between antecedent hydrologic conditions and response of fish community. For instance, previous studies in the JRBD indicated that the distance between smaller barriers control native species richness (Olaya-Marín et al, 2012) while the density of the Eastern Iberian barbel (L. guiraonis) was related to the flow variability, proportion of alien fish species and flow minima (Olaya-Marín et al, 2016).…”

“…Mediterranean fish communities are known for their high endemicity and the predominance of Cyprinids, which possess high specific diversity and show morpho-functional and physiological adaptations to fluctuating environments (Granado-Lorencio, 2000, 1996. For instance, the presence of the endemic Eastern Iberian barbel (Luciobarbus guiraonis) as well as the native fish richness have been negatively related with the percentage of alien species, smaller distance between barriers and the reduction of the mean annual flow (Olaya-Marín et al, 2016). The Iberian Peninsula is climatologically and hydro-geomorphologically heterogeneous (Benito-Calvo et al, 2009).…”

“…It is well recognized that the distribution and abundance of fishes are strongly influenced by flow velocity, resources' availability, and thermal regime, all of which are under hydrological influence (White et al, 2018). In addition to flow regimes, a variety of interacting factors such as competition for space, predation (Olaya-Marín et al, 2016) and biological stochasticity are known to naturally affect fish abundance and distribution. Hence, a suite of other biotic and abiotic factors not related to hydrology can also influence the composition of freshwater fish assemblages (Jackson et al, 2001).…”

Diferencias en el tamaño corporal y la abundancia de peces altoandinos, arriba y abajo de la represa Neusa, Colombia

“…Igualmente, en la condición alterada disminuyó la magnitud, frecuencia y duración de las pequeñas y grandes crecidas, efectos característicos de la regulación de caudales por los embalses (Rolls & Bond, 2017). Al respecto, se ha demostrado que los pulsos de caudales altos son determinantes para el mantenimiento del hábitat físico de las comunidades acuáticas (Magilligan & Nislow, 2005), ya que crean y mantienen los hábitats del cauce y de la llanura de inundación (Bond et al, 2015), incluidos los remansos y rápidos necesarios para el ciclo de vida de los peces (Olaya-Marín et al, 2015).…”

Determination of environmental flows in rivers using an integrated hydrological-hydrodynamic-habitat modelling approach

“…In Mediterranean rivers, various forms of pressure, including alteration of the flow regime, resulted in the decline of fish population and in some cases in the extinction of native species (Smith and Darwall, 2006). Moreover, various characteristics of the flow regime, such as the minimum monthly flow during spawning, exerted a strong effect on the patterns of presence-absence and population densities of extended fish species, such as the Eastern Iberian Barbel (Luciobarbus guiraonis) (Olaya-Marín et al, 2016).…”