A simple approach for assigning the conservation status of freshwater fish based on their natural variability – a case study from the Iberian Ecoregion

Abstract

A simple, non‐lethal method for assigning conservation status is proposed based on three conservation classes (favourable, unfavourable/inadequate and unfavourable/bad) to fish species based on their natural population variability. To demonstrate this approach, conservation classes were allocated to three native fish species (brown trout Salmo trutta L., northern Iberian chub Squalius carolitertii (Doadrio), and northern straight‐mouth nase, Pseudochondrostoma duriense (Coelho) based on basic population variables (density and biomass) using a 9‐year dataset (2004–2012) from 15 different sampling sites in Spain. The classification of the population variables into conservation classes was made using previously described nonparametric methods and percentiles categorisation, and the current conservation status of the studied species was established. Temporal trend analyses showed that S. carolitertii experienced a progressive significant decrease during the study period, whereas both S. trutta and P. duriense exhibited weak increases in density. The study exemplifies the need to quantify the natural variability of fish resources to reveal their current conservation status and to determine whether short‐term and long‐term management actions are needed to rehabilitate native fish assemblages. The proposed approach could easily be employed by fisheries managers to monitor the conservational status of other native species.

Beyond ecological opportunity: Prey diversity rather than abundance shapes predator niche variation

“…Araújo et al., 2011; Costa‐Pereira, Tavares, Camargo, & Araújo, 2017). Some sampling events included high consumer densities (range: 0.01–0.47 and 0–0.65 ind./m 2 for brown trout and Atlantic salmon, respectively) according to a previous categorisation of salmonids densities (Sánchez‐Hernández, Cobo, & Amundsen, 2015). However, it is possible that prey densities were not low enough (range: 43.9–4,351.7 ind./m 2 ) to limit food consumption in comparison to other riverine systems with substantially higher variation in benthic macroinvertebrate production (e.g.…”

Densities and biomass of larval sea lamprey populations (Petromyzon marinus Linnaeus, 1758) in north-western Spain and data comparisons with other European regions

“…An evaluation of the conservation status of fish or lamprey species requires knowledge on temporal changes in population density and biomass and a comparison with established reference condition categories (Cowx et al 2009;Sánchez-Hernández et al 2015). Values of density and biomass of P. marinus larvae recorded in the accessible sections of Galician rivers, in general, changed from moderate to high (reference categories from Silva et al 2014b), showing signs of an upward trend in population.…”

Population variability in species can be deduced from opportunistic citizen science records: a case study using British butterflies

“…Inferring abundance change from distribution data Many species are declining or facing range retractions (Hayhow et al, 2016), and it is important to monitor their population trends. Species with highly variable population dynamics tend to be at high risk of extinction (Pimm et al, 1998;Vucetich et al, 2000;Oliver et al, 2012) and thus our measure of variability in distribution records has ecological value, with the potential to assist conservation assessments by helping to identify species at risk of extinction or habitats in need of management (Meyer et al, 2015;S anchez-Hern andez et al, 2015). Our multispecies analysis (Fig.…”