Fish-habitat relationships and fish conservation in small coastal streams in southern Spain

Abstract

ABSTRACT1. Studies dealing with the fish fauna of coastal streams are scarce in the scientific literature, particularly those from Mediterranean climates. Owing to their small size, these systems suffer extreme seasonal fluctuations, following the typical Mediterranean flood-drought cycle and leading to a high risk of extinction to freshwater fish.2. This work analyses fish distribution in 14 stream stretches belonging to eight basins in the northern sector of the Strait of Gibraltar (southern Spain). Fish-habitat relationships were studied through multivariate ordination techniques at two scales: basin and stretch.3. A principal components analysis clearly discriminated larger and more sinuous basins from smaller and steeper ones. This ordination was related to the non-migratory freshwater fish species richness and to the total number of fish species present in the middle reaches of each basin.4. The main sources of variation in community composition and habitat characteristics in the different stretches were related to a clear upstream-downstream gradient, along which total species richness increased. 5. These small coastal basins are inhabited by two highly endangered species, Andalusian toothcarp (Aphanius baeticus) and Iberian chub (Squalius pyrenaicus), and have similar or higher overall freshwater species richness than larger adjacent basins. The near absences of flow regulation and introduced species make these streams one of the few types of Iberian aquatic system where unaltered fish-habitat relationships can be studied.

Distribution patterns of fish assemblages in an Eastern Mediterranean intermittent river

“…In this, the current study conforms also with some studies conducted in other Mediterranean streams, mostly in Iberia (see Vila-Gispert et al, 2002;Clavero et al, 2005). Clavero et al (2005) examining fish distribution in 14 coastal stream stretches of Southern Spain indicated that the main sources of variation in fish community composition and habitat characteristics in the different stretches were related to a clear upstream-downstream gradient, along which total species richness increased.…”

“…Traditionally, fish assemblages in temperate streams and rivers have indicated a predictable longitudinal change in species composition, associated with specific lotic conditions (Schlosser, 1982;Moyle and Vonderacek, 1985;Lobb and Orth, 1991). Despite the worldwide application of this ichthyofaunal typology, few river zonation studies have been conducted in Mediterranean streams and rivers (Carmona et al, 1999;Vila-Gilspert et al, 2002;Clavero et al, 2005;Franchi et al, 2014), which are characterized by a lack of sentinel fish species, such as trout, grayling and bream, typically widespread in temperate rivers. Mediterranean streams are often characterized by a depauperate native fish fauna (despite the high freshwater fish biodiversity of the Mediterranean region), by assemblage structures dominated by range-restricted endemic species -often with wide niche-breadths-, by high temporal and spatial fish assemblage variability, due to frequent hydrological instability and by non-longitudinal species' distribution patterns often complicated by extensive anthropogenic modifications impacting rivers under high water stress (Ferreira et al, 2007).…”

Addressing longitudinal connectivity in the systematic conservation planning of fresh waters

“…Since biological communities change gradually through natural upstreamdownstream gradients in rivers (Allan, 1995;Welborn, Skelly & Werner, 1996;Clavero, Blanco-Garrido & Prenda, 2005) spatial connectivity is better addressed through continuous probabilities rather than through presence-absence data. It also allows the interpretation of the reserve in terms of a trade-off between river length and probability of occurrence.…”

Seasonal use of coastal resources by otters: Comparing sandy and rocky stretches

“…The category coastal included both pure marine prey as well as estuarine ones. A certain prey type was considered coastal when it occurred in saltwater and was never located in the upper stretches of the studied streams during any of the fish surveys performed in the area (Clavero et al, 2005). Some prey types that were occasionally caught in medium stretches, as sandsmelts (Atherina boyeri) or eels (Anguilla anguilla), were not classified in any of the two categories, even though they were much more abundant in the coastal area.…”