Salinity as the main factor structuring small-bodied fish assemblages in hydrologically altered Mediterranean coastal lagoons

Abstract

SUMMARY: In the Ebro Delta coastal lagoons, one of the main anthropogenic pressures is the artificial freshwater input. Each coastal lagoon has different water management schemes causing profound changes in its physicochemical characteristics. The main objective of this water management is to favour some bird species with interest either for conservation or hunting activities. The present study assesses the influence of hydrological alteration on the fish assemblages of three coastal lagoons in the Ebro Delta. The small-bodied fish fauna was mainly composed of five families: Gobiidae, Poecilidae, Cyprinodontidae, Atherinidae and Mugilidae. Salinity was found to be the main factor structuring fish community in the lagoons. The dominant species was the common goby (Pomatochistus microps) when the lagoons reached higher salinity values, whereas the invasive eastern mosquitofish (Gambusia holbrooki) dominated during the period of higher freshwater inputs. The juveniles of the family Mugilidae showed low catch per unit effort, especially during the period of lower salinity. This same pattern was found for the endangered Spanish toothcarp (Aphanius iberus). Overall, introduced species were favoured by low salinity, which highlights the importance of changing the present water management by reducing the freshwater inputs in order to maintain suitable levels of salinity to favour native species that are important for both commercial and conservation purposes.

Integrated ecological assessment and restoration planning in a heavily modified peri-urban Mediterranean lagoon

“…7b). Since the mosquitofish is a freshwater fish, albeit quite tolerant to polluted a slightly brackish waters, its population has increased with the site's decrease in salinity, a phenomenon that has been observed in other Mediterranean lagoons (Rodríguez-Climent et al 2013). …”

Structure and diversity of fishes in a freshwater and coastal subtropical lagoon

“…*Author to whom correspondence should be addressed: Tel. : +55 048 96730411; email: nicollefer@gmail.com The heterogeneity of morphometric and geomorphological dynamics of coastal lagoons creates different ecological gradients and microhabitats, which support both local and landscape biodiversity (Esteves et al, 2008).The structure and composition of the fish assemblages within coastal lagoons rely heavily on the balance between marine and freshwater inputs (Rodriguez-Climent et al, 2013). Likewise, fish assemblages can also be characterized according to the water characteristics or type of substratum (Pérez-Ruzafa et al, 2011).…”

Environmental Flow Requirements of Estuaries: Providing Resilience to Current and Future Climate and Direct Anthropogenic Changes

“…Altered salinity can create barriers to the movement of organisms, removing access to important habitat and resources (Romañach et al, 2019;Santos et al, 2019) and can shift the distribution of species, causing it to contract or fragment (Alber, 2002;Park et al, 2014;Lauchlan and Nagelkerken, 2020). This can affect population dynamics by increasing the intensity of competition when distributions overlap (Shih et al, 2011) or by promoting the expansion of invasive or dominant species (Shih et al, 2011;Rodríguez-Climent et al, 2013). In some cases, prolongation of these impacts can lead to local extinctions (Nicol et al, 2018).…”