Ecomorphological analysis as a complementary tool to detect changes in fish communities following major perturbations in two South African estuarine systems

Abstract

Ecomorphological changes as a result of natural perturbations in estuarine fish communities were investigated in two South African estuaries (Swartvlei and East Kleinemonde), both before and after the loss of aquatic macrophyte beds in these systems. The fish communities were analysed using an ecomorphological diversity index (EMI) and the results compared to a traditional index, the ShannonWiener diversity index. The EMI revealed that the major changes in fish community composition recorded in both estuaries were associated with quantitative variations at the species level. Both estuaries essentially lost their macrophyte beds and ended up with the same type of bottom habitat (bare sediment). In both cases the fish morphological variability decreased immediately after aquatic macrophyte loss and then increased to end above the initial value. The ecomorphological analysis appeared to be sensitive to major ecological disturbances that occurred during the study period and this was confirmed by the morphospace configuration. The results indicate that the ecomorphology of the fish community responds to habitat changes and that this change corresponds to alterations in the representation of the different feeding types. These findings therefore contribute to the measurement of morphological changes in estuarine fish assemblages as a result of habitat changes within the ecosystem and we propose that ecomorphological analyses add another dimension to the information provided by existing diversity indices in studying changing fish communities.

Habitat influence in the morphological diversity of coastal fish assemblages

“…All percentages from 1.0 to 99.9% were rounded downwards (e.g., 36.4% to 36%). The species with abundance equal to or less than 1% (between 19% and 73% of the species, depending on the community) were analysed as one image to include the largest number of species in the analysis (Lombarte et al, 2012).…”

“…Therefore, the interspecific morpho-functional variation within fish assemblages can help to understand its structure and dynamics (Gatz, 1979;Langerhans et al, 2003;Montaña and Winemiller, 2010;Winemiller, 1991); and even, it can also be used as a measure of biodiversity that captures more ecological properties of fish assemblages than a simple enumeration of species (Farré et al, 2013;Foote, 1997;Karr and James, 1975;Ricklefs, 2010) or as a prediction tool of invasion and coexistence phenomena (Azzurro et al, 2014). In addition, morphological traits of species are also useful to detect variations in the structure of assemblages caused by natural or external perturbations (Lombarte et al, 2012;Villéger et al, 2010), whereas simple ecological measures are unable to determine these changes within communities. Therefore, the incorporation of new approaches, such as morphological and functional information of species, to studies that only use ecological parameters such as specific richness, dominance or evenness, is important to improve the knowledge about the dynamics of communities (Farré et al, 2013;Somerfield et al, 2008).…”

“…Recently, morphological analyses have been accepted as valid methods to define the community structure, offering an additional option when ecological or functional information of communities is absent or scarce (Farré et al, 2013;Lombarte et al, 2012). The aims of this study are (i) to characterize coastal fish assemblages of the Mediterranean Sea in relation to composition and abundance of species, (ii) to describe morphologically these assemblages from body fish shape and compare them to assess their variability, and (iii) to test how environmental factors (substrate composition, depth or location) affect the structure of the assemblages.…”

Spatial and temporal extension of wild fish aggregations at Sparus aurata and Thunnus thynnus farms in the north-western Mediterranean

“…The natural distribution of fish populations in the littoral zone is influenced by different factors, such as depth (Bell 1983, García-Charton & Pérez-Ruzafa 1998 and habitat structure (Letourneur et al 2003, Lombarte et al 2012, which influence the type and distribution of food and shelter (García-Charton & Pérez-Ruzafa 2001). Depth has also been identified as an important factor determining spatial patterns of fish aggregations at fish farms (Dempster et al 2005, Sudirman et al 2009).…”

Selection of landmarks and semilandmarks in fishes for geometric morphometric analyses: a comparative study based on analytical methods

“…However, it has been demonstrated that these structures are key factors in many fish behaviours (Yamanoue et al 2010), such as movement and body position (Zuanon et al 2006), prey capture (Laurenson et al 2004) and receiving chemical stimuli (Kasumyan 2011), so they are important in the functional and ecological role of species within communities. Although many researchers currently question their use in landmark methods, claiming that they are not solid structures, that they have highly variable positions that are difficult to standardize, or even that some of them are absent (Chakrabarty 2005), fins have been applied in evolutionary (Friedman 2010, Dornburg et al 2011), phylogenetic (Vergara-Solana et al 2014, ecological (Wainwright et al 2002, Lombarte et al 2012, Farré et al 2015 and biodiversity studies (Farré et al 2013).…”