Fish assemblages in habitats dominated by Caulerpa taxifolia and native seagrasses in south-eastern Australia

Abstract

Seagrass beds in estuaries are important habitats and nursery grounds for a great variety of fishes, including many economically important species. The introduction of the invasive green alga Caulerpa taxifolia could potentially threaten the seagrasses of south-eastern Australia. This study examined the implications of the spread of C. taxifolia on ichthyofauna in 2 estuaries in central New South Wales. Fish assemblages were compared among adjacent habitats of C. taxifolia and 2 seagrass species (Posidonia australis and Zostera capricorni). Fish were sampled using a small beam trawl to test for differences among habitats in (1) the species composition of the fish assemblages, (2) total abundance and species richness of fishes, and (3) abundances of major fish families. Fish assemblages separated into 3 significantly distinct groupings based on habitat. Total abundances of fishes were similar among habitats; however, species richness was lower in C. taxifolia. The fish assemblages in C. taxifolia were largely characterised by high abundances of gobiid fishes, similar to those in Z. capricorni, and few or no syngnathid and monacanthid species when compared to seagrass fish assemblages. This suggests that if C. taxifolia competitively replaces native seagrass beds in the estuaries of New South Wales, the resulting change in habitat may also cause a change in fish assemblages. This could reduce the abundances of some protected and economically important fish species but may also increase abundances of other opportunistic fishes.

Quantitative characterisation of reef fish diversity among nearshore habitats in a northeastern New Zealand marine reserve

“…agreement between the global pattern displayed in both the unconstrained and constrained ordination techniques suggests that the maximum variability calculated by the unconstrained ordination was owing to the influence of habitat type. The dominant role of habitat type in determining fish community structure revealed in this study is in agreement with other published studies (Choat & Ayling 1987;Syms 1995;Syms & Jones 1999;Anderson & Millar 2004;Valesini et al 2004;Brokovich et al 2006;Feary & Clements 2006;York et al 2006;Wellenreuther et al 2007) and is in opposition to the view of Robinson & Levings (1995) who suggested that fish are too mobile to allow the detection of significant differences in their community compositions among nearshore habitats. The present study also showed that subtle differences in reef fish community compositions can be detected with depth within a singularly defined nearshore habitat type, namely kelp.…”

Impacts of detritus from the invasive alga Caulerpa taxifolia on a soft sediment community

“…Research into C. taxifolia has focused largely on its range expansion (e.g. Meinesz et al 2001) and effects of the live alga on local seagrass populations (Ceccherelli & Cinelli 1997, Ceccherelli & Sechi 2002, Holmer et al 2009), epi-and in-fauna (Gollan & Wright 2006, Wright et al 2007, McKinnon et al 2009) and fish assemblages (York et al 2006). Also, C. taxifolia also has the potential to markedly alter detrital pools.…”

Habitat alteration and community-level effects of an invasive ecosystem engineer: a case study along the coast of NSW, Australia

“…For instance, C. taxifolia decreases water flow and increases sediment and boundary-layer hypoxia , McKinnon et al 2009). In contrast to other habitat-forming invasive species, C. taxifolia can negatively affect many native taxa including algae and seagrasses (de Villèle & Verlaque 1995, Ceccherelli & Cinelli 1997, Ferrer et al 1997, fish (York et al 2006), and invertebrates (Wright & Gribben 2008, McKinnon et al 2009, Byers et al 2010.…”