The Importance of Regional, System-Wide and Local Spatial Scales in Structuring Temperate Estuarine Fish Communities

Abstract

An extensive literature base worldwide demonstrates how spatial differences in estuarine fish assemblages are related to those in the environment at (bio)regional, estuary-wide or local (withinestuary) scales. Few studies, however, have examined all three scales, and those including more than one have often focused at the level of individual environmental variables rather than scales as a whole. This study has identified those spatial scales of environmental differences, across regional, estuary-wide and local levels, that are most important in structuring ichthyofaunal composition throughout south-western Australian estuaries. It is the first to adopt this approach for temperate microtidal waters. To achieve this, we have employed a novel approach to the BIOENV routine in PRIMER v6 and a modified global BEST test in an alpha version of PRIMER v7. A combination of all three scales best matched the pattern of ichthyofaunal differences across the study area (ρ = 0.59; P = 0.001), with estuary-wide and regional scales accounting for about twice the variability of local scales. A shade plot analysis showed these broader-scale ichthyofaunal differences were driven by a greater diversity of marine and estuarine species in the permanently-open west coast estuaries and higher numbers of several small estuarine species in the periodically-open south coast estuaries. When interaction effects were explored, strong but contrasting influences of local environmental scales were revealed within each region and estuary type. A quantitative decision tree for predicting the fish fauna at any nearshore estuarine site in south-western Australia has also been produced. The estuarine management implications of the above findings are highlighted.

Characteristics of the ichthyofauna of a temperate microtidal estuary with a reverse salinity gradient, including inter‐decadal comparisons

“…This presumably reflects the influence of the conspicuous increases in water temperature, which, as a result of climate change, have occurred along the south-western coast of Australia over the past 20 years (Pearce & Feng, 2007;Pearce et al, 2011;Lough, et al, 2012). Such a conclusion is consistent with the fact that, during the past 30 years, the abundance of C. mugiloides has increased in both the Swan-Canning (Loneragan et al, 1989;Valesini et al, 2009Valesini et al, , 2011Valesini et al, , 2014 and Peel-Harvey Estuaries Loneragan et al, 1986;Veale, 2013), which are located c. 140 and 85 km to the north of the Leschenault Estuary, respectively.…”

“…Such a conclusion is consistent with the fact that, during the past 30 years, the abundance of C . mugiloides has increased in both the Swan‐Canning (Loneragan et al ., ; Valesini et al ., , , ) and Peel‐Harvey Estuaries (Potter et al ., ; Loneragan et al ., ; Veale, ), which are located c . 140 and 85 km to the north of the Leschenault Estuary, respectively.…”

Baseline survey of the fish fauna of a highly eutrophic estuary and evidence for its colonisation by Goldfish (Carassius auratus)

“…The ability to osmoregulate in a broad range of salinities is advantageous in the Vasse and Wonnerup estuaries as salinities can change from[90 in April to\1 in June (Lane et al 2011). The total number of six fish species recorded during the present study is far lower than that recorded in the shallow, nearshore waters of the nearby permanently open Swan-Canning (61), Peel-Harvey (53) and Leschenault (43) estuaries (Valesini et al 2014;Veale et al 2014;Potter et al 2016). It is also less than the number of species found in estuaries on the south coast of Western Australia (i.e.…”

Regional differences in the feeding of the ambush predator Neosebastes pandus and comparisons of diets in the Scorpaenidae, Triglidae and Platycephalidae

“…Similarity percentages analysis (SIMPER; Clarke & Gorley, ) and shade plots (Clarke et al ., ) were employed to identify those dietary categories that typified and distinguished the dietary composition of each a priori group (SIMPER) and those that contributed the greatest proportion by volume. Shade plots are a simple visualization data matrix where a white space for a dietary category demonstrates that a dietary category was not consumed, while the depth of shading from grey to black is linearly proportional to the percentage contribution of that dietary category to the total diet (Clarke et al ., ; Valesini et al ., ). Note that the volumetric data for location and length class were averaged prior to constructing the shade plots.…”

“…Note that the levels in the Location factor were not ordered, whereas those in the Length class factor were. Valesini et al, 2014). Note that the volumetric data for location and length class were averaged prior to constructing the shade plots.…”