Relationships between latitude and environmental conditions and the species richness, abundance and composition of tropical fish assemblages over soft substrata

Abstract

Large-scale studies are required to elucidate the environmental factors that structure faunal communities. The relationships between the characteristics of the coastal ichthyofaunas over the soft substrata of tropical north-western Australia and both latitude and environmental factors were thus explored by analysing trawl data obtained for deep and shallow inshore waters at 7 regularly spaced locations along this 1500 km coast during both the dry and wet seasons. In the dry season, species richness and density were greater in the Kimberley and Pilbara bioregions than in the intervening Canning bioregion, where, in contrast to particularly the Kimberley, rivers and mangroves are largely absent. Species richness and density were greatest in the most northern bioregion (Kimberley) during the wet season, when nutrient input from rivers and water temperatures were highest. The high species richness and density at 1 Canning location during the wet season was presumably related to increased productivity brought about by local cyclonic events. Ichthyofaunal compositions in the Kimberley differed markedly from those in the Canning and Pilbara, where tidal range was less and water clarity greater due, in particular, to far greater densities of leiognathids and terapontids. Compositions at all locations in the dry season differed from those in the wet, when chlorophyll a concentrations and/or water temperatures were greatest and large numbers of certain species were recruited. Ichthyofaunal composition at each location almost invariably differed markedly between water depths, reflecting, inter alia, the tendency for some species to use nearshore waters as nursery areas and for others to occupy particular habitats.

Strong population structure deduced from genetics, otolith chemistry and parasite abundances explains vulnerability to localized fishery collapse in a large Sciaenid fish, Protonibea diacanthus

“…The discontinuity between the Kimberley and Canning geomorphology (macrotidal, jagged “ria” coastline with extensive mangrove forests vs smoother coastline with no rivers) creates contrasted marine coastal habitats, inhibiting larval dispersal and reinforcing spatial population structure. Likewise, quantitative analyses of fish assemblages have revealed two main biogeographic regions, the Kimberley and Canning coasts (Hutchins, ; Travers, Newman, & Potter, ; Travers, Potter, Clarke, & Newman, ; Travers et al., ; Wilson, ), matching the genetic groups reported here. Our study is the first to identify a clear genetic break between the Kimberley and the Canning bioregions in coastal fish.…”

Depth and Medium-Scale Spatial Processes Influence Fish Assemblage Structure of Unconsolidated Habitats in a Subtropical Marine Park

“…While broad-scale latitudinal effects have been observed in fish communities of unconsolidated sediments [24], [26], [61]–[62], these patterns are generally evident over a much larger spatial scale than in our study (e.g. [26]).…”

Distribution, abundance, diversity and habitat associations of fishes across a bioregion experiencing rapid coastal development

“…As we avoided sampling bare sandy habitats, there is an underrepresentation of sand-affiliated species in our data (see Supplementary Data S- Table 1). For example, Travers et al (2010Travers et al ( , 2012 recorded high abundances of Synodontidae (lizardfishes) and Monacanthidae (leatherjackets) in soft sediments in the Pilbara, both of which were observed in very low abundances in the current study.…”