LITMIR.BIZ

Figure 2.3 South African estuarine fish faunal groupings based on environmental preferences and the zoogeography of the region (after Harrison & Whitfield 2006a).

      Several authors have described the biogeographic changes in estuarine ichthyofaunal associations in other parts of the world, but not in the same manner as the above analysis. For example, along the California coast of North America, fishes associated with bays and estuaries were distinctly different north and south of Point Conception, with this location more of a boundary for southern species than for northern ones (Horn & Allen 1978). Vieira & Musick (1993, 1994) established that the majority of the species in tropical and warm‐temperate estuaries of the western Atlantic were young‐of‐the‐year that were maintained by recruitment waves from the adjacent marine environment. Ayvazian et al. (1992) found, however, that in the temperate north‐eastern USA, there was a trend towards a decrease in estuary nursery use by marine species and an increase in diadromous and solely estuarine species with increasing latitude. Dame et al. (2000) described a similar pattern in estuaries of the South Atlantic coast of North America, where systems in temperate North Carolina, South Carolina and Georgia were dominated by estuarine spawning species, while fish assemblages in the more subtropical Florida estuaries contained a higher proportion of marine species.

In the north‐eastern USA, Roman et al. (2000) found that fishes with life history strategies classified as nursery, marine, diadromous or transient species represent a greater percentage of fishes using estuarine habitats in more southern latitudes, while resident fishes and seasonal residents dominate the fauna of estuaries in the northeast. Emmett et al. (2000) raise the important point that, unlike the situation on the east coast of the USA, where most fish species reside in estuaries during most of their life history, many North American west coast species (especially anadromous taxa) use estuaries only during a short period of their life cycle. However, these estuaries play an important role in the life histories of these species, e.g. salmonids. From studies in temperate New Zealand estuaries, McDowall (1985) suggested that, with increasing latitude, there was a change from species of marine origin to freshwater/diadromous taxa, and thus similar to the findings above for fishes in estuaries along the eastern North American coast.

The composition and diversity of estuarine fish assemblages in Europe are also often related to latitude and thus biogeographic zones. Records of fish species from European estuarine waters obtained from information published in Elliott & Hemingway (2002) included data of fish taxa reported in 23 European estuaries covering nine countries (Figure 2.4). The presence/absence of each species from each estuary was used to generate a Bray‐Curtis resemblance matrix and subjected to non‐metric multidimensional scaling (Figure 2.5). The results indicate that, based on their fish assemblages, the compositions of European estuaries are broadly arranged according to a latitudinal gradient, with those in systems below 45 °N situated towards the bottom half of the ordination and those at latitudes above 45 °N located in the top half of the ordination (Figure 2.5a).