Freshwater fish species distributions

Freshwater fish species distributions

What these maps show

The maps available here plot the distribution of 103 species of freshwater fish across northern Australia and are based on a large number of point records (>6000) derived from numerous field studies and museum records. Information concerning the study from which these data were derived is available at http://www.jcu.edu.au/archive/actfr_old_Projects/FishAtlas/Index.htm.

Point records are useful but do not, in themselves, indicate whether a species might occur in a stream reach or area that has not yet been sampled. Various methods are available for translating point records to predicted distributions. We have here used a Multivariate Adaptive Regression Splines predictive model to extend the point data to predicted distributions.

Variables used as predictors were a mixture of variables relating to climate (e.g. annual mean solar radiation and mean temperature), terrain (e.g. distance to river mouth, elevation etc.), vegetation (stream and valley forest cover) and hydrology (annual runoff and variation in runoff). The model was calibrated using presence-only species distribution data and externally validated using true presence-absence data for 85 of species examined and validated using presence data only for a further four species. Maps for the remaining 14 species, which were rare or uncommon in the study area, were based on observed records only due to small samples sizes.

Overall, the model predicted species distributions with a high level of accuracy – 87% correct classification. Further information on the modelling procedure, model diagnostic parameters and the importance of individual predictor variables can be found at http://www.track.org.au/publications/registry/track843 and the accompanying document.

The distribution maps show the presence or absence of each species in areas defined as "planning units". There are about 5800 of these units across north Australia, ranging from a few square kilometers to several hundred. The units are based on hydrologically defined subcatchments. For more information about these planing units please see: http://www.track.org.au/publications/registry/track84 (and/or download the shapefile below).

It is important to note that the maps presented here do not show the presence of a species in catchments in which field sampling has failed to previously detect it. Thus, if a species has not been recorded from a catchment, its mapped distribution will indeed reflect its absence from that catchment.

Data Download

[Species-Common Name lookup table] - [Planning Units and Species Distribution (shapefile)]

References

Bibliography of source material

Field Manual

Predictive Distributions