In our experience electrofishing in Greek, Cypriot and Turkish rivers, we find many very-polluted sites that are fishless; yet it seems difficult to use fish as indicators of specific pollution loads. Degradation is so multivariate. In building fish-based multimetric indices for ecological integrity assessment in rivers little is heard of tolerance to pollution. I am refering to Mediterranean-climate, low diversity, wide niche-breadth assemblages. Any refs would be appreciated.
I guess its a difficult question. Or more experienced specialists see it as part of the noisy work of building indices. Anybody have any proof of fish reacting to pollution in Mediterranean climate streams and rivers? (...to be more blunt).
Working in a very low-diversity (probably 14 freshwater fishes including as yet undescribed species), highly endemic (>80%) Mediterranean climatic region in south-western Australia, we grapple with this issue. Modelling drivers of ecological disturbance using low diversity fish communities can be achieved by a simplistic approach: a combination of individual species tolerances (most powerful if both lab-derived and field based thresholds from large distributional datasets exists, including introduced species) and historical physicochemical measures in rivers based on past and present distributions (and some metric of population viability, commonly abundance). This approach is obviously most effective if there is a relatively limited set of pollutants or disturbance variables (and synergistic impacts are difficult to quantify), and best conducted on a smaller spatial scale (sub-region, or even catchment/watershed) and can incorporate expert knowledge of species ecology.
In south-west Australia, we have relatively low population and a limited range of pollutants (relative to say Europe). Secondary salinisation is believed to be the major driver of past decline in the range of fishes in south-western Australia, with climate change and its influence on a range of stressors projected to be the future driver. Another point often ignored is that too often macroinvertebrate and fish indices are used in isolation and, if possible, should be combined.
A couple of references you are probably aware of are:
Ferreira et al. (2007) Fish. Manag. Ecol. 14
Kennard et al. (2005) Freshw. Biol. 50.
Walters et al. (2009) Ecol Indic. 9
Sergurado et al. (2011) Ecol. Indic. 11
Thanks Stephen, your experience in Australia is great. I really enjoyed your reply. I do not think invert & fish indices should be "combined". Combining may eclipse metrics and induce wacky noise (senseless noise - this is my gut-opinion). Thanks for the contact!
Keep up the great work in Australia,
Stam
Thanks Stam. Sorry, by "combined" I meant conducted simultaneously, i.e analysed independently and then compared (not merged into a single index).
Best wishes,
Steve
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