Most populations of salmonids differ from each other in molecular genetics, morphology, life history, etc., with many populations showing local adaptations. While some populations, or groups of populations, meet the requirements for species designation under an integrative framework, to recognise all populations showing adaptive differences and distinct evolutionary trajectories as distinct species would result in taxonomic chaos. In North America important populations can be identified as Conservation Units (CUs) such as Evolutionarily Significant Units or Designatable Units within the appropriate conservation legislation. With a few exceptions, the CU approach does not appear to be widely used elsewhere, possibly due to difficulties with current legislation.
Effective conservation of trout and char should be based on populations, irrespective of whether they are designated as species, subspecies or simply populations, although CUs need to be rooted in accepted species. Each population can then be assessed as to its biological significance based on: genetic distinctness as determined by genomic techniques especially where this is of adaptive significance; genetically-based tolerance of extreme environmental conditions; unusual genetically-based life history traits; phylogenetics; distinct morphology where this has a genetic and adaptive basis; geographical isolation, especially where adjacent populations are extinct; lack of introgression from non-native conspecifics; occurrence as a member of an unusual or rare native species community; cultural, economic, and recreational importance. This biological significance taken together with potential threats to the population’s continued survival can be used to produce a priority ranking. Such a priority ranking can assist in allocating limited resources for conservation thus ensuring that this is carried out in a focused way.
Hi Andy,
in my opinion, your question highlights a very "hot" issue, mainly in Italy. In Italy, the introduction of non-native species and/or population was forbidden by National law. Since 2 April 2020 this law was updated and now there is (in theory) the possibility of allochthonous introductions. However, this new law leaves without description the regulation concerning the management and or protection of the local native biodiversity. Therefore, concepts as management units and similars are without any legal values, as far as I know. This scenario opens the window for a "far west" in the field of the management of local native populations of freshwater fish, in particular, Mediterranean trout, marble trout, Adriatic grayling ecc. Further, in Italy, freshwater fish fauna is not considered a state patrimonial good and this implies that the management of local biodiversity is guaranteed only by rare local programs.
In Romania, there is no legislation on intraspecific conservation units of salmonids. At local level, there are angling associations that are monitoring brown trout populations and have prohibited fish stocking to protect local ecotypes.
Hi Andrea
Many thanks for your pertinent comments especially in respect of Italy. Many authors make comments in their papers that conservation should be population based, with key populations being recognised as Conservation / Management Units, or that particular populations merit urgent conservation action. Both you and I have made such statements! However, I cannot find cases where this has been acted upon by the relevant conservation authorities and no European country / local region appears to have legislation in place to allow protection of such intraspecific conservation units. Clearly this needs to change but the communication gulf between scientists and conservation administrators means that there is little cross fertilisation of ideas.
Andy
Hi Călin
Very many thanks for your comments in respect of Romania. It is good to see that your local angling associations are taking positive action. That is very progressive compared to much of Europe.
Regards
Andy
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