A. Crivelli et al., Conservation biology applied to fish: The example of a project for rehabilitating the marble trout (Salmo marmoratus) in Slovenia, CYBIUM, 24(3), 2000, pp. 211-230
The conservation status of freshwater fish is of concern throughout the wor
ld, a third of all known species having become extinct or being endangered.
Many of them have fragmented populations of small size whose future is in
doubt. Conservation biology is the discipline that is used to study such po
pulations, so that they can be managed in a way that will ensure their long
-term survival. The history, development and future of conservation biology
are described. Following repeated restocking of brown trout (Salmo trutta)
dating from 1906, the marble trout (Salmo marmoratus) seems to have disapp
eared as a result of genetic pollution (hybridisation) from the lower reach
es of the Soca River in Slovenia. A project for rehabilitating the marble t
rout has been undertaken and will serve as an example to illustrate an appl
ication of conservation biology to freshwater fish. A preliminary explorato
ry stage (1993-1995) that resulted in the publication in 1996 of an Action
Plan, written in English and Slovenian, suggested that the cause of the dis
appearance of the marble trout was hybridisation, established the validity
of the project in the region in question and provided us with essential inf
ormation (occurrence of genetically pure populations) that could be used to
define our future strategy. We chose genetic rehabilitation, i.e., the rep
lacement of a population of introduced and introgressed fish by a populatio
n of genetically pure fish of the native species, rather than a programme o
f eradicating undesirable fish by chemical methods, which would have been i
ncompatible with the region's context. Our overall strategy therefore had t
wo main aims: to ensure the long-term survival of populations of pure marbl
e trout (species conservation) and to rehabilitate the genes of marble trou
t in the hybridisation zone until foreign genes have almost been eliminated
.