POTENTIAL BROWN TROUT HABITAT (SALMO-TRUT TA-FARIO, L 1758) IN 3 MASSIF-CENTRAL STREAMS - METHODOLOGICAL APPROACH AND FIRST RESULTS ON INFLUENCE OF RIPARIAN CORRIDORS
L. Maridet et Y. Souchon, POTENTIAL BROWN TROUT HABITAT (SALMO-TRUT TA-FARIO, L 1758) IN 3 MASSIF-CENTRAL STREAMS - METHODOLOGICAL APPROACH AND FIRST RESULTS ON INFLUENCE OF RIPARIAN CORRIDORS, Bulletin francais de la peche et de la pisciculture, (336), 1995, pp. 1-18
An approach using a French version of PHABSIM has enabled us to estima
te the potential habitat relative to the mineral and hydraulic structu
re of channel in three salmonid streams located in Correze (Massif Cen
tral, France). PHABSIM estimates a potential carrying capacity or weig
hted usable area (WUA) by coupling measurements of depth, velocity and
substrate with brown trout habitat preference curves. The WUA calcula
tions enable to extricate from the morphohydrological differences betw
een sites; so it becomes possible to compare and assess the influence
of other environmental factors with a saving on the number of sites an
d operations carried out. The ratio of observed biomass of adult brown
trouts to weighted usable area (WUA) has been compared for the differ
ent streams. The results showed differences between studied sites, due
to the morphohydrological habitat and different vegetative surroundin
gs. The estimation of different shelter structures showed the importan
ce of riparian corridor in the structuration of the brown trout popula
tion. The lack of riparian corridor seemed to be a limiting factor in
one studied site with a low trout biomass of 13 g/m(2) WUA. Conversely
, in another site, the riparian corridor with dense canopy and with we
ll developed root system compensated a poor physical carrying capacity
of the channel dominated by sand (65 g adult trout/m(2) WUA). Potenti
al WUA of this type of river should therefore be interpreted by the mo
rphohydrological habitat estimated by PHABSIM like methodology and the
absence or presence of riparian trees estimated by the shelter struct
ures inside the stream channel.