EVALUATION OF THE CONSTRUCTION OF ARTIFICIAL FLUVIAL SALMONID HABITATIN A HABITAT COMPENSATION PROJECT, NEWFOUNDLAND, CANADA

In 1987, the provincial transportation agency in Newfoundland, Canada requested approval from the Canadian Department of Fisheries and Ocean s (DFO) to destroy a 162m section of fluvial salmonid habitat to accom modate highway construction. The DFO's Policy for the Management of Fi sh Habitat required the proponent to compensate for this habitat loss through the construction of a replacement section of stream. The resul ts are presented from a research programme to evaluate the success of this project focusing on: (1) considerations in the design and constru ction of the replacement habitat; (2) a comparison of key habitat attr ibutes between the destroyed stream section and the compensatory habit at; and (3) the utilization of the compensatory habitat by resident fi sh. The results of the study indicate an increase in habitat area of 1 25m(2) (23%) over the 162m section of stream habitat lost due to const ruction, primarily related to the increase in thalweig length (20% inc rease) resulting from designed sinuosity in the compensatory habitat. Habitat design increased the amount and proportion of pool habitat to benefit the primary resident species, brook trout (Salvelinus fontinal is) and resulted in a 134% increase in pool quantity (increase of 98 m (2)), a 281% increase in pool volume (31.06 m(3)), a 223% increase in the pool to riffle ratio and a 29% increase in the mean depth. Fish bi omass, after an initial decrease after construction (1991), increased to the highest level during the study (93.5 g per 100m(2) unit) in 199 3, a 2.1-fold increase over the average pre-construction biomass. A co rresponding decrease in salmonid densities was evident, primarily refl ecting a shift in use from young of the year (YOY or 0+) Atlantic salm on (Salmo salar) to larger, older brook trout in response to desired h abitat features. Using biomass as an indicator of 'productive capacity ' and considering the increase in habitat quantity, there was a 2.58-f old increase in productive capacity over the stream lost due to highwa y construction and, in the context of DFO's habitat policy, compensati on has resulted in a 'net gain' in habitat.