Numerical Method for Modelling Spawning Habitat Dynamics of Landlocked Salmon,salmo Salar

Abstract

The stability of habitat conditions determined by the hydrological regime of a river can play a major part in fish spawning success. Application of the classical IFIM approach (Instream Flow Incremental Methodology) does not usually take into account this dynamic aspect of the habitat. We developed a numerical method to simulate the rate of variation in spawning habitat conditions using two‐dimensional hydrodynamic modelling coupled with a fish model based on habitat suitability indices (HSI). The approach assumes that, under natural conditions, fish spawning success is maximized under the most common rates of habitat variation. This method was applied during the feasibility study phase of a Hydro‐Québec hydroelectric project on Ashuapmushuan River (St‐Jean Lake region, Québec, Canada). The aim was to evaluate the environmental impact of different exploitation regimes on the rearing and spawning habitats of the landlocked salmon (Ouananiche) of this river. Only the spawning aspect is addressed here. After the hydrodynamic model was well established on a representative reference reach of the river, two spawning areas were identified within this reach and delimited for computational purposes. The per cent usable areas (PUA) were estimated on these two zones for 36 different flow discharges representing a wide rate of the usual hydrological conditions in summer and autumn. In addition, a time series of daily rate of variation of normalized PUA (dPUA′) were obtained from a 35 year habitat time series. Finally, some relevant statistics of dPUA′ (mean and exceedance probabilities of 50, 20, 10, 5 and 2%) were obtained for the natural flow regime. They were then compared with a hypothetical peak exploitation flow pattern currently in use on a neighbouring river. According to our model, this regime would induce a 10–20‐fold increase in the rate of variation compared with the most extreme natural conditions (dPUA exceeded 2% of the time). This regime was considered to obtain a contrasting image of different options that were never seriously envisaged by Hydro‐Québec for this river.

Conceptual Spawning Habitat Model to Aid in ESA Recovery Plans for Snake River Fall Chinook Salmon, 2002-2003 Annual Report.

“…However, consistent with our previous studies, the errors of commission (predicted to be a spawning site but not used) were high at some sites (see Task c for comments on results). At these sites, we plan to conduct a more detailed analysis using ideas that are based in part on the reasoning developed in Leclerc et al (1996). Specifically, we will test whether there are differences in the stability of habitat between cells that are predicted to be habitat and are used versus areas that are predicted to be habitat but are not used.…”

Numerical modeling of flow processes over gravelly surfaces using structured grids and a numerical porosity treatment

“…Third, it is clear that the threedimensional flow structure of rivers, especially gravel bed rivers exerts a crucial control upon habitat, and its spatial variation. Leclerc et al [1995Leclerc et al [ , 1996 demonstrate that 2-D hydraulic modeling allowed a much better match between the spatial scale of salmonid function and hydraulic predictions. Crowder and Diplas [2000] showed that point measurements of habitat did not represent habitat variation in space by using a model that included mesoscale topographic features (e.g., boulders).…”

Multicriteria Decision Analysis of Stream Restoration: Potential and Examples

“…For sea lamprey larval habitat, n= 1, which represents substrate. Depending on the value of exponent p, expression (2) corresponds to either the Interactive Limiting Factor (ILF) method ( p=1) or the Average Value Method (AVM) ( p = 1/n) (Minns and Bakelaar 1999;Leclerc et al 1996). Both methods assume that the overall HSI for a reach j is a function of the product of the characteristics.…”