Development of fishways for longitudinal connectivity of Chilean rivers threatened by small-scale hydropower plant.
Loading...
Date
2022
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
Freshwater ecosystems have become severely fragmented by artificial
instream structures. Significant efforts have been made to reconnect freshwater
systems to support fish movement through the design and installation of
dedicated fish passage structures, or fishways. However, fishway design is based
on a traditionally unique focus on salmonids or a small number of species often
from northern regions. As such, designs may not be effective in other parts of the
world, such as the Southern Hemisphere. Particular examples include Australia,
New Zealand and South America, where native species consist mainly of small-bodied fish, a term that refers to adult fish with a body length of up to 15 cm.
The present research is motivated by the need to develop novel and
innovative approaches to advancing fishway mitigation technologies for small-bodied fish and small juveniles exposed to instream structures. The situation of
Chilean native fish species is used as the basis of a case study for the
development of fishways for small-bodied fish worldwide. Three fundamental
research questions are raised. (1) Which is the target group for the development
of fishways in Chile? (2) What is the swimming performance of target group
species? (3) Is there a fishway configuration suitable for passage of the target
group, and can that suitability be quantified?
Trichomycterus, Diplomystes and Percilia (the TDP group) were the most
prevalent genera within the assemblages present at planned hydropower project
sites in South Central Chile (present at 40% of the sites; Laborde et al., 2020).
The TDP group is composed of two small-bodied fish species (T. areolatus and
P. irwini) and a species that coexists alongside them in its juvenile stage (D.
nahuelbutaensis, juveniles up to 15 cm; Arratia et al., 1983). All three are
benthofagous and resident species. Consequently, the TDP group was identified
as a target group for the facilitation of fish passage.
Swimming capacities of TDP group species were estimated based on
information obtained from the literature concerning applicability of proposed
dimensionless variables and a proposed correlation of swimming capacities with
fish species characteristics. Results showed that the dimensionless swimming
capacities of small-bodied and large-bodied fish species are not comparable,
even for the same taxonomic order, suggesting scale effects. Results also
showed that the distance design curve proposed by Peake (1997) and applied to
Percilia suggests fish passage velocity of up to 41 cm/s
-1 along a 100-metre-long
fishway.
Based on a review of the literature, fishway baffle designs were identified
as the most suitable for the TDP group. Consequently, three different fishway
configurations were proposed and evaluated over a 4-metre-long prototype
fishway: lateral baffles (treatment 1); baffle array (treatment 2); and alternating
lateral baffles (treatment 3). Passage of individual fish and interspecific fish
groups was assessed. Performance was quantified as passage efficiency,
percentage of attempts, and percentage of impingements. In general, results
showed that baffles increased passage efficiency and decreased the percentage
of impingements. The lateral baffles configuration (treatment 1) showed the
highest passage efficiency for T. areolatus (efficiency of 70%, 30% and 0% for
treatments 1, 2 and 3, respectively) and P. irwini (efficiency of 43%, 0% and 20%
for treatments 1, 2 and 3, respectively). In individual and interspecific group
experiments, fish passage performance metrics in the lateral baffles configuration
were not significantly different for T. areolatus, P. irwini and D. nahuelbutaensis.
As such, lateral baffles constitute the optimum multi-species fishway design for
small-bodied fish. Group passage efficiency in the lateral baffles configuration
was 37%.
Description
Tesis para optar al grado de Doctor en Ciencias Ambientales con mención en Sistemas Acuáticos Continentales.
Keywords
Rampas para Paso de Peces, Mejoramiento del Hábitat de los Peces, Natación Animal