[MARMAM] Ecological responses to flow variation inform river dolphin conservation

SHAMBHU PAUDEL spaudel at email.arizona.edu
Fri Dec 18 06:23:59 PST 2020

Dear all:

Hydrological alteration ( by dams/barrage/hydropower) is threatening
freshwater ecosystems and their native biotic inhabitants. Here, we
quantify flow-ecology relationships that aid the formulation of flow
management guidelines across regional scales. As South Asian river dolphins
already at risk of extinction from dams, and hundreds of hydroelectric dams
have been planned throughout the Amazon, we suggest immediate actions to
incorporate flow-ecology relationships in their water use management plans
to avoid the risks of native and sensitive aquatic species extinctions. We
develop flow-ecology relationships in reference to river dolphin
conservation.  Check this out!

Many environmental flow (e-flow) studies and applications have
predominantly used state—(i.e., at a single time point) and rate—(i.e.,
temporal change) based demographic characteristics of species representing
lower trophic levels (e.g., fish communities) to build flow-ecology
relationships, rather than using a process that incorporates population
dynamics. Recent studies have revealed the importance of incorporating data
on species traits when building flow-ecology relationships. The effects of
flow on keystone megafauna species (i.e., body mass ≥ 30 kg) reverberate
through entire food webs; however, the relationships between flow and these
species are not well understood, limiting the scope of the relationships
used in flow management. Here, we fill this gap by incorporating the
habitat selection traits at different flows of a freshwater apex predator,
Ganges River dolphin (GRD, *Platanista gangetica gangetica*), which plays a
significant role in maintaining the structure, functions and integrity of
the aquatic ecosystem. Using temporally and spatially measured GRD habitat
selection traits, we quantified flow-ecology responses in the Karnali River
of Nepal during the low-flow season when habitat was heavily reduced and
water demand was highest. We define ecological responses as suitable
habitat templates with enough usable surface area to support GRD fitness by
improving reproduction and survival. We measured the available and occupied
habitats to develop flow-ecology responses. Variation in flow resulted in
substantial differences in the ecological response across time and space,
suggesting that aquatic species adjusted in a variety of habitats to
support their life histories and maintain viable populations. The limited
availability of suitable habitats combined with uninformed water
regulations by humans likely places GRDs under severe physiological stress
during low-water seasons (i.e., January–April), suggesting that  reduced
flows contribute to the process of endangering and extirpating highly
sensitive endemic aquatic biodiversity. Our study reveals that ad hoc or
experience-based flow management is no longer tenable to maintain the
integrity and functionality of aquatic ecosystems. We stress that
quantifying the flow-ecology relationships of foundational species,
particularly megafauna, in response to flow variation is crucial for
monitoring the effects of water alterations and determining the minimum
flows needed for maintaining healthy and functional freshwater ecosystems
in the Anthropocene.

Link: Ecological responses to flow variation inform river dolphin
conservation | Scientific Reports (nature.com)

Thank you!

Shambhu Paudel


*Ph.D. Candidate / **Russell E. Train Fellow (EFN/WWF-USA) *

School of Natural Resources & the Environment

Wildlife Conservation and Management

Environment & Natural Resources 2

University of Arizona

Tucson, Arizona  85721 USA

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