Capture-mark-recapture of Calopteryx exul in 2011

While climate change severely affects some aquatic ecosystems, it may also
interact with anthropogenic factors and exacerbate their impact. In dry
climates, dams can cause hydrological drought during dry periods following
a great reduction in dam water discharge. However, impact of these severe
hydrological droughts on lotic fauna is poorly documented, despite climate
change expected to increase drought duration and intensity. We document
here how dam water discharge was affected by climate variability during
2011–2018 in a highly modified watershed in northeastern Algeria, and how
an endemic endangered lotic damselfly, Calopteryx
exul Selys, 1853 (Odonata: Calopterygidae), responded to
hydrological drought episodes. Analysis was based on a compilation of data
on climate (temperature, precipitation, and drought index), water dam
management (water depth and discharge volume and frequency), survey data
on C. exul occurrence, and capture–mark–recapture (CMR)
of adults. The study period was characterized by a severe drought between
2014 and 2017, which led to a lowering of dam water depth and reduction of
discharge into the river, with associated changes in water chemistry,
particularly during 2017 and 2018. These events could have led to the
extirpation of several populations of C. exul in the
Seybouse River (Algeria). CMR surveys showed that the species was
sensitive to water depth fluctuations, avoiding low and high water levels
(drought and flooding). The study shows that climate change interacts with
human water requirements and affects river flow regimes, water chemistry
and aquatic fauna. As drought events are likely to increase in the future,
the current study highlights the need for urgent new management plans for
lotic habitats to maintain this species and possible others.