Mesohabitat and macroecological correlates for blue sucker ( Cycleptus
elongatus ) occurrence in regulated rivers
Abstract
Blue sucker ( Cycleptus elongatus) occurs in the Mississippi
River and Gulf of Mexico drainages of North America and is negatively
affected by habitat fragmentation and flow regime alteration caused by
dams. During fish assemblage surveys in August of 2022, we collected
five specimens of juvenile blue sucker (312-428 mm total length) in the
Angelina River upstream of Sam Rayburn Reservoir in east Texas
(46,335-hectare surface area) where the occurrence of the species was
previously unconfirmed. Given this unexpected finding, we (1) analyzed
blue sucker mesohabitat associations to compare habitats we sampled with
reports in the literature, and (2) reviewed blue sucker occurrence in
state, national, and global databases across historical (1950-1980) and
contemporary (1981-2022) periods to assess occurrence across gradients
of habitat fragmentation and streamflow regulation. The blue sucker
population in the Angelina River upstream of Sam Rayburn Reservoir was
previously unconfirmed but is within the native range of the species.
Mesohabitats occupied by blue sucker were consistent with literature
reports, including fast velocity, shallow depth, and coarse substrates.
The low degree of regulation (19% of natural runoff stored by upstream
reservoirs) and a high degree of habitat connectivity (287 rkm of
mainstem habitat) for the Angelina River upstream of Sam Rayburn
Reservoir matched range-wide patterns of persistence within relatively
intact (unfragmented and unregulated) or remnant (fragmented but
unregulated) riverscapes. Our review reveals that blue sucker
populations might persist (1) in remnant river fragments where local
habitat templates are appropriate and (2) where effects of habitat
fragmentation and flow regulation are not coupled.