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--></style><title>On keeping a river together: 2 takes, same
topic</title></head><body>
<div><font face="Geneva" color="#1A1A1A">1-Nunn AD, Copp GH, Vilizzi
L, Carter MG.<b> Seasonal and diel patterns in the migrations of
fishes between a river and a floodplain tributary.</b><i> Ecology of
Freshwater Fish</i> 2010: 19: 153-162.</font></div>
<div><font face="Geneva" color="#1A1A1A"><br></font></div>
<div><font face="Geneva" color="#1A1A1A">Abstract - The population
behaviours associated with the migrations of fishes in lowland river
ecosystems are amongst the most poorly-understood dispersal mechanisms
of temperate freshwater organisms. This study evaluated the influence
of four environmental variables (light levels, river discharge, water
temperature and water velocity) on the timing, intensity and direction
of fish movements between the River Avon (Hampshire, England) and a
small floodplain tributary, Ibsley Brook, over a 12-month period.
Using canonical correspondence analysis (CCA) to identify patterns of
movement (by groups of species) and the relative strengths of
explanatory variables in the data, the probability of fishes migrating
between the river and tributary was determined using Bayesian
modelling. The intensity and direction of fish movements between the
river and tributary varied temporally, both on a diel and seasonal
basis, and there were species- and age-specific patterns in behaviour.
Diel movements appeared to be triggered by changes in light intensity
and brook water velocity, whereas seasonal movements were mostly
driven by changes in river discharge and water temperature,
particularly those associated with floods. This study emphasises the
importance of connectivity in river systems, as fishes migrated in all
conditions, but especially during rapidly-rising
discharge.</font></div>
<div><br></div>
<div><font face="Geneva" color="#141413">2-<i>Ecology of Freshwater
Fish</i> 2012: 21: 165-167.<b> Do small tributaries function as
refuges from floods? A test in a salmonid-dominated mountainous
river</b></font></div>
<div><font face="Geneva" color="#141413">Itsuro Koizumi, Koh Hasegawa,
Daisuke Kishi</font></div>
<div><font face="Geneva"><br></font></div>
<div><font face="Geneva">1st 2 paragraphs:</font></div>
<div><font face="Geneva"><br></font></div>
<div><font face="Geneva" color="#141413">Tributary streams are
important for freshwater fishes, providing rearing, spawning and
overwintering habitats (Northcote 1997). Tributaries may also function
as temporal refuges from floods or droughts. Fisherman's anecdote
often says that many large fishes were unexpectedly caught in small
tributaries during floods, presumably because of immigrants from the
main stem. Despite the plausibility, surprisingly few studies have
examined the hypothesis, and limited observations rather showed weak
evidence (Harvey et al. 1999; Han et al. 2007). As far as we know, a
positive result was shown only by Nunn et al. (2010) in a floodplain
tributary in a cyprinid-dominated lowland river.</font></div>
<div><font face="Geneva" color="#141413"><br></font></div>
<div><font face="Geneva" color="#141413">On 8-10 August 2003, a
powerful typhoon hit Hokkaido Island, Japan, accompanied with heavy
rain, which allowed us to investigate the potential role of
tributaries as refuges from flooding. We had just completed annual
population census in four small tributaries of a river system 1-2
days before the typhoon. Thus, we planned additional census in the
same manner in the four tributaries on 13-14 August (i.e., 3-4
days after the typhoon). This river system is ideal to examine fish
movements between tributaries and the main stem because immigrants can
be distinguished because of large differences in fish species and size
structures between the two habitats.</font></div>
<div><br></div>
<div>Results:</div>
<div><br></div>
<div><font face="Geneva" color="#141413">Overall, our results did not
support the hypothesis that many large fishes immigrate to small
tributaries during floods. Radio-telemetry studies revealed that
stream fishes can have remarkable tolerance to catastrophic floods by
using micro-refuges, such as large woody debris, boulders or stream
margins (Harvey et al. 1999; Makiguchi et al. 2009).</font></div>
<div><font face="Geneva" color="#141413"><br></font></div>
<div><font face="Geneva" color="#141413">Alternatively, fishes may use
tributaries only in the situations where not enough micro-refuges in
the main stem are available. Given that the frequency of severe floods
may be increasing worldwide because of climate change (Groisman et al.
2005), understanding conditions under which fishes escape into small
tributaries during floods would become more important.</font></div>
<div><font face="Geneva" color="#141413"><br></font></div>
<div><font face="Geneva" color="#141413">We, however, cannot exclude
the possibility that the time scale fishes reacted the disturbance may
be more rapid compared with our sampling period. If fishes used
tributaries just during the peak flow and immediately went back to the
main stem, our survey cannot reveal the escaping behaviour. Although
our pre- and postflood comparison was conducted exceptionally within a
narrow time-frame, even this may not be enough to detect the
escapement from the main stem. Although it is dangerous and logically
difficult, surveys during flooding should be favourable.</font></div>
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