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My Masters dissertation used data from
fisheries surveys of the Great Ouse Relief Channel in Cambridgeshire to
ascertain any effect the introduced predatory percid, the zander (Stizostedion
lucioperca) has had on native fish communities and how far it has
spread since its initial introduction to the Relief Channel in 1963.
The study also compared the biomasses of
the fish in the Relief Channel with those of the River Nar, to ascertain
any significant deviations from a comparable system lacking zander.
The study concluded that the zander has
spread throughout the whole of the Relief Channel, but appears to have been
wrongly blamed for an observed decline in the coarse fishery. It appears
that environmental parameters are primarily to blame for the decline. This
contrasts with findings of earlier studies, such as Fickling and Lee
(1983). It appears that in the intervening years between studies, the fish
community of the Relief Channel has settled down into a stable system, this
supported by biomass comparisons with the River Nar. Additionally, No
evidence of competition between zander and pike was found by this study.
The zander was also tested against a set
of empirical rules for freshwater invasions devised by Moyle and Light
(1996). It was found that aspects of both the zander and the Relief Channel
supported the empirical rules and contributed to their establishment and
success in this new habitat.
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