Fish Passage

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Houghton Bottoms weir- one of the fifteen weirs selected for fish passage works.

One of the most important, but lesser talked about factors in conservation is habitat connectivity. In simple terms habitat connectivity refers to the way the landscape allows or prevents the movement of species between resources and habitats.

Rivers are not usually thought of as fragmented habitat as they flow continuously from source to sea, however they do become fragmented when structures in the river channel prevent the natural movement of river wildlife.

Within the Ribble Catchment there are over 1,000 structures which cause habitat fragmentation; some of these simply prevent fish migration whereas others are also hindering the movement of invertebrates and mammals.

During the Ribble Life Together project we will be delivering a range of fish passages which will modify some these structures and enable wildlife to move more freely through the catchment, these have been chosen based on two major factors.

How significant a barrier is the structure?
How much habitat is re-connected through intervention?

As part of the development phase a fish passage prioritisation tool was created which allows us to calculate the amount of habitat that could be reconnected through intervention for each weir based on numerous factors, largely the shape and size of the barrier.

This tool and other research has allowed us to identify the 15 of the most important structures and using the principle that ‘reconnecting habitat should permit migration for all species, of all ages, all of the time’ we will decide on the most suitable intervention for each of these individual weirs.