Question 1 Report
Fig. 1 shows an invasive signal crayfish in a small river in southern England. It is shown beside a native white-clawed crayfish, a burrowed riverbank and eggs carried under the invasive crayfish. Volunteers have reported that native crayfish are becoming difficult to find. Ecologists are concerned that the invasive species may spread through connected streams and alter the river habitat.
(a) Outline two reasons why an invasive crayfish may reduce the native crayfish population. [2]
(a) Any two: competes with native crayfish for food [1]; competes for shelter/burrows [1]; may eat native eggs or young [1]; may carry disease to which native crayfish have little resistance [1]; burrowing can alter habitat [1].
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