Friends of Mitcham Common

We received news from the Conservators about the removal of fish from the Seven Islands and One Island ponds. The reasons were as follows:

• Fish being removed for consumption or being transferred to other ponds
• Low water levels in One Island Pond resulting in fish mortality
• Discarded line and littering causing injuries to wildfowl
• Trees and other wildlife habitats being deliberately damaged
• Ignoring lockdown restrictions during Spring 2020

The One Island Pond was de-stocked on February 1st. The Seven Islands Pond will be de-stocked in the near future.

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Discussion

This is, of course, not the first time that fish have been removed from the ponds. And since the reasons for concern about conditions around the ponds do not change, it will doubtless not be the last.

The main benefits biologically are that Carp (the predominant species) stir up silt and make the pond muddy – suppressing weeds. So the removal of large Carp may result in clearer waters and the development of pondweed, which will give structure needed for water invertebrates.

The main drawback is the loss of food for Cormorant and maybe Heron and Little Egret, which are occasional visitors. Assuming that a lot of smaller fish will remain, the food for Little Grebe might be sufficient to maintain breeding birds – but we cannot be sure as yet. Any negative impact won’t be for long, as the small fish will grow quickly and will reproduce within a few years.