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The rivers in xmoor have been consistently overflowing this winter. Darkened by peat and flowing rapidly over rocks, the Exe, Barle, and East Lyn have surged through the coldest months. I had planned to participate in a survey to count the number of salmon spawning locations, but unfortunately the water has been too murky to conduct the survey.

During the period of October to January, female Atlantic salmon and sea trout form cavities known as redds on the riverbed to deposit their eggs. In calmer weather, these depressions in the gravel can be seen as bright spots where the sediment has been removed. Despite the challenging conditions this year, it is believed that the salmon were still able to reproduce and it is hoped that the offspring were not washed away.

In February, the breeding season begins for various river fish. Exmoor’s clear, pebbly streams are a prime environment for bullheads, also called miller’s thumbs (Cottus gobio). These large-headed, round creatures typically live under rocks and come out at dusk to eat small animals without backbones. They appear to favor spots under bridges, possibly for safety from kingfishers and herons. I have observed them lurking under footbridges along Horner Water, resembling trolls in the dim light.

Carefully lifting a stone and allowing any debris to settle, you may come across a unique creature: a speckled brown fish with large fins on its sides gripping onto pebbles, remaining steady in the current. These fish have remarkable eyes, resembling beads of bubbled glass. Their corneas are like double-paned windows, with a thick outer layer that curves like a deep-sea submersible and a second inner layer over the pupil. When viewed from above, one can see a shimmering fluid-filled space between the two layers.

If you make a careless move, the fish will quickly swim away. After you leave, it will likely go back to the very same rock where you first discovered it. Bullheads have the ability to identify their home rock even if it has been relocated. They are highly protective of their territory and will defend it by repeatedly nodding their heads, causing their skulls to hit against nearby bones and creating a small knocking noise.

Source: theguardian.com