It is World Wildlife Day – a welcome excuse to dive beneath and celebrate the difficult-to-observe world of aquatic wildlife that lives either in the Trent or its many tributaries. Rivers are a life-sustaining wildlife corridor. Its freshwater supports a web of life that stretches way beyond the watercourse. Be it migratory birds, such as the Berwick swan, or year-round residents such as the bittern, it is hard to visit a river and not spot any wildlife.
For this World Wildlife Day, however, we’re focusing on the species that are difficult to encounter on a Sunday walk. The fish, invertebrates and plant life that have found a niche in the Trent catchment – often unbeknownst to those who admire the river’s surface.
Bullhead
Rare in Europe, but locally abundant, the Bullhead is a common find when kick-sampling in unpolluted streams ultimately flowing into the Trent. As the fish does not have a swim bladder, it is a bottom-dweller with a reluctance to migrate or move. Often, the fish holds an affinity to a particular rock that it likes to call its forever home, circumstance permitting.
The Bullhead is also known as Miller’s Thumb. Its plump, bullish head, followed by a slender body, references the allegedly flattened upper thumb of millers in centuries past. Camouflaging with its rocky surroundings, the Bullhead sports shades of brown and beige to avoid predators.
Water crowfoot
Like the Bullhead, water crowfoot is a promising sign of good water quality. Often growing in fast-flowing headwaters, the green weed has adapted to a volatile water cycle. Despite being a water plant, water crowfoot can survive dry spells, growing flowers that can survive above the water surface.
The plant also offers shelter to small fish such as the incredibly rare Spined Loach, a zorro-striped fish that has only been recorded in five English rivers.
Lamprey
The lamprey is a jawless fish that relies on a suction mouth to feed. With small raspy teeth lamprey live parastically of other fish species. Sea Lamprey spend part of their lives in rivers to then go to sea. River lamprey spend their life in the river, travelling up to the Humber Estuary, before they return to spawn. Like sharks, lamprey’s skelton is made of cartilage, rather than skeleton, like most other freshwater fish.
This living fossil has been subject to little change for over 330 million years, which has meant that salmon have more in common with human genes than they do with the lamprey genus.
Case-building caddisfly larvae
This invertebrate is also a common kick-sampling find. The case-building caddisfly larvae lives on the river bed, where it cloaks itself in small twigs and rocks. Connecting its self-made home, the caddisfly creates a silk-like spit to bind its riverbed-sourced case. As the larvae sits at the bottom of the food chain, its protective home is designed to protect it from predators including small fish. With over 200 species, caddisflies range from common to critically endangered.
Atlantic Salmon
Spending some time near weirs in late autumn to early winter you may find salmon on its return journey after spending much its adult life at sea. The Trent sees a small salmon run thanks to some reintroductions, combined with weir removals enabling access to spawning grounds.
Swimming thousands of miles, the salmon remains an endurance icon that not only experiences growing pressure at sea, but a combination of pressures including pollution and heating water temperatures in the catchment.
European Eel
The European Eel completes the arguably most arduous journey of all aquatic species in the Trent catchment. Not only is the eel one of the few species that can move on land for short sections, its most mind-blowing feet is its return journey to the Sargossa Sea, surrounding the Caribbean, via the Trent.
Now critically endangered, due to pressures in our rivers and at sea, the European eel still finds refuge in our rivers. Unlike the salmon, the eel hatches at sea follows ocean currents into our river systems to then spend most of its adult life in the Trent and tributaries.
Diatoms
Not even a dive, or kick-sample will reveal this species at the very bottom of the food chain. It is time to dig out the microscope for them!
This photosynthesising algae can be found in almost every aquatic environment including fresh and marine waters, soils – they’re almost anywhere moist. As base-level food and absolute bottom of the food chain, invertebrates and other bottom-dwelling creatures will feed on them in our rivers. Though often overlooked, they are a fantastic bio-indicator for water quality, as there are many types suited to almost every possible condition.
While this is just a flavour of species that you may encounter here in the Trent – why not subscribe to our newsletter to stay in the loop about events and opportunities to learn more about the wonders, challenges and exciting solutions at work here in the Trent catchment.
