Scientists have discovered a rare species of fish in the River Wyre in Lancashire, which has not been seen in the north west of England for more than 25 years.
The European smelt, Osmerus eperlanus, were caught by Environment Agency workers in the Wyre estuary during a recent fish survey. The fish used to be common in estuaries, but has become very rare over the past few decades as it is extremely sensitive to pollution.
Environment Agency Fisheries Scientist, Dr Brian Shields, told Practical Fishkeeping: "These young fish are predominantly found in large clean estuaries. Their existence in the Wyre is a good indicator of the improved water quality in that area."
Like Salmon, European smelt are euryhaline and live in both marine and freshwater, making them adaptable to life in estuaries. The species typically reaches a size of 20-30cm/8-12" and spawns in the upper reaches of rivers in freshwater. Juveniles move downriver and live in estuaries, while adults are typically found at sea when not spawning.
The fish discovered in the River Wyre are believed to be a couple of years old, which means that they are likely to have bred upriver. Environment Agency experts said that this indicates the water in the Wyre is clean enough to support the species in the future.
While the European smelt of western Europe are anadromous spawners, like Salmon, those found in eastern Europe are typically lake spawners. A number of subspecies of Osmerus eperlanus exist, including Osmerus eperlanus eperlanus, a lacustrine spawning species found in the Baltic.