Complex sentence: It is notable for being one of the best Salmon fishing rivers in the country, though Salmon stocks have declined sharply in recent years due, some believe, to commercial netting of Salmon off the West coast of Ireland.
Split into simpler sentences: It is notable for being one of the best Salmon fishing rivers in the country, though Salmon stocks have declined sharply in recent years. This has been attributed to commercial netting of Salmon off the West coast of Ireland.