Sea trout are a significant economic and social asset as part of a recreational fishery, they are also an important component of our native aquatic biodiversity. Sea trout are trout that make a migration to sea during their life cycle. Also known as white trout locally they tend to spend two to three years in their natal streams before going to sea to feed and grow, returning to freshwater to spawn. It is believed that both a scarcity of food in their native rivers, and genetics may play an important role in trout choosing to undertake a seaward migration.
Trout pursue diverse life history strategies which facilitates some to take advantage of richer feeding in the marine environment. This can lead to Sea trout growing significantly larger than resident Brown trout and may give them a competitive advantage when breeding. Larger Sea trout will carry more eggs. Studies on Sea trout in other areas have shown that a disproportionate number of Sea trout are female.
At present in the Foyle and Carlingford areas juvenile electrofishing surveys are one of the main audit points used to monitor trout populations. Electrofishing surveys are carried out annually at approximately 500 sites across the Foyle and Carlingford areas. Sites are monitored using a semi-quantitative (5 minute timed) electrofishing method. Loughs Agency also conducts targeted Sea trout surveys at a number of locations and other life history stages. Pre spawning adult Sea trout are monitored at a growing number of sites annually. Utilising a longitudinal electrofishing survey method adult Sea trout are caught, key biological information collected and the fish returned to the water. This information can provide both temporal and spatial data within reference reaches at key Sea trout spawning areas. Out migrant Sea trout smolts, early returning adult Sea trout and Finnock (immature Sea trout) are monitored and key information collected as part of the long term river index site project on the River Faughan. This project collects information through the seasonal deployment of a Rotary Screw Trap. A wide variety of species and age classes are recorded including Sea trout. The biological information collected from the Sea trout includes scale samples for genetic analysis. The biological data collected is used to make management recommendations.