Population Structure and Genetic Stock Identification of Trout (Salmo trutta) from three Dublin Rivers: Dodder, Liffey and Tolka

INTERIM REPORT

In 2014, IFI in collaboration with Queen’s University Belfast began a three-year research programme to examine the genetic diversity of brown trout in selected Dublin Rivers in tandem with two other catchments. This study included three of the main Dublin rivers; Dodder, Liffey and Tolka. The main objectives of the study were:

• To investigate if there are a number of discrete genetic stocks in each catchment.
• To understand how important each genetic group is to the fishery.
• Examine the behaviour and other processes occurring within individual populations and between populations over their life span.
• The project also aims to investigate the impact of barriers (natural and manmade) to fish migration on the brown trout populations.

Dodder

• Have manmade and natural barriers divided trout stocks in the Dodder into discrete genetic trout populations?

Liffey

• What proportion of the adult trout stock in the Liffey is recruiting from the 10 known spawning streams?
• Are other small streams making a contribution to the Liffey stock?
• Are there one or more trout stocks that spawn and spend their entire life cycle in the Liffey main channel?
• Are fish of tributary origin widely distributed in the main channel?

Tolka

• There have been two major problems for trout stocks in this river, i.e. man-made barriers and water quality. What effect have these had on brown trout stocks within the catchment?

Preliminary results from the genetic analysis are presented in this report. A final report will be available mid 2017.