East Greenland expedition 2023

In September 2023, the SMOLTRACK team returned to Eastern Greenland in hopes of catching some nice-looking salmon at their natural feeding grounds.

The trip proved successful, and showed that it is possible to capture, sample, and tag Atlantic salmon with electronic tags in these remote waters. Salmon were also caught in net for stomach analyses. All the salmon were immature, and of a size that indicates they would return to their native rivers as 2-SW or older fish. Genetic analysis confirmed the presence of Atlantic salmon from multiple European countries, including Denmark, Norway, and the UK.

Dr Kim Aarestrup (DTU Aqua) proudly presents a net-caught Atlantic salmon.

The development of capture methods and live-well holding in Eastern Greenland opens exciting opportunities for future research on the marine migrations of salmon!

SMOLTrack meeting Portugal

The SMOLTrack team met in Monção, Portugal on the River Minho in June 2023, to discuss their ongoing work tracking salmon from rivers into the North Atlantic and back. Scientists from 8 countries are co-operating to provide the data to underpin the conservation of wild north Atlantic salmon.

Fresh from the press!

Published results

Marine mortality in the river? Atlantic salmon smolts under high predation pressure in the last kilometres of a river monitored for stock assessment

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Abstract

The River Bush (Northern Ireland) is an index river for the estimation of Atlantic salmon, Salmo salar L., stock size, population dynamics and marine survival rates. Marine survival estimates are based on the number of smolts counted at a trap 3.5 km upstream of the river outlet. The survival from release to coastal inshore waters for acoustic-tagged smolts released at the Bushmills trap varied between 32% and 68%, with both year and brightness during river exit playing a significant role in explaining the variations in survival. This constitutes an important survival bottleneck. Contrary to true marine mortality, this significant loss of smolts in the river and nearshore environments could be reduced by focused management actions. More studies on other rivers, where smolts are enumerated above the head of tide, could further partition smolt and post-smolt mortality, help differentiate true marine survival and help understand fluctuations in adult returns.

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Tagging – First results!

Recovered tags

Recovering radio tags allows us to directly link the smolt predation to the predator. In this case, our smolt was eaten by a mammal, most likely an otter. Other common predators are herons, cormorants and bigger fish!