Scottish Marine and Freshwater Science Volume 5 Number 6: Collation of Available Datasets on Smolt Populations in Scotland to Assess Migration Run Times

1. Introduction

Smolt population monitoring is increasingly being used to underpin research and to inform salmonid management in Scottish rivers. The aim of this project was firstly to quantify the range of smolt monitoring efforts undertaken in Scotland, and subsequently to determine the availability of these raw datasets for the purposes of this project.

This work was undertaken in the context of the National Research and Monitoring Strategy for Diadromous Fish ( NRMSD) to investigate the potential for interactions between diadromous fish and wind, wave and tidal renewable energy developments. Further information on this stakeholder led strategy is detailed in Hunter et al, 2014.

The Scottish Government has pledged to meet 100% of our electricity needs by 2020 through renewable energy sources, with offshore wave, tidal and wind devices set to provide a major contribution (Scottish Government, 2014). Relative to our understanding of salmonid ecology in freshwater, migration routes and life strategies in the coastal and marine zone are poorly understood (Friedland, 1998 and references therein). Specifically, Malcolm et al, (2013), identified that " There is limited information available on the timing of migration for both juvenile and adult fish for specific locations on the Scottish coast." Construction of a number of offshore and marine renewable developments is proposed for initial construction phases to begin in 2014. The construction phases of these developments are often considered the period of highest risk due to the additional disturbance within the coastal environment (Malcolm et al, 2013). Thus the ability to identify smolt run timings could be used to design temporal mitigation measures if required.

The initial project specification focused only on Atlantic salmon. After discussion with MSS, the SFCC agreed to increase the scope to include trout, with limited information also presented on other species such as lamprey and eel. Data collected to the individual fish measurement level is provided where available, with count resolution data also supplied.

This report provides a detailed meta-data summary of the raw data supplied including maps, temporal resolution displays, and a description of the raw data formats provided. Further to this, questionnaire responses are presented revealing the research questions being addressed by the trap installations and how these relate to local fishery management plans. Photographs of trap installations are also provided for the majority of locations.

The meta-data summary provided to MSS constitutes an almost absolute coverage of Scotland in terms of the existence or otherwise of smolt monitoring installations. As far as the SFCC and its members are aware, the Shetland Islands is the only remaining region where confirmation or otherwise of smolt monitoring efforts is outstanding.

MSS will subsequent analyse the data supplied under this project to assess its potential for improving our understanding of smolt migration run timings at specific locations on the Scottish coast. A secondary aim will be to ascertain the potential of smolts in the locations provided to carry acoustic tags which can be deployed to track individual fish and are implantable dependent on fish weight and length.