River and coastal marine habitat use and the continuum of migration strategies by brown trout (Salmo trutta) smolts from the River Dee (Aberdeenshire)

Archer, Jonathan Alan (2022) River and coastal marine habitat use and the continuum of migration strategies by brown trout (Salmo trutta) smolts from the River Dee (Aberdeenshire). MRes thesis, University of Glasgow.

Abstract

Brown trout (Salmo trutta) exhibit a continuum of migration strategies variety of ranging from the extremes of river-residency through to anadromy. As a result, various terms have been created to describe these strategies which has led to a confusion of their uses. This study provided further clarity to the various terms used for describing Salmo trutta migration strategies. Changes in salinity between habitats and Strahler stream order was chosen as a method to define the boundaries between due to their biological significance. A practical framework of terms for future studies was created, within this a freshwater resident remains in water with a salinity of less that 0.05ppt, Semi-anadromous fish migrate into water with a salinity of 0.05-30ppt and anadromous trout migrate into waters with salinities >30ppt. If future studies adopt the proposed framework this will enable better comparison and communication within scientific literature with regards to Salmo trutta. Few studies have investigated Salmo trutta migration strategies, and habitat use within a modified coastal plain estuary, that opens into an unconstrained sandy bottom marine habitat. This study investigated the migration strategies, and habitat use of 79 Salmo trutta smolts within the River Dee (Aberdeenshire) in 2018-2019. The Salmo trutta smolts exhibited a continuum of well-established migration strategies which included potamodromous (n=9), semianadromous (n=18) and anadromous (n=22) life histories. Anadromous smolts also exhibited a variety of behaviours, including: estuary staging, returning early to the estuary and repeat migrations between the sea and estuary. Semi-anadromous and anadromous smolts spent considerable time in the estuary (median 2.53 days IQR 0.35-19.56 days). However, most of this time was spend in the river mouth (median 1.32 days, IQR 0.17-11.9 days) than within the harbour (medium 6.72 hours, IQR 2.88 minutes to 2.23 days). This study showed the estuary and coastal areas are critical for the early migration of the River Dee’s Salmo trutta smolts.

• Item Type: Thesis (MRes)
• Qualification Level: Masters
• Additional Information: Due to copyright restrictions this thesis is not available for viewing.
• Subjects: S Agriculture > SH Aquaculture. Fisheries. Angling
• Colleges/Schools: College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
• Supervisor's Name: Newton, Dr. Matthew and Adams, Professor Colin
• Date of Award: 2022
• Depositing User: Theses Team
• Unique ID: glathesis:2022-83299
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 07 Dec 2022 12:21
• Last Modified: 13 Dec 2022 12:20
• Thesis DOI: 10.5525/gla.thesis.83299
• URI: https://theses.gla.ac.uk/id/eprint/83299