Natural selection, evolution, and demography of salmonine populations experiencing intrusion from non-local stock

• Main Author: O'Sullivan, Ronan J.
• Other Authors: Reed, Thomas, Mcginnity, Philip
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University College Cork 2021
• Subjects: Atlantic salmon; Eco-evolutionary dynamics; Captive-wild interactions; Local and non-local stocks; Introgression; Intrusion
• Online Access: http://hdl.handle.net/10468/12391

Many salmonine taxa experience intrusion into their wild, free-living populations from non-local conspecific and heterospecific individuals. Such intrusion arises most commonly as a result of releases from captive breeding programmes for conservation, or to provide a demographic excess that can be exploited commercially or recreationally. Furthermore, the relocation of conspecific individuals from one population to another, the deliberate stocking of sexually compatible foreign taxa into areas outside of their natural range, and domesticated individuals escaping from fish farms provide additional pathways for intrusion. The relative fitness of non-local to local fish, as well as the effects intrusion has on wild populations, is highly dependent on the ecological context that both types of fish experience and the level of adaptation displayed by the introduced fish. In this thesis, I examine how natural selection and, thus, evolution affect the performance of free-living salmonine populations that have experienced intrusion from non-local (captive-bred, translocated, domesticated) stock. Exploring this interplay can help to identify what conditions allow for, and the extent to which, non-local fish successfully breed in a given wild setting, as well as to determine the effects their breeding has on the demography of the recipient wild population. A better understanding of the roles natural selection and evolution have on demography and population viability is crucial for designing better captive breeding programmes and mitigating against the negative effects sexually compatible foreign taxa and fish farm escapees can have when they spawn in the wild. In Chapter 2, I use a molecular pedigree to estimate the lifetime reproductive success of individual Atlantic salmon and demonstrate that captive-bred fish are 64% less fit than their wild-bred conspecifics when both spawn together in the wild. Furthermore, I found evidence of a transgenerational carry-over effect from the hatchery where the wild-spawned offspring of ...