Does immigration affect wages of indigenous people?

The honest answer is I don't know. In a previous job we used to do drugs of abuse testing in a meat processinv factory. Most of the staff were Portuguese and eastern European. The management said they couldn't find local staff despite high unemployment. Impossible to say if they could afford higher wages or if the locals would then take them. Similar situations around farm labour, especially in the east of England. Another factor to bear in mind there is the power the large supermarkets have in driving down prices to farmers and so wages. Are we prepared to pay more for food? I worked one summer picking strawberries. There were no migrant workers, but there were no local workers either. All the workers were students, so maybe student summer jobs have disappeared, or is that because they're now all in south east Asia?