Edward Ingle was caught using nets to illegally take salmon from the River Tyne, in East Lothian, in April this year.
And despite being ordered by the courts not to go within 25 metres of the river, Ingle was again caught poaching for fish on the same river just three weeks later.
Haddington Sheriff Court heard Ingle was appearing for the 33rd time on a poaching charge, in a criminal career that goes back to 1985.
The former-oil worker, from Dunbar, East Lothian, who racked up 11 poaching convictions in 2006 alone, was sentenced to five months in prison.
Ingle pleaded guilty to fishing for salmon, other by rod and line or net and cobble, at the River Tyne, near to Dunbar, on April 19 and 20 this year.
He also admitted to using nets to fish for salmon at the River Tyne, at Tyninghame Bridge, East Linton, on May 12, and to breaching a court order banning him going within 25 metres of the river with the intention of catching fish that day.
Solicitor Graham Lowe said his client "accepted the seriousness of his position" but was trying to turn his life around by applying for work.
Sheriff Peter Braid sentenced Ingle to five months in prison for the first poaching offence and for breaching his bail conditions banning him from the Rivers Tyne and Tweed. The sheriff also fined the thief £200 for the poaching offence committed in May.