The numbers of frontline officers joining and leaving the prison service have reached their highest levels for years.
New data on staffing levels reflect the competing impacts of a major government recruitment drive and rising departure rates amid the safety crisis behind bars.
Official figures published by the Ministry of Justice show that the year to March saw the highest level of new starts in operational roles in prisons in England and Wales since 2010, when the current statistics started.
In 2016/17 there were 2,314 officers appointed in one frontline staffing category, band 3.
This was an increase of 338 (17.1%) compared to 1,976 in the previous year. The figure is made up mainly of new recruits, as well as existing staff converting to the posts.
Last year, ministers announced plans to add 2,500 officers as part of a wide-ranging package of measures aiming to reform jails hit by surging levels of violence and self-harm.
At the end of March there were 18,403 "full-time equivalent" staff in frontline categories, bands 3 to 5, which was an increase of 75 on the last year and 515 on the previous quarter.
However, the figures also lay bare the continuing problem with retention of personnel which has been felt in parts of the country, particularly London and the South East.
The headcount number of band 3 to 5 officers leaving the National Offender Management Service in 2016/17 was 1,834, an increase of 290 (18.8%) compared to the 1,544 officers departing in the previous year.
Excluding periods where there were voluntary exit schemes, this was the highest number of leavers in a 12-month period in the time series, the MoJ report said.
It added that the number of band 3 to 5 officers leaving in the latest quarterly period fell by 73 (15.4%) compared to the previous three months.
The figures also showed a dip in the numbers of operational support staff in prisons.
Ministers have previously announced a number of steps to boost recruitment and retention of staff, including pay increases and mentor schemes for new recruits.