The 33-year-old former Wales U20, Cardiff Blues and Cardiff full back worked under Steve Law last season and now fills the vacancy created by his departure.
Fish will have Craig Everett, the former Wales U20 defence coach, newly appointed academy coach Josh Turnbull, who has taken up a role as line out and contact area coach, and former Cardiff Met and age-grade coach Nick Fish, who will be scrum coach, working alongside him.
Cardiff Rugby Academy manager Gruff Rees will remain in overall charge as director of rugby. Their brief will be two-fold – to bring through more young players for the regional team and to try to repeat the success the club enjoyed under Law, who won a league title, two cups and reached the Premiership final and semi-final in the past two seasons.
“We have a good coaching group, and we’re all looking forward to finding and developing the next Cam Winnett, Alex Mann and Mackenzie Martin,” said Fish.
“The new league structure will allow plenty of opportunities for players to develop and compete at a higher level and that’s something I’m really looking forward to.
“It’s an exciting time for the club with a good group of academy players and senior semi-professional players, who pass on a huge amount of experience to the younger lads.
“We wish the retiring players and those moving on all the very best and thank them for everything they have given in a Blue & Black jersey. A special thank you also goes to ‘Spot’ (Steve Law), who I’ve had the pleasure of playing under and working alongside.
“It has been enjoyable and testing, and I look forward to seeing him at the Arms Park soon.”