1.Cook pasta in large saucepan of boiling water, uncovered, until almost tender. Add peas to pan with pasta and cook until peas and pasta are just tender; drain.
2.Meanwhile, make dill dressing. Place ingredients in screw-top jar; shake well
3.Heat oil in large frying pan; cook fish, uncovered, until cooked as desired. Remove from pan; stand 5 minutes. Discard skin and any bones. Flake fish into large chunks.
4.Place pasta, peas and fish in large bowl with onion, spinach and dressing; toss gently to combine.