Have the child crumple the newspapers into small paper balls.
Stuff the paper bag with the crumpled newspapers.
Use the yarn or a ribbon to tie a knot close to the edge of the open end to close the paper bag.
Ask the child to paint the filled paper bag using either a brush or cotton balls.
Glue large googly eyes.
For grading, you can ask the child to draw eyes on construction paper and cut/glue it onto the paper bag.
Lay a piece of yarn on the fish (below the eyes) to make a mouth. Use some glue to hold it in place.
To promote tactile perception, you can let the child finger paint the paper bag instead of using other media.