Step 1: Understand the question.
We must name the fertilizer that is made from scrap fish, that is, leftover and waste fish material.
Step 2: Think about why fish makes fertilizer.
Fish bodies are rich in nitrogen and other nutrients that plants need. So waste fish can be turned into a useful plant food.
Step 3: Recall the correct name.
The nitrogen rich fertilizer prepared from dried, ground scrap fish is called fish guano.
Step 4: Rule out isinglass.
Isinglass is a clear substance from fish air bladders used to clear drinks, not a fertilizer. So it is out.
Step 5: Rule out shagreen and ovaprim.
Shagreen is the rough skin of sharks and rays used as an abrasive, and ovaprim is a hormone used to help fish breed. Neither is a fertilizer.
Step 6: State the answer.
So the fertilizer from scrap fish is fish guano.
\[ \boxed{\text{Fish guano}} \]