Why Some Stingray have Ammonia, Urine or Urea Smell? How to get rid of it?

Alice Law and SuiTuaPui commented about their experience with Ammonia smell in stingray at my post, Simple spicy Stingray with Butter and Masala Recipe. I have once bought a stingray that reeked of urine smell and no matter what strong spices I used, the smell is still there. There are several reasons why stingrays have urine, urea or ammonia smell. Stingray is a cartilaginous fish related to the shark. Their body and tissues are designed to be isotonic with sea water. In order to do so, stingrays and shark kidneys are designed to excrete urea into the body tissues. Therefore, when their body is in osmotic balance with sea water, they can prevent water loss from the body cells. When a stingray dies, bacteria will break down the urea compound and turn it into ammonia. This explains why stingrays that are not fresh have very strong ammonia smells. Fresh stingrays have clear bright red coloured blood and those that are not fresh would normally have darker red blood. Since ammonia is alkaline, soaking the stingray in light cooking vinegar which is acidic would neutralize it into salt and water. A possible reason for Stingrays to have urine or urea smells is very likely that they are not gutted properly. The person handling the fish might have accidentally cut the kidneys and other organs that have high urea content. The urea can leak into the flesh, thus contaminate it. Since urea is acidic, soaking the stingray in Sodium Bicarbonate (Baking soda) which is alkaline might help to rid off the urine smell. So, the questions is, how do we know the smells is from ammonia or urea? If the fish doesn’t look fresh and have a nose piercing smell that very likely it is from the ammonia. If the fish is fresh and have clear bright red blood colour, then the smell is very likely from the urea content. I was lucky to have only one bad experience with stingray with terrible odour. Whenever I buy stingray, I would smell it first and check the blood whether is clear bright red in colour. Please note that you might not see much blood in stingray cut after the fishmonger washes them. This doesn’t mean that they are not fresh. It is always good to ask the fishmonger for advice. I normally buy fish from a few fishmongers that I know are reliable and have been my regular supplier for years. This really helps a lot in ensuring that I get the best fish. Happy marketing and cooking!