Awe of watching River Monsters in Animal Planet

Yesterday was a lazy day for me as the weather is all dull and I got up very late. It is one of those days where you feel like not moving an inch and being bored at the same time. The only task I'm doing, religiously, during these pandemic days is using up the data balance of my Internet before midnight. Streaming movies online became a regular thing too and this animal planet channel in Airtel Xtreme caught my attention. The title "River Monsters" itself is Intriguing. 

River Monsters is a show about predatory fishes found in rivers across the world. Jeremy Wade was in Thailand trying to catch a live stingray in the local water bodies. He caught another fish too which is a plain herbivore and doesn't have teeth. But all through the show, his intention was to see a real living huge stingray in those water bodies. I have always studied that rays and sharks are found in marine water. Especially rays are bottom dwellers being predatory with huge bodies they can easily survive in oceans. But when Jeremy wade was searching for ray in the river I thought the fish would have migrated here and it might be common in that country. But later in the show, he said that these are born in the river and live in a freshwater environment which is surprising. Two stingrays were caught.

A quick search on the internet has shown that there are different species of freshwater rays and sharks. 

 The second fish which was caught was about 400 pounds female and it was having three babies inside. Two of the babies came out and scientists collected data from them too. I watched the lady scientist take scrapings from the skin around the eyes and the genitalia. The sting is on its large tail and they collected the poison mucus from it. The scientist put an ultrasound inside the fish and said there is another baby inside, but it wasn’t delivered during the program. The baby fishes born were comparatively darker than their mother and it was said that they don’t have stings (or poison I guess) when they are inside the womb probably as a protection to the mother. After birth within a few minutes, they develop that defense mechanism.

 Jeremy Wade, in the show, broke his fish gear when he was trying to catch the first fish and said that it was strong and was built to catch sharks. Later they caught an (eel) which doesn’t have teeth inside and said that it is probably an herbivore. All the caught fishes are safely sent back into water and the rays were never completely out of water. I think it is because the rays are bottom dwellers and they can’t survive out of water for too long. Whenever a ray is caught they are first disarming it by tying a tape around the tail and attaching a bob. Then they are measuring its length and breadth and then weight.

Jeremy went to the local market and found some rays of different sizes there and he has shown the dorsal and ventral sides clearly. He found a local fisherman at a place on the roadside shop and took a photo of his ray fish catch. It was a large ray of 350 kgs – 700 pounds and they have shown a video also.

So many questions are running in my brain now. 

Are there more rays that are freshwater? If so, what are those species and how many species and where are they found? 

Why are they growing in freshwater? What is the difference in physiology? 

Why they are predatory when other fishes found in the same place are herbivorous?

What is the gestation period of a ray? 

How does it eject poison? 

Why is the ray caught and released went silently away and didn’t sting them after releasing? Don’t they have a revenge mentality?

What is the actual function of the gear? How are they catching fishes?