There is a world somewhere between reality and fiction. Although ignored by many, it is very real and so are those living in it. This forum is about the natural world. Here, wild animals will be heard and respected. The forum offers a glimpse into an unknown world as well as a room with a view on the present and the future. Anyone able to speak on behalf of those living in the emerald forest and the deep blue sea is invited to join.
My point on the size discrepancy might have been missed. My conclusion is under the assumption of a non-fat captive specimen. A seriously obese animal will of course weigh more than even the most robust yet fit of its healthy counterparts. In that sense, like I stated earlier, the heaviest specimen in a species will more likely than not be found in captivity.
Though, for aquatic animals, a thought occured to me. In fish (at least your aquarium species), growth is stunted in low water volume conditions whereby concentrations of toxins (ammonia, nitrate, etc.) are unavoidably greater than the vast oceans (I am quite certain of this saying as well, I've experienced it first hand). Fish grow dimensionally their whole lives, and seem to have a hormonal system which reacts to living conditions such as space and toxin levels. This is known as phenotypic plasticity, where one genome can produce multiple different results based on the environment it is put in. I wonder if aquatic mammals undergo the same stunting based on hormonal reactions to the lack of space, as in no way are those tanks enough for such goliaths of the sea. It's certain that aquatic conditions are more sensitive than land conditions, as there are more chemical factors in water which have a direct effect on life. For aquatic mamals, it's all conjecture, the sample size in captivity is too small and the wild sample size is essentially nonexistant.