Dasyatis sabina

I picked up the ray yesterday. It's a Dasyatis sabina, which is actually a marine ray with some... complications. Their range stretches from Chesapeake Bay in the summer to central America, along the coastlines and in brackish estuaries. This species can navigate in marine water, brackish water, and full freshwater.
There is also a variant of the species which spends its entire life in freshwater, and these are found in the St. John's river of Florida. Unfortunately, like most rays (and especially freshwater rays) much more study is needed on these animals to learn more. I was up to past midnight last night trying to definitively ID the species. Finally nailed it on fishbase.org
Of course, I also ran across "information" on various Internet forums, which was pure unmitigated crap. Contradictory "advice," flame wars, and a hodgepodge of misinformation. I finally gleaned some good hobbyist data from this excellent ray keeping site: http://www.raylady.com

I'll summarize the little solid info we have on these animals and then provide a few interesting links.

Unlike the freshwater rays of South America, like the p. motoro, d. sabinas are capable of transversing waters of varying salinities and even undergo rapid salinity changes without ostensible harm. Their South American cousins have lost this osmotic gimmick of a gland and thrive in freshwater.

What's so fascinating about the rays of St. John's river is they appear to live their entire life span in freshwater. Indeed, these rays can be found in springs that feed into St. John's. This variant is also significantly smaller than the main species which live primarily in marine waters. Other than that, they are identical.

http://www.ecofloridamag.com/archived/stingrays.htm
http://nersp.nerdc.ufl.edu/~pmpie/dsabina.html
http://www.flmnh.ufl.edu/fish/Gallery/Descript/AtlanticStingray/AtlanticStingray.html

I selected this ray as we had seen him three weeks ago at an LFS outside Asheville. And he was the most alert and healthy ray I'd ever seen in a store. He had been in the store for two months prior to that so we knew he was in good shape. I also watched him eat. With rays, it's common to see many that don't eat at all and you're playing Russian roulette as a good number die a few days after arrival or simply wither away. This is why it's always good to pick out a specimen that's been in the store for several weeks and clearly eating.

In conclusion, you may be thinking it odd I set up this tank on Thursday and introduced a massive fish like this yesterday. It is absolutely critical to have a fully cycled tank for sensitive fish like rays. So what I did was poach a hundred or so biorings from my established (and somewhat overstocked) tanks and filled an Aquaclear filter full of them. This in essence jumpstarted the nitrogen cycle as the nitrate producing bacteria were simply moved from two tanks into one. I like to play things safe and have a level of redundancy so I'm going to shock the tank with Biospira tomorrow when I'm confident a fair amount of fish excretions are in the water for which to feed the bottled bacteria.

Always remember to cycle your tank. Whether it's fishless cycling (which I don't like), seeding from established tanks, or using Biospira (my preference), your tank must be producing nitrate before you introduce any sensitive fish.

- Josh
joshday.com