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FAQs about Rays, Skates, Guitarfishes Behavior

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Sharks and Rays in Aquariums
Gaining an understanding of how to keep these fishes in captive saltwater systems   

New Print and eBook on Amazon

by Robert (Bob) Fenner

Round ray- nose tilted up    3/7/16
Dear wet web media crew, I have a couple of small round rays. They're about 5 inches in diameter. A lot of the time they like to rest with their noses tilted up, as you can see in the image below. Is this a bad sign?
<Maybe... is this tank chilled? Urobatis concentricus. These fish are not tropical... >
Does it mean anything and if so what could be causing this ? Both are active, I suspect they are bullseye stingrays. They eat silversides, shrimp and fresh marine fish once or twice a day.
<See, as in read on WWM re feeding Rays, and Thiaminase. Don't write back till you do>
The temperature is at a steady 74 degrees
and the water parameters are good. Nitrites and ammonia at 0 and nitrates are at 10. Thank you so much for your feedback! I look forward to hearing from you.
<I look forward to your enlightening yourself. Bob Fenner>

Request for bg info for my Senior Thesis Project, Neale  12/27/10
Dear WWM Crew,
Hello my name is Theresa. I'm writing to you with, what I see as an unusual question. I'm currently doing background research for an experiment I will be performing on 9 Cortez Round Stingrays (Urobatus maculatus) and I'm having a very difficult time finding any information on them. My experiment will entail working with a local aquarium store's touch tank and the rays that are housed in it to find a diet that will allow for a healthier living experience.
<Quite a topic! How will you assess such... healthiness?>
This research will be my Senior Thesis for my undergraduate degree in Biology. I will be measuring Oxidative stress, Growth, Bacteria loads on the top and bottom of the rays and well as in their feces, behavior patterns and what they are eating.
Although I do already have a good amount of research done I was wondering if you have any peer reviewed research articles that might help me with background information and methods for measurement.
<I do not... but having taught H.S. to college level Bio. courses, and attended college myself for many years, and generating articles utilizing bibliographic searches... I am aware of how to go about looking up pertinent literature. Please read here:
http://wetwebmedia.com/litsrchart.htm and the linked FAQs file above>
The two main sections that I need more information on is how I might measure oxidative stress without drawing blood and without stressing the rays out from transferring them into a holding tank and just the basic signs of an unhealthy ray.
<The first, not able to discern w/o manipulating the specimens... as far as I'm aware. The second; you'll have to do a bit of reading and develop a quantitative protocol... A random revisiting time-wise of observing the animals, counting aspects of their behavior you determine is "health" related. Further, do investigate common statistical methods for judging "confidence limits" on the significance of your findings>
Thanks for your time. Sincerely Theresa
<Am going to share your mail w/ (Dr.) Neale Monks, who helps out here as well, as he has more recently been involved w/ "doing" real science than I. Cheers, Bob Fenner>
<<Hello Theresa. As Bob says, there are a few issues here that will need further investigation. Measuring "healthiness" is always difficult and with fish tends to involve things like growth rate and fecundity, things of value in aquaculture but may not be practical here. There have been some nice works on Tetraodontiform fishes over recent years thanks to their value in genetic research, and like your Stingrays, these aren't easy to breed or as fast-growing as, say, cichlids or sunfish, so they're more challenging lab animals. Do review recent studies of Tetraodon nigroviridis and Takifugu spp. for example. An interesting and very readable paper is "Takifugu obscurus is a euryhaline Fugu species very close to Takifugu rubripes and suitable for studying osmoregulation" by Akira Kato et al. One very real problem you have is a small sample size; nine specimens may be too small a sample for your results to have statistical significance. In your case you might try to compensate for that by studying the animals across a long period, arguing that growth rate is sufficiently slow that it mightn't affect your results. If this was me, I'd be using something I could measure very simply, for example ventilation rate. I'd collect data at least twice per day, ideally at least once during the resting phase and once during the active phase. I'd collect data across several weeks, preferably 3-4 months. To ensure the data was reliable, I'd control other factors as far as practical: temperature and water chemistry/salinity especially. Obviously diet would need to be controlled too, because digestion will affect the rate at which oxygen is required, if only because fish can adjust activity rate depending on the availability of food in their environment. Alternatively you could measure swimming activity using a video camera to record the distances swum within a certain randomised period, such periods taken several times per day. I suppose it might be possible to measure oxygen concentration in the water, and if you know the oxygen concentration in the same tank without any fish, you might determine how much oxygen the rays were using. But honestly, I think variation in oxygen taken up by filter bacteria and other microbes would make this unworkable. Hope this helps. Cheers, Neale.>>
Re: Request for bg info for my Senior Thesis Project, Neale   12/29/10

Dear Neale and Bob,
Thank you for the suggestions. I will assessing healthiness by looking at the oxidative stress, bacteria loads, and behavior. There are three articles done by Christina Semenuik that look at the effects of unnatural diets on Southern Rays at the Stingray City Sandbar in the Cayman islands.
These articles are really where I'm basing my study off of. Semenuik found that the fatty acid profiles of the unnatural diet was not providing the proper fatty acids to the rays, she also looked into the costs that the group living was having on the rays themselves, and the final study she did was on the hematological aspects such as immunosuppressants, oxidative stress, and general health. I am unable to draw the blood of the rays so I was hoping that looking at their ability to ward off bacteria during different diets would show basic health. Semenuik et al. found that the rays that were not only unnaturally grouped but also eating unnatural diets showed higher oxidative stress, lower general health and higher amounts of immunosuppressants. So going off of that if the rays exhibit higher levels of bacteria loads, and high levels of oxidative stress then the diet currently being fed to them is not providing the proper nutrients.
<I see. Sounds a worthy topic for investigation.>
The plan would be to study the rays once or twice a week for a month while on one diet then at the end of the month the diet would be changed (due to my distance from the study site and the fact that it is a store I would be unable to take measurements everyday). As far as I know the temperature, salinity and pH levels of the tank are controlled as much as possible (The rays are housed in a touch tank). What do you mean by "measure the ventilation"? Do you mean count the amount of times that the spiracles open?
<Yes, breathing rate in fish can be estimated by counting gill movements per minute or some similar measurement.>
Thank you for your time.
Articles by Semenuik et al.
"Using Fatty-Acid Profile Analysis as an Ecologic Indicator in the Management of Tourist Impacts on Marine Wildlife: A Case of Stingray-Feeding in the Caribbean" "Costs of group-living for a normally
solitary forager: effects of provisioning tourism on southern stingrays Dasyatis americana"
"Hematological differences between stingrays at tourist and non-visited sites suggest physiological costs of wildlife tourism"
<Would consider doing a pilot study on something smaller, easier, e.g., Mosquitofish that would allow easy measurements of growth rate and fecundity, and perhaps compare these against sampled gill ventilation rates. If you can establish that growth rate and fecundity go down as gill movements go up, i.e., the more stressed the fish is, the less rapidly it grows and breeds, you'd have some objective connection between breathing rate and the healthiness of the fish (assuming growth and fecundity are the same thing as healthiness). Or something along these lines anyway. Cheers, Neale.>

Florida ray beh.  -- 06/10/10
I have a florida ray, she is sometimes swimming in circles and lifting her body up with her disc, what does this behavior mean?
<Mostly: "Lemme out of here!". Read here:
and the linked files above. Likely this animal is in too small a volume, but there are a myriad of other aquarist-caused issues...>
She is still eating very well, does not refuse any of it.
Sent from my iPhone
<Mine from a desktop. Bob Fenner> 

Research Paper on stingrays  9/9/06 Hey crew,   I'm going to be writing a research paper for my physics class soon and I'm going to be doing it on either the Urolophus halleri or Pteromylaeus bovinus (bull ray). I would like to know if there is a calculation in order to calculate the rays growth a year depending on feeding. <Mmm, not as far as I'm aware... likely you could formulate some empirical formula here... accounting for food volume, type, temperature, metabolite effects... much more> How many inches do you think both of the rays grow a year? In the wild and in public aquariums.   <Age/length data exist at least for halleri (have you seen fishbase.org re yet?>   Thanks,   Ben <Bob Fenner>

Yellow Stingray Hi Bob, I found out what that stingray was, a yellow stingray like I thought.  I would have gotten it too if I was for sure.  I was just wondering if you know how active yellow stingrays are?  Are they nocturnal?  Also do you think it would be more active then a bamboo shark? Thanks Adam Siders <Yellow stingray? Urobatis jamaicensis? http://www.fishbase.org/Summary/SpeciesSummary.cfm?genusname=Urobatis&speciesname=jamaicensis Likely so... not active... spend almost entire time still, setting on top or just under the substrate. Bob Fenner>

Sharks and Rays in Aquariums
Gaining an understanding of how to keep these fishes in captive saltwater systems   

New Print and eBook on Amazon

by Robert (Bob) Fenner
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