Jay Hemdal Live

Upcoming Article for Amazonas Magazine

 

An upcoming article for Amazonas magazine written by myself and Dr Paul Loiselle will feature information about the endangered cichlid fishes of Lake Victoria.  Due to space constraints, the suggested reading list could not be included in the magazine itself, so it is presented here for readers wishing further information.

 

Recommended Reading

Witte, F., T. Goldschmidt, J. Wanink, M. van Oijen, K. Goudswaard, E. Witte-Maas, and N. Bouton. 1992.  The destruction of an endemic species flock:  quantitative data on the decline of the haplochromine cichlids of Lake Victoria.  Env.. Biol. Fishes 34:1-28.

 

Seehausen, O.  1996.  Lake Victoria Rock Cichlids – Taxonomy, Ecology and Distribution. Verduijn Cichlids,  304 pp.

 

Chandler, M., Hemdal, J.F., Bailey, S.L.  2001.  The Lake Victoria Haplochromine – AZA’s first fish SSP.  AZA Communiqué (March 2001)

 

Johnson, T. C., Scholtz, C. A., Talbot, M. R., Kelts, K., Ricketts, R. D. Ngobi, G., Beuning, K., Ssemmanda, I. and J. W. McGill.  1996.  Late Pleistocene Desiccation of Lake Victoria and Rapid Evolution of Cichlid Fishes.  Science  273:1091-1093.

 

Elmer, K. R., Reggio, C., Wirth, T., Verheyen, E., Salzburger, W. and A. Meyer.  2009.  Pleistocene dessication in East Africa bottlenecked but did nor extrirpate the adaptive radiation of Lake Victoria haplochromine cichlid fishes.  Proc. Natl. Acad. Sci. 106: 13404 -13409.

 

Steeves, G., Hansen, D. and A. Lamboj.  2010.  Cichlids of Africa.  Volume I.  Haplchromines.  Granda Publications, 141 pp.

 

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Aquarium Press Release Photographs

Over the past year or so, I've been having fun searching on-line auctions such as EBay for sales of original news photographs.  It seems that as more and more newspapers digitize their files, the old original prints are being made available for purchase through outside vendors.  For public aquarists, this allows you access to old press photos from your facility - you can find historic images of news events, or embarrassing photos of your boss when he/she was younger.  On the back of most of these images is the newspaper clipping of the text that accompanied the photo.  Some photos have editing marks on them, but others are suitable for framing (or turning into dartboards in the case of some ex-bosses!)

Here is a sample search on EBay:

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p5197.m570.l1313&_nkw=aquarium+press+photo&_sacat=See-All-Categories

There is no real standard for these listings, so you need to try different search terms - some vendors use the term "press photo" and some do not.  If you type in "aquarium photo" you'll get too many unrelated listings.

To date I've found a press photo of my father from 1981, photos of people I've worked with over the years, and one photo of a nurse shark being removed from a tank (I was diving in the tank at the time, but wasn't in the image).

I'm not certain what the copyright status is of these photos.  While you are buying an original photo, the copyright of most images is probably still retained by either the newspaper or the photographer.

I posted this idea to a public aquarium list-serve, and quite a few people responded that they also found images of themselves, or people they knew.

8x10" image of a sea turtle from the Detroit Free Press - taken at the Toledo Zoo the second year I was curator there.

 

 

Reverse of the sea turtle photo with newspaper clipping and notes.

 

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Nikon AW100 Coolpix underwater camera

In my constant attempt to produce better images through technology, (rather than trying to improve any talent I might have!) I purchased a Nikon AW100 Coolpix camera.  This replaces my Pentax Optio that I wrote about a few years ago.  The Nikon is waterproof to 10 meters and shock-proof from 1.5 m.  Its 16 megapixel sensor and image stabilization has some promise towards my meeting my goal of "better images through better equipment".  Important to this is the ability to get "in tank" shots of animals.  This removes the problem of aquarium front glass glare, but does bring on its own issues of backscatter; where the flash reflects off of small particles in the water, causing white spots in the image.  Photoshop can take care of this backscatter problem, but can't do anything for glare. 

The AW100 took a little bit of getting used to - having the lens opening in the upper left corner of the camera meant that my finger sometimes strayed into the shot.  The close proximity of the flash and the lens (common to many pocket cameras) means that red-eye and backscatter can be more of an issue than with a camera having a remote strobe. 

The GPS function of this camera is just a novelty for me now - but who knows, it may have some use while on collecting trips or other outdoor excursions.

 

 

In-tank image of a Acropora fragment, The chromatic aberration at the bottom is due to the LED lights over this tank, not the camera itself.

 

 

One problem with in-tank underwater photography is the vantage point - usually from above the subject.  While this can be used for its novel effect, you wouldn't want every image shot from this angle.

 

In-tank macro shots are also possible with the AW100.

 

Soft corals - taken while holding the camera horizontal in the aquarium.

 

 

In tank shots taken while standing next to the tank make it very difficult to frame your image.  This was taken by shooting in the hawkfish's general direction and then cropping the image.

 

The Nikon AW100 can also take 1080p hd video, here is a short underwater video of flashlight fish in a public aquarium exhibit:  http://www.youtube.com/watch?v=AkqlzycFJ5k

 

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John G. Shedd Aquarium - Chicago

 

I recently re-visited the Shedd Aquarium in Chicago while in town for a meeting.  Our group was given a VIP tour of the facility by their staff.  It was very interesting for me to return, as I worked at the Shedd from 1985 until 1989.  Although I've been back for various visits during the ensuing 22 years, I was simply amazed at the changes which have taken place in the past few years.  Other than the landmark architecture of the building itself, I had a difficult time identifying ANYTHING that looked the same as when I worked there.  They have completely re-done the entire facility and it looked great!  This is also borne out by the increase they have seen in their attendance:  from around 850,000 people per year when I worked there to well over 2 million visitors a year now.

 

 
The iconic front entrance to the Shedd Aquarium

 

 
When you visit the Shedd, always take some time to admire the beautiful details such as this octopus lamp.

 

 
Here is a snapshot of their coral reef exhibit - where I got my start in public aquariums as their reef tank diver back in 1985.

 

 
Here is the Shedd's Amazon Rising exhibit - where they modified the old fashioned "tanks in a row" exhibits of their older galleries into an open, modern exhibit.

 

I saw half a dozen employees that worked there 20+ years ago, and it was fun catching up with what they've been doing.  Next year, the Shedd will be hosting the Regional Aquatics Workshop (the RAW meeting I discussed in my previous post).  Public aquarists from North America and around the world will spend a week there learning more about public aquariums. 

If you want to visit a world class aquarium (but one with historic roots and classical architecture), be sure to see the Shedd Aquarium!

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2011 Regional Aquatics Workshop

May 2 – 6

Virginia Aquarium & Marine Science Center

This RAW meeting will likely be the premier event for public aquarists in North America for 2011.

http://www.rawconference.org/

 

History of RAW:

The Regional Aquatics Workshop held its first official meeting in 1989.  The name was designed to provide lots of elbow room for future development.  The meanings intended for each title word by the founding attendees evoke the sentiments that led to RAW and help us understand and preserve its unique character:

 

“Regional”  Intentionally vague enough to include a future region of any size.  (Originally encompassing the Great Lakes/Midwest region, attendees now come from all over North America, Europe, etc.)

 “Aquatics”  The group is not limited to those interested in fishes, or to those working at traditional public aquariums.  Over the years “Aquatics” has been occasionally garbled to “Aquarium” or “Aquatic”.

 “Workshop”  An intentional attempt to avoid the creation of (or reference to) a traditional governing body that would evolve unnecessary hierarchical structures.  Read “Workshop” as “public aquarium professionals of all levels learning from one another”.

 From 1989 to 2000 RAW meetings were organized by the host institution with informal help from previous hosts and other interested RAW enthusiasts.  Attendance has grown from 10 to over 200.  The sheer size of the meetings, increasingly complicated logistics, and associated communication issues prompted previous organizers to establish a RAW Advisory Committee in 2001.

                RAW is not part of any other organization.  However its attendees are members of other organizations (AZA, EUAC, etc.) that have found it productive to conduct some of their business in conjunction with RAW meetings [the day before RAW has become the working meeting venue of choice for many AZA conservation committees including the Coral Reef CAP, the Fish and Aquatic Invertebrate TAGs, and the Lake Victoria SSP].

 

0	7/22/89	Columbus Zoo John Culbertson & Doug Warmolts	Casual chat arranged by John, a vendor and aquarium fan, leads 4 attendees to support what would soon become RAW #1
1	11/3/89	Toledo Zoo Jay Hemdal	Single day.  Name coined and guiding principles developed.  Jay invites all aquariums within half-day drive.  20 attendees.
2	3/9?/90	Fort Wayne Children’s Zoo Warren Pryor	Last meeting fit in a single-day or held around a conference table.  29 attendees?
3	10/26-27/90	St. Louis Zoo Joe Norton	First auditorium and formal program for talks.  19 attendees.
4	4/25-26/91	Milwaukee County Zoo Rich Sajdak & Craig Berg	Group brainstormed on planned exhibit renovations at zoo.
5	10/4-6/91	Ohio DNR Hatchery. Put-In-Bay, South Bass Island, Lake Erie, Ohio Doug Warmolts & Dave Ross, Ohio Division of Wildlife	A small RAW group helped ODNR develop plans to convert the hatchery to an aquarium.  Gales kept a drunken sailing regatta in port.
6	6/12-13/92	Sea World of Ohio & Cleveland Metroparks Zoo Pete Mohan & Dan Moreno	Last semi-annual RAW.  Tours of Rainforest (Zoo) and Shark Encounter (SWO), both under construction.  Vote of support from attendees for Pete to relaunch Drum and Croaker.  Last ice-breaker held in someone’s motel room.  21 attendees
7	6/16-17/1993	Tennessee Aquarium Chris Coco	First RAW at a large stand-alone aquarium.  Attendance jumps to 35-40 as East-Coast and Southern facilities attend for first time.
8	7/29-30/94	John G. Shedd Aquarium Roger Klocek & Mike Mulligan	Amnesia?  Nobody including the planners seems to recall much.  We therefore assume a good time was had by all!
9	7/21-23/95	National Aquarium in Baltimore Perry Hampton, Bruce Hecker, & Chris Andrews	First East-Coast meeting.  Discussion groups on LSS and Conservation.  AZA TAG meetings are first held in conjunction with RAW.  55 attendees.
unofficial	3/15/96	ReRAW at Frisch's  Big Boy, in Findlay, Ohio Warren Pryor	5 or 6 aquariums drove to a central point for a long lunch to attempt to recreate the original semi-annual RAW tradition.  The joke: Form a new organization called LUNCH (Landlocked Underwater Naturalists and Curators Hanse).
10	6/6-8/96	New England Aquarium Steve Bailey	RAW hosted a paper session and TAG meetings for AZA conservation efforts…and confusion of RAW with AZA begins.  72 attendees from 26 institutions (4 overseas).
11	6/11-13/97	Omaha’s Henry Doorly Zoo Kathy Vires	Concurrent workshops held on several subjects.
12	4/8-10/98	Texas State Aquarium Charles Smith & Tom Schmidt	Many attended a 3-day pre-RAW tour of Texas Aquariums.   Bad judgment in San Antonio results in ‘discovery’ of what would become “The Chalice”.
13	5/13-15/99	Underwater World, Mall of America Craig Atkins & Jeff Krenner	Chalice first awarded to aquarium professional with most challenging year.
14	5/24-27/00	Aquarium of the Americas Rich Toth & Toni Davi	Last free RAW as attendance and costs skyrocket.  AZA TAGs fixed as a pre-RAW event, instead of mixed with RAW sessions.  120 attendees.
15	6/3-7/01	Atlantis Resorts Michelle Liu-Ferguson & Steve Kaiser	Modest registration fee of $25.  Advisory Committee formed to deal with administrative issues on an “as-needed” basis.  163 attendees.
16	3/24-27/02	Colorado’s Ocean Journey Rich Lerner	RAW meets as the closing of the facility seems imminent.  RAW in the Rockies…almost to the continental divide.  138 attendees
17	6/5-8/03	Riverbanks Zoo and Aquarium Melissa Salmon	Sea Turtle Symposium held in conjunction with RAW.  First “Aquarist Olympics”.  198 attendees.
18	5/18-23/04	Mote Marine Laboratory Aquarium Kevin Curlee	A series of talks and workshops were directed at improving communication among and within aquariums, and identified priority issues on many topics for further action by RAW attendees.  ~170 attendees.
19	6/20-24/05	Aquarium of the Pacific & Cabrillo Marine Aquarium Perry Hampton & Jeff Landesman	RAW finally crosses the continental divide and touches the Pacific. 200 attendees!
20	5/14-19/06 (Sea Turtle Symposium on 5/20-21)	Aquarium at Moody Gardens Greg Whittaker	Cephalopods, sea turtles and more with a combined attendance of about 225.  A unique use was found for a ton of expired frozen capelin.
21	6/18-21/07	Pittsburgh Zoo and PPG Aquarium Alan Marshall	Back to the Homeland of RAW (Great Lakes and Ohio Valley). A cruise.  Unfortunately, a pond was included at the Olympic site.
22	6/16-19/08	Atlantis Marine World Joe Yaiullo	The second Atlantis to host a RAW, but this time the one on Long Island! 200 attendees.
23	6/8-6/13/09	Newport Aquarium Jeff Gibula	Newport, Kentucky brings RAW back to its roots....kind of. It's right across the river from Cincinnati, Ohio.
24	6/7-6/11/10	Henry Doorly Zoo Mitch Carl	The Oracle of Omaha, Mitch Carl, predicted we would all attend RAW in 2010. 185 attendees.
25	5/2-6/2011	Virginia Aquarium Beth Firchau	RAW heads to Virginia Beach!
26	2012	John G. Shedd Aquarium Mark Schick	Back to the Windy City after 18 years!

Solving the Unknown

Making the rounds of the interwebs last week was the video from a Charlie Chaplin film from 1928 apparently showing an elderly women walking along talking into a cell phone:

http://www.youtube.com/watch?v=TiIrpEMbQ2M

(You may need to cut and paste the link into a new browser window)

Dubbed the “time traveler cell phone”, people seriously feel that this clip shows something unusual.  Why on earth do people think she has a cell phone?  I heard NOBODY ask who in the world she might have been talking to (so there are at least two time travellers?) and then, more importantly, how was the cell phone working without cell towers?  It would be more likely that this “time traveller” would be using a simple two-way radio.  What makes this video so compelling for some people is that we are all so in tune with the body language of a person walking and talking on a cell phone, and that makes it difficult for us to see this video any differently.  IMO, in this scene, she is holding a hearing aid to her ear and is talking to the elderly man in front of her. 

So – what does this have to do with fish?  In solving problems, applying Occam’s razor is usually the best course of action:  basically, selecting which of the competing hypothesis that makes the fewest new assumptions.  So; a new photograph of the Loch Ness monster is likely to either be a hoax, or can be explained by some other known natural phenomena, as these have already been shown to have been the cause of previous Loch Ness monster sightings.  It is much less likely that the photo is actually OF a monster, because that would require proof of a new hypothesis.   

Things aren’t always what they seem.  Many years ago, a person called me and said they had found an unidentified eel while cleaning out a storm drain.  After asking many questions, I finally admitted I was stumped and asked if they could bring it in for me to see.  When they arrived, I examined what looked like a brown, eyeless lamprey eel.  It had a 1” diameter opening at one end, and you could distinctly see myomeres (muscle banding) running around its body.  At the distal end, the body tapered to a flat tail.  It was about 18” long and 1.5” in diameter.   A number of people observed and commented on it.  Some felt it was indeed a lamprey, others thought it was some sort of giant segmented worm.    I got a scalpel and cut the thick rubbery skin.  Inside was a weird network of fibers, a bit lighter than the skin.  I suddenly had an idea – I gave the creature a sniff and determined exactly what it was - What did I smell?  A very strong odor of paint! This “eel” was a huge drip of oil-based paint that somebody had dumped down a storm drain.  The glob of paint had adhered to a root (the reason they were cleaning the drain).  Flowing water had stretched to glob of paint out until it dried.  The smooth rubbery skin looked so real, everyone wanted to come up with a biological answer to what it was.

     Then there was the case of a spinner shark caught in Lake Erie.  Other aquarists struggled to determine just how this species of shark could have come to live in the Lake.  They debated salinity tolerances of the species, could it have migrated through the Saint Lawrence Seaway, etc.  I was more interested in the wrinkly skin of the shark seen the its photograph – obviously to me, someone had caught fish shark in Florida or the Carolinas, froze it, brought it back to Ohio, thawed it out and “caught” it in Lake Erie.  Of course, to follow this line of questioning, one would have to call the person who caught it, a liar….but the same hoax had been perpetrated in Chicago years ago with a bull shark.  The prankster had brought the shark back from Florida.  Early one morning he went to a beach in Chicago, rammed a hook in the shark’s mouth and swam it out into deeper water.  He then sat there until enough bathers showed up later in the day.  He then started jumping around and reeling in his catch.  When he got it to shore, he beat it to “death” with a baseball bat.  Of course, nobody questioned why he was fishing in Lake Michigan with a baseball bat by his side and a hook the size of his fist….

If you think about it, virtually every major challenge facing us as aquarists is a direct result from our needing to solve a particular unknown animal husbandry problem, (or series of problems) concerning our aquariums.  Specimen loss is the penalty for failing to meet this challenge.  The rewards are healthy, growing, or reproducing organisms.  Use Occam’s razor in your development of a solution – the weird new disease your fish have is more likely something commonly dealt with by others before, and is just new to you.  High ammonia levels most likely are derived from your animals, not the window cleaner somebody used in the next room, or as the result of some nefarious poisoning plot.

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Online Odds and Ends

 

I have been active in various hobbyist forums since I was a Sysop for Compuserve's FISHNET back in the mid-1980's.  While my posts from that era have evaporated into the ether, some of my more recent posts, (aside from hopefully being more accurate than 25 years ago) are still retrievable.  I extracted some text from them and saw a lot of repeated information - meaning that as new people move into the hobby, they have many of the same questions.  The following are my thoughts on a few of these topics:

 

Mycobacterium marinum:

Actually, this isn't a rare disease at all, it is just difficult to isolate in culture, and most fish don't die from it until late in life. It is the number one killer in some (many?) fish collections, but it is almost always attributed to "old age".

It is found in nature in soil and uncooked seafoods, so its presence in aquariums is virtually assured. In cases where it has NOT be isolated in aquariums, it generally means that the proper culture was not performed, this bacteria is very slow growing, and it is difficult to culture because in the 6+ weeks it takes to grow, other bacteria tend to over-grow it on the test plates.

I know of no effective treatment for it, and besides, if you could "cure" the fish, they would get re-infected the next time it got introduced to the tank through feeding, etc.

It can become a huge problem in some fish collections because some species of fish are very sensitive to it; notably seahorses, pupfish, pirate perch and Haplochromine cichlids. In these fish, even middle-age specimens will die. I manage it by breeding the population fast enough to "outrun" the tendency for it to kill off the older fish.

Finally, it is a zoonotic disease and can be transmitted to humans. It doesn't flourish in the human system (98 degrees is too warm for it) but it can cause lesions in the extremities. Wear gloves and never siphon by mouth, and if you think you might have immune system problems, check with a doctor.

 

  A female Piceatus cichlid with egg-binding, positive for Mycobacterium

 

 

Small hepatus tangs:

I cringe whenever I see those really tiny hepatus tangs offered for sale for two reasons: First, if they have not been fed properly as they move through the supply chain, they get too thin and then it is hard to get them back into good condition. Secondly, ask yourself WHY the baby hepatus are being collected - they didn't used to be seen, ever. Why now?

Could it be due to over collecting? The same thing happened to Atlantic angels in the 1970's - we suddenly starting seeing 3/4" French angels, because collectors couldn't find enough of the 2" ones. Florida passed slot size limits for those fish, but nobody seems to be doing that for hepatus tangs.

 

 

Neobenedenia:

I've never been able to break the life cycle of Neobenedenia using formalin dips. The dips will kill the adults (166ppm for 45 minutes under good aeration) but returning the fish to the tank just re-infects them. Moving them to an uninfected tank *might* work after a formalin dip.  I sometimes go 10 (or even 14) days between treatments with Praziquantel if I suspect Neobenedenia...since they are egg layers, I want to make sure that any eggs have had a chance to hatch before hitting them with the second course. The dose should be 2 to 2.2 ppm, hobbyists who use Prazipro (which isn’t dosed in ppm), would have to rely on the label instructions.

 

 

Feeding trumpetfish:

One of my aquarists has had great luck in getting trumpetfish switched over to prepared food. The basic technique is this:

1) Get the fish feeding well on live guppies - but don't wait too long at this stage - perhaps a week.

2) Next, fresh kill some guppies and get it feeding on those. Slap them into the water to get it interested.

3) Then freeze some killed guppies and transfer the fish over to feeding on them (this is a big deal - frozen fish must SMELL different or something).

4) Keep feeding it frozen guppies, then get the trumpetfish converted to feeding on frozen guppies with their heads cut off (predators often fixate on the eyes of their prey).

5) Once the trumpet is feeding well on the bodies of dead frozen guppies with their heads cut off, start introducing guppy-sized slices of other fish flesh, like smelt. When that is working well, you can pretty much toss anything in and the trumpet will eat it, krill, mysids, etc.

 

 

Chloroquine:

Typically use it at around 10 ppm - I'm not positive what that works out to be in terms of mg / gal, but I think it is on the order of 36 mg/gal.

In quarantine systems, it has a tendency to kill back your beneficial nitrifiers, and there is usually an ammonia spike. I deal with that using Amquel. In a well-established tank, I don't know if you would see the ammonia spike or not.

A bit of historical perspective - back in the late 1970's many aquarists used a "miracle drug" in their FO tanks called Marex. I learned last year that it actually was just chloroquine HCL.

 

 

Moribund fish:

Hobbyists often ask for help when they notice that their fish is laying on its side, or upside-down.  The term for that behavior is "moribund". Fish rarely recover once they reach that level of a problem. If it’s a disease issue, generally, any medication will take more time to work than the fish has left. If it is some water quality issue, then moving the fish might bring it around - but you can use your other animals to determine that - if other, more sensitive species are fine, then you can rule out water quality.

 

 

Fish size estimation:

I would like to expound a bit on my work on maximum fish sizes in captivity (previous blog entry). There seems to be some confusion about the study. Although only 19 fish met the criteria as outlined in the project, fully 2300 fish were analyzed as candidates, it is just that 2281 of them did not meet the strict criteria:

"None of them has grown appreciably in the past two years, and all have been in captivity at least 5 years (the range was 5 to 20 years)."

Also, the ONLY conclusion that I drew from this is that the maximum size of fish on Fishbase tends to run larger than what is seen as a maximum size in captivity - to the extent of it being 66% of that value. Remember that Fishbase lists the maximum recorded size for a fish - not the normal adult size. Their sample size (taken from the literature) is just ONE fish. They also tend to "round up" their numbers. Think of their max size as the record size for that species.

This was just a starting point. The problem is getting enough additional data. How many fish in your own aquariums would meet the criteria? Still, I think we can safely say that stating the Fishbase maximum size as being the "adult size" for fish (as is often done on message boards) will be less precise than using a figure of say, 75% of that value.

Finally, there is still no real way (yet) to use the size of a fish and calculate what size aquarium that fish will need....so what does it really matter if you say that a particular fish will reach the Fishbase max. size or only 66% of that value, you still don't have any real way to objectively apply that information...

 

 

Temperate animals:

Water temperature is very important for some species. You can infer this by their depth distribution. A fish that is found deep in tropical areas, but shallow in temperate regions is NOT going to handle warm water very well. An example would be Chaetodon modestus that is found at 200+ meters in Taiwan and at only 20m in cooler Suruga Bay.

With a few other fish, light is the limiting factor, two examples that come to mind are flashlight fish (found shallow on moonless nights and deep when the moon is out) and Liopropoma mowbrayi, that hides deep in caves in shallow water, but comes out more in deeper water.

The only case of physical damage from light that I can think of is with deep sea isopods, Bathynomus. They will become blind when kept under normal aquarium lighting.

I think that most people "play it safe" and mimic the fish's natural environment as close as possible, so that means keeping true deepwater fish at say < 20 footcandles of light.

 

 

Estimating the age of fish:

Physical size is probably the most important factor. Even with captive stunting effects, an older fish is going to be larger than younger ones of the same species.

Older fish tend to develop chronic issues, such as tattered fins, skin damage, cataracts, etc., that do not heal as quickly as in younger fish - and may not heal at all.

In captivity, many older fish suffer from fatty liver disease that can cause lethargy, ascites (abdominal swelling) and anemia.

Very old fish are less able to respond to environmental changes as well as younger fish, so moving an old fish to a new aquarium may result in serious problems.

Eventually, extremely old fish slow down and become moribund - just like people do. However, while they may slow down in regards to movement, their respiration rate may actually increase.

 

 

Hyposalinity:

You can lower the specific gravity for a hypo treatment rather quickly - people routinely drop the specific gravity in half in just 24 hours time. This does not overtly stress marine fish. In fact, in cases where there is in active outbreak of Cryptocaryon, if people lower the S.G. too slowly, the disease keeps an upper hand, and the treatment may fail.

Raising the specific gravity at the end of the hypo treatment is where people get into trouble - this needs to be done VERY slowly, I'll take five days or more to go from 1.011 to 1.022.

Also, if you decide to go as low as 1.009 (I don't do that myself) you must be CERTAIN that your hydrometer is accurate and precise at that range. Too many times people go this low, not realizing that their hydrometer reading is off, and they end up with an actual S.G. of 1.008 or something, and fish may die.

Finally, be on the look out for an outbreak of Uronema while running hyposalinity...

 

The views expressed on this weblog are mine alone and do not

necessarily reflect the views of my employer.

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Raising Clownfish - one more time

 

 

True perc pair fanning their nest

 

I first raised clownfish when I worked for the Shedd Aquarium back around 1986.  Myself and another aquarist worked on raising some skunk clownfish, but since we did not have rotifers, we used “algae squeezings” basically microbes that we isolated from algal mats growing in our display tanks.  I think we raised a dozen or so that way.  In 1991, at the Toledo Zoo, we raised some Clark’s clowns in 1991 using Brachionus plicatilis rotifers being fed Nannochloropsis.  Since that time, I hadn’t worked with any clownfish until this year.  One of my departmental goals for 2008 to 2010 is to develop some marine propagation projects, but after a year of beating our collective heads against the wall trying to raise boarfish, Capros aper (We had gotten the boarfish to day 18, but then their spawning season ended). I decided to take a step back and try some easier clowns, to give my staff a chance to have some success before the boarfish season starts again in the fall.  

 

Larval boarfish at 12.5 days post-hatch 

 

We have a nice pair of true percs from PNG, so I thought we would try those first. Our rotifer culture had lapsed when the breeding season for the boarfish ended, so the first task was to start that up again. Of course, the clowns laid eggs before we had any rotifers to speak of, and my staff still wanted to try with them, so we dipped up a 150 or so larval clowns the night they hatched and started them off on Tisbe nauplii being fed Isochrysis.

My recollection of my previous clownfish work doesn’t match what I saw this time around. I recall that the larva were gray/tan, couldn't swim very well, and we were lucky to raise a dozen per brood. These true percs were a lot more active,  were a deeper orange color, and our mortality had been minimal (excepting a few lost in the first 24 hours due to trauma from being dipped up and moved to the black rearing tub).   We raised the larva at 82 degrees F.- pretty warm, so I thought things would be a bit quicker, but as of day 11 only one has metamorphosed, with four others having head stripes.  There was zero mortality from day 2 to post-metamorphosis, something I did not expect.  I feel that our painstaking work with the boarfish, although not yet successful, gave us the experience to make clownfish rearing much easier.  The copepod naups and the Iso probably worked together to enhance the nutrition of the larval clowns to a much higher level than we had seen before.  When we worked with rotifers, we would aim for a density of 5 rotifers per milliliter.  With the copepods, we had nowhere near that density, probably more on the order of one nauplii per 25 ml, yet the clowns thrived.  Using a round black polypropylene tub seems superior to the standard aquariums we used in the past – with the only drawback being that you don’t have lateral viewing of the larvae.

I came up with a quick, accurate and fairly efficient way to count the baby clowns.  I  took an overhead digital photo of the rearing tub, imported the image into Photoshop, enhanced the contrast so that the larval clowns showed up better, then used the computer mouse to click on each clown, counting them in turn.  By setting Photoshop to leave a blue dot with each mouse click, I could avoid counting a larva more than once. 

 

 

True perc day four

 

 

 

Day ten

 

 

 

Day 16 - post metamorphosis

 

 

 

Each blue dot represents a larval clown in the rearing tub

 

 

 

Day 26 - in the grow out tank!

 

 

 

Day 67 - Around 1/3 to 1/2" long

The views expressed on this weblog are mine alone and do not

necessarily reflect the views of my employer.

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A Refinement of a Fish Length Estimation Method

 

This installment informally ties together three previous blog entries: photography, fish size estimation and the HLLE project. Much public aquarium work operates in this fashion, many different small topics and projects may be tightly woven together:

While attending a public aquarium conference, I saw a video presentation in which a deep sea submersible was operating, and it was projecting two red laser beam spots onto the sea floor as it passed on by. I immediately concluded that this was being done in order to give a size reference to any objects or animals that were filmed by the operators of the submersible. I decided to try and apply the same technique to aquariums, hopefully resulting in a more accurate way to measure aquarium inhabitants for growth studies and the like.

 

A tarpon calculated to be 40.5" long

 

The idea of determining fish lengths in-situ has been around probably since the inception of aquariums. Obviously, catching up fish just to measure them is time-consuming and hard on the fish. However, the farthest I had ever gone with this idea before was to take a picture of something underwater with a ruler next to it for scale. While I didn’t find much similar work posted on the Internet, I did discover that some other public aquarists had set up similar laser systems, but these were fairly basic and there was room for improvement.

The laser holding system that I developed incorporated two red lasers designed to attach to golf putters and help golfers direct their putts. I attached them to the twin arms of a Stroboframe flash bracket. Not including the digital camera, this apparatus cost less than $120. Other methods have been used by others, but are not as rigid, and can introduce errors into the measurements (such as mounting the lasers on PVC pipe). Stroboframes are expensive, and enterprising aquarists may find other devices, such as fly tying jigs will work equally well, but for less cost. For measurement by divers, there are underwater lasers available (used by SCUBA divers to point out objects underwater) that could be combined with an underwater camera to achieve the same results while diving.

 

Twin lasers and camera attached to a Stroboframe

The basic idea is that two lasers, set parallel to each other, at a known distance from each other, would produce two laser spots at a far distance at the same width apart. Three unknowns were identified; what would the effect be if the subject was not exactly perpendicular to the twin laser beams? What effect would light refraction have? And what amount of error would be introduced if the beams were not exactly parallel?

Surprisingly, a small amount of error between the fish subject and the laser device does not create a larger error in the estimated measurement. The graph shows that up until around 10 degrees from parallel, the percentage error is less than 1.5%. However, it also shows that the percentage error increases rapidly beyond that point, so it is not a linear relationship. Luckily, most people can visually estimate the angle between objects to within 10 degrees.

Tests using rulers show that while refraction does occur, it involves all components, so laser spots set 12" apart outside the aquarium, will show up 12" apart on the ruler, but both the ruler and the spots will seem to be about 30% larger than they really are – this has been the bane of all outside-the-aquarium fish measurements to date. The black tip shark in the attached image had been estimated to be 50" long. The lasers show that it is actually only 39" long.

 

During bench testing, with the lasers set 13" apart and shining on a wall 15 feet away, it was shown that an infinitesimal change in the angle of the lasers created a large change in the distance between the projected dots. In fact, this can be used to advantage when adjusting the beams to make them parallel.

It had been proposed that green laser lights might produce better penetration through the water than red lasers. I also wondered if the green laser would elicit less of a predation response than the red lasers (see below). A green laser (532 nm, < 5 mw) was tested. The beam of the green laser seemed more coherent (less divergence at the endpoint) but it was not as visible in aquariums as the red laser was (635 nm, < 5 mw). The predatory fish did not follow the green laser quite as much, but this may be a function of it being less visible. In brightly lighted coral exhibits, the green laser was not visible at all. It seems then, that red laser light would be preferable for aquarium applications.

One difficulty in designing a laser system is that most laser pointers have a momentary switch, as opposed to an on and off switch. One work around for this is to loosely attach a small hose clamp to the body of each laser. When you need them to operate, just slide the clamp up, over the button switch, activating the device.

Two additional problems involve the laser lights themselves. Reflection occurs as the laser penetrates different materials, so that in some images, instead of seeing two red dots, there are multiple dots along the same plane. Knowing where the two original dots lay along the subject when the image was taken makes it possible to just ignore the reflected dots. The second problem is that as mentioned, some predatory fish react to laser dots as they would small prey, and try to chase and eat the laser dots as they project on the tank walls, etc. This can make it difficult to align the dots properly.

 

Using dial calipers to measure the size of fish from an on-screen image

Originally, the fish lengths were calculated by bringing the image of the fish up onto a computer screen and using dial calipers to measure the distance between the two laser spots. Then, this distance was used to set the scale of the image, and the fish on the screen was measured with the calipers as well. While this seemed to work well, another aquarist told me about this free software:　

http://ddsdx.uthscsa.edu/dig/itdesc.html　　 　

You use your mouse to draw a line on the computer screen between the two dots, and then enter in the known distance between them.　 This sets the scale for the image.　 Then, draw a line on the fish’s image that corresponds to its nose to tail distance (SL, FL or TL) and the program gives the length.　 The interesting thing is that the software then allows you to draw a multi-sided polygon around an object.　 When this is done, the software calculates the area of the polygon.　 For example, the catfish in the attached image is 18.5" total length, and its eye is 0.20 square inches in area. This process will have application in my upcoming HLLE study, where I’ll need a means to measure the size of the HLLE lesions over time to see if they are increasing or decreasing in size.

 

This catfish was estimated to be 18.5" long

 

The views expressed on this weblog are mine alone and do not

necessarily reflect the views of my employer.

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Underwater Photography in Aquariums

Public aquarists often have difficulty photographing their exhibits.  Not only do they have the same problems as home aquarists (flash reflection off the glass, issues with white balance, fast moving fish, etc.) they have the added distortion caused by thicker viewing panels (often with fingerprints or scratches on  the surface).  In some cases, the answer is to photograph the subject in a special photo tank.  In other cases, this simply is not practical.  I had explored both photo tanks and "top down" photography as potential solutions to these issues in my book, Advanced Marine Aquarium Techniques.  Another method I presented in the book was the use of underwater cameras in aquariums.  At the time, I was using a 3.2 megapixel Canon in a waterproof case.  This allowed for barely tolerable results as the housing was bulky and the camera had low resolution. 

I recently acquired a 10 megapixel Pentax Optio W60 that is waterproof to 14 feet without a special housing.  Costing only $210 to $260 on Ebay, this camera gives fairly good results, and I wanted to share some images that I've made over the past few weeks.  In-tank photography can be done by divers (in large tanks) or by simply immersing the camera in the tank from above.  These images were taken by the latter method.  Obviously, being unable to frame your subject is an issue, but with digital cameras, you can keep shooting and deleting shots until you get one with good framing.  Don't be afraid to think outside the box.  In one shot, I wasn't able to hold the camera at the proper angle, so I made the shot with the camera upside-down and then flipped the image in Photoshop.

UW photo of a Longnose hawkfish balanced on a gorgonian

 

 

UW photo of green Zoanthids in macro mode

 

 

Cryptic sponges living under rocks n a sump - UW photography would be required for shots like this.

While this technique has benefits, it also has drawbacks; backscatter when the flash hits particles in the water can be worsened in underwater photos.  Avoid disturbing any detritus or feeding the tank before taking UW shots, and use image editing software to remove any particle "flares" that might remain.

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