I have found a very useful technique for shipping air breathers. If you ship air breathers with a 100% oxygen enrichment, apparently it shuts down the reflex to surface for air. In turn these obligate air breather's with their less effective gills, cannot extract enough oxygen from the water, and actually drown. PLEASE CORRECT ME IF I AM WRONG!

Well you are all certainly familiar with Kordon Breathing bags? I add a breathing bag inside of the actual shipping bag filled with 100% O2. This bag floats on the water. I wrap several rubberband around the breather bag to pressurize the bag. The semipermeable breather bag slowly releases O2 into the bag for about 36 hours.

This allows for a very slow O2 enrichment that doesn't seem to shut down the surfacing reflex of our native airbreathers.
Matt

skipjack Matt -- Wow ! Ive never heard of fish suffocating beacuse their air-breathing reflex was suppressed by too much oxygen. where did this info come from ? what kind of fish ?? I always thought surface breathing was a secondary strategy & not necessary if dissolved O2 is adequate (at least 6 mg/l). what fish spp are "obligate" surface breathers ? i didnt know we had any N. Amer ones.

BTW, i just tried a fish transport experiment that worked quite well. ive often had trouble with wild-caught fish collected in late summer, presumably due to the double-whammy of heat and ammonia. This time i brought along a nice slimy polyurethane foam block taken from a filter on a well-established tank, let excess water run out but did NOT rinse it. I put the foam block in the styrofoam cooler with the newly-caught fish plus my usual 1 teasp salt per gal. (styro box with a black trashbag liner reduces snout damage). Much of the bacterial gunk fell out and muddied up the water, and the fish ALL did great: about 40 2-inch shiners and 2 darters in 3 gallons of water for 8 hours. 6 of those 8 hrs were WITHOUT aeration (car motion probably helped -- "officer, i was just trying to aerate my fish"). Next day all were happily eating, no cloudy fin edges, hazy eyes, or labored breathing. I'm gonna do this again !!.

gerald, hangin on the Neuse

Gerald,

Do toy think the "dirty" filter media has any advantages over, say, just a heavy dosing of Amquel and/or Polyaqua/Novaqua? I really believe the salt is a key here. This is an underutilized collecting tool. I don't think anyone should attempt to transport fish without it.

Just out of curiosity, what kind of salt do you prefer? I have always used marine salt because I can get it in bulk and have ahd a free supply for some time. I am about to run out though and wondered if the plain old aquarium salt might work just as well, or better. I have always been a little concerned about the buffering capacity of marine salt.

I also seem to remember that you advocated taking your own water with you into the field rather than using collection site water. Do you still do this? Why or why not?

Good to see you here.

As a note on the obligate air breathers, the two fish that Matt was referring to are the bow fin and the gar spp. I have found that these fish ship much better if shipped in poly fish bags with a large air space(we use atmospheric air, rather than O2 enriched air) as opposed to breather bags. We use breather bags to ship everything else and feel like these are the best things ever, but have been concerned about using them for air breathers.

What is your take on this?

hi dustin & matt --Ive never tried to ship (or receive) gar or bowfin. thats useful to know. Maybe the suffocation problem in breathing bags has more to do with moving enough water through the gills, due to restricted movement in bag. That just sounds too weird that such ancient & successful fish could "drown" due to high dissolved O2. As i understand it CO2 in the blood is what controls the breathing reflex, not O2 concentration in the water.

i use Kosher salt, about 1 teasp/gal - plain NaCl has no effect on pH. with marine salt i'd be afraid of pH shock in blackwater, and ammonium to ammonia conversion. keeping it a little acid is probably safer in terms of ammonia risk.

i tried bring-my-own water a few times collecting in stagnant swamps & acid waters, (mixed about half & half) and it worked well for delicate species i'd previously had trouble with. But i havent done that in recent years & its probably not necessary IF you take other precautions. Now i use salt, and if collecting in swamps i scoop my take-home water BEFORE i start collecting. I figure the smelly gases (and maybe ammonium ??) that bubble out of swamp muck while i'm wading around might be an added stress the fish dont need on top of normal collecting stress. If you KNOW youre going to a place with poor water quality (urban or agric watershed) then i'd say yes, bring some good water from home or another stream.

gerald, hangin on the Neuse

One reason, I have been suspicious of the bowfin "drowning" is due to incidents I have seen with others using fish traps. Bowfin, nearly always, are found dead in these if there is not an area where they can reach the surface. I have also noticed that smaller bowfin especially seem to gulp air more frequently when stressed. I would imagine being jostled around in complete darkness for an extended period of time could be considered stressful.

The water in the breather bags keeps a very high level of O2. I do not have the means to check the specific levels, but I have shipped higher gradient shiner spp.(such as fieryblack) with several in a bag for several days with 0 loss of fish. It's hard for me to believe that an ambush predator like a bowfin, that spends most of its days sitting perfectly still, would have a problem staying well-oxygentated due to lack of water over its gills. I can see your point here as well, but I would prefer to remain cautious.

Good to hear another opinion on the salt. I suppose I never really considered the ammonia implications at higher pH. Thankfully, I haven't had an issue yet and have time to switch it up. What do you think about using any type of buffer in the transport water? I ask since pH is likely to drop a fair amount in an overcraowded transport container.

Just for the record. I'm not very proud to say that I've killed bowfin by shipping them with pure oxygen. I lost about half this way. Some traveled within the state (less than 24 hours) and died while others traveled 3 days (about 1000 miles) via USPS priority without any loss. Conditions were identical. Water and oxygen volume, box size and insulation. They even traveled on the same days.

Skipjack on the otherhand has nearly if not a %100 live record with his method.

We live we learn.

I had no idea pure oxygen could shut them down

Hey guys, I may be wrong, and am sure Brooklamprey will correct me, but bowfin and gar have degenerate gills, and cannot extract enough dissolved O2 from the water. Therefore they have to surface and gulp air. If not allowed this ability, they will perish. I am not fully sure whether the Pure O2 shuts down their reflex to surface for air, or if their bodies cannot handle a full shot of O2 when they breach. Water can only absorb so much O2 before it becomes saturated, which is within the parameters of gill breathers, but maybe the 100% O2 going into the air bladder of an obligate air breather wreaks havoc on its bodies gas balance? By the way welding O2, which is commonly used is 100% oxygen. Our atmosphere is less than 50% oxygen.

I was on a crayfish survey in Congaree National Park last year. The grad student I was helping had set many traps out to capture crayfish. We had many young bowfin in these traps. In the traps that had bowfin, those that were completely submerged had none alive, while in those that were partly above the surface, all were alive. This indicated to me that they required access to the surface or they would drown. I asked Jan Hoover about this since I knew he had been involved in some bowfin research and got basically the same info from him.
-Chip in SC

I keep gar and they are always coming up and gulping some atmospheric air.