October 2008 - Rising fins?
I have an observation for you...re: the Activity question below.
Today, I cast to every big boil I saw when I realized the boils were from bowfin and not gar. Around 1 out of 10 times I got a fish....and I cast a lot. I let it sink 2 seconds and jerked then slow retrieve across the weeds. The Bayou is about 3-4 feet deep, with holes of maybe 5 feet ,and it was a hot day with the bayou dropping in height around a foot over the last week. They definitely hit more when surface breathing...the same observed in gar.
October 2004 - Mercury?
Based on the EPA study,
I'm curious why bowfins have a higher concentration of mercury than other
predators with a similar diet. We know from our weight/length info that
they are denser than other sportfish and that may have some bearing. Is
mercury metabolized at all, and if so, do fins have a slower rate?
Hey Chuck...I will attempt to answer your question, but don't
be offended if I insult your intelligence. I just want to make it as
understandable as possible and I'm sure much of it is common knowledge
to many fishermen and conservationists.
Mercury accumulation in fish occurs through what is called biomagnification. The process goes like this: 1) Mercury enters the system through the burning of fossils
fuels, specifically coal, and proceeds into the atmosphere. 2) The
mercury in the atmosphere is re-introduced into the system either
through rain or simple deposition. 3) The mercury enters the aquatic
system and is held in the water and soils. 4) This is where the
Biomagnification is the process by which
mercury concentrations magnify as you go up the food chain. Plankton
and macroinvertebrates are the first level of mercury consumers. They
are subsequently eaten by your minnows, juvenile predators, other
inverts, etc. These are then eaten by the larger predators and so
on.... The level of mercury concentration rises with each level of the
Now you ask why would a bowfin be that much higher than a
largemouth? Consider how much food a bowfin eats compared to a largemouth. Comparable, right? Now consider the maximum age of each species, this is where the difference comes about. Bowfin are longer lived fish than largemouth, pickerel, etc. Thus the amount of food a bowfin eats in its lifetime will be considerably higher than that of
To answer your other question about mercury metabolism, fish do not have effective methods of metabolizing mercury; once it is in the fish it is basically there for good. So
overall it is relatively easy to make an estimate on the mercury
concentration you will find in fish within the same system. Fish that
eat fish will be higher in general, and the oldest of these fish eating
fish will be the highest. NOT ALWAYS TRUE, BUT IT IS PRETTY CLOSE!!
September 2004 - Historical Range and Stocking
I had a pic posted a few
months back of my first fin catch out here in North Carolina. I have a
scientific question, and one questions regarding population.
1. Have Amiidae fossils been found in the western United States, such
as California, Arizona or Nevada?
2. Has there
ever been consideration to stocking select lakes and reservoirs in
western states with Bowfin? My personal research of the fish indicates
that several bodies of water in my home state can benefit from the
presence of the Bowfin. Thanks in advance.
Yes, bowfin fossils exist out west. At one time much of the west was under water. This expedition
at Bryce Canyon in Utah reports Amia at several levels in the
strata. Several Eastern states have stocked
bowfin, but this was many years ago. The only current
stocking ideas are for aquaculture, since bowfin roe is sold as a "poor
Self-stocking is discouraged, and there is no current interest is
stocking bowfin as a sportfish. Washington State explictly bans the
stocking of Bowfin, but I was unable find a similar statement in the CA
2006 Freshwater Fishing Regs. It may there, I just couldn't find it.
Is there a database or
clearinghouse of active biology research projects that we could search
for Amia related activity?
If you or any of the BAG members want to do your
own database searches, you can logon to the National Library of
Medicine website (http://www.ncbi.nlm.nih.gov/)
and get a list of articles (some will have links to the actual
articles) on whatever topic you wish. Go to the site and click on the
'PubMed' tab. Type in any keywords in the the 'for' box (e.g. Amia
calva), hit 'GO' and see what comes up. I got 78 hits for Amia calva.
This is not a comprehensive site since it will only find journals that
submit results to the National Library of Medicine, but it's not bad.
You can also try the FishBase website (http://www.fishbase.org/),
but I think I saw that listed somewhere on the GASSBAG website.
researching your Periodicity
paper, did you observe any bowfin that did not surface
breathe? If faced with a threat at the surface, can bowfin "hold" their
breath? Is there a link between surface-breathing and mood, i.e., might
an active, feeding fin surface frequently while a neutral or passive
fin will be content to sit on the bottom? If we don't see them
surfacing does it mean thay aren't there or are inactive?
The periodicity paper was based on videotaped
observations of 8 hr sessions (overnight) with individual bowfin in
aquaria. I saw lots of interesting behaviors, including 'yawning' and
the ability of bowfin to 'abort' air-breathing attempts. They certainly
can sit on the bottom and not surface breathe if there is a threat at
the surface. This is well-known from observations of other
air-breathing fish, too. They appear to rely more heavily on gill
ventilation during times when they are avoiding air-breathing.
Air-breathing will also depend to a large extent upon water temperature
- the higher the temperature, the higher the metabolism and the greater
reliance on air-breathing to support that metabolism and buoyancy. I
don't have any data on whether feeding or satiety influences
air-breathing behavior. My gut feeling is that it probably doesn't
influence it very much - but if it does, then I might expect them to
breathe more after feeding since feeding will raise metabolism. But I
am just speculating here. There may be some data on
feeding/air-breathing in other species and I will see if I can find it.
Bottom line is that air-breathing is a complex behavior that
can't be classified as an involuntary reflex; although 'simple' signals
like decreases in oxygen and lung volume may trigger the air-breath,
higher centers in the brain can override these signals under certain
conditions (e.g. the threat of a BAG member).
From Troy H, A question
on fins based on your paper:
There are two types of air breaths that the bowfin conducts. Type 1 air
breath is exhalation followed by inhalation and type 2 is inhalation
only. When observing fins gulping air is there any way to tell what
type of air breath the fin(s) are conducting? For example, when a fin
that is conducting type 1 air breath, does it stay at the surface
longer to exhale and then inhale as oppose to type 2 which it would
just come up to take a gulp of air within a split second? In a type 1
air breath would there be any air bubbles coming out of the fin's mouth
as it rises to signal it might be exhaling to inhale?
The distinction, and purpose, between Type I
breaths and Type II breaths was a major part of my research on bowfin.
Type I breaths had been described, but Type II breaths had not. It is
clear to me that Type II breaths (inhale only) serve a buoyancy
function while Type I breaths (exhale-inhale) are used to gain oxygen.
This makes 'sense' because fins (and gar) must use the same organ (gas
bladder) for both purposes. The two functions (gas exchange and
buoyancy) have different requirements: a good 'lung' needs to have
oxygen leave quickly (and loses volume) while a good 'buoyancy organ'
needs to retain the gas, but is a lousy gas exchanger. I think that
fins (and perhaps other air-breathers) have 'invented' the two breaths
to take care of these different roles of the gas bladder. Type I
breaths do take slightly longer (about 0.5 sec) than Type II breaths
(0.1-0.2 sec), but you may not notice this at the surface. If you took
a fin home and put in in an aquarium, you could easily distinguish the
two breaths. Sometimes bubbles are lost through the opercular (gill)
cavity after inhalation during descent. Again, you probably wouldn't
notice them unless it happened right next to you. Exhalation occurs
through the mouth in fins, which is different from gar which exhale
through the operculum just before breaking the surface.
surface breathe because their gills are less efficient at extracting O2
than more modern fishes?
There is a large spectrum of fish gill
'efficiencies'; bowfin are not the worst or the best. My friend, Steve
Katz, and I created a computer-generated model about this and found
that air-breathing could enhance the efficiency of the gill, but
whether this happens in 'real life' we can't say with certainty.
Another hypothesis (Colleen Farmer) is that air-breathing improves
cardiac oxygen levels and is there to improve cardiac function. In
other words, like an external coronary circulation. My own view is that
air-breathing evolved to regulate buoyancy first, and then became
important in low oxygen situations.
Can fins sustain
strenuous activity for longer periods than other fishes because of air
breathing? If so, wouldn't strong currents be a more likely niche than
Air-breathing can reduce the recovery time after
strenuous activity, which has been shown in both bowfin and gar. But
bowfin are generally not too active in general (i.e. not continusly
swimming), but are more 'sit and wait' predators that will strike at
prey (or your favorite lure). But if they are active, chances are they
will air-breathe more to help in the recovery process.
gills are not significantly different, nor activity levels, why surface
breathe at all? What advantages does surface breathing offer? It would
seem to have greater risk of predation by terrestrials -- bears, herons,
Did air breathing develop as a
response to aquatic hypoxia, and current behaviors are a result of "use
it or lose it" conditioning, so that the ability remains should hypoxic
Both questions are related, so I'll give one
answer: The question of 'why' something evolved is almost impossible to
answer. But, again, my own view is that buoyancy was the dominant
reason for air-breathing, and hypoxia occurred secondarily. The reason
I think this way is starting from basic physics: any gas taken into the
body of an aquatic animal automatically changes the buoyancy of the
animal, regardless of whether that gas (oxygen) is used by the tissues.
The earliest fish were very heavy-bodied, bottom feeders; having a way
to exploit a bigger niche by air-breathing and adjusting buoyancy is a
nice way to increase survival. Most of the modern air-breathers evolved
in hypoxic habitats and became air-breathers secondarily.
any indications that the bowfin was evolving toward becoming a
land-based animal (or vice-versa like whales), and if so, any theories
on why it stopped?
Bowfin are the sister-group to all modern
teleosts. That is, all teleosts are more closely related to bowfin than
other fishes. Gar are older than bowfin. All of these fish are
ray-finned fishes which split from the other group (lobe-finned fishes)
several hundred million years ago. True lungfish are lobe-finned fishes
and are the only air-breathers that lead to the lineage of all
terrestrial animals, including us. Therefore, bowfin are just part of a
continuum of fishes that split from the group that was evolving toward
No evolutionary changes
for 100,000,000 years would indicate to me that the design works well.
Why did other Amiidae die out, and why aren't more fish surface
breathers? Were air-breathers more common in the past?
The design apparently does work well. Teleosts
probably displaced all of the bowfin (except Amia calva) because of the
'invention' of a true gas bladder and the ability to exploit more
niches. It's not clear how common air-breathing was - it could have
been pretty commmon. Modern air-breathing teleosts have used a number
of structures to hold air, especially in hypoxic environments (e.g.,
mouth, gut, etc) while using the gas bladder for buoyancy.
What is the purpose of
the gular plate? Is it found in other fishes?
A large bony plate in the ventral part of the mouth, the gular
plate probably serves to protect the animal. It moves a lot during an
air breath. Other fishes do have a gular plate.
Does the bowfin use its
barbels to locate prey? Are they chemoreceptors?
It wouldn't surprise me to find that the barbels
serve some tactile function for finding prey; I don't know of any
studies that have looked at them for a possible chemoreceptive
function. There are lots of data on catfish (John Caprio at Louisana
State Univ. has done a lot of work with this) but none that I know of
with bowfin. In the grand scheme, very few of us care at all about
bowfin. That is shocking, I know, but true. I really appreciate the
efforts of the BAG members in raising the awareness of the bowfin!
Are there any active
bowfin research projects that could use BAG members as volunteer
Being on the west coast, where there are no
bowfin, I am not in touch with any potential projects. You could
contact your local F&G guys and ask them if they know about any
Does the bowfin gas
bladder have any internal features similar to lungs on mammals, e.g.,
alveoli, bronchi, capillaries for blood-gas exchange?
The gas bladder is vascularized, but is a very
simple structure. It doesn't have any real elaborations like alveoli.
The capillaries drain into a venous sinus that empties into the venous
supply just outside the heart.