Physiological stress in the smalltooth sawfish
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Physiological stress in the smalltooth sawfish


All right you guys thank you for coming
to the Knauss Brown Bag I’m excited to introduce Bianca Prohaska who is a
Knausss Fellow working with International Activities. Bianca earned a bachelor’s in
science and biology and marine biology from Florida Institute of Technology, a
Masters of Science in Marine Science from the University of New England and a
doctorate of philosophy in ecology and evolution from Florida State University.
Her main research interests lie in studying the physiological
ecology of elasmobranch just sharks skates and rays so that the results can
be applied to management and conservation. Today she will be
presenting Physiological Stress in Small-tooth Sawfish: Effects of Ontogeny,
Capture Method, and Habitat Quality. Thank you all for coming today I’m just going
to be presenting some of my dissertation research on small-tooth sawfish and I
also want to note that I did this work in cooperation with some NOAA
researchers as well as some FWC researchers particularly at NOAA Panama
City lab and for fish and wildlife in Port Charlotte and if you are interested
in this research at the end you’re welcome to check out our publication
online or I can email you a PDF of it but the people in red here are the the
NOAA researchers from the Panama City love so I like to start out just with a
really general overview of my research topic during my dissertation work and
basically why do we care about physiology so we know that physiology
can dictate the life history behavior and fitness of an organism so it’s a
really important topic in that context and looking at stress within physiology
basic definition is that it’s a disruption of homeostasis of an organism
by intrinsic or extrinsic stimuli that can elicit 8 elicits a compensatory
response and we can use this information from different species to help formulate
conservation and management strategies and so my basic overlying
question for all of my dissertation work was just looking at how ecological and
anthropogenic forces may affect stress in a lhasa brakes and I also studied
this in a lot of other different species of sharks deeps deepwater sharks and a
couple squeaks of hammerheads so a little bit more on saw fishes because
that’s what I’ll be talking about today there are a small family at bat toys so
they’re a species of Bray they’re not a shark even though they seem to have more
about body shape of a shark and there’s five living species they occur in
coastal subtropical and tropical waters and they’re among the largest bachelors
so they can get up to about five meters long which is about 17 feet and they
have a really slow life history which might be a little bit technical or
jargony but that just means that they mature late in life and they have low
fecundity which are attributes that can make them pretty vulnerable to fishing
pressures so a little bit more background in terms of their
distribution in the past this is their distribution in the Atlantic Basin the
orange here their historic distribution in the US they were found from Texas to
New York historically but their core was always in Southwest Florida and now
they’re really only found in Southwest Florida I’ll be using this term a lot
young of the year or yoi and these are just our zero to one year olds and also
small juveniles and they are born at seventy centimeters which is about this
big so pretty big when they’re born they inhabit shallow estuaries and coastal
bays until they’re about three years old reaching about 220 centimeters and then
the adults in larger 100 centimeters or 5 meters in length
and adults and large juveniles will also inhabit shallow coastal estuaries but
they also go offshore into about 100 meters depth of water on the continental
shelf so in terms of nurseries in the United States there’s two known nursery
habitats the first is the Charlotte Harbor estuary unit located here by the
circle and that’s the piece includes the hatchery rivers in Southwest Florida and
this is unfortunately a pretty anthropogenically influence area as a
nursery habitat there’s a lot of coastal development and not too much natural
coastline left there’s also the 10,000 Islands National Wildlife Refuge and
Everglades National Park unit located here and it is still relatively for
seeing a lot of natural habitat as far as their status over the 20th century
there’s believed to be about a 95% population decline and small-tooth
sawfish in the US and this is from a peer-reviewed paper a quote that saw
fishes are arguably one of the most threatened marine fishes in the world
and so why is that so some sources of their population decline in the u.s. are
thought to be some targeted commercial fishing while limited and this picture
is from the Florida Keys in the 1940s and they were captured not just for
their flesh but mostly for their rostra so here is a picture of a bunch of dried
rostra they were sold pretty heavily it’s just curio items something somebody
would slap up on their wall and interesting talking point unfortunately
there’s still of interest today these are mostly plastic ones but this is at a
hotel and these are plastic replicas of Sasha song fish rostra is sold at
Bloomingdale’s so still of interest unfortunately today for people to look
at I guess another source of population decline is sport fishing so they were a
fun fish to go out and catch and get a cool picture with your buddy afterwards
and there’s also directed harvest common outside of the US which is still ongoing
not just for consumption but for ceremonial objects and then in some of
the rooster are fighting in South America they will take the teeth off the
sawfish rostra and attach them to the roosters feet for better fighting
another source of population decline is five catch mortality which is pretty
common they’re caught in gill nets trawls and on long lines if you think
about this giant hedge clipper they have it can get entangled really easily and
then one that people don’t think about it often it’s habitat loss so this is
kind of a silent threat in terms of population decline but like I mentioned
sawfish spend a lot of time in shallow coastal estuaries they really utilize
mangrove habitats for protection during those early years so unfortunately in
Florida people like to build their houses and those types of habitats so a
lot of mangroves have been taken out which is probably one of the sources of
population decline luckily in 2003 small-tooth sawfish were listed on the
endangered species act and so their current status today they’re listed on
IFC n as critically endangered they’re still listed on the u.s. Endangered
Species Act making it illegal to catch harm harass or kill and they’re also
listening on Sadie’s appendix one as endangered which bans international
trade so their current threats are still existing in the u.s. particularly rod
and reel fishermen they still routinely capture sawfish while not targeted it
still happens and they can be on the line for up to one to three hours before
the fishermen even know what they have they haven’t pretty gonna deal what they
have but before they see it and land they’re caught in bottom longline
fishery still and what keys they’re caught in shrimp trials and this is
probably the most direct source of mortality because when they’re brought
up in a shrimp trawl they almost always come up dead or dying they can become
entangled in marine debris very easily like I mentioned
federal Gill net fishery there still have been found to be caught in that
fishery as well unfortunately some people when they catch them they
purposely injure or kill them as well and habitat loss is still an ongoing
problem because people are still building their houses on the coast so
getting back to stress physiology so when I’m talking about it today I’m
mostly talking about anthro genic stress so these are stressors that surpass
natural stress so here’s a picture of a crocodile eating a sawfish in Australia
that would be a natural stressor but this group of guys over here that felt
the need to take the sawfish out of the water to get a picture with it would be
surpassing natural stress anthropogenic and it can have direct life history
behavior and fitness effects even if it’s not a direct source of mortality
unfortunately in the last banks of sharks skates and rays we’re not able to
directly assess the primary stress response to looking at hormones like we
can look at and other species of fish or mammals and birds but we look at the
secondary stress response things like blood gases and acid-base status and
these can be indicators of immediate and delayed post release mortality and they
have been used pretty frequently so some of those stress parameters I’ll just go
over them very quickly so you have a little bit of an idea what I’m talking
about my results we look at glucose pretty frequently so this is your
fight-or-flight response and if we see inkless increases in glucose in the
blood that’s usually indicative of a hormone response that’s telling the
liver to release a bunch of than kosis the blood so that you have this extra
energy to fight for we can see increases in pco2 and that’s related to
respiratory stress so any sort of respiratory inhibition over the gills or
say a ram ventilating shark that needs to swim to breathe isn’t able to swim
we’ll see increases in pco2 we can see increases in lactate and decreases in
bicarbonate that’s related to metabolic stress so the more the animal is moving
whether it’s trying to find safe refuge or it’s on the line and it’s struggling
to get away you get a buildup of lactate muscle
bitches into the blood you can also think about this if you go for a long
run you get a muscle cramp afterwards sort of the same concept it’s just a
buildup of lactate and we have naturally-occurring bicarbonate in our
blood that will decrease while it’s trying to buffer the acidic response of
lactate we can see an overall depression in pH because both pco2 and lactate are
acidic and we also look at hematocrit and potassium which are directly linked
to lactate so the more lactate you have in your muscle the more fluid I’ll ships
from your blood into the muscle to dilute it there and we’ll see an
increase in hematocrit was just is the percent of red blood cells so if we took
the whole blood and spun it down there would appear to be more red blood cells
and then potassium can also leak out of the muscle tissue and into the blood and
this can have effects on heart functioning and also just neuromuscular
issues in general but today I’ll just focus on respiratory stress and
metabolic stress in my results and I’ll keep it pretty brief for time so our
overall rationale for this study was we really just wanted to understand the
response to end / genic influences in the small-tooth sawfish so that we could
hopefully better inform species specific management and help the recovery team
with the rebound of the small-tooth sawfish population in the u.s. so my
major questions were does the stress response change over ontogeny so
unfortunately basic definition it’s just different life stages so the young in
the year – the juveniles for the adults does capture method affect the stress
response so I’ll go over the different capture methods we used right after this
and do anthropogenic influences on those young of the year in juvenile habitats
affect their stress physiology so the first type of capture method I’m going
to talk about is longline and we use this to capture adults and large stupid
house and we would trailer or vote down from Florida State and to the keys and
we do day trips for about a week where we set these scientific long lines
baited with lady fish trying to mimic what we’d see in the bottom longline
three and I have a short video to play describing that so here is my adviser setting out our
longline gear we had about 9 foot long engines that are attached to a mainline
and they’re all late they did with half pieces of lady Finch like they do in the
commercial industry and then our lines are set for an hour and at that time we
then haul back in the line and sample anything as quickly as possible thank you that’s a good yeah so then if
we did catch a sawfish we would restrain it as quickly as possible the first
thing we do is we get rope around its rostro that’s the business end and you
don’t want to get hit with and then we get a rope around its caudal fin and
basically string it up alongside the boat the animals in the water the whole
time and we sample it as quickly as possible and get it on its way and just
before there are any questions about it we’ve had no mortalities we acoustically
tagged and satellite tagged almost all of our set our sawfish and we’ve had no
mortalities just another picture of us sampling the saw finish and then we
sampled large juveniles and adults in two separate regions in this shallow
area which is Florida Bay it’s two to five meters deep it’s pretty shallow and
then also off the coast the continental shelf in 40 to 80 meters of water so
then the next capture method we used was gill net and this was primarily to catch
young of the year and small juveniles and we did this with Noah Panama City
down in the Everglades and also with FWC in Port Charlotte and it’s kind of hard
to see because they blend in really well but there’s a little sawfish there and
there and we set our line perpendicular to shore and it’s pretty easy to tell as
soon as you caught anything we’re right next to the the gill net the whole time
if we see anything in the net we jump in the water and go investigate it if it’s
a sawfish we start just tangling it right away and getting blooded and
sampling it so that’s the first thing we do is we collect a blood sample as soon
as possible and this is getting blood from a couple of the little ones and
it’s a little bit different getting blood from the big guy it’s a little bit
harder and then I have another video so this is actually us in Andros Bahamas
so a different survey but still a small-tooth sawfish
you can see the first thing that we’re doing is when we pull into sawfish is
we’re trying to get that rostral rope this guy was actually pretty calm
sometimes they can be thrashing around like crazy like like that and then the
next thing we get the line around the caudal fin and like I said we’re trying
to get blood as quickly as possible so I just jump in the water and start to
sample it generally I don’t jump in the water
it was shallow at first but then by the end of this you see I’m swimming our
boat started drifting into deeper water but we get the blood sample that’s
priority number one after we know that the animals are strained and safe so
then once we have the blood we have a meter on the boat that can tell us
lactate bicarbonate pco2 and pH immediately so we know even before we
release the animal what these levels are and then back at the lab we can analyze
glucose using a glucose meter like some of you may use yourselves we can analyze
hematocrit back at the lab and then we spin down the remaining blood and we
keep the plasma and we can analyze potassium in the lab afterwards and we
also have a lot of saved plasma that we’re hoping to use to analyze those
hormones I told you about there’s a group working on an assay to validate
that and hopefully when that’s finished we’ll be able to actually look at stress
hormones with our blood so just a quick review of the samples I’ve collected
we’ve sampled 83 sawfish for this paper 42 young of the year 13 juveniles and 28
adults and as far as capture methods it’s pretty spread out we had 22 shallow
long line 11 deep long line and 46 gilma we also had a couple serendipitous
captures three on rod-and-reel and one be a dip net where we just saw one in
the water and stuck with dip method and we sampled it within about 30 seconds
the last two men kids are just anecdotal and aren’t
included in any of my analyses but I do want to point out here unfortunately
this isn’t a perfect design we don’t have all of our ontogenetic stages
sampled in the same way so it’s hard to say exactly if it’s capture method
affecting something or age just keep that in mind and know that the results
are confounded like that but we did the best that we could so looking at
ontogeny and capture method and I’m just gonna go through those two parameters
that I mentioned so I don’t for you all but first pco2 so that’s respiratory
stress if you remember higher concentrations would be indicative of
higher respiratory stress so looking over ontogeny here’s young of the year
juvenile an adult we saw significant significantly higher concentrations in
our young of the year higher yet higher concentrations and juveniles and adults
but we’re not sure if that’s affected by capture method as well so we looked at
gill net only captured young of the year in juvenile scenes they were also caught
by the same method and when we did that we saw no significant difference there
is certainly slightly higher concentrations than the young of the
year but it wasn’t significant so it’s likely that it’s the capture method
that’s driving these higher concentrations which isn’t super
surprising gill net being that the animal is completely restricted and
there’s potential and pigment of ventilation versus a long line where the
animal screens swim so it’s likely capture method increasing its P co2
concentrations and then I also included here the rod and reel and dip net just
for context but still pretty anecdotal other studies on a lots of banks have
found that there were higher concentrations of pco2 and rod and reel
and gill net captured a lot some rates as well so that’s not entirely
surprising it could be the active retrieval during rod and reel capture
that’s driving that increase of pco2 in terms of these concentrations
compared to other lots of rates that have been studied because sawfish have
not been studied before our concentrations are in range with other
sharks studied and other rates that have been
studied average concentrations ranging four to fourteen and tour so we’re
falling in that range and these are also of concentrations that animals that have
survived capture for lactate if you remember this is related to metabolic
stress so the more you’re moving the higher concentrations of lactate we
would see for ontogeny we didn’t see any significant differences over those life
stages we did see a lot more variation in young of the year but it wasn’t
significantly different if we look at only gill net captured young of the year
and juveniles we do see a significant difference but again it’s probably being
driven by that a lot of variation in the young of the year stage so it could be
age that’s driving this difference maybe there’s more frequent energetic demands
and that young of the year stage they’re probably trying to seek refuge more
frequently than larger juveniles and there’s some other factors I’ll talk
about in the next section and then if we look at capture method there was no
significant difference just again a lot more variation in gill net but that’s
probably being driven by those younger the years making up the majority of that
class robbing real and if net were very low for lactate like I had mentioned for
the dip net we captured and sampled that animal in 30 seconds and then lactate
response really takes three to six minutes to occur so it’s not surprising
that both of those capture methods were pretty low and just to mention I think I
said this already but lactates one of the best indicators of post release
mortality and lots of cranks it’s been noted in a lot of different scientific
studies and in terms of our concentrations they’re coming out very
low compared to other published numbers they’re most supposed to southern
stingrays after capture which have it on average 3.1 millimoles per liter so this
is indicating that they’re pretty resilient to capture at least in terms
of lactate for context sharks can range anywhere from four to 50 millimoles per
liter in lactate and dead or dying blue sharks
typically have around 20 millivolts per liter so our highest concentrations even
have which is pretty promising results in
terms of habitat loss so if you remember the two different nursery habitats I
mentioned down here is Florida Bay and lower Everglades and then this next star
is upper Everglades this is the police’ hatchery River and this other star is
the Peace River these bottom two represent those more pristine habitats
and these upper two represent the two more altered habitats so in terms of
pco2 we didn’t really see any significant changes between the two
different habitats which isn’t surprising it’s probably more lengths to
capture method and all of these were capturing the same way for lactate we
saw significantly higher concentrations in the altered habitats which again
could be linked to that habitat loss so they’re probably trying to seek out
refuge more frequently which is causing just an overall chronic increase in
lactate in their blood and noting time I’m going to try to go through this
little quickly so just general conclusions Guilmette likely is inducing
greater stress because of the limitation and mobility and possible improvement of
ventilation so fishes seem to have a similar or less pronounced stress
response to other lots of regularly studied they’re more similar to more
resilient species and if you were to look at all of the parameters that I
didn’t discuss today we saw similar results in those as well and there’s
possibly chronic metabolic stress occurring in those regions with habitat
loss which is unfortunate likely from less refuge from human predator
interactions and this can cause behavioral and physiological
compensations and it can get down to population level affects things like
affecting immune systems reproduction and growth so in terms of future
directions I hope to work on this again one day or I hope that somebody does but
people should really investigate the tertiary stress response which is
looking at those population level effects and we could easily look at
stress from habitat loss in those two regions that I mentioned and effects on
growth we have the data and we could do that pretty easily also looking at broad
and rail captures this is the most common interaction most likely on top of
us comparing fight times if possible
although getting the permits do that would be very difficult but like I
mentioned they’re captured on one-two-three our fight times so if we
were able to compare between different fight times I think that would be very
interesting as it’s a continuous active retrieval the whole time so the animal
is just fighting the whole time curious to see what lactate would be like and
then as far as shrimp trawl it’d be really interesting to collect some blood
from a moribund sawfish from a trip control because like I mentioned we’ve
never caught a dead or dying sawfish which is a good thing but to have that
data would be very useful for post release mortality studies and that is
the end I’m sorry I ran a little I did oh oh sorry
so Zack was asking if I saw any interactions between sight and capture
method and unfortunately with our young of the year we only ever captured that
by the one caption of good except for the dip net and rod-and-reel but our
sample sizes would have been too small to really look at interaction there but
that would be ideal if we were able to do that anybody yes so spoiler with all of our long line
captured sawfish we we do do that I take a blood sample immediately and I also
take another blood sample before you release them probably not even allowed
to say that I’ve done that but the results are actually there’s not too
much of an increase in lactate for most of them and I actually have another
figure could you go to this one just to give you an idea we caught a a pregnant
mother in Andros and we actually had her restrained for quite a long time and
this red here is her beginning lactate we sampled her really quickly is that
about one and then her release lactate was about 3.5 we had her for about an
hour and a half because she pumped five pups and the fact that her lactate only
increased by 2.5 was pretty pretty good it’s down below it they are online I
don’t know if they’re on the NOAA website another and there’s a video of
it on YouTube of the birth and everything didn’t have time to show
today but if you’re interested I can also send you the links I have lots of
videos ok thank you Bianca we’re just going to take a quick two minute break
before the next presentation

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