Friday, December 17, 2010

Adorable



This adorable little fellow is an adult hairy frogfish and the little guy marching along behind him/her is a juvenile.  At the end of the video the frogfish attempts to lure in prey using it's lure, which extends from the head.  It's pretty interesting behavior for a muppet or fish rather.

Monday, December 13, 2010

But they don't even have bones...

This video shows laser ablation of shark vertebrae.  Laser ablation is the same method used when analyzing trace elements in otoliths.  However, since sharks don't have otoliths (they have a similar structure called a statolith), the vertebrae is often used for aging and I'm guessing elemental analysis of a vertebrae would yield the same type of data that can be obtained from an otolith.  The video is kind of long and monotonous, but I was interested because it is a relatively new concept to me, and I have a few shark obsessed colleagues

Friday, December 10, 2010

When Your Powers Combine...

ResearchBlogging.org

Atlantic bluefin tuna Thunnus thynnus are a highly migratory, pelagic, marine fish species.  Although I have never personally indulged myself by eating this fish, I have little doubt they are delicious.  How can I make such an assessment?  Well, Atlantic bluefin tuna are one of the most endangered animals on the planet and most assessments suggest they are on the brink of extinction.  The obvious solution to this problem would be to close down the Atlantic bluefin tuna fishery, but alas, as with most fisheries issues the solution is not so cut and dry.  The demand for bluefin tuna is incredibly high and in some countries, like Italy, the fishery represents a culturally important event.  Because of the importance and current status of Atlantic bluefin tuna, significant effort has been put forth to address questions regarding migrations and stock structure of the species. 

Studying the movements of highly migratory species is a difficult task to say the least, but solutions to these difficulties are quite interesting.  A suite of methods including otolith microchemistry, genetics and electronic tagging has been used to decipher the life history of this species.  Block et al. (2005) suggested that using each of these methods individually would be insufficient, and combining these methods paints a more powerful, more complete picture of the life history of bluefin tuna in the Atlantic Ocean.

Using otolith microchemistry, Rooker et al. (2003) identified unique chemical signatures in the otoliths of age-1 Atlantic bluefin tuna from the western and eastern Atlantic.  This information is important, because it can be used to classify adult bluefin tuna to natal origins and suggests that there are probably two separate spawning stocks.  This information is augmented by the findings of Carlsson et al. (2007) who used both nuclear loci and mtDNA to distinguish differences between Atlantic bluefin spawned in the Gulf of Mexico and the Mediterranean Sea.  Finally, electronic tagging by Block et al. (2005) revealed that bluefin tuna have trans Atlantic migrations and may show spawning site fidelity to the Gulf of Mexico and the Mediterranean Sea. 

Of course there is significant room to expand on all of this research, but when the current information is combined, the life history of Atlantic bluefin tuna becomes clearer.  Using otolith microchemistry and genetic analysis to examine the origins of adult tuna should provide information on the mixing of individual stocks, which could answer questions like which side of the Atlantic is producing more fish?  This information would complement findings from electronic tagging studies quite nicely.  Whatever direction this research takes, it is pretty clear that one method will not provide all of the answers needed to make proper management decisions.  It is only in combining their powers that a clear life history and stock structure can be identified for this critically important species.

Block BA, Teo SL, Walli A, Boustany A, Stokesbury MJ, Farwell CJ, Weng KC, Dewar H, & Williams TD (2005). Electronic tagging and population structure of Atlantic bluefin tuna. Nature, 434 (7037), 1121-7 PMID: 15858572

Carlsson J, McDowell JR, Carlsson JE, & Graves JE (2007). Genetic identity of YOY bluefin tuna from the eastern and western Atlantic spawning areas. The Journal of heredity, 98 (1), 23-8 PMID: 17158466

Rooker, J.R., D.H. Secor, V.S. Zdanowicz, G. De Metrio, & L. Orsi Relini (2003). Identification of Atlantic bluefin tuna (Thunnus thynnus) stocks from putative nurseries using otolith chemistry Fisheries Oceanography, 12 (2), 75-84

Tuesday, December 7, 2010

Holiday Gift Idea

If your looking for the perfect holiday gift for the otolith lover in your life, looking to expand your own fashion horizons, or looking for new ways to express your fondness for the ear stones of fish then this is the place for you.

  
Otolith Necklace
Very Nice

Earring
Fancy 

Thursday, November 18, 2010

Putting it to Use

This is kind of old but interesting nonetheless.  Researchers used chemical signatures (in this case isotopes) in the otoliths of bluefin tuna  to distinguish between fish spawned in the Mediterranean Sea and the Gulf of Mexico.  Clearly with the state of bluefin tuna populations, gathering information about life history is essential and otoliths can provide this information.  As I've written previously, it is difficult/improbable to capture and tag larvae and juveniles therefore the natural tags in otoliths are often the only record or natal origins available.      

Wednesday, November 17, 2010

Perspectives

Willy Phillips is the commercial fisherman that I have been working with to conduct my research this summer.  He has been integral in helping me formulate ideas about how to conduct my work.  Willy has been working on the Albemarle Sound for years, and in addition to fishing has worked on a number of research projects.  During his time on the Albemarle, he has witnessed many changes and trends in the system.  Often times Willy and I have discussed observations I have made in the field, like low oxygen or high salinity events, and he was able to give me reasons for why these things were happening.  

This local ecological knowledge is the perfect starting point for many research projects and is important for researchers to consider. Often times, commercial fishermen are considered to be rather "shallow" and to only care about what fish they can harvest.  This is far from the truth, because they depend on fishing for their livelihood, they have an intimate understanding of the resource and care deeply about protecting it.  In this video Willy discusses the plight on commercial fishermen in North Carolina.   

Thursday, November 11, 2010

Justification

A quick view of the website for the Herring Alliance gives the impression that the biggest issue impeding the recovery of river herring stocks is by catch from the Atlantic herring fishery.  While there are certainly other factors contributing to the consistently low levels of river herring, including habitat loss and direct commercial catches, there is no doubt that by catch is a major factor.  The dilemma that occurs when attempting to restrict or manage river herring by catch is that so little is known about their marine migrations. 

Enter otolith microchemistry.

I have already written, and it has been well documented in the literature, about the ability of otoliths to record the natal origins of fish.  Theoretically, as long as there is data about the elemental signature of individual watersheds, river herring caught in the open ocean could be classified to natal rivers.  Knowing the natal origins of a fish captured in the open ocean is an incredible piece of information but is incredibly difficult to obtain.  Traditional tagging studies, where the fish is physically given some type of mark or tag, are difficult because of the large sample size, and amount of effort that is needed to carry out these studies.  Capturing small juvenile fish, while they are still in their natal area, and marking them is pretty much a death sentence and in most instances probably not practical.  The most effective larval/juvenile tagging studies utilize hatchery raised fish that have been marked with fin clips or been given chemical marks on their otoliths.  However, marking and recapturing hatchery-raised fish gives us no information about the behaviors of wild spawned fish.    

Knowing the natal origins of ocean caught fish (combined with age data also obtained from otoliths)  can provide valuable information about migration patterns, schooling behavior, stock structure, recruitment, and exploitation rates.  This data can then be used to strengthen management decisions.  As research on elemental signatures in otoliths continues to progress networks of signatures for rivers along the east coast can be built up so that some of these questions can be answered.    

Monday, November 8, 2010

Reflections On The Field Season That Was...

My field season has now been over for about 2 weeks, and I now feel as though I have had adequate time to reflect and evaluate myself on the good, bad and ugly that was my 2010 field season.  First, I should provide a little background information on why exactly I was in the field in the first place.  If you have read previous posts you know that I did a fair amount of water sampling throughout the summer (yes I know collecting bottles of water is just about as exciting as it gets).  However, this was not my only objective this summer, I was also attempting (emphasize attempting) to conduct a caging experiment using river herring to validate otolith elemental signatures from individual watersheds. 

My field work officially started in June, collecting my first water samples of the season.  I'll just get this out of the way now and say that I collected water samples from June-October and unless something interesting happened with regards to those trips (which nothing did that hasn't been mentioned in previous posts) I won't bring them up.  My first trip went surprisingly smooth...I think, it was along time ago and I was incredibly vague when I wrote it in my log.  The caging experiment portion of my field season was also supposed to start in June.  We had ordered a number of cages from Seagear and were set to deploy them in June.  However, on April 20, 2010 oil started leaking into the Gulf of Mexico, and the ensuing effort directed toward the Gulf of Mexico pretty much consumed the time Seagear had allotted toward building cages for me.  Now, I absolutely do not want to sound like I am complaining Seagear handled the situation extremely professionally, and losing a portion of my research is in no way on the same level as what was lost by residents of the gulf coast as a result of this spill.

July rolled around and I regrouped.  I threw together a couple of cages with parts from an experiment done a few years prior to mine and deployed them in July.  With cages in the water, I was feeling pretty good, all I needed was some fish.  Unfortunately, this is easier said than done.  Our goal was to catch juvenile river herring with a seine and plant them in cages however, it's no secret that juvenile river herring aren't particularly abundant, or easy to keep alive, as they have a tendency to die if you look at them the wrong way or make loud noises.    Our first seining expedition took place in the Roanoke River.    
We initially tried seining in downriver areas with a lot of vegetation.  However, the Roanoke River in this area is quite deep and the bottom is covered in about 1 meter of mud, not exactly the best seining location.  Regardless, we pulled a bunch of seines, and despite catching a lot of fish there were no herring.  We decided to move upstream, to a more favorable area. 
The water here was more shallow with less mud covering the bottom, and immediately we had success!  We caught two very small juvenile blueback herring.  My heart was pounding when I saw them in the net it was probably the most excited I had been in a while (to be honest I really wasn't expecting to catch anything so these fish were pretty breathtaking).  We brought the fish aboard the boat and it was a race against time to get the fish into the cage.  Unfortunately, one of the fish died in transport (not a huge deal it's otoliths are still valuable), but the other one lived and was successfully added to the cage!  I was pretty high on life after this trip, and was hoping this would set the tone for the rest of the field season.  Two weeks later we attempted to recover the fish we had put in the cage and it had mysteriously vanished.  Throughout the season we caught and added about 5 more fish to the cage in the Roanoke River, always with the same result, the fish would disappear, I will elaborate on this more later. 

Despite having a more favorable seining location in the Scuppernong River (shallow, sandy bottom with no stumps) we were never particularly successful in adding fish to this cage.  We caught flounder, lady fish, three trillion menhadden, and two 15 inch striped bass.  In total we caught one juvenile river herring, this one in fact:
This little guy was added to the cage, but met the same fate as the fish from the Roanoke River, mysteriously vanishing. 

The Alligator River presented the greatest challenge when it came to seining, not only because it is very deep and the bottom is covered by stumps and mud but mostly because I am slightly terrified of bull sharks and alligators. 
boat launch at the Alligator River

Now, I never saw either of these animals in the river, and there is basically zero chance of being attacked but it's something that hung in the back of my mind every time we were there.  The only site we could effectively seine was a downriver section of the river.  Seining here was pretty interesting because of the diversity of fish we caught, we pulled in everything from juvenile bluefish and some kind of mackerel (or jack) to an adult hickory shad who had apparently forgotten that she was supposed to be in the Atlantic Ocean.  We only caught one juvenile river herring, that never got added to a cage, however given the circumstances I consider this to be a small success. 

By far the river where we had the most success was the Chowan River.  We never failed to catch river herring here and when we caught them we usually caught pretty decent numbers.  I was pretty confident about this river from the very start, part of the river has sandy shores which are perfect for seining, and we caught close to 80 river herring in our very first seine.


We were even able to add most of these fish to the cage
Things in the Chowan River usually went pretty smooth, despite the fact that all of the fish added to the cage vanished.  Also, I wouldn't be doing this post justice if I didn't mention the boat running out of gas about two miles from the boat launch and having to swim/push/pull the boat into shore.
Not one of our more proud moments but it could have been worse. 

To address the issue of vanishing fish we hypothesized a few possible causes.  The first was they were escaping through holes in the cage.  This was possible but unlikely because there really weren't large holes in the cages, and if we found new holes throughout the season we closed them.  Another potential cause was predation.  Again this was unlikely as a predator would have to get into the cage, and if it was a very small predator I don't think the whole fish would be devoured so quickly.  I think the most likely scenario involved the fish dieing from stress or low oxygen and decaying quickly in the high water temperatures.  Towards the end of the season when the water temperatures were slightly cooler we found portions of the fish in the cage, which somewhat supports this hypothesis.  In the future, I really think the only way to do an experiment like this would be to do it in the lab which unfortunately doesn't allow you to directly validate the elemental signature from a watershed, but can be used to gauge how elements are incorporated into the otolith.     

Looking back if I had to choose one word to describe the field season it would have to be "mediocre".  For everything that went right something else would go wrong.  We did get a lot of data and were incredibly successful overall in capturing juvenile river herring.  We were even pretty successful in keeping the fish alive during transport, which is no easy task.  This was the first time I had really been in charge of planning field work and I learned a lot from the experience.  I have certain strengths when it comes to field work but I also have weaknesses.  At times I was poorly organized and under prepared, but I do think I learned and improved as the season went on. 

I definitely have to thank the people who helped me out with field work throughout the season: Coley, Chuck, Jeff, and especially Joey Smith.  Joey was the undergrad who worked in the field with me and was there for every trip, I thank him for the knowledge he brought about the Albemarle watershed and his commitment to the project.  

Monday, October 18, 2010

Pictures!

Today was another field day.  I helped out lab mate Jeff in collecting water samples in the Neuse River.  Jeff is investigating the natal origins of striped bass in the Neuse and Pamlico Rivers using otolith microchemistry.  Today, was awesome!  Nothing went wrong (which is unusual for field work that I am involved in), the work went quickly, the water was calm, and the weather was beautiful. 

The only thing really interesting or different about today was that it was the first time that the responsibility of captaining the boat was put solely on me.  Throughout the summer I have been conducting my research in conjunction with a commercial fishermen, so I haven't needed to drive the boat myself.  I am by no means afraid or inexperienced when it comes to driving boats.  I have been driving boats for most of my life, but mostly on small lakes and it's a whole different experience driving boats in large rivers/estuaries.  Also, I find that recreational boating is way different than boating for work, when you have a specific goal, like completing research, it can be a bit stressful.  Fortunately everything went swimmingly so I will just present a short pictorial narrative of the days events.

As stated previously the day was beautiful
We launched in the Neuse River and headed upstream.  I haven't really spent anytime on the Neuse River and didn't realize how narrow and winding it could be in some places.  It kind of reminded me of the Roanoke River in some places.  Our first site was around the route 43 bridge
And we started collecting water
Using this sophisticated piece of machinery
It was a really nice location, it was nice to see some trees with leaves starting to change
From there we headed downstream to the hwy 70 bridge
This is where we had the only minor snag of the trip.  We had to wait about a half hour to go under a railroad bridge because a train was crossing at a snails pace. We took water samples and water quality data
We then headed to our next location.  The world famous Dawson's Creek
Yes this is where the TV show Dawson's Creek was supposed to have taken place, although it was not actually filmed here.  Unfortunately, we did not have any James Van Der Beek or Katie Holmes sightings, but the creek was really nice.  From the creek we headed upstream
Then downstream
And the day was done.  So although nothing really exciting happened, I can always appreciate when things go smoothly even if it doesn't necessarily make for a good story.

Sunday, October 17, 2010

"You boys better watch them tides"

I have gone back and forth on whether to write about this particular field work adventure for a while now and finally decided the story is pretty much to good not to be told.  Last weekend I was helping out a friend with some field work, he is using elemental fingerprints in the shells of hard clams to investigate natal origins and dispersal, which is really cool and very interesting so I decided to help out.  We were collecting newly settled clams and water samples in the Moorehead City/Beaufort area, I can't remember exactly what rivers we were in but I think it was the Newport River, North River, Core Sound and Back Sound.  The plan was to head out Saturday morning, camp out at Cape Lookout Saturday night then finish up work on Sunday.

The trip started out innocently enough, we got out on the water with no problems, and it was absolutely beautiful outside, unlike previous field work endeavors.  We started collecting clams in a tidal marsh and immediately had success!  It was really cool and I was impressed that we had success so quickly.  We finished up at the first location with a decent number of clams and moved on to another location, this is where the story get interesting so it's important to pay attention to details, I'll bold the important parts.

We got to our second location, which was an island near Core Sound I think.  We anchored our boat a few yards offshore and headed around to the other side of the island, where there was a salt marsh to find some clams.  This marsh on this side of the island looked promising as a clam nursery area.  The location was pretty awesome, the water was shallow and clear with a nice sandy bottom.  We immediately started to find some clams in the marsh area and were completely focused on the clams.  Eventually we started collecting closer to the beach an I noticed the beach had begun to expand.  I mentioned this to my friend and he agreed, the beach was getting bigger.  Almost immediately after this conversation he said "I think I should go check on the boat", I agreed.  He made his way back to the boat and I started gathering up our gear, and then made my way back to the boat. 

I was greeted by "we might be fucked".  The boat was about three quarters on the beach with only a small amount of water lapping against the side.  The tide had gone out quite quickly leaving our boat minutes from being landlocked.  We tried to push the boat into the water with no success before deciding to try and dig it out.  Unfortunately, we had no shovels so we were forced to dig by hand.  We dug frantically for an hour periodically stopping to push the boat a little into the water.  However, the whole time we were battling against the receding tide.  We had some success digging and pushing the boat and eventually we had the majority of the boat in the water.  Unfortunately, the part of the boat that wasn't in the water was the stern (the heaviest part of the boat) giving the engine no access to the water.  This was frustrating as it rendered our digging efforts useless because there was no way for us to push the stern of the boat off the beach.


Luckily, we had camping gear, food and water with us because we had planned on camping out anyway and we had gotten comfortable with the idea of camping on this island until the tide came back in.  We sat on the beach for a while, then decided to collect more clams.  After a few minutes of collecting we noticed a boat motoring up to us.  My friend walked over to talk to the man in this boat, I followed shortly after.  The first thing this guy says to me is;

guy: "you ever dissected a badger?"
me: "huh?"
guy:  "you're shirt says Wisconsin veterinary medicine, there the badgers right?"
me:  "oh yeah, no can't say I've ever dissected a badger"

We talked to this guy for a while and he introduced himself as Davey, and said he was a commercial fishermen who mostly gill-netted for flounder.  We explained who we were and what we were doing.  Naturally he found our situation pretty funny and offered to try and pull us off the beach with his boat.  Unfortunately, this effort was futile and we remained stuck.  After chatting for a bit more this conversation took place;

Davey:  "what are you guys gonna do until the tide comes in?"
my friend:  "we'll probably just camp out here for a while"
Davey:  "ya'll can come back to my place, it's right across the river (he pointed to his house), you'll be able to see your boat from there, then I can bring you back later"
Davey:  "I mean I'm a trustworthy guy"
my friend:  "that sounds great, thank you so much"

I'm pretty sure I was standing there during this whole conversation wide eyed with my mouth agape looking particularly nervous.  Not that I didn't trust this guy, I mean he seemed like a really nice dude, but I've seen way to many horror movies that start out this way.  We got on Davey's boat and headed toward the other shore.  His house was in a really nice location overlooking the water (and we could see our boat), and he had two really awesome dogs, it was about what you would expect from a commercial fishermen.  We had some good conversations about the North Carolina gill-net regulations, amongst other fishing related topics, as well as our travels.  However, we mostly talked about sports specifically about college football, which we watched all day (Davey is a die hard Duke fan so hearing him bash UNC was pretty funny).  Occasionally, Davey would say something along the lines of "just can't believe you boys didn't realize the tide was going out", we were still pretty embarrassed about about this leaving my friend to compare the interaction to this scene from the movie Happy Gilmore.

Davey really is one of the nicest people I have ever met and he had a really good sense of humor.  The tide finally came in at round 10:30 pm that night, and we went to push the boat of the beach, and it slid gracefully into the water.  Since it was so late at night Davey offered to let us stay at his house and since we had already spent the whole day with him we said "sure".  I can't really say I slept much that night, and we woke up pretty early to leave.  We said our farewells to Davey, and graciously thanked him for saving us from being stranded on an island and his hospitality.  I'm pretty sure Davey's final farewell to us was "you boys better watch them tides" and we wholeheartedly agreed.

It was another beautiful day and our work went quickly, we even saw about 100 dolphins throughout the course of the day.  We had a ton of success finding clams on this day and finished late in the afternoon and headed back home.  This will probably be one of my more memorable field work adventures, and I can almost guarantee I will never let my boat get stranded on the beach by the tide again.   

Monday, October 11, 2010

Where are you from? Where have you been?

ResearchBlogging.org
In my opinion one of the most interesting questions asked about fish is where are you from?  Or where have you been?  Unfortunately, fish don’t carry around birth certificates that make answering these questions easy and uncomplicated…or do they?

Enter otolith microchemistry.  In a sense the elemental makeup of the core of an otolith can act as a “birth certificate” for a fish.  The idea is that the elemental composition at the core of the otolith will reflect the chemistry of the water it was born in.  If there is enough differentiation between different habitats you should be able to see clear separation between fish born in different areas.  The clearest examples of this technique have been in looking at fish from different rivers, and estuaries.

An example of this technique put to use is Thorrold et al. (1998).  In this study elemental and isotopic ratios in otoliths were used to classify juvenile weakfish to natal estuaries along the east coast of the United States.  Fish from different estuaries showed pretty clear differences in elemental and isotopic ratios, which allowed accurate classification of these fish to their natal estuaries. 
Me with weakfish
Other examples of classifying juvenile fish to their natal area include Brazner et al. (2004), which classified juvenile yellow perch to natal areas of Lake Superior and Walther et al. (2008), which classified juvenile American shad to natal rivers along the east coast.

So why is any of this important?   Well, believe it or not investigating and understanding the life history of a fish is really hard.  Traditional mark and recapture studies, which usually involve sticking a tag into a fish, releasing and then hoping to recapture it at some point are often ineffective and typically wind up relying on pretty low recapture rates.  Also, tagging young juvenile fish can be tedious and unfortunately usually has fairly high mortality.  However, if you are able to identify a reliable elemental signature for a river that is reflected in fish otoliths it acts as a “natural tag”.  Therefore, if in the future you capture an adult fish you can examine the elemental signature at the core of that otolith to determine where that fish was born.  This is what Thorold et al. (2001) did as a follow up to Thorrold et al. (1998).

This information is useful in looking at natal homing; straying rates between spawning locations, stock discrimination, movements and migrations, and by catch rates.  This technique forms the basis for my project.  I am attempting to classify juvenile river herring to natal watersheds within the Albemarle Sound NC.  While this area isn’t on the same scale as some of the studies mentioned previously, I think I should be able to find some differences in the elemental composition of fish otoliths from these waters. 

Brazner, J., Campana, S., Tanner, D., & Schram, S. (2004). Reconstructing Habitat Use and Wetland Nursery Origin of Yellow Perch from Lake Superior using Otolith Elemental Analysis Journal of Great Lakes Research, 30 (4), 492-507 DOI: 10.1016/S0380-1330(04)70365-2

Thorrold, S., Jones, C., Swart, P., & Targett, T. (1998). Accurate classification of juvenile weakfish Cynoscion regalis to estuarine nursery areas based on chemical signatures in otoliths Marine Ecology Progress Series, 173, 253-265 DOI: 10.3354/meps173253

Thorrold, S. (2001). Natal Homing in a Marine Fish Metapopulation Science, 291 (5502), 297-299 DOI: 10.1126/science.291.5502.297

Walther, B., Thorrold, S., & Olney, J. (2008). Geochemical Signatures in Otoliths Record Natal Origins of American Shad Transactions of the American Fisheries Society, 137 (1), 57-69 DOI: 10.1577/T07-029.1

Thursday, October 7, 2010

More Field Adventures!

This past Monday (October 4, 2010) a few fellow students and myself headed out to the field to collect some water samples.  This particular work was for Coley Hughes, a lab mate and fellow otolith investigator.  Coley is investigating the natal origins of Striped bass in the Albemarle Sound.  Since our study area overlaps slightly and I generally just like to be in the field I tagged along. 

The sampling areas on this particular day included the Pasquotank River, Currituck Sound, the North River and the Little River, these areas are situated in the northeastern part of the Albemarle Sound.  The day started off in the Pasquotank River;
Gorgeous autumn day!
Coley Hughes and Jeff Dobbs excited to be in the field
it was cold and windy.  Of course me being a rugged northerner decided shorts and an t-shirt were all I would really need on a day like today, I mean it's North Carolina right, how cold could it be.  To answer "pretty damn cold".  When the wind is howling and you get soaked by crashing waves it can be pretty frickin cold as I would come to find out.  To make things worse we experienced some minor boat issues that had all of us thinking our day would be cut short.  However, when those issues were sorted out things ran pretty smoothly with the exception of the rough weather.
video
It's always fun trying to stay balanced when boating in rough weather and I give Joey Powers mad props for getting us back to the boat launch with no problems (the video doesn't really give a good perspective on how big some of the waves actually were).

After getting off of the Pasquotank River we headed over to Currituck Sound (no pictures due to be soaking wet and not having a water proof camera).  By this time I had put on some waders, so even though I was not that much warmer I was slightly more dry.  From there it was off to the North River;
Joey Powers and Jeff Dobbs Collecting water in the North River
Things starting to calm down
Fortunately by this time the weather had started to calm down and the North River was actually quite pleasant, until...
Back to the Pasquotank!
we headed back to the downstream section of the Pasquotank River and were immediately greeted by more rough weather.  However, a funny thing happened on the way to the Little River;
Could it be?

Maybe?
It is! The sun started to come out just as we were finishing up
The sun started to come out, the wind died down, and we finished up collecting our samples on a high note. 

Having seen the entire Albemarle Sound region over the course of the summer and early fall I can definitely appreciate how beautiful the sound really is.  For the most part large areas of the shoreline remain undeveloped and are lined by conifers and cypress trees (at least I think that's what some of these trees are, what can I say I'm no dendrologist), I even saw a pod of dolphins in the early spring when I was sampling with the NCDMF.  Yet anthropogenic activity is well represented by the numerous houses and agricultural activity surrounding the watershed. 

I think the reason I am so intrigued by the sound, and estuaries in general, is because they represent an interface between the marine and terrestrial ecosystems, and increasingly humans.  This is probably why I am interested in anadromous species, because for at least one part of their life they are dependent on a habitat that is so closely linked to humans, and I have always been curious and fascinated by this interaction. 

Wednesday, October 6, 2010

CARP!

Nothing about otoliths in this blog, but still focusing on fish and an issue near and dear to my heart.  Asian carp have been in the news quite frequently for a few years now with stories ranging from their steady trek north to the Great Lakes, to people getting smacked in the head and red neck fishing derby's (do a quick search on Youtube for Asian carp, it's pretty entertaining).  It seems as though these carp have become the poster child for the damage invasive species can do. 

It appears now that scientists in the United States and Canada are teaming up to examine the impact these fish could potentially have on the Great Lakes ecosystem.  I think this is a brilliant idea and one of the reasons I love the Great Lakes, because the lakes are shared by the U.S. and Canada there is a lot of collaboration between the two countries on how to best protect the lakes (and yes I love Canada!  I love the people, the beer, the culture, curling, and of course hockey).

This issue is near and dear to myself because I spent three years working at the Lake Michigan Biological Station in Zion, Illinois after I graduated undergrad.  Part of this time was spent working on the electric barrier, located in the Chicago Sanitary and Ship Canal, designed to repel Asian carp and round goby.  We were using common carp as a surrogate to see if carp would be repelled by the barrier (they probably are, but there are other ways around).

Barrier or not, I am not completely sold on the idea of Asian carp being able to take hold in the Great Lakes because naturally, the lakes aren't the most productive systems.  The strong effort to clean the lakes has decreased eutrophication and thus productivity. Also, the introduction of zebra/quagga mussels has shifted the productivity from the water column to the benthos, leaving little in the way of food for pelagic fish like Asian carp, as well as other fish larvae.

However, I do have little doubt that if Asian carp do become established in the Great Lakes the effects would be devastating.  You could probably say bye bye to yellow perch and alewife, and without alewife there would be no salmon fishery.  Not to mention the potential hazards to boaters.  I am certainly interested in the outcome of studies dealing with these fish and hope that efforts to keep them form the Great Lakes prove effective.       

Saturday, October 2, 2010

Tour de Albemarle

After NC got something like 15 inches of rain this week we decided it might be a good idea to collect water samples from our sample locations in the tributaries of the Albemarle Sound.  The reasoning behind this is that the increased precipitation could cause drastic shifts in the elemental makeup of the water, due to increased runoff and higher flows in the river.  Many people are interested in how the elemental signature of a river changes over time, and severe weather events like heavy rain and hurricanes could be a driving force behind these changes.  This is an issue I am attempting to touch on with my research.  We have taken water sample from fixed stations in 5 different rivers from June-October hoping to examine the stability of the elemental signature. 

However, today was an extra sampling trip that was thrown together at the last minute.  After the rain finally stopped I hastily decided to drag myself into the field to scrape together some data.  Unfortunately, I could not get my hands on a boat for the weekend so I had to improvise and try and take samples from shore.  Because I was confined to land for this sampling trip I was unable to take samples from our fixed stations, although I was able to get close to a few. 

I left pretty early in the morning and was greeted by multiple road closings, due to flooding.  This made the already long trip even longer and slightly more treacherous.  I eventually made it to Plymouth NC to sample the Roanoke River and was greeted by this;

The top picture shows a submerged boardwalk, while the bottom picture shows a dock that is ominously close to being submerged.  I took my sample and headed to the Scuppernong River, then to the Alligator River and found this;

the river is almost as rough and unforgiving as the women who tried to kick me out of the marina for "trespassing on private property", sounds a bit nit-picky if you ask me.  Either way I took my sample and headed north to the Perquimans River;




there used to be docks at this boat launch and an old wooden ship if I'm not mistaken.



After the Perquimans I headed to the Chowan River and finally back to Greenville.  The whole trip was probably around 300 miles or something and it was the first time I have been to all of my sites in one day.  It was pretty interesting to see the changes these rivers had undergone due to the rain, and I am very curious to see if these changes are reflected in the elemental composition of the water.

Thursday, September 30, 2010

The Magic of Strontium

ResearchBlogging.org

While I attempt to stay afloat during this seemingly endless torrential downpour Eastern North Carolina is experiencing I decided to finally take the time to write about anadromy and how it can be examined using otolith microchemistry.

Anadromous fish spend most of their adult life in the ocean returning to freshwater to spawn, the classic example of anadromy is Pacific salmon. While it is all well and good to say that a fish moves between salt and freshwater the timing and frequency of these movements can have implications on the management of anadromous species. The goal of tracking migrations between the marine and freshwater environment can be accomplished through traditional mark and recapture studies, however, these lack corresponding age data and fail to provide a complete history of the fishes migrations the way otolith analysis can.

In studies of anadromy, it seems as though the element strontium (Sr) is some sort of miracle element. Although exceptions do exist Sr is typically more highly concentrated in marine waters than freshwaters (Limburg 1995). In addition to showing differences between marine and freshwater environments Sr also incorporates into the otolith quite nicely, perhaps becaucuse Sr is similar in size to Ca, and otolith Sr usually reflects Sr in the ambient water (Campana 1999).

If everything stated previously holds true (there is higher concentrations of Sr in saltwater than freshwater, and Sr is incorporated into the otolith in ratios similar to the ambient water) then the pattern of Sr in an otolith should increase and decrease when a fish moves between saltwater and freshwater. The classic pattern of anadromy can be illustrated by this picture (although this picture may or may not have been for the purpose of investigating anadromy) from Dr. Norman Halden at the Univeristy of Manitoba


The bottom plot shows Sr. The center, or core, of the otolith, representing growth when the fish was young shows low Sr. This pattern could be interpreted as the fish was remaining in a low Sr environment (freshwater). As this fish gets older there are peaks and declines in Sr. This could be interpreted as the fish moving between salt (peaks) and freshwater (declines). This pattern is pretty typical of what you would see from an anadromous fish species. The Sr pattern for a fish that spends its whole life in freshwater would theoretically be relatively flat, without the peaks and declines in Sr.

However, there are limitations to this method and the pattern of Sr is not always clear cut, as I am coming to find out with my own data. Dealing with an anadromous species like river herring I would expect to see a pattern of fluctuating Sr. River herring are born in freshwater (where you would expect low Sr), then move to the ocean (where you would expect high Sr). River herring then move between the ocean and freshwater in order to spawn, therefore, I would expect to see low Sr at the core of the otolith and then fluctuations throughout its life. However, I have not necessarily seen this pattern, and at least in some of the fish I have looked at the pattern appears to be backwards. I think this is pretty interesting, and am still trying to determine if it is the result of instrument error or some natural phenomenon.

Sources

Campana, S. (1999). Chemistry and composition of fish otoliths:pathways, mechanisms and applications Marine Ecology Progress Series, 188, 263-297 DOI: 10.3354/meps188263

Limburg, K. (1995). Otolith strontium traces environmental history of subyearling American shad Alosa sapidissima Marine Ecology Progress Series, 119, 25-35 DOI: 10.3354/meps119025

Friday, September 24, 2010

Huh?...Otoltihs?

Since the purpose of this blog is to write about otoliths and the research I am doing using otolith microchemistry, I am palnning to write a series of posts on the applications of otolith microchemistry and then attempting to explain how I will be applying these to my research.  However, before I do this, I think I should briefly explain what the heck otoliths are and how otolith chemistry works.

Otoliths or earstones (yes humans have similar structures), used for hearing and balance, are metabolically inert and made of calcium carbonate typically in the form of aragonite, however portions of otoliths can be formed of vaterite or calcite (Campana 1999).  The different forms of calcium carbonate are differentiated by crystal shape, and at this point it is unclear as to why otoliths can occasionally be made of forms other than aragonite (Tomas and Geffen 2003).  Fish have three pairs of otoliths--saggital, lapilli, and asteriscii—but because saggital otoliths are typically the largest they are most often used for research (Campana and Neilson 1985). Otoliths have long been used in fish ageing studies because of the visibility of daily growth increments.  Otoltihs form growth rings, similar to that of a tree, by counting these rings you can make estimates of the fishes age in years, or sometimes in days.

While ageing studies have been quite common in fisheries research, otolith chemistry is a somewhat new field.  Otolith microchemistry relies on the assumption that the chemical composition of the otolith is similar to the chemical composition of the water the fish has lived in, thus acting as a sort of natural tag (Elsdon and Gillanders 2003).  The process in which otoliths are formed is at the moment not completely understood (particularly by me), and at this point in my life the entire process is somewhat over my head but I will take a shot at briefly explaining what I know.  The gills absorb elements from the water and the intestine absorbs elements from food, these elements are then passed into the blood plasma and finally into the endolymph fluid, where they crystallize into the otolith (Campana 1999). 

Because otoliths are made of calcium carbonate the most important element in their formation is…you guessed it, calcium.  Because of this, uptake of other trace elements is correlated to the concentration of calcium in the water.  When high concentrations of calcium are present in the water less trace elements are absorbed than when low concentrations of calcium are present. Elements like, Sr (strontium), Zn (zinc), Pb (lead), Mn (manganese), Ba (barium) and Fe (iron), are less physiologically regulated than other elements and thus are used more often in otolith elemental analysis (Campana 1999).

Because otoliths are metabolically inert (meaning they are not reabsorbed, even during periods of starvation), elements incorporated into the otolith should reflect the environmental history of the fish from its time of hatch to time of death (Elsdon and Gillanders 2003).  In combination with age information, otolith elemental analysis can be used to hypothesize about the environmental conditions a fish has experienced throughout its life.  For example, the center, or core, of the otolith represents otolith growth of juvenile fish, whereas the outer edges of the otolith represent recent, or current, otolith growth just prior to capture (Elsdon and Gillanders 2003).  Therefore, the elemental composition of the center of the otolith gives us an idea of the elemental composition of the water the fish was in when it was born, the elemental composition of the outer edge gives us an idea of the elemental composition of the water the fish was in before it was captured. 

Again the easiest way to visualize this is to think of tree rings.  The innermost rings represent the growth of the tree when it is was very young.  Layers of new wood material form as the tree grows.  The outer most rings represent the newest tree growth.  The same concept is used in otolith chemistry. 

Stay tuned for a post about how otolith chemistry can be used to investigate the movement of anadromous fish!


On these images of river herring otoliths you can see annual rings near the center and near the edges.  The center portion of the otolith represents growth as a juvenile.  The outer portion of the otolith represents the most recent growth.
Sources

Campana, S.E., and J.D. Neilson.  1985.  Microstructure of fish otoliths.  Canadian Journal of Fisheries and Aquatic Sciences 42:1014-1032.

Campana, S.E.  1999.  Chemistry and composition of fish otoliths:  pathways, mechanisms and applications Marine Ecology Progress Series 188:263-297. 

Elsdon, T.S. and B.M. Gillanders.  2003.  Reconstructing migratory patterns of fish based on environmental influences on otolith chemistry.  Reviews in Fish Biology and Fisheries 13:219-235.

Tomas, J., and A.J. Geffen. 2003.  Morphometry and composition of aragonite and vaterite otoliths of deformed laboratory reared juvenile herring from two populations.  Journal of Fish Biology 63:1383-1401.

Monday, September 20, 2010

Link fest - check it out!

For those of you interested in otolith science particularly the microchemical aspects of otoliths you should check out www.otochem.net

This site was put together by Benjamin Walther.  There is a forum where those working with otoliths or even those who are just interested in otoliths can ask questions and share ideas with other otolith scientists.

I think this site is a great idea and kind of gets at what I am hoping to accomplish with this blog, putting ideas and experiences in otolith research out there and getting feedback from people who may (or may not) be helpful.

Other otolith links of interest

Otolith Research Laboratory
Online otolith manual
The otolith page

Sunday, September 19, 2010

Field work funday!

Over the summer I pretty much had the freedom to conduct field work whenever I wanted with the only limiting factor being weather, which was pretty pleasant and cooperative.  However, since school started up in August I have been limited to conducting field work on weekends and holidays (best labor day ever!).  I don't really mind being out on the water every weekend but I do feel for my crew, having to wake up at 6 am on Sundays isn't easy when you are an undergrad.

With that being said we were off to the field today bright and early!  I, of course, stupidly stayed out until one last night and miraculously was able to wake up at 5 to get things ready (all this while still trying to recover from the debauchery of a week in Pittsburgh).  Once everyone assembled we headed up to Columbia NC to pick up the boat and then made our way to Gum Neck NC to launch in the Alligator River.  The purpose of this trip was to collect water samples from the Alligator, Scuppernong and Roanoke Rivers.  We have been collecting monthly water samples from and upstream and downstream location from these three rivers (plus the Chowan and Perquimans Rivers) since June, and we will continue collecting through October.  We are doing this to examine the elemental composition of the water and compare this to the elemental composition of river herring otoliths.  Presumably the elemental composition of the water should be similar to that of the otolith.  If there are differences in the elemental composition of the water in each river we may be able to classify juvenile river herring to their natal river using the elemental composition of their otoliths.  

We got out onto the Alligator River pretty early, but the wind was already howling, and the waves were building, as they tend to do on a large river like the Alligator.  We were able to brave the conditions and collect our samples, however most of our equipment decided to crap out.  First our YSI (used for recording temperature, dissolved oxygen, and salinity etc.), then our GPS batteries died, and finally a hole burst in our filtering tube (this was easily fixed).  This was the first time things have really gone wrong during my field work, and I should feel lucky because these are relatively minor situations and much worse could have happened. 

Work in the Scuppernong and Roanoke Rivers went fairly smooth.  I would have liked to have been able to record salinity and dissolved oxygen from the rivers though, because we did observe some blue crabs pretty far up in the Scuppernong River, and there was a bass tournament in the Roanoke River so I think it would have been interesting to have some water quality data while that was going on.  Also, I saw my first NC black bear which was very exciting!  I haven't seen a black bear in the wild in probably 10-15 years despite spending a lot of time in the Adirondack Mountains.

Sadly I only have one more month of field work left.

Friday, September 17, 2010

Big ol' AFS Review: Part II

Below is a review of some of the more interesting otolith talks I attended on Wednesday and Thursday while in Pittsburgh for the 140th annual meeting of the American Fisheries Society.

Wednesday

Wednesday was a big day in terms of otolith talks and started bright and early with three heavy hitters in the shad and herring symposium.  First up was Benjamin D. Walther on “Estimating origins of migrating American shad with otoliths chemistry”.  Using a combination of elemental and isotopic ratios this research was able to classify American shad juveniles to natal watersheds along the east coast with 93% accuracy!  This is very interesting and this study currently represents the largest database of otolith chemical signatures.  In addition, the otoliths of adult American shad were examined in an attempt to classify them to natal origins and found these fish to be from a small number of rivers. 

Next up was Sara M. Turner on “Determination of river herring natal origin by otolith microchemical markers”.  The goal here was to use elemental and stable isotope ratios to identify chemical signatures in the otoliths of juvenile river herring that could be used to classify them to their natal river.  This work was mostly being carried out in the Hudson River but I believe fish from Virginia and maybe Massachusetts were also being analyzed.  Migration patterns of juvenile river herring were also examined, which I will discuss more in about two paragraphs.

Following Sara was Banjamin I. Gahagan on “Estimating anadromous river herring natal stream homing rates using otolith microchemistry”.  Again the goal of this project was to utilize elemental signatures (no isotopes here, although he did admit that it would strengthen his analysis) in otoliths to classify juveniles and adults to natal origins.  This work was carried out in a number of watersheds in Connecticut.  Migration patterns of juveniles was also investigated, which I will now discuss.

Both Sara and Ben examined the migration patterns of juvenile river herring and found pretty similar patterns of fish entering what could be interpreted and marine water fairly early in life.  This is indicated by increasing strontium levels in otoliths (higher strontium is associated with saltier water).  This pattern is further backed up by my own findings of juvenile river herring appearing to be found in marine or brackish water at a very young age.  I have mixed thoughts about this finding, the juvenile fish have been collected in what would be classified and fresh to low salinity brackish water (at least mine have anyway).  Most of the strontium profiles show a pattern of increasing strontium, which is consistent with larval river herring being transported downriver into a more saline environment.  However, the fish would then be expected to move back upriver into a lower salinity environment.  Many of the fish I have looked at have an increasing strontium profile but do not show any decrease (unfortunately I don’t know were in the river some of the fish were collected).  It is an interesting situation and it appears that Sara, Ben and myself have all come up with similar findings (even though my own data is pretty meager at this point). 

Also, on Wednesday was Stacy K. Beharry on determining fish origin by mining the otolith.  This research utilized stable isotopes, elemental ratios and varying growth rates to classify spotted sea trout to natal grass beds in the Chesapeake Bay.  The factors that were included the higher the classification rate to natal grass beds (I think classification was somewhere between 85 and 95%).  This data could then be used to attempt to classify adult seatrout to natal grass beds.  I thought this talk went very well, however this research is based on the assumption (this has been demonstrated in the literature somewhere but I’m not sure of where) that juvenile spotted seatrout do not leave natal seagrass beds.  It seems strange to make this assumption, when it would be simple enough to test using a laser scan across the otolith and examining potential habitat shifts.  Migrating juveniles could potentially result in lower classification success. 

Other talks of interest on Wednesday were by; James R. Jackson on movements and habitat use of bowfin in Oneida Lake (which is was really really mad that I missed), Jian Yang on relating otolith Sr:Ca ratios to marine, brackish and freshwater habitat use, Ruth E. Haas-Castro on distinguishing between alewife and blueback herring using scales, Courtney V. Holden on the effects of water temperatures on American eel using otolith isotopic analysis, and Roger A. Rulifson on tidal power development in the Bay of Fundy.

Thursday

Since we left on Thursday morning I was only able to attend one talk, but it was definitely worth only getting four hours of sleep to hear.  Karin E. Limburg presented the work of Todd A. Hayden entitled Searching for the needle in the haystack:  Identifying natural otolith tags to determine natal origins of the humpback chub in the Grand Canyon.  This work utilized some pretty advanced and very interesting techniques in order to analyze the otoliths of these fish, and was able to decipher migration patterns of these fish. 

Closing

I thought the conference was great I had a blast getting to hear about a lot of new things, and talking to some interesting people.  I got to present my research for the first time and from most accounts I did pretty well.  I was kind of bummed that I didn’t get to speak during the shad symposium because I really think I might have gotten some better feedback from that group.  Based on the otolith talks I attended I really think I should consider incorporating stable isotope analysis into my work.  I am unsure about the feasibility of this but I think if I can do it my data analysis would really be strengthened.  

Big ol' AFS Review: Part I

The 140th meeting of the American Fisheries Society in Pittsburgh PA is over and I am sure most people would say it was a huge success.  I met some interesting, and helpful people and reconnected with others who could potentially help me with my research along the way.  I was able to attend a number of talks that dealt with otolith chemistry and its application so I will briefly review some of the most interesting.

Monday
 
The first otolith talk I attended was “Isotopic signatures of otoliths in identification of Pacific hake stocks” was given by Yongwen Gao.  I find this topic pretty interesting because it utilizes otolith chemistry rather than genetic techniques, which have apparently been somewhat ineffective in stock discrimination of marine species.  Essentially the core of Pacific hake otoliths was analyzed for oxygen and carbon isotope ratios and significant differences were found between fish caught on the Washington Coast and fish caught in Georgia Strait, British Columbia, indicating that there are separate stocks of Pacific Hake.  I have read a couple papers on stock discrimination of marine fish using otolith chemistry and it appears to be pretty accurate especially when utilizing stable isotope ratios (this will be a running theme throughout this review).  

I then attended “Using a combination of genetic markers and otoliths chemistry to examine connectivity issues and management implications for spotted seatrout” presented by R. Deborah Overath.  This research wanted to address connectivity of seatrout between coastal and in shore habitats on an area of the Texas coast.  While most of the genetics data was over my head, the otolith data was interesting.  Stable oxygen and carbon isotopes were utilized to classify fish to habitat type.  If I am not mistaken the outer edge of the otolith was used for analysis because the research wanted to focus on classifying trout to their most recent habitat area.  

*Begin Tangent*

One of the interesting things about otoliths is that they accrete calcium carbonate sequentially throughout the entire lifetime of the fish and otolith material is not reabsorbed.  The easiest way to think of how an otolith is formed is to think of tree rings.  If you cut a tree you see growth rings, which allows you to make age estimates.  If you cut an otolith you see similar patterns, so much so that we can even count daily rings in some instances.  However, otoliths are more like rocks than trees, and a more accurate method of visualizing the structure of and otolith is to think of an onion.  Onions are made of layers of material in a spherical shape; this is pretty similar to the arrangement of otolith material.  It is this structural pattern that allows us to examine the life history of a fish from birth to death.   

*End Tangent* 

Using isotope ratios 64% of samples were assigned to their correct region.  This number seems a bit low but I believe the area they were working in was pretty small.  It also appeared that straying of fish occurred between habitats that were adjacent to each other.  Perhaps this research could be useful in examining ranges of fish?  I also think that had elemental ratios been incorporated rather than just stable isotopes, the classification success may have been greater (again this will come up later). 

One of the best talks I attended was by Renee Reilly called “Time series applications in otlith chemistry”.  For the life of me I cannot recall many of the details of this talk.  It dealt with the interpretation of elemental ratios across the entire scan of an otolith, and methods to properly interpret this data.  This research is useful when looking at migration patterns and habitat shifts of fish.  Essentially, it involves looking at a string of data and determining where the significant differences are if there are in fact any.  I really hope this research is published, because it would be very helpful in my own data interpretation.

Also of interest on Monday were talks by; Roger Rulifson on restoring river herring in North Carolina, Anthony Overton on growth and mortality rates of larval river herring in the Tar-Pamlico River, Sarah E. Friedl on mortality estimates of juvenile spot in North Carolina, Johnny E. Moore on site fidelity of sand tiger sharks, and Jordan R. Allison on Walleye reproduction in Lake Michigan.  

Tuesday

As far as I can tell there was really only one talk on Tuesday dealing with otolith chemistry (given by me), and I don’t really want to discuss that any further here.  However, Tuesday was the first day of the Shad and River Herring symposium so I attended many of those talks.  Included in the symposium was the work of Kenneth L. Riley and Samantha M. Binion who both presented on different aspects of river herring work on the Roanoke River.  Both of the talks dealt with early life history of river herring and American shad and were very well done. 

Many of the talks given on the first day of the shad and herring symposium dealt with the removal of dams and the effectiveness of this in restoring populations.  It seemed as though the results were mixed.  Even though spawning habitat was opened up if it was a river with multiple impoundments the amount of habitat opened could be insignificant.  It also seems as though these species may not immediately utilize new upstream habitat.  Many theories were bounced around as to why this may be, I found the most interesting to be “the lack of leader fish hypothesis” (not exactly sure who said this but I know I heard Karin Limburg mention this).  Essentially, while the dam has been in place fish that spawn successfully below the dam have been selected for, once the dam is removed there are no fish that are conditioned to make the longer upstream migration so this habitat is not utilized.  The theory is that younger fish will follow “leader” or older fish into the river to make spawning migrations.  If there are no older fish making these longer spawning runs younger fish will not make them either. 

Also of interest on Tuesday were talks by; Mike Bednarski on population trends of shortnose sturgeon in the Altmaha River (which he nailed!), Daniel W. Cullen on the influence of temperature on monkfish distribution, Elizabeth Fairchild on spawning movements of winter flounder (which was one of my favorite talks).

Keep reading part II for reviews of Wednesday, Thursday and some closing thoughts.