Tuesday, August 13, 2013

Upping the ante

For the past 48 hours, Benja and I have been finishing up the ongoing fish excretion component to the project. It’s pretty similar to last year’s endeavor except that it occurs primarily at NIGHT (in year 3, we have to find creative ways to up the proverbial ante…). At this point we have a pretty good handle on fish peeing rates during the day, but the suspicion is that things probably tail off at night (which is personally true for me, so it may hold true for the fishes as well.). 
Two eretmodus, probably peeing... (photo by Benja)
Just to be clear, we’re not interested in peeing for peeing’s sake. As I’ve mentioned before, since Tanganyika is so lacking in nutrients, we suspect the fish themselves facilitate nutrient cycling in the lake (Meaning: all the attached algae probably take full advantage of the fact that hundreds of fish pee on them constantly, providing them with nutrients to create biomass that, in turn, feed the fish. I heart cycles.).

There’s a fair amount of prep work involved (like filtering 100 liters of water, labeling all the Ziplocs and vials, etc.…) and the field experience is a bit nuts since a job that was formerly performed by 6 people is now done by 3.

And, like I said, it’s all in the dark.

Once at site, we fill the bags with filtered water and our old pal Georgie starts catching fish (I have No Idea how he holds the flashlight AND manages to trap fish in the net at the same time, but he’s a professional!). 
Georgie is ready (as always) to catch some fish.
Each fish gets dropped into his own bag, and after 30 minutes of incubation time, we collect pee-water samples that will be analyzed for nitrate, phosphate, and ammonium. We also get lengths and weights on each fish and hold each bag until all the poop settles. 

Ben sucks up poop. This was taken during a daylight endeavor, but you get the idea.
We left at sunset the first night and were back sleeping soundly in our beds by 2am or so. But this morning we were up at 3:30am, which meant trying to go to bed by 8pm to get some semblance of a full night’s sleep. It’s been like Spring Break Kigoma for a seemingly-endless number of consecutive days, with celebrations including the end of Ramadan, Nane Nane (literally 8/8), and now, continued partying because no one said to stop. Even my industrial grade ear plugs couldn’t block out the backbeat from the Prison Bar speakers (yes, we’re close to the prison, and yes, they have a bar…), but I took a Benadryl to seal the deal and it was lights out.
Attack of the mayflies! They really liked the low beam on my headlamp. That, and the water I guess?

Luckily our endeavor was cleverly (accidentally?) timed to coincide with the Perseid meteor shower, which made me feel marginally less sorry for myself for being awake at a time of night I reserve exclusively for sleeping. While it’s not super fun assembling the boat/motor/gear with the aid of a headlamp, it is SUPER AWESOME driving full-speed on a Zodiac in nearly-complete darkness to a random spot on shore 6km down the beach in the middle of the night (that’s not sarcasm). 
Benja measures a bigger-than-normal Petrochromis kasumbe. Their giant mouths are especially good at chowing down on periphyton.
And today marked a milestone in LT field work as we collected our very last pee sample (I won’t write “ever,” but I kind of want to…). No one’s shedding too many tears over that one.
I celebrated by eating some passion fruit. Om nom nom...

Wednesday, August 7, 2013

Non-transferrable skills

I’ve been working on Lake Tanganyika for three summers now, which would normally be enough time for me to get sick of a place or a job for that matter*. But instead of field work becoming dull and monotonous, it’s been genuinely fascinating trying to figure out what makes this place work.  
I REALLY wish I had a filter for this camera, because this is NOT what it looks like while diving. Check out the adorable Mastacembalus at the bottom of the picture!
Most days, I can’t believe this is my life.
Seeing my little buddy is becoming the new normal.
Even though we are well-settled into the groove of work here, every once in a while we get to dip our toes into new aspects of lake work. Team Madison membership has stayed pretty constant over the years, but our counterparts from Ohio are down to just 2 members this season. In the interest of amassing long-term data sets, Ben, Pete, and I have picked up the slack and are adding some new procedures to an ever-growing list of non-transferrable skills**…

Case in point: PPR.  Today Ben and I took a second crack at measuring benthic primary productivity in the field, which (it turns out) is a hoot. Since no one present had ever done it before, we managed to screw it up badly on our first attempt but nailed it on Try 2. Yay, us. 
Ben doesn't think diving with a snorkel is necessary; I disagree.
One of the big mysteries of this place is how such high productivity and fish diversity (nearly 300 fish species, most of which are found NOWHERE ELSE ON EARTH) can exist in such a nutrient-scarce place***. The attached algae (periphyton) on the rocks are low in biomass but super-productive, and they form the energetic base for the entire food web in Lake Tanganyika.

So to measure that, we incubate periphyton in light (15 minutes) and dark (2+ hours) chambers, collect an initial and final water sample in a syringe from each, bring the samples to the surface, and measure the dissolved oxygen levels.
Ben and Cortney gear up for the task at hand.
Ben did most of the work, making sure there were no bubbles in the syringes, stirring the chambers, and drawing all the samples. I schlepped the sausage weights around and wrote down all the times and ID’s on my dive slate while Cortney read all the DO measurements back on the boat.
Ben pulls a sample, I note the time.
Since my tank had a good chunk of air remaining when it was all said and done, I went diving for funsies for what will likely be the last time this season. 
I fell into a school of Cyprichromis at 30ft.
And tonight after a quick trip to town for ice cream and kicking back with pineapple vodka and mango juice as I watch the sun go down, I’d have to say it’s been a pretty perfect day.  

* Up until I moved to Madison, my longest residence post college–discounting the Peace Corps and grad school—was a year. I’m told that someday I’ll want to “settle down”…but I don’t really know what that means.
** I seem to be acquiring a whole lotta skills that make me extremely adept at my current position but unemployable elsewhere. Hmmm…
*** There is almost NOTHING in this water. I know, because I’ve run and re-run and re-re-run the water samples from 4 years, and most of the time nutrient levels hold steady at about 1 PART PER BILLION. Holy moly.

Saturday, August 3, 2013

That's not a fish...

For the past few days, Pete, Benja, and I have been doing our best to collect poop. It’s one of the missing pieces to the nutrient puzzle in Lake Tanganyika, and a top priority this season has been to figure out just how much nitrogen and phosphorus get released when these guys decide to drop a load.
And we're off! Our morning commute is pretty sweet.
This has led to many an interesting conversation regarding poo (poo jokes, poo puns, etc.), which I fully support.

In addition to figuring out what it’s made of, Benja is also interested in poop rates, which requires catching fish, putting them in a ziplock bag, handing them a newspaper (just kidding…), and timing just how long it takes for nature to take its course.  
This adorable little eretmodus never did poop.
Luckily my fish-catching skills have multiplied exponentially, and I’ve spent a fair amount of time manning the gillnet for this project task. 
Well hello!
That leaves Benja with the all-important duties of shore guy: processing fish (weights, lengths, time-in/time-out, waiting for poop to settle, etc.), guarding our lunches from the band of Vervet monkeys inhabiting the area, and working on an even tan.
They're cute...right up until they run into the trees with your popcorn.
Each fish gets at least 30 minutes in the mini-toilet, but for some fish, that’s not long enough. The algivores poop constantly, but the piscivorous fish need much more time (sometimes upwards of 6 hours, it turns out. No judgement...).

We’re also collecting what’s come to be known in our little circle as “wild poop." Basically Pete swims  around, catches a fish in the act, and collects the fresh droppings into a turkey baster. It gets handed off to us on shore, put in a pre-weighed vial, and eventually (back in Madison) prepped for CNP analysis.
Pete returns with some fresh poo in hand.
The shore handoff! (We're making good use of the new GoPro ;))
Today I caught fish all day, and while Ben waited for the last of our bagged fish to poop, I thought I’d grab some field footage with our new GoPro video camera. We’d heard rumors recently that a crocodile had been spotted in this particular part of the lake, but none of us really believed (or rather, wanted to believe) it was true.

"Holy shit, Benja...I just saw the crocodile!!"
It’s hard to summarize the thoughts that ran through my head in the course of a milli-second, but here, in no particular order are a few…
* That’s not a fish…  Holy shit.
* It’s ok because you saw how to survive a croc attack on NGC once upon a time…
* Is its mom nearby?
* Should I be worried? Should I be in the water? Shore’s probably not safe either? Crocs are ambush predators, right?? It’s not too big…

I eventually high-tailed it to shore and told Ben the tale of my epic encounter. I’d put him at just over a meter or so, and I’m still not sure how I feel about this swimming-with-crocodiles business. Something about it doesn’t seem safe…

Friday, July 26, 2013

Fish Rodeo

It’s all fun and games…

until someone wrecks their right ear by  diving too deep hunting clams and can’t equalize because of a sinus infection.   

I’ll back up.

Last summer, we collected 4 species of fish along with some clams and snails at each of our 12 survey sites, cut out a little piece of their muscle, and prepped the dry, ground powder for stable isotope analysis. It basically tells us who’s eating what (or whom, as the case may be) in the lake, and based on those data, it would appear that the food chain is getting shorter (gasp!).
A Perissodus, one of our target species! Their foraging strategy is to EAT SCALES OFF OTHER FISH (what the what!), so they (usually) manage to catch themselves in the net when they prey on other net-victims.
To convince ourselves that it’s real, we’re re-doing the entire survey this summer. Pete has years of experience wrangling fish, but I’m new to this game and have marginal (at best) skills to bring to the team. To date, I’ve only caught one Lepidiolamprologus (!), and Pete has captured the other 83 fish solo (I’m such a failure!). But since we still have 5 sites to go, I’m counting on the chance to improve my stats in the 11th hour.
Pete, doing what he does
My supposed contribution was to collect the clams and snails, and usually this isn’t too hard since even in my ineptitude, I’m brilliant at hunting things that don’t move too fast or too much.  But clams were hard to come by at certain sites, and I ended up freediving a bit deeper than I’m (apparently) capable of going. The clotty blood in my spit was a sign that all was not well up in my sinuses. That, and the fact that it felt like someone was stabbing me in the ear with a sharp object every time I went under.
It's no big deal when they're nice and shallow, but that's not always the case.
Luckily my far-sighted teammates were ready for such an event, so I’ve been bumming ear meds from buddies and trying to keep my face out of the water in the meantime. 

Fish rodeo days get kind of long, especially when most of the cutting and tagging occurs after dinner. We’re pickling these guys and bringing them back to the States with us, so if you want to see them up close and personal, come to the Zoology Museum in Madison this fall! 
Since death by hammer awaits my unlucky victims, these clams have good reason to remain evasive.
As for the food chain question, we won’t have stable isotope data in hand for quite awhile...but it would appear that big changes have occurred in this lake in the past 10 years. Stay tuned.