July 7, 2011

Searching for Mongolia’s Landlocked, Mouse-Eating Salmon

In swift Mongolian rivers lurks a fish with crocodilian tendencies.  Taimen, a primitive member of the trout and salmon family reach upwards of one-hundred pounds in drainages that are not ecologically productive.  How is this possible?  By eating anything that moves, including not only the expected smaller fish, but rodents that try to cross the rivers they inhabit, plus young ducklings, and even bats that swoop too low for insects.  All may disappear in a savage surface attack. This proclivity is also just one of the factors that make them among the most desirable gamefish in the world, with international anglers paying thousands of dollars to fish for them with guides from camps on remote rivers.

Giant Salmon

Fish biologist David Gilroy holding a 140 cm long taimen that was found dead on the river bank, with a 90 cm taimen protruding from its mouth. Inside the 90 cm taimen was another 40 cm taimen. Credit: Zeb Hogan

Being “apex” predators at the top of the riverine food chain, taimen are not abundant, in the same way that eagles and tigers are never numerous. This renders them especially susceptible to overfishing and environmental degradation.  To this end, not enough is known about their current status and basic biology, the fundamental information required for enlightened management.

Taimen are just one of the reasons I’m in Mongolia.  I’m part of an National Science Foundation-funded expedition of three professors and five undergraduate and graduate students, all led by Dr. Olaf Jensen of Rutgers University.  With me is a Queens College Biology Department undergraduate, Ivana Roman, a recent immigrant from Serbia who typifies the role of CUNY–she learned English only three years ago and has her sights set on a Ph.D. in Marine Biology.  We’ll be joined along the way by Mongolian partners and even Russian scientists.

Mongolia is a land of stunning open landscapes that once were the province of Ghengis Khan’s horse-borne warriors.  This vast territory, twice the size of Texas, is the least densely populated nation on Earth.  And yet even Mongolia is not devoid of environmental problems.  Few regions of the world have felt the effects of climate warming as acutely.  Wildcat mining is poisoning rivers.  And illegal fishing is reducing populations of taimen.  Beware if you drink the water in the capitol, and the air there in winter is not for breathing.

Just over one-million of Mongolia’s 2.6 million residents live in Ulaan Bator, or “UB,” the centrally-located capitol city.  Although the very notion of Mongolia strikes many westerners as exotic, and I was told that UB was something of a post-Soviet backwater a decade ago, it has not escaped the flood of globalization–on my first visit, one year earlier, stores routinely used bar code scanners, everyone seemed to be on a cell phone, and I watched a Yankees – Red Sox game in my hotel room.  But unlike many world cities where the central core grades slowly across miles to suburbia, UB can change in a mere few blocks from modest high rises to a ghetto of felt gers (yurts), to open steppes.  Many of the gers are a recent addition, having moved to UB’s outer edge because of the ravages of a zud, a winter so harsh (surprisingly so, in a time of warming) that many livestock herders lost their flocks, leaving them little option than to move to UB to scrape by on any work they could find.

Our plan is to drive two days northwest to the area of the confluence of the Eg and Uur rivers, part of the drainage that links Mongolia’s Lake Hovsgol to Russia’s Lake Baikal.  There we will focus on taimen but also work on a variety of other Mongolian fishes.  For Ivana’s study we will collect fish tissues for DNA analysis from possible source populations there that might have provided colonists to Lake Hovsgol after a period when all evidence suggests it was devoid of fish.

Lakes Hovsgol and Baikal are two of the most unique lakes on the planet.  Both are of grand scale: Hovsgol reaches 262 m in depth and holds 2% of the earth’s fresh waters.  Baikal is simply gargantuan, averaging more than 700 meters deep and holding about one-fifth of the worlds fresh water.  Baikal is believed to the oldest lake in the world; Hovsgol the second oldest.  Both felt the effects of glaciation, with heavy icing, and then turbid meltwater also slowing down, and even shutting off photosynthesis.  Hovsgol also dropped dramatically in water level.  But despite similar glacial histories, the two lakes now display dramatically different levels of biodiversity.  Lake Baikal, an ancient rift valley lake that once was marine, still has marine forms such as seals that have evolved to live in fresh waters.  And it is a biodiversity hotspot, with some 1600 plants and animals found only there.

Hovsgol Ship

The ship that the group will work from on Lake Hovsgol. Credit: Noreen McAuliffe

In contrast, Lake Hovsgol has only a total of 390 plants and animals, of which only about 20 are endemic.  This low biodiversity includes a remarkably scant fish community of 10 species.  The last glacial maximum may have allowed fish to re-enter the lake no more than 10,000 years ago.  But where did they come from?  And when did they actually arrive?

Our expedition will launch a number of studies.  Expeditions are romantic notions that evoke thoughts of searches for the dramatic find, e.g., does the snow leopard still roam high Asian mountains or does the Tasmanian wolf still exist?  Todays’ reality though is less dramatic, typically an expedition provides essential samples and raw data that are fully analyzed back in the university laboratory.  This includes Ivana’s study, which will attempt to answer the question of the age of recolonization of Lake Hovsgol by comparing DNA sequence variation between populations of fish from the lake itself and from possible source populations that somehow survived glaciation.  Resultant data will be analyzed with the help of Dr. Mike Hickerson of Queens College, who has developed powerful algorithms for this very purpose. Other major focuses will include placing radio transmitters on taimen to track their movements, examining the feeding habits of another trout-like species, lenok, and modeling the food chain of Lake Hovsgol.  However, the value of major field forays also should not be undersold, it provides scientists with an essential familiarity with the organisms and their place in the environment that enriches later laboratory work.

Expeditions—in their intimacy with the landscape and its peoples and its creatures, also always provide surprises—both pleasant and unpleasant.  Stories from previous taimen expeditions told of wonderful encounters with native Mongolians, and also gripping views raw nature: of taimen showing v-wakes as they came up behind and engulfed ducklings, and even of a pack of wolves attacking a herd of horses.  After travel delays our two vans are loaded and we are ready to go. What lies ahead this time?

Read more about John Waldman’s Mongolian Expedition >>