Monday, June 6, 2016

PIT Tags and Passive Antenna Systems Part 2: Arctic Adaptability

Greg Hill, Florida International University

Hi Folks,
Last post I discussed the use of PIT tags and Passive antenna systems (PAS) in studying fish movement and fine scale habitat selection of Everglades sunfishes at an experimental facility.  In this post I’m going to talk about scaling up the application of PAS- at both spatial and latitudinal gradients.

            While this technology can be very effective at monitoring an organisms use of one habitat patch or another (Such as in my first blog post), another major area of research which employs PAS is anadromous fish migration.  There is an extensive body of literature from the Pacific Northwest detailing the use of PIT technology in studying salmonid spawning, survival and migration.  More recently this technology has also show its versatility and hardiness in extreme environments- such as arctic tundra river systems.

            Last summer (or fall in arctic time) I was fortunate enough to be a part of a study examining arctic grayling adaptability to climate change.  “FISHSCAPE” is a Woods Hole Institute project led by Principle Investigators Linda Deegan (MBL at Woods Hole) and Mark Urban (Uconn) that conducts its research out of Toolik field station on Alaska’s North Slope.  Here the project’s focus was on 3 river systems of different size, gradient, thermal regimes, and seasonal connectivity.  By better understanding the growth, movement patterns, and genetic linkages of arctic grayling in each system, FISHSCAPE hopes to shed light on the impact of shifting seasonality in arctic aquatic ecosystems. 

            However, working in an unforgiving environment such as the arctic presents its own set of unique problems- particularly when it comes to year-round monitoring of fish over many miles of remote river system.  Here, the major challenge of using PAS to monitor fish movement is just keeping the equipment in operating condition and protected from the elements and wildlife.  This requires a bit of electrical engineering and field ingenuity.    Below is a more detailed breakdown of the FISHSCAPE’s focal region, species, and methodology

Toolik Field Station:

Established in 1976 as an extension International Biological Program, TFS has become a premier research base for arctic science.  Now managed by the Institute of Arctic Biology at the University of Alaska Fairbanks, TFS has cooperative agreements with a number of agencies and Universities which support numerous studies to help better understand the arctic environment and its impact at the global scale.  Just getting to TFS can be quite an adventure. Its location just off the Dalton Highway on the North Slope of the Brooks Mountain range puts 357 miles north of the nearest city (Fairbanks) and 117 miles south of the Arctic Ocean.  Researchers here enjoy round the clock sunlight from May 26 to July 17- but never see the sun rise from November 27 to January 14.  However, the Aurora Borealis does provide its own magical lighting once night returns to the arctic. 

Arctic Grayling (Thymallus arcticus)

Arctic grayling are a circumpolar member of the salmonid family that is widespread throughout the arctic and subarctic regions of the world.  They are long lived (20+ years), can grow up to lengths of 24 inches, and are easily distinguished from other salmonids by their exceptionally large dorsal fin and small mouth.  When looked at closely in the water they exhibit a mixture of iridescent colors that seem to shimmer in sunlight.  I would describe their appearance in the water as almost “electric”.  Primarily insectivorous, they are beloved by fly fishermen for their enthusiasm to take dry flies.  Grayling are also a vital part of biotic linkages in arctic aquatic ecosystems.  As spring spawners, their seasonal movements between productive riverine habitats and overwintering areas such as headwater lakes or spring pools play a large role in nutrient transfer and diet subsidization for other organisms- especially other fish such as lake trout and arctic char. 

Importance of Biotic Linkages

PIT tagging and PAS setup on the North Slope:

An extreme environment such as the arctic presents a number of unique factors that must be dealt with accordingly in order to achieve continuous monitoring of fish movements across the seasons.  First off, the rivers flowing out of the Brooks Range are very low in conductivity which makes electrofishing difficult.  Fortunately, the voracious appetites of arctic grayling awakening from a long winter’s slumber make them fairly easy to catch with angling techniques.  Small spinners and flies with barbless hooks are also less harmful and easily removable.  With a team of 2-4 anglers it is not uncommon to capture and tag over 100 grayling in a single day!  A weir built at the outlet of a headwater lake in the fall is another effective method for fish capture as they migrate back to overwinter. 

            We used both 12 & 23 mm half duplex PIT tags since each size provided its owe advantages.  12 mm tags allowed us to tag much smaller specimens but did not afford the same detection range as the 23 mm tags.  The mesh holding pens we used while processing & tagging fish needed to be carefully placed and easily movable as conditions in some rivers could change to flood stage rapidly depending upon weather.  

            With many PAS stations set up at points along river sections only accessible via helicopter or snow machine, a solar power provides a reliable means of keeping the equipment running year round.  Three properly angled 100-watt panels are able to harness and store enough energy from the arctic summer sun to keep a series of car batteries charged and supplying power to the reader & antenna system even through the dark winter months- Keeping this setup protected from wildlife and the elements in another matter.

            Heavy duty army ammo boxes lined with Styrofoam help keep the readers and batteries protected and insulated from the elements.  The local wildlife, however, has been found to be quite fond of messing with the solar panels and electrical wire connected to them and the antenna.  Grizzly bears seem to enjoy tearing apart the solar panels while arctic ground squirrels or “sik sik’s” have a habit of gnawing on wire.  Project coordinator Cam Mackenzie has found that erecting a small electric bear fence around the panels and adding thick metal shielding to the wires and cable deters these tundra residents fairly well- Not exactly your everyday troubleshooting!

The arctic may be a difficult place to work in at times, but its raw beauty and importance in understanding climate change are well worth the challenges.  Hope you’ve enjoyed both posts on adapting passive antenna systems to the top and bottom of America.

Greg Hill

Masters Student
Florida International University

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