Fisheries biologists have known for a long time that many factors affect fishing success. The most important environmental factor is the conductivity of the water, i.e. its ability to conduct an electrical current due to the concentration of ions in the water. Water conductivity has been used as independent variables in multiple regression equations or as covariates to estimate catch per unit effort or some measure of capture efficiency. For decades, biologists made equipment adjustments to compensate for varying water conductivity in an ad hoc fashion without a guiding principle.
Alan Temple wrote a blog, Setting Doses for Lab Experiments, which I followed with Setup for Lab Experiments in Tanks. That was followed by a short one, Size Matters, on the effect of fish size on the threshold voltage gradient and power density for immobilization or other responses. This blog discusses some aspects of how a tank study is conducted. Specifically mentioned are the fish themselves, the desired response to be assessed, how that response is to be evaluated, and two primary approaches for quantifying the results.
Yes, size matters…and that includes fish size when electrofishing. Large fish are immobilized with less field intensity or power density than are small fish. Large fish sustain a higher total dose of electrical energy than do small fish; this is sometimes referred to as whole body voltage. An excellent paper on this topic is Dolan, C.R. and L.E. Miranda. 2003. Immobilization thresholds of electrofishing relative to fish size. Transactions of the American Fisheries Society 132:969-976. This short blog provides results of a simple study with various sizes of alligator gar.
Dr. Alan Temple posted a blog on December 9, 2015 entitled “Setting Doses for Lab Experiments.” He suggested that I submit a blog on other aspects of lab studies in tanks. This blog covers the setup of tank studies for electrofishing research, and I plan to submit a companion blog on procedures for tank studies. Important aspects to consider for lab studies are the test tank, the electrodes, the power supply and the electrical field.
Here’s a few pics of electrofishing porn from the American Fisheries Society meeting in Portland, OR, 2015. Lots of new goodies. Enjoy!
Most boat electrofishing pulsators (control boxes) are powered with portable generators that provide 240-V, single-phase AC. These generators are available from common commercial sources such as hardware stores or electrical supply houses. (Note: a notable exception is the GPP pulsator made by Smith-Root, Inc., that requires a specially-constructed generator; it will not be discussed further here.) This short blog explains the electrical outlet of a generator, how to test for the safety of a generator if used for boat electrofishing, and what to do if the test indicates that a generator is not safe for electrofishing.
|Course Title:||Backpack Electrofishing: Principles and Practices|
|Course ID:||BIO 407|
|Date(s):||June 7, 2016: 8:30am – 4:30pm
June 8, 2016: 8:30am – 4:30pm
June 9, 2016: 8:30am – 4:30pm
|Location:||William Jack Hernandez Sport Fish Hatchery
N Reeve Blvd
|Instructor:||Dr. James B. Reynolds|
|Tuition:||$945 / $895*|
|$845 / $795* (Before May 7, 2016)|
|Course Title:||Boat Electrofishing: Principles and Practices|
|Date(s):||May 10, 2016: 8:30am – 4:30pm
May 11, 2016: 8:30am – 4:30pm
May 12, 2016: 8:30am – 4:30pm
|Location:||Red Lion Inn
1830 Hilltop Dr,
|Instructor:||Dr. James B. Reynolds|
|Tuition:||$995 / $945*|
|$895 / $845* (Before April 9, 2016)|
Electrofishing is a primary sampling method for near-shore fish species in lakes and rivers, and for fish species and assemblages in streams. We must admit, however, that it is a sampling technique with inherent risks. People, water and electricity are in close proximity. This blog describes the potential for human injury or death if someone falls into water having an electrical field. It specifically involves boat electrofishing, but the same idea can be used for tow/push barges, shore-based units and backpack electrofishing.Continue Reading..
Testing equipment, particularly current clamps and scopemeters, have a substantial role to play in electrofishing sampling programs. I was first introduced to this notion years ago by A. Lawrence (“Larry”) Kolz and Jim Reynolds, two people that made substantial advances in the conceptual basis for electrofishing. Since then, Jan Dean and I have used test equipment in a number of situations, built Excel-based programs to utilize collected information, and have worked on identifying inexpensive yet accurate meter alternatives.
In this blog, I will attempt to describe purposes of testing equipment, some approaches and considerations regarding their use, share a few of our test results, and provide a list of suggested models.