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Habitat, timing, and stealth: Hunting skills applied to electrofishing

The technique of electrofishing is ubiquitous and universal for fish assessment work. When we teach the electrofishing course we focus, most appropriately, a great deal on the safety of passing electricity through water (pop quiz: those of you that electrofish what are the three mandatory safety features on an electrofishing unit?1). However, in priorizing safety we do not discuss much about how to actually be effective in finding and catching fish when doing this. And effective use is very important as so many management decisions are made based upon electrofishing results. Therefore, this month, please join me, a hunter, as I explore how to fish with this tool.

Many years ago I read a popular fishing article in which the author emphasized that, at least when fishing brown trout, you actually hunt them. You must use the same skills of the hunter. That left a mark on me as I realized the profound truth of it. To be effective we must actually ‘hunt’ the fish to determine where and when they are most likely to be available, and approach them in a way that allows their capture.

The Where: Habitat

Any time we want to observe or capture an animal – be it fish, amphibian, reptile, bird, or mammal – we need to know as much as we can about where they prefer to spend their time. Your fish species of interest… does it prefer pools and calm water or riffles? Glides? Shallow water? Deep? Lots of cover? We need to know where to look intensively and, equally importantly, where to not waste our effort. We also need to deeply appreciate that this preferred habitat changes with life stage, season, and even with time of day. The more we know about their daily and seasonal preferences, the more effective we will be. And yes, this means a lot of reading.

To complement the office research on habitat preferences, while conducting electrofishing in the field really pay attention to the microhabitats you are pulling fish from. Note the specific condition where the trout come from, the sculpins, the minnows, the catfish, the lamprey. The microhabitats will differ and help you to identify the small scale habitat requirements of the life stage of fish you are capturing. These observations will also strengthen your ability to generate strong and defensible fish habitat assessments as you understand the precise conditions required by different species. I trust that you can imagine how this deeply observational understanding also allows you to envision exactly what you need to construct for fish habitat restoration for those species. Over time you will build a profound and real-world understanding of exactly what the habitat requirements are; this is hard won knowledge that then allows you to identify and protect habitats and also effectively design restoration.

The When: Timing

Sometimes we are forced to sample fish at stupid times. Sorry, no sugar coating here. Electrofishing mid-winter or middle of hot summer day. These are very poor times to fish using electricity – our finned

quarry are hunkered down avoiding wasting valuable energy due to extreme cold or heat. We can shock them, even repeatedly, but we don’t capture them. I understand that project managers will send us out to meet their demands, not those of the fish, but please understand you are going to get an unreliable proportion of what is actually there.

If we have choice, we go back to basic hunting principles. Most animals by far are active dawn and dusk (or overnight) and quieten down during the mid-day period. If we want greatest effectiveness we should be electrofishing when the fish are active: early to late morning and late afternoon to early evening. Numerous studies report that electrofishing at night doubles (or more) the catch made. Wise hunters pursue their quest early morning and late afternoon; during the mid part of the day they scout for sign and where animals are spending their time. We can do the same – fish morning and late afternoon then do your fish habitat assessments in mid day.

The How: Stealth

Hunting is based upon getting around an animals stupendously impressive sensory defences of vision, smell, and hearing. With fish we need to add their exquisite ability to detect vibration in water and, in some cases, even magnetic fields. If you think you can sneak up on a fish unawares, I must disabuse you of that notion. When you see the fish scatter as you walk a stream, they knew you were there for tens of metres before you saw them; they only scatter when they did because you have gotten uncomfortably close. But they felt you coming long before you saw them, even with your polarized glasses. It is very challenging to stealthily sneak up on fish, but some basic guidelines are:

  • Don’t step into water until necessary. I am always surprised when teaching electrofishing how as soon as the waders are put on people step into the water. Poof! Every fish for ten metres upstream and downstream now knows we are there. They actually likely already knew from the vibrations of our walking on the bank. The lateral line of the fish is like the unbreachable security in a high tech thriller film; largely unbeatable and so we need to work around it.
  • Lift feet when wading: This is straight from hunting. On land if we drag our feet we make a great amount of noise, frightening the game we seek. In water we knock rocks together, creating a sound that carries a long way underwater. Those fish outside the range to detect us from the vibrations can certainly hear the noise we make. Lift your feet, step slowly, ensure you have solid footing before placing weight onto that leg – classic stalking guidance from the terrestrial environment.
  • Minimize movement: Animal eyesight is highly attuned to motion. So, while the fish may know we are in the water with them, by moving slowly we can, hopefully, approach them more closely, ideally close enough to put them in the attraction zone of the anode. I understand that your manager has given you an impossible schedule to complete the work, but slow down as much as you can… you will catch more fish, be less exhausted at end of day, and are more likely to see other wildlife or features of concern or interest while in the field.
  • Be wary of overhead shadows: Fish are well protected in the water by their vibration detection system, but they also have overhead avian predators that do not trigger this system. To avoid these hunters the fish are dependent upon eyesight, in particular shadows moving across the water surface or substrate. Therefore, to avoid appearing as a threatening bird we need to avoid casting shadows on the water surface during sunny days. This applies whether we are standing on the shore or waving the anode around to point at where we are going to fish. This is another reason to fish early and late in the day; at these times long shadows are cast over the water from the surrounding trees and so there is less direct sunlight on water surface.

I hope, gentle reader, that these words may help you appreciate that the electrofisher is a valuable tool… but it is not magic. To be used well requires conscientious effort on the part of the electrofishing crew and the use of the same skills that hunters use to surmount animal sensory defences. And as any proficient hunter will tell you, your skills and abilities will certainly improve with diligent effort and practice.

Sean Mitchell

1 Mandatory safety features on electrofishing unit: (1) quick release harness; (2) audible tone;  and (3) tilt switch. The immersion switch is optional, and valuable, but not mandatory.