TV3

[OAB]

This was on TV3 news tonight for anyone interested.

http://www.3news.co.nz/Doc-go-electric-fishing-to-save-a-species/tabid/1160/articleID/197318/Default.aspx

[livingart]

gotta love this part

The electricity stuns the fish but there has not been a fish fatality yet - although the rangers do take precautions, like wearing rubber boots and gloves and sounding warning signals.

i wonder if the fish hear the warning signals

[Stella]

I daresay the fish notice us crashing around in the stream trying to get in position before any warning signals or zapping happens!

It is rather scary playing with this, more than enough electrickery to stop your heart, and you are deliberately making the water around your feet LIVE :nilly: though it is also a rather handy sampling method.

I have a video on my youtube channel of some friends electrofishing. Somehow this got onto a Russian fishing site where they decided it was all about poaching fish and this video now has over 49,000 undeserved views.... :facepalm:

Gives you and idea of what electrofishing is though:

http://www.youtube.com/nznativefish#p/u/14/UK4QC7AE8L4

Once I was going fishing and got to the site and realised the trailing earth cable was missing from the box. My supervisor did an amazing macgyver trick using an straightened wire coathanger, jump cables and a safety pin! And it WoRKED!

[Mikey]

Yeah I saw it last night.

it was cool seeing it in action... and actually knowiing something about the fish they were talking about

[Aquila]

:facepalm: I dislike articles like this...

They make it sound like the fish are being electrocuted close to death...

Trout are just harder to take down because they are more athletic then most natives. Their muscles are design for very fast twitch contraction and are capable of bursts of speed and jumping. Which is exactly what happens when they feel the electric current...most of the time they try to bolt down the river/stream and it hard to net them. You can up the voltage a bit to help this problem, but they are still tricky to grab.

Natives handle it much better. Basically the electric current disrupts their ability for controlled muscle contraction and thus they lose equilibrium and are easily netted. The fish recover almost immediately when the power is turned off or when the fish is lifted out of the water.

The electric current produced by the machine has a limited area it works on, so you can move upstream and work in sections. The trigger is pressed for only a few seconds at a time and is turned off immediately once a fish is spotted. The voltage used on natives is low... and trust me most of the time the workers do not wear gloves. The reason you occasionally get fish that don't recover immediately is not because of the strength of the electric current but the length you leave it on for. Sometimes fish are tricky to net and occasionally try to retreat under some rocks, thus it takes a prolonged zap or several zaps to get them.

I have been accidently zapped by an electrofishing machine in canada (where they use even higher higher voltages) when my glove sprung a leak and although my forearms contracted a bit, there was no pain or heart attack involved... :roll:

[Stella]

Interesting point about the fast twitch contraction, makes sense. Though kokopu are short-burst swimmers, so you would think it would affect them similarly but it doesn't. Torrentfish are also hit hard by it, not sure why.

Apparently the effect of the electricity on trout's muscles can break their spines and I have certainly seen many trout with dark bands on their bodies indicating nerve damage. As such we don't tend to use electrofishing to specifically sample trout.

Regarding wearing gloves, I was taught not to as you shouldn't need to put your hands in the water when it is live, and developing a habit of doing that makes it more likely that you will accidentally do it without gloves. That and they are made for enormous tradesmen hands! Electrofishing is clumsy enough as it is

I guess different people have different preferred methods.

I haven't heard of turning the current off as soon as you spot a fish. Have you seen that here or is it a Canadian thing? Since our fish come around immediately, the moment you turn off the current most of them will dive under the nearest rock. That and much of the fishing happens in places where there is no hope of seeing the fish until they are caught, although we carry hand nets just in case.

[Aquila]

I have never seen a trout break its spine, but i suppose its possible, especially if u crank the power up. Did the trout with the dark bands touch the anode? I've seen fish get burnt if that accidently happens. I also haven't come across Torrentfish while sampling so i'm not sure how they are specifically affected. Bullies seem be harder hit then galaxids for some reason though, but still recover almost immediately.

Sorry for the confusion, what I meant to say by 'the current is turned off when a fish is spotted' is that by the time you see the fish belly up, you are there with a net and the fish is caught before it can even right itself so there is no need to keep the current on too long.

Wearing gloves is defintely the health and safety recommendation, but i don't like it either unless i'm working in deeper water. I keep my hands out of the water otherwise I'm definetly more paranoid about actually touching the cathode or anode itself! ouch!

What I remember about eletrofishing in canada is that we used a lot more power, which was unfortunate for some of the smaller fish. At times were were going for huge trout and carp in deep pools so you really didn't want to get your elbows wet. When a carp or trout was hit, alot of the time it would first jump straight out of the water before turning belly up. When fishing shallow parts of the stream then the power was shut off. The worst thing I saw during this work was when we were grabbing the bigger fish and didn't notice a bunch of little fish get stuck to the cathode wire. They were gone-burgers