Weather Loach – An Extreme Story Of Survival

Many birds and other vertebrates have innovative strategies for survival and the weather loach is certainly one of them.

I’ve mentioned before that the weather loach (pond loach, dojo loach) is a slender and eel-like freshwater fish native to East Asia that has become invasive in many of our waterways largely because aquarists release them into our streams and ponds. Though they’re a great food source for our fish-eating birds they’ve become an ecological nuisance. I didn’t even know they existed until I began photographing birds ten years ago but since then I’ve become aware of just how prevalent they’ve become in the valley waterways of northern Utah.

These fish are often called weather loaches because they’re extremely sensitive to slight changes in barometric pressure and they become hyperactive and even “stand on their tails” in aquariums when a weather front is approaching.

 

1/2500/ f/7.1, ISO 500, Canon 7D Mark II, Canon EF 500mm f/4L IS II USM + EF 1.4 III Extender, not baited, set up or called in

As regular readers know weather loaches have been the staple food of “my” male Belted Kingfisher this fall at an old oxbow wetland near the Jordan River. I’ve watched and photographed him (and this female) catching and eating dozens of fish and without exception every fish I’ve been able to see well enough to identify has been a weather loach.

To demonstrate just how pervasive this invasive fish has become here’s a few examples of other birds I’ve documented capturing and eating weather loaches over the years at places like Farmington Bay Waterfowl Management Area, Bear River Migratory Bird Refuge and near the Jordan River:

 

 

1/2000/ f/6.3, ISO 500, Canon 7D Mark II, Canon EF 500mm f/4L IS II USM + EF 1.4 III Extender, not baited, set up or called in

Ring-necked Duck.

 

 

1/2000/ f/6.3, ISO 500, Canon 7D, Canon EF 500mm f/4L IS USM + EF 1.4 III Extender, not baited, set up or called in

Greater Yellowlegs.

 

 

1/3200/ f/9, ISO 640, Canon 40D, Canon EF 500mm f/4L IS USM + EF 1.4 III Extender, not baited, set up or called in

Common Goldeneye.

 

 

1/1000/ f/11, ISO 500, Canon 40D, Canon 40D, f/4L IS USM + EF 1.4 III Extender, not baited, set up or called in

Snowy Egret.

Roughly eight years ago I asked management personnel at Farmington Bay WMA if they knew what species the fish was but they had no idea so I sent some photos to my good friend and Director of The Great Salt Lake Nature Center at Farmington Bay Justina Parson’s-Bernstein. She forwarded them to a vertebrate specialist with the State of Utah and he keyed the fish out as weather loaches. I’ve been seeing them regularly ever since.

 

Ok, here’s the “extreme survival” part of the story.

Earlier this fall the very small oxbow wetland “pond” where I’d been photographing the kingfisher dried up completely. This time of year its only source of water is storm drains (I know that because I talked to Murray City Parks Superintendent Kim Sorenson about it) and we hadn’t had any rain for months. That small pond was bone dry for about a week before we had a storm which immediately filled it up again. Of course the kingfisher had stopped showing up and I figured it would be next year sometime before enough time would have passed for the fish to repopulate the pond and lure the kingfisher back.

 

1/5000/ f/6.3, ISO 640, Canon 7D Mark II, Canon EF 500mm f/4L IS II USM + EF 1.4 III Extender, not baited, set up or called in

So I was blown away when two days after the pond filled again the kingfisher was back and catching loaches with almost every dive (I believe this photo was taken on that very day). Where had all those loaches come from? The only water to have entered the pond was from storm drains which wouldn’t have any fish and two days isn’t nearly enough time to repopulate the pond through natural reproduction.

Then I remembered something I’d read about weather loaches some years ago. In drying conditions they burrow down into the mud, secrete a mucus “cocoon” around their body to prevent drying, and simply wait until the water comes back. They “breathe” by gulping small amounts of air into their gut so oxygen can be absorbed into their intestinal blood. There are a  few other types of fish that do the same thing.

So that explained the mystery.

What an incredibly effective and innovative survival strategy for weather loaches! That’s good news for my kingfishers (and for this bird photographer) but bad news for natural resource managers who might want to control invasive loaches by diverting water from ponds and streams.

Ron

 

 

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