Summer of Chub

June 14, 2016

Just in time for summer, baby Arroyo chub have hatched in our Nature Garden pond!  Sharp-eyed Will Hausler from live animal programs spotted dozens of tiny black fish darting around in the shallows at one end of the pond.  He shared his discovery with Leslie Gordon, our live animal programs manager, who arranged the chub introduction and has been keeping tabs on them.  

baby chub in pond

The tiny chub in the pond (left) and darting out of the photo (right).  Chub have a black stripe on the side which is very obvious in the juveniles.  Photo credit: Will Hausler, Chris Thacker.

Her first thought was that they must be the offspring of the chub we released in March, but she wasn’t sure. It’s hard to tell what kind of fish you’re looking at when you only see it from above, especially if it’s tiny and fast. So I got to pull out my aquarium nets and go do some field work just steps from my office!  The little guys were indeed zippy, but I captured one and confirmed the identification: definitely baby Arroyo chub (Gila orcutti).  The adult chub are very elusive and rarely seen, and we were unsure whether or not they liked their new home.  Confirmation that they are breeding is very good news, because it means they are thriving and have found places to spawn in the vegetation.

Arroyo chub are a kind of minnow, and they are one of Los Angeles’ few native freshwater fishes.  They only live here in Southern California, where they are classified as threatened.  Urbanization has reduced Arroyo chub populations in the Los Angeles, San Gabriel, and Santa Ana rivers, where they were once common.  The amazing thing about chub is how well-adapted they are to our natural cycle of hot, dry summers and occasional floods in rainy winters.  Before the rivers were channelized with concrete, they would overflow their banks in years of heavy rain, and spread in wide puddles across the flatlands.  These intermittent floods were a fantastic opportunity for Arroyo chub, allowing them to move between our rivers and creeks, mix, and even found new populations.  For a fish, dispersing like that is a big gamble, and chub are experts at it because they can tolerate tough conditions like wide variations in water temperature and low oxygen levels.  They will eat any tiny thing they can get, mostly insects and algae.  They are also great at controlling mosquitos by eating their larvae, which is why we brought them into our pond in the first place.

preserved Arroyo chub

Preserved Arroyo chub from our Ichthyology collection. They still have the black stripe on the side, but it's not as distinct.  Photo credit: Chris Thacker. 

The ways that animals move and invade new habitats are things we think about a lot here at the Museum.  We study many species of lizards, frogs, snails, spiders, squirrels and insects that have come from somewhere else and made a home in Los Angeles. These new arrivals have to contend with different environments, food, and predators than they are used to, and many don’t survive.  The ones that do tend to be generalists, easygoing about tolerating various environments and the food and conditions they find there.  Our chub are natives here, but they share those same characteristics, making them tough invaders and good adapters to new habitats. When they get to a new place, they can quickly reproduce and increase their numbers, which is exactly what they’ve done in our Nature Garden.


(Posted by: Chris Thacker)


Related

Arroyo #Chubwatch 2015

July 2, 2015

After three long years of planning, 45 arroyo chub were finally released into the Nature Garden's pond last week. 

Arroyo chub (it's alive, don't worry!) held for a quick photo op before release into the pond! Photo by Richard Hayden.

Arroyo chub, Gila orcuttii, are a native freshwater minnow found only in the coastal streams of Southern California, says Chris Thacker, Museum Curator of Ichthyology (fishes). They are classified as threatened in this native range and are noticeably missing from the lower reaches of the Los Angeles river. So, when it came time to think about fish in the Nature Gardens pond, all our scientists and educators wanted Arroyo chub.

 

The chub were transported from the Riverside Corona Resource Conservation District in an extra large cooler. Photo by Jason Goldman.

Our philosophy about purposefully introducing animals into the Nature Gardens is pretty strict-we generally don't do it. However, we knew we were going to make an exception for fish in the pond. Why? Because, mosquitoes!

Although we're fascinated by all nature here at the Museum, we are definitely taking a stance against breeding mosquitoes in our pond. Which is a good thing, because the Greater Los Angeles County Vector Control District would step in and solve the problem for us if we didn't. Their solution would involve releasing 6-10 mosquitofish, Gambusia affinis, into our pond. But, we didn't want mosquitofish, we wanted a fish that was native to Los Angeles, something that could tell a better story about nature in L.A..

Arroyo chub have a great story.

According to Thacker, "these minnows were historically found in arroyos and rivers in Southern California, but are now only known from the upper reaches of our watersheds." This is true for the highly altered and concretized LA River, where the chub are noticeably absent. When Friends of the Los Angeles River studied the fish of the river in 2007, they found zero arroyo chub and 668 mosquitofish, more than any other sort of fish!

Although, these non-native fish are helping us to keep mosquito-borne disease cases down, they're also impacting other creatures that live in our rivers and streams. Museum herpetologist (reptiles and amphibians), Greg Pauly explains, "the name mosquitofish makes one think they are highly specialized on mosquitos, when in fact they are actually broad generalists and consume native amphibian eggs and non-target insects." The chub on the other hand are much more effective at eating mosquito larvae and predate less often on the frogs, toads, and native insects we are trying to encourage in our waterways. Because we wanted to encourage as much biological diversity as possible in our pond–especially all those dragonfly and damselfly nymphs–we pushed for chub.

So why don't vector control use chub instead of mosquitofish? There are a few reasons. Chub are much harder to rear in captivity than mosquitofish, and it's therefore easier for vector control facilities to keep up with demand. More importantly, as a native fish arroyo chub require permits from California Department of Fish and Wildlife for us to keep them. Interesting that no permits are needed for the non-native mosquitofish. 

So, if you want to meet our new arroyo chub, come on down to the Museum. Thacker advises you to be patient, "They are skittish little fish and like quiet spots in the pond, so they will often be hiding, but can hopefully be spotted with a bit of dedicated observation." 

 


(Posted by: Lila Higgins)


Related

Urban Foraging: Carp Caviar from the L.A. River!

March 21, 2014

Ask me where my favorite spot to explore urban nature is in Los Angeles, and I'll almost always say the river. This is particularly true during, and after, our seasonal rain storms. We're used to extreme heat episodes, wildlfires, and the odd earthquake* or two. But, by and large, us Angelenos are unaffected and unimpressed by the elements. Going down to the river after a good rain, you get a rare chance to see, hear, and feel the raw power of nature.

*Anyone else wake up abruptly last Monday morning after the 4.4 trembler, wondering how much water you could salvage from your toilet's holding tank?

River patrol after the El Nino rains in January 2010

During our most recent rain storms (February 28-March 2) I, along with a number of other people, ventured down to the river to watch all that water flowing through the concrete channel.

 

View of the river and the Fletcher avenue bridge March 1, 2014

Unfortunately, the above pictures just don't do it justice. They don't let you feel the power of that much water flowing past you. Maybe this photo collage, created by Damian Robledo, can do a better job?

Damian works right next to the river in Elysian Valley (aka Frogtown), and was able to duck outside his office at RAC Design Build, to document the dramatic change.

As you can see, the river filled the channel almost to the very top. Which, according to The River Project, means a flow rate of about "183,000 cubic feet of water per second," or in terms easier to understand that's, "40 million garden hoses going full blast," or, "14 times the flow of New York's Hudson River!" Whoa, that is one heck of a lot of water flowing through the heart of Los Angeles and on out to the Pacific Ocean. While watching this spectacle, I couldn't help but wonder about the animals that live in the river. What happens to them when 14 Hudson rivers are forced between the river's banks?

Obviously, some creatures, like the white egret pictured above (long-necked bird hanging out in the middle of the frame), can just fly out of the river and hole up until the storm is over. Other fauna native to California, have evolved different strategies to deal with our sudden influxes of water. According to Dr. Greg Pauly, our curator of Herpetology, amphibians are much better than we are at sensing changes in barometric pressure. When they sense cues that a storm is coming (i.e. a drop in barometric pressure), frogs and toads will hop out of the watercourse and find a place to shelter, like under a nice big bush, or down an abandoned ground squirrel burrow. Some amphibians even thrive after massive disturbances like winter floods. Greg told me that after the Mount Saint Helens eruption, Western Toad, Bufo boreas, populations exploded.

But, what about the water-bound creatures, do they fare as well? In the case of this introduced carp species, Cyprinus carpio, not so well:

I found this fish while exploring the river on March 2nd, during an ethnobotany tour put on by River Wild. Although, we were focusing on urban foraging of edible plants, none of us could help taking time to marvel at this massive fish. As you can see, it was was lying there dead, with much of its insides spilling out, including the roe (all those orange bits are fish eggs)! Apparently, carp roe are sold as a caviar substitute, but I just wasn't willing to try them early on a Sunday morning. Yes, a part of me worried that they could be contaminated with toxins present in stormwater*, but mostly it was because I grew up vegetarian in England and accidentally ate taramasalata at a friend's birthday party. Incidentally, taramasalata, is a Greek or Turkish dip made from vinegar, olive oil, lemon juice, and taramas (aka preserved roe). As you can imagine, this has permanently affected my taste for carp caviar!

*In 2008 FoLAR (Friends of the L.A. River) commissioned a fish study to determine species presence and toxicity levels. They sent five L.A. river carp to a lab to be tested for mercury and polychlorinated biphenyls (PCBs) levels. All the fish tissue tested came back with mercury and PCB levels below those designated by the Office of Environmental Health Hazard Assessment's for fish contaminants.

But, how did this impressive creature die, and how did it end up in a dry side channel of the river? I think, one of two things happened. Either, the carp was battered around and killed by debris during the flood, and was then deposited in the side channel as the water receded. Or maybe, the water receded so quickly that the fish was stranded and then, unfortunately suffocated. Either way, post-mortem, it seems that another animal came along to have a snack, apparently wild creatures are into carp caviar too! Then, for some reason (maybe we disturbed them), the epicurious scavenger fled the scene of the crime and left this mighty fish to decompose on the river bank.

 


(Posted by: Lila Higgins)


Related

Piranhas Found in L.A.!

December 6, 2011

Piranhas are the stuff of B-movies, sensationalized nature television, and the tropical rainforest. Most would think they have little bearing on life here in L.A., however as I learned last week, this is not the case.

Taxidermied Red Piranha, Pygocentrus nattereri "lips" removed to accentuate teethPiranhas are here in L.A.! They are sometimes confiscated from pet stores and, on occasion, they are even found in our waterways. The Museum's Ichthyology collection houses over 30 confiscated piranha, and at least one that was caught in the "wild." According to the collections record, this Red Piranha (see below) was netted from "Simi Valley Public Golf Course, Lake B." It was collected on April 28, 1988 and measured 275mm (almost 10 1/2 inches)! Most interestingly the capture method box of the record states that that the "fish was in distress." I wonder if the piranha would ever have been discovered had it not been in distress? Before any of us decide to never go fishing for our wayward golf balls with our bare hands again, I have some happy news. Even in the Amazon basin, where Red Piranhas are native, humans are extremely unlikely to be injured by them, let alone die. The image of a school of piranha stripping all flesh from a whole cow or indeed a whole human, isn't much more than a sensationalized Hollywood gimmick (think James Bond's You Only Live Twice). This is because Red Piranha are actually scavengers preferring to eat dead, not living flesh. So next time you're fishing for your golf ball in the water trap, be safe in the knowledge that you're much more likely to get bitten by your neighbor's dog!

The Simi Valley Golf course piranhaOther piranha collected in L.A. come to the Museum directly from the California Department of Fish and Game (CDFG). CDFG staff often patrol pet stores and upon finding illegal creatures will confiscate them under California Law Title 14 Section 671. The fish are promptly brought to the Museum for identification and sometimes for permanent storage, though they may be taken briefly into a court of law as evidence! In May 2002, the Museum received 16 Red Piranha specimens confiscated from one pet store alone!

Red Piranha confiscated from pet storeI wonder if we'll ever find a piranha in the North Campus pond?


(Posted by: Lila Higgins)


Related