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plecos in texas


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#21 Guest_AussiePeter_*

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Posted 16 December 2012 - 12:05 PM

The trick is that diaboli were doing ok in the creek, but declined after the plecos took off. I'm sure the algae community has changed some and diaboli are largely herbivores (from memory). It's all hand waving, but time and time again there are cases where an exotic establishes and the native declines. Sure, there could be other factors operating, but once you see enough of these type of changes you tend to believe it.

The other quirk is there are always places where the same species gets introduced, but the native persists. Nothing is ever simple in biology, it is a complex relationship between habitat and biotic interactions and every creek and community is a bit different and responds differently to the same perturbations.

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Peter

#22 Guest_rjmtx_*

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Posted 16 December 2012 - 03:26 PM

Yeah, but the region has a number of exotics established, and strangely most of them really have relatively little impact on the ecology of the system (genetics can be a whole different issue in instances like smallmouth bass). Tilapia spp, common carp, redbreast sunfish, Rio Grande cichlids, smallmouth bass, etc are established in multiple drainages across the state with generally low impacts to the systems. There are streams that harbor plecos, but they aren't of epidemic proportions, and in some streams where their numbers are high, their impacts on the fauna seem somewhat small. I don't know, we could be seeing a silver carp-like impact here, but I have to ask, what's so different about San Felipe?

I'm not an invasive apologist by any means, believe me, but without knowing more about San Felipe (I haven't been in it in years, and at this point it's blended with all the other W. TX streams I've stomped around in), I wouldn't rush to judgement about plecos being the primary reason for others' declines. They could be, but there are so many other factors that hammer streams in that area, that it would be a serious jump based on speculation.

#23 Guest_don212_*

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Posted 17 December 2012 - 08:20 AM

i'm not an expert and i guess it's a chicken vs egg question, but the natives are not doing well, except forlarge pools the plant life is down, there is a terrible drought, and there are a startling large number of plecos, which are physically capable of doing a lot of damage to the stream beds, and plant populations, not all invasives are capable of as much damage. the drought is probably a big additional factor

#24 Guest_wargreen_*

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Posted 12 January 2013 - 05:17 PM

i'm not an expert and i guess it's a chicken vs egg question, but the natives are not doing well, except forlarge pools the plant life is down, there is a terrible drought, and there are a startling large number of plecos, which are physically capable of doing a lot of damage to the stream beds, and plant populations, not all invasives are capable of as much damage. the drought is probably a big additional factor

I agree, from all that ive read on Plecos they dig 18 inches into the soil to lay eggs and are voracious eaters of other fishes eggs top that with the fact they have no natural predators in Texas I do not see how their population explosion wouldnt have an impact on local species.

#25 Guest_rjmtx_*

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Posted 15 January 2013 - 04:01 PM

I agree, from all that ive read on Plecos they dig 18 inches into the soil to lay eggs and are voracious eaters of other fishes eggs top that with the fact they have no natural predators in Texas I do not see how their population explosion wouldnt have an impact on local species.


Sure they dig, but the "voracious eaters of fish eggs" could be disputed. Here's a study from the San Marcos River showing that eggs were not found in gut contents, but they did exhibit slightly elevated trophic status (than that of a pure herbivore) from stable isotope analysis.

http://www.bio.txsta...uth catfish.pdf

Edited by rjmtx, 15 January 2013 - 04:02 PM.


#26 Guest_gerald_*

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Posted 15 January 2013 - 04:30 PM

If they did eat fish eggs, would the eggs be recognizable in pleco gut contents, or just mush? I imagine lots of squishy things are "not found in gut contents" of fish with strong pharyngeal teeth simply because they are not identifiable, rather than because they're not present.

#27 Guest_wargreen_*

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Posted 15 January 2013 - 07:48 PM

Sure they dig, but the "voracious eaters of fish eggs" could be disputed. Here's a study from the San Marcos River showing that eggs were not found in gut contents, but they did exhibit slightly elevated trophic status (than that of a pure herbivore) from stable isotope analysis.

http://www.bio.txsta...uth catfish.pdf From what Ive just read, they only studied 36 plecos gut contents in a years time in the San Marcos river, which according to the study already has a well established population of plecos. I have read (and you can find on almost any forum) where people have had plecos eat there convict,angelfish or Oscar eggs. There may not have been any eggs available in the part of the San Marcos they studied.



#28 Guest_rjmtx_*

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Posted 16 January 2013 - 04:48 PM

Yeah, I've seen them eat eggs in my own tanks, but I wouldn't make assumptions of wild fish diets based on aquarium specimens. Do they eat eggs? Sure, when they run by them. Does that make them "voracious eaters of eggs" in the wild? Not necessarily. I haven't dug up CPUE numbers (which aren't worth much unless you're looking at decades of data), but there are still plenty of broadcast spawners out there.

#29 Guest_don212_*

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Posted 16 January 2013 - 08:29 PM

if they suck up eggs as they cruise and the bottom is covered by plecos cruising then what

#30 Guest_rjmtx_*

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Posted 16 January 2013 - 11:13 PM

Then you'd expect drastic declines in numbers of all broadcast spawners where there are plecos, and I don;t think we're seeing that.

#31 Guest_rjmtx_*

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Posted 16 January 2013 - 11:35 PM

I think a lot of it has to do with substrate types and sizes, where plecos generally hang out and eat, and where eggs usually settle out or are deposited. There is quite a bit of diversity of substrate from silt to bedrock and everything in between in these systems.

I don't want to come off as a pleco apologist. I hate the fact that they are like cockroaches out there. I just know that in the headwaters of some streams where plecos are thriving, there is still healthy diversity and abundance of endangered species that are only found in said headwaters.

#32 Guest_wargreen_*

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Posted 27 January 2013 - 09:27 PM

According to this article, "^ a b Lopez-Fernandez, Hernan (18 October), "STATUS OF DIONDA DIABOLI AND REPORT OF ESTABLISHED POPULATIONS OF EXOTIC FISH SPECIES IN LOWER SAN FELIPE CREEK, VAL VERDE COUNTY, TEXAS", The Southwestern Naturalist 50: 246–251" The Devils river minnow a "broadcast spawner", has a dwindling population which is directly influenced by several factors including non-native species of fish and water degradation.

Edited by wargreen, 27 January 2013 - 09:27 PM.


#33 Guest_Irate Mormon_*

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Posted 14 April 2013 - 11:17 PM

Yes, I've eaten a few. They'll tear up your hands and knife for about a thumb-size piece of meat out of a 12" fish. It's firm white meat. I ate mine steamed with garlic butter.


..And of course you went back for seconds!

#34 jamie1976

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Posted 04 February 2018 - 04:01 PM

I found this old thread.

Theee is scant anecdotal or scientific evidence showing negative consequences of invasive texas plecos,so ill add mine.

I reside in a medium sized city just a half hour north of the rio grand river. I first saw presence of plecos about 8 years ago in our canals, ponds and streams. As an avid fish collector, i saw the naked goby all but dissapear. I saw a retention pond that had bullhead for years stop producing them. Ive seen a n overall drop in all native catfish species.

The San Marcos river sample showed that 50% of total aquatic biomass were plecos.
That is an obvious sign of an invader taking over.

Plecos dont just eat algae, they rasp away entire surface layers of submerged surfaces, which consists of slimy layer that harbors innumerable organisms and micro plant life the forms the basis of food chain for fish and crustaceans. Ive also read that plecos feeding habits result in them absorbing all the available fosphorous in an invaded enviornment, which cripples the balance as well.

I asked a fisherman and he said he sees the local pelicans eating them.




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