Tag: catfish

In Japan, a civil engineering legacy provides habitats for threatened fish

Historic detour canals built during Japan’s Edo Period are providing a crucial habitat for the endangered Ariake catfish.

The Ariake catfish (Tachysurus aurantiacus) is a freshwater fish only found on Japan’s Kyushu Island. It is nocturnal, and during the day it hides in places like submerged vegetation and rocks on stream beds. Unfortunately, environmental changes have left its populations endangered: the species is listed as Near Threatened in the IUCN Red List of Threatened Species.

T. aurantiacus can be found in the Yabe River, which features a unique irrigation system containing “detour canals”—a remarkable, three-centuries-old example of civil engineering. These canals were constructed during the Edo period (1603–1867) as a result of competition for water resources between the Kurume and Yanagawa domains, both of which sought to divert water into their own territory for rice cultivation. Today, approximately 300 years after their construction, detour canals are still in use, and over time, a stable aquatic environment has developed in them.

Diagram of the detour canals constructed as the result of a historical water struggle between the Kurume and Yanagawa Domains. Red parts show the study sections.

Curious to find out how this historical civil engineering heritage contributes to biodiversity conservation, researchers from Japan studied surveyed local catfish populations in detour canals. They found that the population volume of the Ariake catfish was significantly higher in canals than in ordinary branch rivers: out of 70 Ariake catfish observed in the study, 68 were found in the detour canals.

Average individual number of Ariake catfish per 50 m section in each canal/river. The error bar shows the standard deviation.

The detour canals, then, had conditions suitable for catfish life, becoming a vital lifeline for this rare species. Unlike regular rivers, they weren’t affected by river floods, and they were subjected to very little human modifications over time. This stability, along with the fact that Ariake catfish prefer the slow-moving water found in the middle reaches of rivers, is likely why the Yabe River detour canals offer such good habitat for this species.

This fascinating finding underscores the unexpected ways in which cultural heritage sites can contribute to biodiversity conservation. “The detour canals are valuable in their own right as civil engineering heritage sites, but their ecological function of providing habitat for the rare Ariake catfish species can be clearly stated”, the researchers write in their study, which was published in the open-access Biodiversity Data Journal.

Unfortunately, detour canals face an uncertain future. Ageing infrastructure and pressure from local populations are leading to the renovation of canals with concrete, threatening their ecological function and the cultural landscape they represent.

“As these canals represent a remarkable example of a contribution by a civil engineering heritage structure to biodiversity conservation, our study should be used as a potential justification for preserving the canals, as well as conserving the aquatic species that utilise them as vital habitat,” the authors write. “We hope that the findings of this study will lead to a review of the value of detour canals and contribute to the maintenance of catfish habitats and, eventually, the conservation of biodiversity and culturally important sites,” they say in conclusion.

Research article:

Yamasaki Y, Hayashi H, Kubo S, Namiki T, Kano Y (2024) Detour canal, a civil engineering heritage created through historical struggle for water resources, now provides the habitats for a rare freshwater fish. Biodiversity Data Journal 12: e119517. https://doi.org/10.3897/BDJ.12.e119517

Invasive species as biomonitors of microplastics in freshwater ecosystems?

Microplastics forming the disproportionate amount of plastic garbage, and catfish have become numerically dominant in some ecosystems thanks to their tolerance to pollution and anoxic environments.

Armored catfish (Pterygoplicthys spp.) and microplastics, as invasive species and emerging contaminants, respectively, represent two socio-environmental problems in the globalized world, since both have negative effects on faunistic communities and freshwater habitats, as well as on rural community fisheries and public health.

Non-native invasive species of armored catfish have become numerically dominant in some ecosystems, with efforts to eradicate them a seemingly endless task. Due to this, a possible scenario of biological homogenization in Mesoamerica can be expected, mainly given by the wide dispersion of the Pterygoplichthys species, added to the introduction of other non-native catfish species.

Photo: Miguel Ángel Salcedo. Drawing: Diana Ríos-Hernández.

The omnipresence of plastics in terrestrial and aquatic environments is caused by their excessive use and inadequate management of waste. The discarded plastics are fragmented, degraded, and dissolved by solar radiation, wind, and water, among other agents, to be incorporated into the food web in aquatic environments.

Microplastics found in the digestive tract of armed catfish (Pterygoplichthys spp.)

Both persist in the aquatic environment, microplastics forming the disproportionate amount of plastic garbage, and catfish thanks to their tolerance to pollution and anoxic environments, and their ability to survive for several hours breeding atmospheric oxygen. What is the relationship between the two? Microplastics, depending on their origin and composition, are sedimented in the wetlands, where they can be ingested by detritus feeders, such as armored catfish, mainly in areas where there is runoff or discharge of liquid waste.

In this context, we ask ourselves, can armored catfish be used as biomonitors of microplastics deposited in wetlands? Taking the above into consideration, the doctoral student Gabriela Angulo-Olmos under the guidance of the researchers Nicolás Álvarez-Pliego, Alberto J. Sánchez, Rosa Florido, Miguel Ángel Salcedo, Allan K. Cruz-Ramírez and Arturo Garrido Mora from the Laboratorio de Humedales, from the División Académica de Ciencias Biológicas, Universidad Juárez Autónoma de Tabasco, decided to answer the aforementioned question based on the numerical dominance of armored catfish recorded in the aquatic ecosystems of the Metropolitan Area of Villahermosa (MAV) in the coastal plain of the Gulf of Mexico.

A) Study area; Metropolitan Area of Villahermosa. Map modified from INEGI (2021). B) La Pólvora lake (Satélite Airbus 2023).

The stomach contents of the specimens from a lake located in the MAV were reviewed and the results showed that all the specimens had consumed microfibers. This result corroborated that these organisms can ingest sedimented microplastics due to their benthophagous habits.

Microplastics. Image by Oregon State University under a CC BY-SA 2.0 license.

The use of armored catfish as a resource in the food industry has had positive results, but is still insufficient. Therefore, we propose that another option to control their populations is to subtract and use this organism to verify which are the most frequent and abundant emerging contaminants deposited in the bottoms of urban wetlands.

Research article:

Angulo-Olmos G, Alvarez-Pliego N, Sánchez AJ, Florido R, Salcedo MÁ, Garrido-Mora A, Cruz-Rámirez AK (2023) Microfibers in the gut of invasive armored catfish (Pterygoplichthys spp.) (Actinopterygii: Siluriformes: Loricariidae) in an urban lake in the floodplain of the Grijalva River basin, Mexico. Acta Ichthyologica et Piscatoria 53: 81–88. https://doi.org/10.3897/aiep.53.102643

Chinese scientists discover a new species of catfish in Myanmar

During a survey of the freshwater fishes of the Mali Hka River drainage in the Hponkanrazi Wildlife Sanctuary, Myanmar, scientists Xiao-Yong Chen, Tao Qin and Zhi-Ying Chen, from the Chinese Academy of Sciences (CAS), identified a new catfish species among the collected specimens. It is distinct with a set of morphological features including its mouthparts and coloration. The discovery is published in the open access journal ZooKeys.

The new catfish belongs to a genus (Oreoglanis) of 22 currently recognised species. They are characterised with unusual teeth. While pointed in the upper and the back of the lower jaw, the teeth at the front of the lower jaw are shorter and broad. The latter are placed in a continuous dent. Out of the 22 species of the genus, there are only two known to live in Myanmar.

The new catfish, scientifically named Oreoglanis hponkanensis, has a moderately broad and strongly depressed head and body, and small eyes. The species is predominantly brown in colour, with light yellow belly and several yellowish patches across the body. Noticeable are also two round, bright orange patches in the middle of the fin.

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Original source:

Chen X-Y, Qin T, Chen Z-Y (2017) Oreoglanis hponkanensis, a new sisorid catfish from north Myanmar (Actinopterygii, Sisoridae). ZooKeys 646: 95-108. https://doi.org/10.3897/zookeys.646.11049

Long-snouted Amazonian catfishes including three new species to form a new genus

Being close relatives within the same genus, eight catfishes showed enough external differences, such as characteristic elongated mouths, hinting to their separate origin. Following a thorough morphological as well as molecular analysis, a team of researchers suggested that five previously known species along with three new ones, which they have found during their survey, need a new genus to accommodate for their specificity. The study, conducted by a Brazilian research team from Universidade Estadual Paulista and led by Dr. Fabio F. Roxo, is available in the open-access journal ZooKeys.

Among other physical peculiarities, the longer snout-like mouths of the herein discussed catfishes is a characteristic that sets them apart. This is also why the authors have chosen the name of Curculionichthys for the proposed genus, formed by the Latin word for “elongated snout” and the suffix “ichthys” meaning “fishes” in Greek.

Furthermore, one of the new species the researchers describe in the present paper surprises with its several dark-brown spots spread across its body. This colouration is unlike any other in its relatives that have various pigment patterns, yet never dark brown spots.

However, other overlapping morphological features as well as the closeness in the species’ researched habitats suggest they have a common ancestor, once lived in the Amazonian drainages.

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Original source:

Roxo FF, Silva GSC, Ochoa LA, Oliveira C (2015) Description of a new genus and three new species of Otothyrinae (Siluriformes, Loricariidae). ZooKeys 534: 103-134. doi: 10.3897/zookeys.534.6169