A recent update introduced to the CMSY methodology used to assess the status of fish stocks has proven to more accurately predict the catch that a population can support than highly valued data-intensive models.
In a paper published in the journal Acta Ichthyologica et Piscatoria, the international team of researchers that shaped the improved CMSY++ model noted that its results better correspond with what is, in reality, the highest catch that a fish stock can support in the long-term, given that environmental conditions do not change much.
Now powered by an artificial neural network that has been trained with catch and biomass data of 400 stocks to identify plausible ranges of the initial and final state of the stocks being assessed, CMSY++ allows managers and scientists to input only catch data to estimate how much fish is left in a given stock and how much fishing pressure can be applied.
Schematic representation of the surplus production model used by CMSY, with indication of impaired recruitment due to small stock size, where FMSY is reduced linearly with decline in biomass.
Maximum sustainable catches or yield (MSY) is a concept developed in the 1950s by US fisheries scientist M.B. Schaefer who proposed that if fishers left in the water a biomass equivalent to at least 50 per cent of the unexploited fish population, that is, of the biomass it had before being commercially exploited, then the highest possible catches could be sustained over time.
“By comparing the results of CMSY++ to models that are considered superior because they require large amounts of initial data inputs, such as the Fox surplus-production model and the Stock Synthesis (SS3) age-structured model, we noticed that these models badly overpredicted the catch that a population can support when previous overfishing has reduced it to a small fraction of its natural size, as is the case with most exploited fish populations in the world.”
Dr. Rainer Froese, lead author of the study and a senior scientist at the GEOMAR Helmholtz Centre for Ocean Research.
In other words, the model underlying the CMSY++ method fitted the observed data, while the predictions of the ‘gold standard’ models were too optimistic in estimating sustainable catches.
Examples of graphical output of CMSY++, here for European plaice (Pleuronectes platessa) in the eastern English Channel.
“These models tend to estimate the biomass required to produce maximum sustainable yields as less than half of unexploited biomass, which is lower than M.B. Schaefer originally proposed based on the widely observed S-shaped growth curve of unexploited populations or population size that the ecosystem would normally accommodate.
“This finding could explain the often-observed failure of fisheries managers to maintain or rebuild depleted stocks even when the predictions of the gold standard models were followed.”
Daniel Pauly, co-author of the study and principal investigator of the Sea Around Us initiative at the University of British Columbia.
Research article:
Froese R, Winker H, Coro G, Palomares MLD, Tsikliras AC, Dimarchopoulou D, Touloumis K, Demirel N, Vianna GMS, Scarcella G, Schijns R, Liang C, Pauly D (2023) New developments in the analysis of catch time series as the basis for fish stock assessments: The CMSY++ method. Acta Ichthyologica et Piscatoria 53: 173-189. https://doi.org/10.3897/aiep.53.e105910
Biologists at Eawag have identified ten species of whitefish in the lakes of the Reuss river system. Of these, seven have been described as distinct species for the first time – although in two cases this required inspection of specimens from historical collections, since eutrophication of lakes in the 20th century also led to the extinction of fish species in Central Switzerland.
These seven whitefish were described as separate species for the first time, including the “Albeli” from Lake Lucerne, which now bears the name Coregonus muelleri in memory of the whitefish expert Rudolf Müller. Image by Eawag
The “Edelfisch” (Coregonus nobilis) was, after the smaller “Albeli”, the second most commonly caught species of whitefish in Lake Lucerne until, in the second half of the 20th century, phosphate from domestic wastewater and nutrient-rich run-off from farmland led to a massive increase in algal blooms. Compared to the lakes of the Central Plateau, nutrient levels in Lake Lucerne were moderate, and eutrophication was short-lived; even so, due to algal decomposition, oxygen was depleted in the deeper layers of the lake. The “Edelfisch”, which reproduces in the late summer at a spawning depth of 80 metres or more, suffered as a result. Shortly before nutrient inputs decreased following the ban on phosphates in detergents and the expansion of wastewater treatment plants, stocks of this species collapsed and it was considered to be extinct in 1980. Only from the late 1990s were individual specimens caught once again, unequivocally identified as C. nobilis in 2000 by the whitefish specialist and Eawag researcher Rudolf Müller.
Coregonus nobilis, Lake Lucerne, Switzerland.
Five whitefish species in Lake Lucerne
Coregonus nobilis, Lake Lucerne, Switzerland.
As the “Edelfisch” is now a protected species, Lake Lucerne has not lost any of its historically recorded whitefish species. Indeed, in addition to the familiar “Edelfisch”, “Albeli” and “Bodenbalchen”, Eawag scientists have identified two new species – two large whitefish, differing from the previously known species in their habits, morphological characteristics and genetic composition. The pelagic “Schwebbalchen” (Coregonus suspensus) probably lives permanently in the open water, not only for foraging but also for reproduction – a spawning behaviour only previously observed in the “Blaufelchen” (C. wartmanni) of Lake Constance. Occupying a position intermediate to the pelagic “Schwebbalchen” (C. suspensus) and the “Bodenbalchen” (C. litoralis) is the littoral “Schwebbalchen” (C. intermundia).
Lake Zug survivor
Coregonus supersum.
Particularly affected by eutrophication in the mid-20th century were whitefish in Lake Zug, which – like other Central Plateau lakes – was exposed to higher nutrient levels, for a longer period, than waterbodies further upstream. As only the uppermost water layers of this 200-metre-deep lake maintained oxygen levels sufficient to support fish, two whitefish species spawning in the depths of the lake died out – the (Lake Zug) “Albeli” (C. zugensis) and “Albock” (C. obliterus). Indeed, the Lake Zug “Albock” would have been completely forgotten if specimens had not been found by Eawag scientists Oliver Selz and Ole Seehausen in the historical Steinmann-Eawag Collection. Its morphology and historical accounts indicate that the Lake Zug “Albock” was a deep‑water specialist – a specialisation only otherwise observed to the same degree in the (likewise extinct) Lake Constance Kilch (C. gutturosus) and the (still extant) Lake Thun Kropfer (C. profundus).
The only whitefish species still found in Lake Zug today, spawning near the shore, is the “Balchen”. Testifying to its survival is its new scientific name – Coregonus supersum (“I have survived”).
Species endemic to each lake
Also new are the scientific names of the Lake Lucerne “Bodenbalchen” (C. litoralis) and “Albeli” (C. muelleri). For the morphological and genetic studies carried out by Oliver Selz and Ole Seehausen in order to revise the taxonomy of whitefish showed that almost every lake in Central Switzerland has its own species of “Albeli” and “Bodenbalchen”.
Previously, the “Albeli” of Lakes Zug and Lucerne had been classified as members of the same species (C. zugensis), while the “Balchen” spawning near the shore of the various Central Swiss lakes were known as C. suidteri. These collective species names have now been inherited by the extinct Lake Zug “Albeli” (C. zugensis) and the Lake Sempach “Balchen” (C. suidteri).
The Lake Lucerne “Albeli” received the new name C. muelleri in honour of the fisheries biologist and whitefish specialist Dr Rudolf Müller (1944–2023).
Ruedi Müller with the then Lucerne fisheries and hunting administrator, Josef Muggli, catching whitefish. Photo by Robert Muggli, Archive
A reflection of Switzerland
The lakes of the Reuss river system are a reflection of Switzerland as a whole. Since the last ice age, at least 35 whitefish species evolved in the pre-alpine lakes, usually two or more in each lake. Switzerland lost a third of these species during the period of lake eutrophication around the middle of the 20th century. Many of the lost species are known to researchers only thanks to historical collections, such as that created before the eutrophication period by the naturalist Paul Steinmann and currently curated by the Natural History Museum of Bern.
Original source:
Selz OM, Seehausen O (2023) A taxonomic revision of ten whitefish species from the lakes Lucerne, Sarnen, Sempach and Zug, Switzerland, with descriptions of seven new species (Teleostei, Coregonidae). ZooKeys 1144: 95-169. https://doi.org/10.3897/zookeys.1144.67747
“This is why Mikolji’s Oscar is a highly appreciated species in the aquarium hobby. It is more than just a fish in an aquarium when it is considered a true pet.”
In this last part, we talked with ichthyologist Oscar Miguel Lasso-Alcalá about what makesAstronotus mikoljii – a new to science cichlid species that he recently described in ZooKeys – so special.
What makes this species so charismatic and loved by aquarists and ichthyologists?
I already spoke about my experience as an aquarist from an early age, where the qualities of the species of the Astronotus genus, known as Oscars are highlighted.
Different varieties and color patterns have been obtained from them through selective breeding, or genetic manipulation, which are called living modified organisms (LMOs) or genetically modified organisms (GMOs).
However, the true lovers of nature, the aquarians of the “Biotope Aquarium” movement and the like, prefer pure specimens to manipulated or artificially modified ones. This is why Mikolji’s Oscar is a highly appreciated species in the aquarium hobby. It is more than just a fish in an aquarium since it is considered a true pet.
For ichthyologists, it is remarkably interesting and at the same time very challenging to study a genus like Astronotus, which already has only three described species (Astronotus ocellatus, A. cassiprinnis and A. mikoljii).
This is an unusual situation, which, as we have reported, requires an integrative approach and the work and experience of different specialists for its study. With all certainty, as in the case of Mikolji’s Oscar, other species of the genus Astronotus remain to be studied and described, and we hope that we will have the fortune to participate with our experience in these new works.
Local people have long known this species. What role does it have in their lives?
It is important to clarify that Astronotus mikoljii is a new species for science, but it is not a “new species” for people who already knew it locally under the name of Pavona, Vieja, or Cupaneca in Venezuela or Pavo Real, Carabazú, Mojarra and Mojarra Negra in Colombia. Nor for the aquarium trade, where it was known by the common name of Oscar and scientific name of Astronotus ocellatus, or, to a lesser degree, as Astronotus cassiprinnis.
This species has been of great food importance for thousands of years for at least nine indigenous ethnic groups.
Much less is it a new species for the nine thousand-year-old indigenous ethnic groups that share their world with the habitat of this fish, who baptized it with some 14 different names, known in their languages as mijsho (Kariña), boisikuajaba (Warao), hácho (Pumé = Yaruro), phadeewa, jadaewa (Ye’Kuana = Makiritare), perewa, parawa (Eñepá = Panare), yawirra (Kúrrim = Kurripako), kohukohurimï, kohokohorimï, owënawë kohoromï” (Yanomami = Yanomamï), eba (Puinave), Itapukunda (Kurripako), uan (Tucano).
Hence, the importance of scientific names, since the same species can have multiple common names, in the same language or in multiple languages.
It is important to note that very few studies that describe new species for science include the common names of the species, as given by the indigenous ethnic groups or natives of the regions, where the species live.
This species has been of great food importance for thousands of years for at least nine indigenous ethnic groups, and for more than 500 years to the hundreds of human communities of locals who inhabit the Orinoco River basin in Venezuela and Colombia. In our studies, in the plains of Orinoco from 30 years ago, we were able to verify its consumption, as well as high gastronomic value, due to its pleasant taste and enhanced texture.
However, due to my imprint as an aquarist, I have not wanted to consume it on the different occasions that it was offered to me, because it is very difficult to eat the beloved pets that we had in our childhood.
Why is this fish important to people and to ecosystems?
It is especially important to highlight that the Astronotus mikoljii species plays a very important role in the ecosystem, due to its biological and ecological background.
Although it can feed from different sources, it is a fundamentally carnivorous species, and therefore, it “controls” other species in the ecosystem.
Without Mikolji’s Oscar, the aquatic ecosystem would lose one of its fundamental links and the delicate balance of its functioning, because the species it feeds on could increase their populations uncontrollably, becoming veritable pests. This would put in great danger the entire future of the aquatic ecosystem of the Orinoco River basin and the permanence of other species of ecological importance.
In addition, it would surely affect other species used by man, both those of commercial importance (sold as food or as ornamental species), and for the subsistence fishing of native and indigenous inhabitants.
Mikolji’s Oscar, although a carnivorous species, also has its natural predators, for example piranhas and other predatory fish. For this reason, it evolved with an ocellus, or false eye, at the base of the caudal fin, to confuse its predators and guarantee its survival. Obviously, this species will be compromised if we don’t learn about it, use its populations wisely and preserve it in the long term.
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Photos by Ivan Mikolji.
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You can find Part 1 and Part 2 of the interview with Oscar.
“Working in science in a country under these conditions, and getting to publish the results of the investigations in high-level scientific journals such as ZooKeys, is an act of “true heroism”.
Oscar Miguel Lasso-Alcalá, MSc. is a Spanish-Venezuelan ichthyologist. This summer, his team described a new species of Oscar fish in the journal ZooKeys.
In this second part of his interview, he tells us about the challenges in his work and shares the story behind the new cichlid’s name.You can find Part 1 of the interview.
What did you find to be the biggest challenge?
Throughout the past seven years, the description of this species has been a real challenge. Our group of researchers knew from the beginning that it was going to be a difficult job. However, we never imagined the magnitude of the problems or challenges we would encounter.
We had to study the specimens from the Orinoco River basin in Venezuela and Colombia, and rivers from the hydrographic basin of the Gulf of Paria in Venezuela, which were within our reach, in the main scientific collections of fishes in Venezuela. Similarly, we studied the specimens from the Amazon River basin in one of the main collections in Brazil. We studied the traditional external morphology (morphometric characters, or the body, and meristic measurements, or the number of structures or parts such as scales, fins, etc.) and their coloration, as well as their internal morphology, that is, the study of structures of their skeleton, with the use of high-definition radiographs, where we found the main differences with other species.
A novel technique was the study of the shape of the otoliths, or “ear stones”, a technique not used before in the study of this group of fish. That is why I mentioned before that we also made some great scientific discoveries.
In addition to the long and meticulous laboratory work, we also had to conduct field work, not only to capture new specimens for the morphological study, but also for the genetic and molecular study, a new methodology that has become popular in recent years as a way to support taxonomy and systematics in the description and classification of species.
For this latest work, we also relied on a recent study in this area of research, carried out by the genetics specialists on our work team. This means our research was based on what is currently called “integrative taxonomy”, which is the sum of different techniques, methods, and technologies, at the service of achieving our goal: the description of a new species for science and for the world.
Many other difficulties came up along the way, which is why this research took over seven years to be published. Normally, researchers cannot focus 100% of their time on one single research, and workloads fluctuate. Sometimes we think that a greater number of specialists would help distribute the workload evenly or that getting input from others with different fields of experience, sometimes specialized, would help enrich the work, but that also makes it more difficult to reach agreement. Reaching perfection is never possible, and it took a long time for us to reach a level of results that was both acceptable to all and well accepted in the field of taxonomy and systematics.
One of the biggest challenges was purely financial. While we had some funds from Brazilian research support organizations and two universities, this was not the case in Venezuela, a country plunged in a serious political, social, economic, and humanitarian crisis.
Working in science in a country under these conditions, and being able to publish your results in high-level scientific journals, including ZooKeys, is an act of “true heroism”, as my brother José Antonio often says when cheering on my publication.
How come you named it after Ivan Mikolji?
People who do not know about the great work carried out by river explorer Ivan Mikolji might wonder about that, but the thousands of people, connoisseurs and followers of his work are absolutely clear on the justification for this appointment.
In addition to being an excellent professional explorer, author, underwater photographer, audiovisual producer and even plastic artist, he is a tireless and enthusiastic disseminator of the biodiversity and natural history of freshwater fish in Venezuela and Colombia.
His work has contributed greatly to the knowledge and conservation of the aquatic ecosystems of both countries. His motto is: “You cannot preserve something that you don’t know exists.”
He has made dozens of photography and art exhibitions in Venezuela, Mexico and the United States, as well as award-winning documentaries on the Orinoco River and its biodiversity that have acquired millions of views.
Mikolji has also inspired thousands of “conservationist” aquarists, as a judge in a worldwide movement called “Biotope Aquariums,” where people try to simulate, as much as possible, the ecosystems and aquatic biodiversity of their places of origin, for the conservation of their local biodiversity.
In addition, his educational work further includes the “Wild Aquarium”, a new movement and methodology, where he recreates in the same place (in situ), a “Biotope aquarium”, helping local communities (children and adults) learn about local aquatic ecosystems and biodiversity and their conservation.
In addition to his great artistic, informative, and educational work, with the enormous data accumulated in more than 15 years of work and field observations, in the recent years, he has participated in different research projects, publishing books and numerous scientific articles, some of them with us. For this reason, in 2020, he was appointed Associate Researcher of the Museo de Historia Natural La Salle (Caracas) of the Fundación La Salle de Ciencias Naturales, in Venezuela. By the way, we are planning research that we hope to announce soon in various publications.
Regarding Astronotus mikoljii, our good friend and now colleague Ivan Mikolji, was the one who initially proposed that we describe this species that he loves so much. He selflessly supported all the authors throughout the study in diverse ways, even in the field work in Venezuela. Ivan helped us in the search for equipment and materials, in the search for information, in the photographic work, and now in the dissemination of this study. For this reason, the article, in just one week, achieved more than 4,500 downloads, both on ZooKeys and ResearchGate web platforms, a true record for a study of this type.
Most importantly, throughout these years, Ivan has always encouraged us not to lose our course and objective, even in the most difficult moments. After years of knowing him, we have cultivated an excellent friendship. This is why we decided that it was just and necessary to recognize his work, help, companionship, and friendship, naming this beautiful and beloved species in his honor.
Oscar Miguel Lasso-Alcalá, MSc., is a Spanish-Venezuelan ichthyologist with undergraduate studies in Oceanography, Fishing Technology and Aquaculture, and Postgraduate studies in Agricultural Zoology and Estuary Ecology. He has worked in diverse areas such as taxonomy, biology, ecology, freshwater, estuarine, and marine fisheries and management. For 33 years, he has participated in more than 70 research projects and published over 250 studies. He has made more than 250 scientific expeditions to different regions of Venezuela and six other countries in America. He has dedicated much of his work to studying, educating, and managing introduced species and their invasions.
This summer, Oscar’s team described a new species of cichlid fish from northern South America in our journal ZooKeys. We spoke to him to find out how they came to the discovery and what it means to him.
When did you discover the new species?
Although some taxonomists have specimens that they believe, or have preliminarily diagnosed, to correspond to different, undescribed or new-to-science species (in my case I know of around 15 species I’ve diagnosed as new), Astronotus mikoljii was different. We did not discover that it was a new species overnight.
Normally, the process of discovering a new species takes a long time and a lot of work. It is not an easy task. First, you need to analyze the external and internal morphology. You study the color pattern and other characteristics and compare them to those of known, described species that are akin or similar to the one being studied, looking for the main differences. It is also very important to carry out exhaustive documentary and bibliographical research, to learn about all related species that have been previously described. Then, if there is complete certainty that it’s a different species that has not been previously described and published, there’s an entire process of formal description of the new species.
Did you immediately recognize it as a new species?
Absolutely not. Mikolji’s Oscar is difficult to differentiate externally. The first researcher who evidenced the main differences of Astronotus ocellatus (a binomial as it was previously known) from the Orinoco River basin, was the Swedish ichthyologist Sven Oscar Kullander, curator at the Swedish Museum of Natural History in Stockholm. He is one of the greatest specialists in the world on species of the Cichlidae family, to which the species we were studying belongs. This was first published in 1981, followed by his 1983, 1986, and 1989 studies (including his Ph.D. thesis) and later in other studies of his published in 2003 (all cited in our recent article published in the ZooKeys journal).
Likewise, my brother, the Spanish and Venezuelan ichthyologist Carlos Andrés Lasso, currently a researcher at the Instituto de Recursos Biológicos Alexander von Humboldt of Colombia, with more than 40 years of experience, also recognized this species from the Orinoco River as different from the one present in the Amazon River basin. In 18 different studies carried out in Venezuela and Colombia (all cited in our article), he records this species as Astronotus cf ocellatus (“cf” means the species name is yet to be confirmed), or directly as Astronotus sp., already assuring that it was a different species and new to science.
We are letting the world know a defined and individual species exists.
With this background, we responsibly acknowledge that it was Sven and Carlos who discovered Mikolji’s Oscar, and not us. Our credit and recognition are given for the process of describing the new species and for its publication. It is very important to clarify here that the discovery of a new-to-science species and its description (and publication) are two different facts, situations, and processes. However, in our study, we discovered some very important morphological characteristics, as well as genetic information, that allowed the differentiation of this species from those already known.
What was most exciting about this finding?
As an ichthyologist, I feel pride in collaborating and contributing to science, nationally, regionally, and globally. I feel satisfaction every time I share my research results at a scientific event or meeting (congress, symposium), or publish them in a scientific book (or part of it) or in a popular journal. This is not just an ordinary job for me, since I really like to investigate, and almost always have a lot of fun with this activity. As I have said in many of the interviews that I have had throughout my over 30-year career: to me, it’s not a job, it’s a way of living.
It fills me with great satisfaction to have the opportunity, more than 40 years after first meeting these Oscars, to be able to study them, describe them, and give them the name and place they deserve in science, and in the world.
The description of a species which is new to science is something really special, not only for me and my colleagues in this study, but for the vast majority of taxonomists. This is not only due to the fact that our last names will always appear next to the scientific name, but also to the fact that we are letting the world know a defined and individual species exists. By adding another species, we increase the known biodiversity of a country, a region, and the world, and therefore, we demonstrate that biodiversity must be studied, managed, conserved, and used rationally and independently.
Astronotus mikoljii is a very charismatic species, highly appreciated, valued, and loved in the aquarium hobby.
I remember that as a kid (between 7 and 13 years old), in the aquariums built at home by two of my older brothers, José Antonio and Carlos, to whom I largely owe being an ichthyologist today, we had some specimens of Oscars from Orinoco. We bought them in a local aquarium store in Caracas and took care of them, loved them like little children. I remember that in addition to feeling happily identified with the name (Oscar), they felt like real pets. They “got excited” when they saw us, took food directly from our hands without biting our fingers, and even let themselves be caressed, as if they were docile puppies or kittens. They were my favorite fish.
Years later, as an adult, beginning my research years, in the late 80’s and early 90’s, even with aquariums in our house (I had more than 20 in my good time as an aquarist), we had new specimens of these Oscars. This time, they were specimens captured by my brother and me, in the floodplains of the Orinoco River (Llanos de Apure), where for more than five years we studied the biology and ecology of some 200 local fish species, many of them unique in the world just like Mikolji’s Oscar. From that field study came the doctoral thesis of my brother Carlos, and the undergraduate theses of half a dozen other researchers, including mine.
It fills me with great satisfaction to have the opportunity, more than 40 years after first meeting these Oscars, to be able to study them, describe them, and give them the name and place they deserve in science, and in the world. It also fills me with deep satisfaction, having the opportunity to describe a “large-sized” species that was apparently already known, both locally and nationally (for its importance in fishing), as well as internationally in the world of aquarism. That is why, as I shared our study and finding on social media, I wrote: “Oscar describes the Oscar: Mikolji’s Oscar.“
We are also extremely grateful to the many people who helped us and collaborated with us in this study, by collecting new specimens in the field, reviewing fish collections under their care, taking X-rays, searching for specialized bibliographies, studying the native or indigenous names, and even editing and publishing the article in Zookeys journal.
Likewise, it was exciting to share this research experience with colleagues from Brazil (co-authors of this study, just like me), who trusted us and our meticulous work.
Somatic growth rate is a central life-history parameter, especially in species like fishes or invertebrates which grow throughout their lives. It is needed in conservation and fisheries management but it can sometimes be tricky to estimate.
A school of Jacks pass overhead at Viuda (Widow) dive site, in Coiba National Park, Panama, a UNESCO World Heritage site. Photo by LASZLO ILYES under a CC-BY 2.0 license.
Dr. Froese presents two new data-limited methods to estimate somatic growth from maximum length combined with either length or age at maturation or with maximum age. They are applicable to a wide range of species, sizes, and habitats. Using these new methods, growth parameter estimates were produced for the first time for 110 fish species.
“The growth estimates derived with the new methods presented in this study appear suitable for consideration and preliminary guidance in applications for conservation or management,” Dr. Froese points out in his study.
He goes on to suggest that journals accept growth estimates performed with the new methods as new knowledge, if they are the first for a given species.
In order to facilitate the conservation and management of natural resources, FishBase will continue to compile growth parameters, including results obtained with these new methods.
Research article:
Froese R (2022) Estimating somatic growth of fishes from maximum age or maturity. Acta Ichthyologica et Piscatoria 52(2): 125-133. https://doi.org/10.3897/aiep.52.80093
Revolutionary environmental DNA analysis holds great potential for the future of biodiversity monitoring, concludes a new study
Collection of water samples for eDNA metabarcoding bioassessment. Photo by Till-Hendrik Macher.
In times of exacerbating biodiversity loss, reliable data on species occurrence are essential, in order for prompt and adequate conservation actions to be initiated. This is especially true for freshwater ecosystems, which are particularly vulnerable and threatened by anthropogenic impacts. Their ecological status has already been highlighted as a top priority by multiple national and international directives, such as the European Water Framework Directive.
However, traditional monitoring methods, such as electrofishing, trapping methods, or observation-based assessments, which are the current status-quo in fish monitoring, are often time- and cost-consuming. As a result, over the last decade, scientists progressively agree that we need a more comprehensive and holistic method to assess freshwater biodiversity.
Meanwhile, recent studies have continuously been demonstrating that eDNA metabarcoding analyses, where DNA traces found in the water are used to identify what organisms live there, is an efficient method to capture aquatic biodiversity in a fast, reliable, non-invasive and relatively low-cost manner. In such metabarcoding studies, scientists sample, collect and sequence DNA, so that they can compare it with existing databases and identify the source organisms.
Furthermore, as eDNA metabarcoding assessments use samples from water, often streams, located at the lowest point, one such sample usually contains not only traces of specimens that come into direct contact with water, for example, by swimming or drinking, but also collects traces of terrestrial species indirectly via rainfalls, snowmelt, groundwaters etc.
In standard fish eDNA metabarcoding assessments, these ‘bycatch data’ are typically left aside. Yet, from a viewpoint of a more holistic biodiversity monitoring, they hold immense potential to also detect the presence of terrestrial and semi-terrestrial species in the catchment.
In their new study, reported in the open-access scholarly journalMetabarcoding and Metagenomics, German researchers from the University of Duisburg-Essen and the German Environment Agency successfully detected an astonishing quantity of the local mammals and birds native to the Saxony-Anhalt state by collecting as much as 18 litres of water from across a two-kilometre stretch along the river Mulde.
After water filtration the eDNA filter is preserved in ethanol until further processing in the lab. Photo by Till-Hendrik Macher.
In fact, it took only one day for the team, led by Till-Hendrik Macher, PhD student in the German Federal Environmental Agency-funded GeDNA project, to collect the samples. Using metabarcoding to analyse the DNA from the samples, the researchers identified as much as 50% of the fishes, 22% of the mammal species, and 7.4% of the breeding bird species in the region.
However, the team also concluded that while it would normally take only 10 litres of water to assess the aquatic and semi-terrestrial fauna, terrestrial species required significantly more sampling.
Unlocking data from the increasingly available fish eDNA metabarcoding information enables synergies among terrestrial and aquatic biodiversity monitoring programs, adding further important information on species diversity in space and time.
“We thus encourage to exploit fish eDNA metabarcoding biodiversity monitoring data to inform other conservation programs,”
says lead author Till-Hendrik Macher.
“For that purpose, however, it is essential that eDNA data is jointly stored and accessible for different biodiversity monitoring and biodiversity assessment campaigns, either at state, federal, or international level,”
concludes Florian Leese, who coordinates the project.
Original source:
Macher T-H, Schütz R, Arle J, Beermann AJ, Koschorreck J, Leese F (2021) Beyond fish eDNA metabarcoding: Field replicates disproportionately improve the detection of stream associated vertebrate species. Metabarcoding and Metagenomics 5: e66557. https://doi.org/10.3897/mbmg.5.66557
For the first time, scientists report a vampire fish attached to the body of an Amazonian thorny catfish. Very unusually, the candirus were attached close to the lateral bone plates, rather than the gills, where they are normally found. Since the hosts were not badly harmed, and the candirus apparently derived no food benefit, scientists believe this association is commensalistic rather than parasitic. The research is published in the open-access journal Acta Ichthyologica et Piscatoria.
Guest blog post by Chiara C. F. Lubich, André R. Martins, Carlos E. C. Freitas, Lawrence E. Hurd and Flávia K. Siqueira-Souza
The Amazon River Basin is home to about 15% of all freshwater fish species known to science, and an estimated 40% yet to be named. These include some of the most bizarre fishes: the vampire fishes, locally known as candiru, members of the catfish subfamily Vandelliinae.). They survive by attaching themselves to the bodies of other fish and sucking on their blood, hence their common name. Yet, it was only recently that we found out that one candiru species, belonging to the genus Paracanthopoma,seems to be making use of its host in quite a different way.
During a sampling study of freshwater fish fauna in a lake of the Demeni River Basin, a left bank tributary of the Negro River, we found candirus attached to the surface of the body of an Amazonian species of a thorny catfish. By the end of the survey, we had observed a total of twenty candirus attached to the outside of the bodies of nine larger Doras phlyzakion, one or two per host. Very unusually, the candirus were attached close to the lateral bone plates, rather than the gills, where these fish are normally found.
Location of the study: Demeni River, left bank tributary of Negro River, Amazonas State, Brazil.
As a result of these observations, we recently published the first record of a candiru attached to the body surface of an Amazonian thorny catfish in an article in the open-access scholarly journal Acta Ichthyologica et Piscatoria.
Vampire fish have long and robust snouts, with strong dentary teeth that help them stay attached to the epidermis of their host and feed on its blood. However, when we performed a macroscopic analysis of the stomach contents of the preserved Paracanthopoma specimens, we were surprised to find no coagulated blood, nor flesh, skin or mucus. This might indicate an interaction between parasite and host that is more benign than usually attributed to vampire fish.
Doras phlyzakion with vampire fish (Paracanthopoma sp.) fixed into its epidermis close to the bony plates of the lateral line. Arrows: areas with reddish wounds.
We believe the association between candiru and host in this case might be commensalistic (where one organism benefits from another without harming it), rather than parasitic, because the hosts were not badly harmed, and the candiru apparently derived no food benefit.
But what else would they seek on the back of Amazonian thorny catfish? One explanation could be that, since candirus are tiny and nearly transparent, they might be avoiding getting noticed by visual predators by riding on larger fish. Another hypothesis is that they could be using their big cousins to transport them over longer distances that they wouldn’t be able to cover themselves, eventually making it to safety or new food sources.
Research article:
Lubich CCF, Martins AR, Freitas CEC, Hurd LE, Siqueira-Souza FK (2021) A candiru, Paracanthopoma sp. (Siluriformes: Trichomycteridae), associated with a thorny catfish, Doras phlyzakion (Siluriformes: Doradidae), in a tributary of the middle Rio Negro, Brazilian Amazon. Acta Ichthyologica et Piscatoria 51(3): 241-244. https://doi.org/10.3897/aiep.51.e64324
Named for Black Panther’s mythical nation of Wakanda, a dazzling new “Vibranium” Fairy Wrasse enchants with purple scales and a preference for deep, little-known mesophotic reefs up to 260 feet below the surface
Africa has new purple-clad warriors more than 200 feet beneath the ocean’s surface. Deep-diving scientists from the California Academy of Sciences’ Hope for Reefs initiative and the University of Sydney spotted dazzling fairy wrasses—previously unknown to science—in the dimly lit mesophotic coral reefs of eastern Zanzibar, off the coast of Tanzania.
The multicolored wrasses sport deep purple scales so pigmented, they even retain their color (which is typically lost) when preserved for research. The scientists name this “twilight zone” reef-dweller Cirrhilabruswakanda (common name “Vibranium Fairy Wrasse”)in honor of the mythical nation of Wakanda from the Marvel Entertainment comics and movie Black Panther. The new fish is described in the open-access journal Zookeys.
Yi-Kai Tea, lead author and ichthyology PhD student from the University of Sydney, says:
“When we thought about the secretive and isolated nature of these unexplored African reefs, we knew we had to name this new species after Wakanda. We’ve known about other related fairy wrasses from the Indian Ocean, but always thought there was a missing species along the continent’s eastern edge. When I saw this amazing purple fish, I knew instantly we were dealing with the missing piece of the puzzle.”
The Academy scientists say Cirrhilabruswakanda’s remote home in mesophotic coral reefs—below recreational diving limits—probably contributed to their long-hidden status in the shadows of the Indian Ocean.
Therefore, Hope for Reefs’ scientific divers are highly trained for the dangerous process of researching in these deep, little-known mesophotic reefs, located 200 to 500 feet beneath the ocean’s surface. Accessing them requires technical equipment and physically intense training well beyond that of shallow-water diving. The team’s special diving gear (known as closed-circuit rebreathers) includes multiple tanks with custom gas blends and electronic monitoring equipment that allow the divers to explore deep reefs for mere minutes before a lengthy, hours-long ascent to the surface.
Dr. Luiz Rocha, Academy Curator of Fishes and co-leader of the Hope for Reefs, comments:
“Preparation for these deep dives is very intense and our dive gear often weighs more than us. When we reach these reefs and find unknown species as spectacular as this fairy wrasse, it feels like our hard work is paying off.”
Using a microscope, the team examined the specimens’ scales, fin rays, and body structures. DNA and morphological analyses revealed the new fairy wrasse to be different from the other seven species in the western Indian Ocean as well as other relatives in the Pacific. The new species’ common name is inspired by the fictional metal vibranium, a rare, and, according to Rocha, “totally awesome” substance found in the nation of Wakanda. The Vibranium Fairy Wrasse’s purple chain-link scale pattern reminded the scientists of Black Panther’s super-strong suit and the fabric motifs worn by Wakandans in the hit film.
Precious life in deep reefs
In a recent landmark paper, the Academy team found that twilight zone reefs are unique ecosystems bursting with life and are just as vulnerable to human threats as their shallow counterparts. Their findings upended the long-standing assumption that species might avoid human-related stressors on those deeper reefs. The Hope for Reefs team will continue to visit and study twilight zone sites around the world to shed light on these often-overlooked ecosystems.
In addition to this new fish from Zanzibar, Rocha and his colleagues recently published descriptions of mesophotic fish from Rapa Nui (Easter Island) and Micronesia. Luzonichthys kiomeamea is an orange, white, and sunny yellow dwarf anthias endemic to Rapa Nui, and the basslet Liopropoma incandescens (another new species published today in Zookeys) inhabits Pohnpei’s deep reefs—a neon orange and yellow specimen collected from a rocky slope 426 feet beneath the ocean’s surface.
“It’s a time of global crisis for coral reefs, and exploring little-known habitats and the life they support is now more important than ever,” concludes Rocha. “Because they are out of sight, these deeper reefs are often left out of marine reserves, so we hope our discoveries inspire their protection.”
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(Text by the California Academy of Sciences, USA)
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Research articles:
Tea YK, Pinheiro HT, Shepherd B, Rocha LA (2019) Cirrhilabrus wakanda, a new species of fairy wrasse from mesophotic ecosystems of Zanzibar, Tanzania, Africa (Teleostei, Labridae). ZooKeys 863: 85–96. https://doi.org/10.3897/zookeys.863.35580.
Pinheiro HT, Shepherd B, Greene BD, Rocha LA (2019) Liopropoma incandescens sp. nov. (Epinephelidae, Liopropominae), a new species of basslet from mesophotic coral ecosystems of Pohnpei, Micronesia. ZooKeys 863: 97–106. https://doi.org/10.3897/zookeys.863.33778.
The new species is the only coral-reef fish that lives exclusively within the marine protected area, which was recently expanded by the President
Scientists from the Bishop Museum, NOAA, and the Association for Marine Exploration published the description of a new species of coral-reef fish that they named in honor of President Barack Obama. The fish, which now bears the formal scientific name Tosanoides obama, was discovered during a June 2016 NOAA expedition to Papahānaumokuākea Marine National Monument in the remote Northwestern Hawaiian Islands. The study is published in the open-access scientific journal ZooKeys.
“We decided to name this fish after President Obama to recognize his efforts to protect and preserve the natural environment, including the expansion of Papahānaumokuākea,” said Richard Pyle, Bishop Museum scientist and lead author of the study. “This expansion adds a layer of protection to one of the last great wilderness areas on Earth.” The Museum is currently showcasing the exhibit Journeys: Heritage of the Northwestern Hawaiian Islands, featuring the Northwestern Hawaiian Islands and the Monument.
On August 26 of this year, at the urging of Sen. Brian Schatz (D-Hawaii), conservationists, and many marine scientists, President Obama expanded Papahānaumokuākea Marine National Monument. At 582,578 square miles, it is the largest permanent marine protected area on Earth. On September 1, during his trip to Midway Atoll within the Monument, legendary scientist, conservationist and deep ocean explorer Dr. Sylvia Earle gave the President a photograph of the fish that now bears his name. The exchange will be featured in the National Geographic global broadcast special, “Sea Of Hope” scheduled to be released on January 15, 2017.
The small pink and yellow fish is a kind of basslet, a group that includes many colorful reef fishes popular in the marine aquarium fish trade. There are two other species in the genus Tosanoides, both from the tropical northwestern Pacific Ocean. Males of the new species have a distinctive spot on the dorsal fin near the tail, which is blue around the edge and red with yellow stripes in the center. “The spot on the males is reminiscent of President Obama’s campaign logo,” said Pyle. “It seemed especially appropriate for a fish named in honor of the president.”
“The new fish is special because it is the only known species of coral-reef fish endemic to the Monument (meaning that the species is found nowhere else on Earth). Our research has documented the highest rate of fish endemism in the world — 100% — living on the deep reefs where we found this new species,” said NOAA scientist Randall Kosaki, chief scientist of the research cruise, and co-author on the paper. However, unlike all the other Hawaiian endemic species, which also occur in the main Hawaiian Islands, this new species is special because it is the only one that is limited to within the Monument itself. “Endemic species are unique contributions to global biodiversity,” Kosaki added. “With the onslaught of climate change, we are at risk of losing some of these undiscovered species before we even know they exist.”
The new fish was first discovered and collected on a dive to 300 feet at Kure Atoll, 1200 miles northwest of Honolulu. Kure is the northernmost of the Hawaiian Islands, and is the highest latitude coral atoll in the world. Deep coral reefs at depths of 150 to 500 feet, in the so-called “Twilight Zone” (also known as mesophotic coral ecosystems), are among the most poorly explored of all marine ecosystems. Located deeper than divers using conventional scuba gear can safely venture, these reefs represent a new frontier for coral-reef research. Pyle and co-authors Brian Greene and Randall Kosaki pioneered the use of advanced mixed-gas diving systems known as closed-circuit rebreathers for Twilight Zone research, and have been documenting the previously unexplored deep reefs throughout Hawai’i and the broader Pacific for the past three decades.
“These deep coral reefs are home to an incredible diversity of fishes, corals, and other marine invertebrates,” said Brian Greene, an experienced deep diver and researcher with the Association for Marine Exploration, and co-author of the paper. “There are many new species still waiting to be discovered down there.”
This is the second new species of fish from Papahānaumokuākea named this year. In August, Pyle and Kosaki published the description of a new species of butterflyfish (Prognathodes basabei) based on specimens collected on deep reefs at Pearl and Hermes Atoll earlier this year. President Obama also has several species from other locales named after him: a trapdoor spider, a speckled freshwater darter (fish), a parasitic hairworm, and an extinct lizard.
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Original source:
Citation: Pyle RL, Greene RD, Kosaki RK (2016) Tosanoides obama, a new basslet (Perciformes, Percoidei, Serranidae) from deep coral reefs in the Northwestern Hawaiian Islands. ZooKeys 641: 165-181. https://doi.org/10.3897/zookeys.641.11500
