Sharks and rays of Florida, USA


This 29 July 2020 video says about itself:

For the third straight year, we have had the privilege of filming giant hammerhead sharks hunting blacktip sharks off the beaches in Florida. The average size of a blacktip shark is 6ft in length, with an estimated weight of around 80lbs. The hammerhead sharks are much larger, measuring over 14ft in length and weighing well over 1000lbs. We filmed some incredible footage with our drone of giant hammerhead sharks hunting and eating blacktip sharks within the beach’s swimming distance.

From Florida Atlantic University in the USA:

Scientists catalogue shark and ray distribution in Florida lagoon

August 25, 2020

Summary: A study is the first long-term, in-depth analysis of the elasmobranch community in Florida’s Indian River Lagoon and develops capacity to understand how these species may respond to further environmental changes. From 2016 to 2018, researchers caught 630 individuals of 16 species, including two critically endangered smalltooth sawfish. Results showed that many elasmobranchs use the southern Indian River Lagoon throughout their life histories and the area may serve as an important nursery habitat for multiple species.

Many elasmobranch species, which include sharks, skates, and rays, use estuaries as nurseries, for birthing, and as foraging grounds. Florida’s Indian River Lagoon is one of 28 estuaries designated as an “estuary of national significance” by the Environmental Protection Agency’s National Estuary Program. In recent decades, this estuary has experienced many environmental impacts, such as habitat degradation and harmful algal blooms resulting in degraded water quality and fish kills. Currently, there is a substantial data gap surrounding the status of elasmobranchs in this estuary system.

Researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute conducted a fishery-independent survey to characterize the elasmobranch community and understand distribution patterns and habitat use in the Indian River Lagoon from Sebastian to St. Lucie Inlet. This study provides the first long-term, in-depth analysis of the elasmobranch community in the southern Indian River Lagoon and develops capacity to understand how these species may respond to further environmental changes.

Results of the study, published in Estuaries and Coasts, the journal of the Coastal and Estuarine Research Foundation, showed that many elasmobranchs use the southern Indian River Lagoon throughout their life histories and the area may serve as an important nursery habitat for multiple species.

From 2016 to 2018, researchers caught 630 individuals of 16 species, including two critically endangered smalltooth sawfish (Pristis pectinata). They characterized the species composition and distribution of elasmobranchs, examined spatial and temporal variability in the elasmobranch community, and assessed how temperature, salinity, dissolved oxygen, depth, water clarity, distance to an inlet, and distance to a freshwater source affect elasmobranch community composition. The two most commonly caught species were bull sharks and Atlantic stingrays, the only two species to each comprise greater than 20 percent of the catch. The remaining 14 species comprised 53 percent of the catch.

Researchers also observed size and compositional differences by region and season; for example, bull sharks were most abundant in Vero Beach and the St. Lucie River, and both bull sharks and Atlantic stingrays were more abundant in the fall than in the spring and summer. Clearer, relatively deeper, and higher salinity waters farther from freshwater sources and closer to inlets resulted in a more diverse community; while bull sharks and Atlantic stingrays dominated shallower, less clear waters closer to freshwater sources and further from inlets.

“As global human populations increase and environmental pressures on estuaries become more widespread, it is essential to continue to monitor changes in elasmobranch communities in order to effectively manage and conserve these populations,” said Grace Roskar, M.S., lead author, current Knauss Fellow with NOAA Fisheries and former graduate student working with Matt Ajemian, Ph.D., co-author and an assistant research professor at FAU’s Harbor Branch. “Establishing updated records of the diversity and distribution of elasmobranchs in the Indian River Lagoon is a critical first step to understand how varying environmental and pollution impacts may affect these species, which are integral to the fish community of the lagoon and surrounding habitats.”

The interconnected nature of abiotic parameters such as distance to freshwater sources or inlets and salinity that influenced elasmobranch distributions suggest important implications for future hydrological changes in the Indian River Lagoon.

“If freshwater discharges into the Indian River Lagoon increase in duration and/or volume, the elasmobranch community could shift even further to bull shark and Atlantic stingray dominance. Less tolerant species may be driven closer to the inlets or even out of the estuary to nearshore ocean habitats,” said Ajemian. “These community shifts could result in both decreased elasmobranch diversity and biodiversity of the estuary as a whole, possibly altering the dynamics of prey populations as well. Moreover, displaced species may face increased risks of predation or competition as well as declines in habitat quality or prey availability.”

The researchers emphasize the importance of continuing the survey for additional years to yield greater sample sizes and allow for the formulation of standardized relative abundance indices that will be useful in the stock assessment process, which is essential to fisheries management.

Quadruped evolution and Australian lungfish


This 11 July 2020 video is called Australian Lungfish Release – lake Gkula. it says about itself:

The lake is finally ready for the Lung Fish population. Snail, mussel and eel grass beds are established allowing plenty of food for these endemic species to thrive. The ecology of Lake Gkula is well advanced in such a short time (at this publishing it has been running for 8 months). We look forward to snorkeling to visit the Lung Fish and will keep you updated on their growth and progress.

From the University of Konstanz in Germany:

Lungfish fins reveal how limbs evolved

August 19, 2020

Summary: New research on the fin development of the Australian lungfish elucidates how fins evolved into limbs with hands with digits. The main finding is that in lungfish a primitive hand is already present, but that functional fingers and toes only evolved in land animals due to changes in embryonic development.

The evolution of limbs with functional digits from fish fins happened approximately 400 million years ago in the Devonian. This morphological transition allowed vertebrates to leave the water to conquer land and gave rise to all four-legged animals or tetrapods — the evolutionary lineage that includes all amphibians, reptiles, birds and mammals (including humans). Since the nineteenth century several theories based on both fossils and embryos have been put forward trying to explain how this transformation unfolded. Yet, exactly how hands with digits originated from fish fins remained unknown.

An international team of biologists based at the University of Konstanz (Germany), Macquarie University in Sydney (Australia) and the Stazione Zoologica Anton Dohrn in Naples (Italy) has determined how limbs have evolved from fins using embryos of the Australian lungfish (Neoceratodus forsteri) for their study. The Australian lungfish is the closest living fish relative of tetrapods and is often considered a “living fossil” as it still resembles the fishes that were around at the time when the first four-limbed vertebrates began to walk on land. For these reasons the fins of lungfish provide a better reference to study the evolutionary transition of fins into limbs than any other extant fish species.

The team’s research, which is reported in the latest issue of Science Advances, shows that a primitive hand is present in lungfish fins but at the same time suggests that the unique anatomy of limbs with digits only evolved during the rise of tetrapods through changes in embryonic development.

Insights from embryonic development: limb “architect” genes

To solve the puzzle of how limbs emerged from fins during evolution researchers have focused on embryonic development. “During embryogenesis, a suite of ‘architect’ genes shapes an amorphous group of precursor cells into fully grown limbs,” explains Dr. Joost Woltering, first author on the study and an assistant professor in the Evolutionary Biology group at the University of Konstanz led by Professor Axel Meyer. The very same “architect” genes also drive fin development. However, because evolutionary changes have occurred in the activity of these genes, the developmental process produces fins in fish and limbs in tetrapods.

To compare this process in fins and limbs, the team studied such “architect” genes in the embryos of the Australian lungfish. “Amazingly, what we discovered is that the gene specifying the hand in limbs (hoxa13) is activated in a similar skeletal region in lungfish fins,” explains Woltering. Importantly, this domain has never been observed in the fins of other fish that are more distantly related to tetrapods. “This finding clearly indicates that a primitive hand was already present in the ancestors of land animals.”

Developmental patterns: differences and similarities

The lungfish “hand,” in spite of this modern genetic signature, only partially resembles the anatomy of tetrapod hands because it lacks fingers or toes. To understand the genetic basis for this difference the team went on to analyse additional genes known to be associated with the formation of digits, finding that one gene important for the formation of fingers and toes (hoxd13 — a “sister gene” to the above-mentioned hoxa13) appeared to be switched on differently in fins.

During tetrapod limb development, the hoxd13 gene is switched on in a dynamic manner. It first becomes activated in the developing pinky finger and then expands all the way throughout the future hand towards the thumb. This process coordinates the correct formation of all five fingers. While Joost Woltering’s team observed a similar activation pattern of this gene in lungfish fins, it did not show this expansion but only remained activated in exactly one half of the fin. Additional differences were found for genes that are normally switched off in digits. In lungfish fins these genes remain active, but on the opposite side of the domain where hoxd13 is activated.

Old hypotheses — future directions

“All of this goes to show that while lungfish fins unexpectedly have a primitive hand in common with tetrapods, the fins of our ancestors also needed an evolutionary ‘finishing touch’ to produce limbs. In this sense it looks as if the hand was there first, only to be complemented with digits later during evolution,” says Woltering. One influential hypothesis regarding the evolution of limbs first put forward by early 20th-century palaeontologists Thomas Westoll and William Gregory, and in the 1980s famously developed further by Neil Shubin, postulates that fingers and toes arose through an expansion of the skeletal elements on one side of the fins of the tetrapod ancestor. This inferred expansion of fin elements corresponds exactly to the differences the team found in the expansion of the digit genes between lungfish fins and tetrapod limbs. The team’s observations on the activation and deactivation of limb “architect” genes in lungfish fins thus provides evidence in support of this classical transformational model.

In the future, to fully understand what causes this domain to expand, making our limbs so different from fish fins, the researchers plan to conduct further analyses on the development of fins and limbs, using lungfish but also more modern fish species such as cichlids as their embryos are easier to investigate using techniques like CRISPR. “To complete the picture of what happened in our fish ancestors that crawled onto land hundreds of millions of years ago, we really rely on currently living species to see how their embryos grow fins and limbs so differently,” concludes Woltering.

Background

– A new study by an international team of researchers from the University of Konstanz (Germany), Macquarie University in Sydney (Australia) and the Stazione Zoologica Anton Dohrn in Naples (Italy) provides an evolutionary model of how hands with digits emerged from fish fins.

– Studying the embryos of Australian lungfish (Neoceratodus forsteri), the closest extant fish relative of tetrapods, the researchers identified similarities and differences in the way lungfish fins and tetrapod limbs form during embryonic development.

– The presence of a primitive hand domain common to fins and limbs is revealed by the expression of a gene responsible for the specification of the hand in limbs (hoxa13). This gene becomes activated in similar skeletal domains in tetrapods and lungfish.

– One of the main morphological differences between fins and limbs, namely the absence of digits, can be explained by differences in the activation (hoxd13) and de-activation (alx4, pax9) of genes involved in digit development. This suggests that limbs with digits evolved from fish fins through changes in the activation of digit specific genes within a primitive hand domain.

How pregnant male seahorses feed embryos


This 29 March 2020 video from Ireland says about itself:

Seahorse Mating Dance

Filmed at Seahorse Aquariums in Dublin. Shortly after putting away the camera the female started laying eggs into the male’s pouch – typical! Three types of seahorse appear in the video and if you look carefully you will see a baby seahorse floating through the water.

Music Royalty free from: Kevin MacLeod (incompetech.com)

From the University of Sydney in Australia:

Who’s your daddy? Male seahorses transport nutrients to embryos

Male seahorse pregnancy could be as complex as female pregnancy

August 13, 2020

New research by Dr Camilla Whittington and her team at the University of Sydney has found male seahorses transport nutrients to their developing babies during pregnancy. This discovery provides an opportunity for further comparative evolutionary research.

Seahorses and their relatives are the only vertebrates that have male pregnancy. The expectant fathers incubate developing babies inside a pocket called a “brood pouch.” We know a male seahorse can have more than a thousand embryos in the pouch at once but until now, researchers had limited understanding of how the babies are fed.

“This work adds to the growing evidence that male pregnancy in seahorses could be as complex as female pregnancy in other animals, including ourselves,” said Dr Whittington, from the School of Life and Environmental Sciences. “We now know that seahorse dads can transport nutrients to the babies during pregnancy, and we think they do this via a placenta. It’s not exactly like a human placenta though — they don’t have an umbilical cord, for example. We need to do further histological work to confirm this.”

Seahorses are emerging as important model species for understanding the evolution of live-bearing reproduction, said Dr Whittington.

“We can draw some parallels between seahorse pregnancy and human pregnancy,” she said. “Seahorse dads seem to do some of the same things that human mums do, including transporting nutrients and oxygen to developing embryos, and immune modulation to protect the babies from infection.”

The research published in Journal of Comparative Physiology B was led by University of Sydney Honours student Zoe Skalkos in collaboration with Dr James Van Dyke at La Trobe University.

The study builds on previous genetic evidence suggesting that male seahorses might transport nutrients to developing embryos. This new study confirms, in the first experimental evidence of ‘patrotrophy’ (nutrient transport from dad to babies). It also identified one of the classes of nutrients being transported: energy-rich fats.

“My team is using a range of techniques to investigate the biology of seahorse pregnancy,” Dr Whittington said. “We want to understand more about the seahorse pouch and the ways it protects and supports the baby seahorses.”

Honours student Zoe Skalkos, who led the research, said: “It’s really exciting because it’s a big step in understanding the relationship between dad and baby in male pregnancy.”

Key Points:

  • Seahorses and their relatives are the only vertebrates that have male pregnancy. Dads incubate developing babies inside a pocket called a “brood pouch.”
  • Male seahorses transport nutrients, including fats, to developing babies during pregnancy. The babies use these energy-rich fats for growth and development.
  • The new results raise the question of whether seahorse embryos can influence how much nutrition they can get from dad while they are in the brood pouch.

Nestlé corporation accused of killing many fish


Dead fish in the Aisne river in France, photo by Fédération de pêche des Ardennes

Translated from Dutch NOS radio today:

Nestlé sued for thousands of dead fish in French river

A French fishing federation is suing food corporate giant Nestlé after finding thousands of dead fish in a river near a Nestlé factory. “Everything is dead over a length of seven kilometers,” says the fishing federation.

The dead fish were spotted on Sunday night in the river Aisne near the village of Challerange, between Reims and Verdun. According to local authorities, the fish died from a lack of oxygen in the water. The Ardennes fishing federation estimates the damage at several thousand euros and wants this to be paid by Nestlé France, the owner of the factory in Challerange. Where milk powder is made for in coffee cups.

“Fourteen fish species have been affected,” the federation told AFP news agency. “Including the protected eel and the lamprey.” Volunteers from the Fish Federation and the Fire Department have been working all week to remove dead fish that have washed up. At least 1 ton of fish has already been removed. The banks of the Aisne are off-limits until further notice because there are still many fish that are decomposing by the heat.

The factory says that a liquid was indeed accidentally spilled into the river on Sunday evening. …

It is still being investigated what exactly was in the water.

Pink catfish discovered in Venezuelan cave


This 10 August 2020 video from Venezuela says about itself:

Pink Catfish Discovered In Mountain Cave | The Dark: Nature’s Nighttime World | BBC Earth

This tiny pink catfish is a welcome surprise for the team. It has never seen daylight or an ocean. The crew inspect it closely and document their discovery.

Sea angels, sharks or rays?


This April 2020 video from California in the USA is called Angel Shark Quest | JONATHAN BIRD’S BLUE WORLD.

From the University of Vienna in Austria:

Between shark and ray: The evolutionary advantage of the sea angels

Threatened with extinction despite perfect adaptation

August 4, 2020

Summary: Angel sharks are sharks, but with their peculiarly flat body they rather resemble rays. An international research team has now investigated the origin of this body shape. The results illustrate how these sharks evolved into highly specialized, exclusively bottom-dwelling ambush predators and thus also contribute to a better understanding of their threat from environmental changes

The general picture of a shark is that of a fast and large ocean predator. Some species, however, question this image — for example angel sharks. They have adapted to a life on the bottom of the oceans, where they lie in wait for their prey. In order to be able to hide on or in the sediment, the body of angel sharks became flattened in the course of their evolution, making them very similar to rays, which are closely related to sharks.

Flattened body as indication for a successful lifestyle

The oldest known complete fossils of angel sharks are about 160 million years old and demonstrate that the flattened body was established early in their evolution. This also indicates that these extinct angel sharks already had a similar lifestyle as their extant relatives — and that this lifestyle obviously was very successful.

Angel sharks are found all over the world today, ranging from temperate to tropical seas, but most of these species are threatened. In order to understand the patterns and processes that led to their present low diversity and the possible consequences of their particular anatomy, the team has studied the body shapes of angel sharks since their origins using modern methods.

Today’s species are very similar

For this purpose, the skulls of extinct species from the late Jurassic period (about 160 million years ago) and of present-day species were quantitatively analysed using X-ray and CT images and prepared skulls employing geometric-morphometric approaches. In doing so, the evolution of body shapes could be explained comparatively, independent of body size.

The results show that early angel sharks were different in their external shape, whereas modern species show a comparably lower variation in shape. “Many of the living species are difficult to identify on the basis of their skeletal anatomy and shape, which could be problematic for species recognition,” explains Faviel A. López-Romero.

Angel sharks are well adapted, but react slowly to environmental changes

It has been shown that in living species the individual parts of the skull skeleton are more closely integrated than in their extinct relatives. This led to a reduced variability in appearance during the evolution of angel sharks. “The effect of integrating different parts of the skull into individual, highly interdependent modules can lead to a limited ability to evolve in different forms, but at the same time increases the ability to successfully adapt to specific environmental conditions,” explains Jürgen Kriwet.

In the case of the angel sharks, increasing geographical isolation resulted in the development of different species with very similar adaptations. “But modular integration also means that such animals are no longer able to react quickly to environmental changes, which increases their risk of extinction,” concludes Jürgen Kriwet.

How steelhead trout build their nests


This January 2020 video from Oregon in the USA says about itself:

The Guardian Who Stands Watch For North Umpqua Steelhead

There was a time not long ago when poachers came to Steamboat Creek along the North Umpqua River and dropped sticks of dynamite into pools filled with hundreds of steelhead. Then, a man named Lee Spencer started spending every day there — to watch the fish and keep poachers at bay.

From the GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre in Germany:

Eavesdropping on trout building their nests

Seismic sensors can record signals produced by fish building spawning pits

July 28, 2020

Steelhead trout (Oncorhynchus mykiss) stir up the sediment of the river bed when building their spawning pits, thus influencing the composition of the river bed and the transport of sediment. Until now, this process could only be studied visually, irregularly and with great effort in the natural environment of the fish. Now, researchers led by Michael Dietze of the GFZ German Research Centre for Geosciences in Potsdam have used seismic sensors (geophones) to analyze the trout’s nest-building process in detail. The study was published in the journal Earth Surface Processes and Landforms.

To lay their eggs, trout use their caudal fins to dig pits up to three metres long on each side and ten centimetres deep into the river bed. The aim of the researchers was to locate these spawning pits and to analyze the chronological sequence of the construction process. To this end, the researchers set up a network of seismic stations on a 150-meter section of the Mashel River in the US state of Washington. The geophones embedded in the earth are highly sensitive and detect the slightest vibrations in the ground. Small stones moved by the fish caused short frequency pulses in the range of 20 to 100 hertz and could be distinguished from background frequencies of flowing water, raindrops and even the pulses of passing airplanes. “The same signal arrives at each of the stations slightly delayed. This enabled us to determine where the seismic wave was generated,” says Dietze, first author of the study.

The researchers listened to the construction of four spawning pits for almost four weeks from the end of April to the end of May. The geophones revealed that the trout were mostly busy building their nests within eleven days of the measurement period. The fish preferably started at sunrise and were active until early noon, followed by another period in the early evening. The trout dug in the sediment for between one and twenty minutes, typically at two- to three-minute intervals with 50 to 100 tail strokes. This was followed by a break of about the same length.

“Normally, the nest-building behaviour of the trout was recorded only very irregularly, at most weekly. We can now resolve this to the millisecond. In the future, we want to extend the method to the behaviour of other species, for example animals that dig along the banks and destabilize them,” explains Dietze. The new measurement method might support fish and behavioural biology and provide a more accurate picture of the biotic and abiotic contribution of sediment transport in rivers. “Fish can move as much sediment as a normal spring flood. The biological component can therefore play a very important role,” said Dietze.

Locally extinct fish back in the Netherlands


This 28 July 2020 Dutch video is about a rare fish species, the allis shad.

It had been considered extinct in the Netherlands, because of pollution, overfishing, and human-made obstacles in rivers had stopped its migration from the North Sea up the river Rhine.

Recently, a small opening was made in the Haringvliet dam, to enable fish to travel up the Rhine.

This week, researchers discovered two adult allis shad fish in the Haringvliet.

Lahontan Cutthroat Trout in Nevada, USA


This video from the USA says about itself:

The Pyramid Lake Lahontan Cutthroat Trout was declared extinct in the 1940’s as a result of a badly planned diversion dam on the Truckee River. Built with no consideration of the downstream Indigenous Peoples of the Pyramid Lake Paiute Tribe and their cherished homeland, the dam desiccated the lake and destroyed the habitat of its native fish. However, the fish made a near-impossible return, aided by the efforts of biologists, tribal litigators, and a carpenter.

This documentary was completed as part of a graduate study in media innovation at the University of Nevada, Reno. It premiered at the Wild and Scenic Film Festival in Nevada City, California in January of 2019.

From the University of Nevada, Reno in the USA:

Lahontan Cutthroat Trout thrive at Paiute’s Summit Lake in far northern Nevada

July 22, 2020

Summit Lake in remote northwest Nevada is home to the only self-sustaining, robust, lake population of Lahontan Cutthroat Trout, North America’s largest freshwater native trout species. Research to understand the reasons why this population continues to thrive, where others have not, will be used to protect the fish and its habitat — as well as to apply the knowledge to help restore other Nevada lakes that once had bountiful numbers of the iconic fish that historically reached 60 pounds.

A team of researchers from the University of Nevada, Reno and the Summit Lake Paiute Tribe has been studying the watershed ecosystem and recently authored two papers published in scientific journals describing their findings about the relatively small desert terminal lake.

This project is part of a 9-year collaboration to conserve habitats and promote a healthy ecosystem for the lake. University researchers Sudeep Chandra and Zeb Hogan — as well as students from their aquatics ecosystems lab and Global Water Center — work with the tribe’s Natural Resources Department, formerly led by fish biologist William Cowan before he retired from the U.S. Fish and Wildlife Service.

“An objective to implement holistic management at Summit Lake is to blend science with traditional knowledge to protect and conserve natural ecologic processes, species diversity and tribal cultural practices,” Cowan said. “The partnership with the Global Water Center, as well as many other researchers, agencies, and organizations has complemented this objective by implementing science-based research and technological advances to investigate the viability of trout in the Summit Lake watershed.”

Monitoring data, including climate, hydrology, fish and wildlife population trends and habitat integrity, is used to develop, revise or validate the tribe’s management plans and regulations. This approach is a stark contrast to when the lake ecosystem and associated resources were at risk of irreversible impacts caused by non-point source pollution, irrigation diversions, livestock grazing, and the unknown affects caused by exporting trout eggs for establishment or supplementation of other populations.

“Our team at the University wants to support the efforts initiated by the Summit Lake Tribe,” Chandra, a professor in the College of Science, said. “Our goals are to assist them in developing their science-based program to protect Nevada’s only strong, self-sustaining lake population of Lahontan Cutthroat Trout. We believe that investigations in this robust ecosystem like Summit, where there is little human impact, could improve recovery efforts in other lake systems that are less fortunate and that have lost their trout like the Walker and Tahoe. Surprisingly there are still few comparative investigations of these lake ecosystems and how they could support trout during a time for increasing global changes.”

The Lahontan Cutthroat Trout, with its crimson red-orange slash marks on the throat under the jaw and black spots scattered over steel gray to olive green scales, is Nevada’s state fish and holds a cultural significance to the Summit Lake Paiute Tribe while providing the tribe with bountiful food and fish resources.

As an important traditional food source, Lahontan Cutthroat Trout composed a large part of Tribal member’s diets and were the focus of many gatherings held to honor the fish and to learn oral history, traditional practices, and cultural resources from elders of the tribe.

“The tribe has exercised their sovereignty to protect, manage and enhance tribal homelands, including the lake ecosystem and associated resources by working with federal agencies and other organizations that enable the tribe to holistically manage and protect the land, water and resources that fish, wildlife and tribal members depend on for survival,” Cowan said.

Climate Change, drought impacts watershed

The lake is about one square mile of surface area, has a mean depth of 20 feet with the southern end generally deeper with about 50 feet of depth at the deepest. The lake elevation decreased about 13 feet during the severe drought in the western United States that lasted from 2012 to 2016.

“One thing we learned is that the climatically induced drought can change the hydrology, or flow of water and connections of stream to lake, but even with these changes, the trout populations remain relatively stable in the lake,” Chandra said. “They look for the opportunity to spawn every year and likely wait for better conditions with higher flows for better access to upstream spawning grounds.

“So it is critical to support the tribe’s efforts to protect the watershed and understand how the long term changes in water resources, like the flow of water, will change with pending climate change projections for the Great Basin.”

James Simmons, doctoral student with the Ecology, Evolution and Conservation Biology program at the University said the population appears resilient to today’s climate disturbances/drought, which is very positive, but should the frequency and severity of drought increase in the future, will the population remain resilient in the face of continued low abundance, survival, spawners and a skewed sex ratio.

“I think the key going forward will be for the tribe to try to understand how the long-term flow of water in the watershed will be impacted by the future changing climate in the Great Basin — so that the tribe can formulate a game plan to get ahead of any potential negative repercussions,” he said. “Like cutthroat populations across the western U.S., this population faces unknown impacts from climate change.

“Declining abundance and diverging male and female abundance under changing drought cycles and conditions may have negative long term consequences. The prediction of increased frequency, severity and duration of drought and an increased percentage of rain may decrease abundance, reduce the effective population size and skew the sex ratio at Summit Lake.”

The research team found that connections between the upper watershed and the lake are essential for maintaining a healthy population during a drought. During the drought of 2012-2016, Summit Lake had a strong, stable population of naturally reproducing Lahontan Cutthroat Trout. The numbers of trout spawning up Mahogany Creek, one of the lake’s only inflow streams, was also relatively stable in number. Some of the trout in the lake migrated all the way to the upper watershed, about eight miles.

“Lahontan Cutthroat Trout can live in streams and lakes,” Chandra said. “The trout that live in lakes need rivers to spawn to keep their populations healthy. The numbers do show with little to no major changes to the watershed by human development, there is still a highly variable amount of spawning from lake to stream.”

Stream flow studied

Adequate stream flow is necessary for spawning and movement to the lake-dwelling component of the population. In rivers where flow is regulated, enough flow must be preserved in the spring to allow “lake spawners” to come upstream and in the fall to allow juveniles to migrate to the lake.

“Healthy habitat and ecological connectivity between habitats, such as no man-made migration barriers and adequate stream flow, should be preserved throughout as much of the watershed as possible (and of course between the stream and the lake) to facilitate movement for both stream- and lake-dwelling fish, and to support a robust overall population,” Teresa Campbell, a biologist and staff researcher in the University’s Global Water Center and lead author of one of the scientific papers, said.

“Strong connectivity between healthy stream and lake habitats is crucially important to the long-term survival of the Summit Lake Lahontan Cutthroat Trout because it seems that the exchange of individual fish across habitats contributes to the resilience and vitality of the population as a whole.”

The study also found that in drought-prone systems, streams should have adequate pool habitat and cover such as trees and woody debris to provide a refuge area from the drought and cooler temperatures for trout.

“During the drought, in the stream, these refuge pools with structure in the form of wood, cobbles, or boulders supported higher densities of stream-dwelling trout,” Campbell said. “Therefore, this habitat type is an important component of healthy stream habitat for trout.”

Forward thinking on the part of the tribe led to early habitat protections for the stream and the lake that now contribute to the success of this population. The tribe took measures to protect much of the stream habitat, erecting grazing enclosures in the 70s that prevented cattle from trampling the stream and allowed the stream to recover into the healthy habitat it is now. This is one of the reasons that trout are thriving here.

“The lake and surface water on the Reservation are further protected by restricting public access and monitoring resources necessary to sustain endemic species diversity in the area,” Cowan said.

The Summit Lake Paiute Tribe Reservation is the most remote Native American reservation in Nevada. Located in the northwest corner of Nevada, the reservation is 50 miles south of the Oregon border and 70 miles east of the California border.

Whitespotted eagle rays’ behavior, new research


This 26 October 2018 video from the USA says about itself:

Off the coast of Sarasota, Florida, lives the spotted eagle ray—a beautiful, yet mysterious, sea creature. Very little is known about the eagle ray, so research teams from Florida Atlantic University and Mote Marine Lab are pioneering new techniques to better understand them. Along with tagging the rays to track their movements, the team records and analyzes the sounds the rays make when they eat. These new research methods could shed light on the rays’ eating habits and give researchers a deeper understanding of the animal, and, by extension, the ocean as a whole.

Join wildlife biologist Wes Larson on a mission across the United States to find the next generation of conservationists.

From Florida Atlantic University in the USA:

Biotelemetry provides unique glimpse into whitespotted eagle rays’ behavior

Ecology of this ‘near threatened’ species in Florida

July 22, 2020

Summary: Researchers are the first to characterize the ecology and fine-scale habitat use of ‘near threatened’ white-spotted eagle rays in Florida while also identifying areas of potential interactions between this species and multiple environmental threats. Biotelemetry provided unique insights into this species’ occupancy, which is not apparent at the landscape-scale. Prolonged observations showed affinities for habitats of considerable recreational and commercial importance, like inlets, channels, and clam aquaculture lease sites close to shore.

The whitespotted eagle ray (Aetobatus narinari), found in estuaries and lagoons throughout Florida, is listed as “near threatened” on the International Union for Conservation of Nature’s “Red List of Threatened Species.” Keeping tabs on this highly mobile species for conservation efforts can be extremely challenging, especially for extended periods of time.

Researchers from Florida Atlantic University’s Harbor Branch Oceanographic Institute used uniquely coded transmitters and acoustic telemetry to give them a leading edge to unravel fine-scale movement, behavior, and habitat use of whitespotted eagle rays in Florida’s Indian River Lagoon. Biotelemetry provided the researchers with unique insights into this species’ occupancy, which is not apparent at the landscape-scale.

Despite being a state-protected species in Florida for more than two decades, this study is the first to characterize the ecology and fine-scale habitat use of whitespotted rays in Florida while also identifying areas of potential interactions between this species and multiple environmental threats. For the study, researchers followed seven mature individuals (six males and one female) and individually tracked them for a total of 119.6 hours. They used a tracking vessel to continuously and manually track the rays between June 2017 and August 2018.

Results of the study, published in the journal Endangered Species Research, show that rays use the deeper portions of the Indian River Lagoon, along Florida’s southeast coast, during the day and shallower portions during the night. In addition, they move faster while in the ocean and lagoonal habitats and slower in channels and inlets. This information suggests that whitespotted eagle rays may spend more time foraging at night in the shallow water of the lagoon than during the daytime. These prolonged observations revealed affinities for habitats of considerable recreational and commercial importance, such as inlets, channels, and clam aquaculture lease sites close to shore.

“Understanding channel use is crucial to evaluating risks and potentially developing strategies to mitigate negative impacts to the whitespotted eagle ray, as both channel and inlet habitats have high levels of human activity such as boating and fishing and are prone to coastal development impacts from dredging,” said Breanna DeGroot, M.S., lead author, research technician and former graduate student working with Matt Ajemian, Ph.D., co-author and an assistant research professor at FAU’s Harbor Branch. “In addition, these high traffic areas experience increased noise and chemical pollution.”

Rays also spent a larger proportion of time in the channels and inlet during the lighter and warmer portions of the day and used shallower depths during the cooler and darker portions of the day. Rate of movement significantly increased with temperature, suggesting that rays are more active during warmer periods. While previous studies have found that whitespotted eagle rays are influenced by tidal cycles, this study did not find any tidal patterns in ray habitat use or distribution.

Because more clammers work on lease sites during the day, interactions between the rays and growout sites may therefore be underestimated. Findings from this study will help to inform statewide conservation plans for the species and provide critical information to hard clam aquaculture farmers and restoration managers for the successful production of bivalves in the area.

“As coastal populations and development increase, there is more potential for whitespotted eagle rays to interact with human activities,” said Ajemian. “In addition, intense coastal development such as dredging, construction, and pollution have been linked to habitat alteration, which may change the abundance and distribution of this species as has been documented with shark species in degraded habitats.”

As whitespotted eagle rays already display an affinity for these modified habitats, increased interactions with humans and added pollution and/or disturbances could result in changes to the species’ movement patterns and health. Ultimately, such human-induced habitat alterations could reduce the overall productivity of estuarine areas and, with time, exacerbate pressures already facing populations of aetobatid rays.