A clever painted comber in its natural habitat at the coast of Mallorca.
Credit: Josep Alós
To avoid overfishing and aid in sustainable exploitation, the status of the fish stocks has to be monitored regularly. In many cases stock assessment is based on fishery-dependent data generated from fish markets or creel surveys. The assumption is: the lower the catches in a certain unit of time, the smaller the stock of fish should be. The scientists Dr. Josep Alós and Prof. Dr. Robert Arlinghaus from the German Leibniz-Institute of Freshwater Ecology and Inland Fisheries and the Humboldt-Universität zu Berlin have now shown that some fish species show enhanced gear-avoidance behavior in regions with high angling intensity compared to fish exposed to low levels of exploitation near marine protected areas. The consequence is the impression that there are less fish in the sea, which does not necessarily agree with underwater reality.
The coast of the Spanish Island Mallorca is a holiday paradise for sun worshippers and for those loving water sports. But few are aware of the exiting phenomena that happen below the water surface. Here, a competition between increasingly clever fishes and the catch-addicted fishers takes place. Within a project funded by the European Union, the Spanish scientist Josep Alós and the German-Spanish scientist Robert Arlinghaus from the German Leibniz-Institute of Freshwater Ecology and Inland Fisheries and the Humboldt-Universität zu Berlin have investigated the fish populations at the coast of Mallorca using novel mathematical models and monitoring methods . Their research aims at understanding the behavior of fish in response to recreational fisheries. Based on standardized angling catch methods in a study from 2013 the scientists concluded that marine protected areas host higher fish quantities and bigger fishes than sites with a high exploitation pressure. A follow-up study now released in the Canadian Journal of Aquatic Sciences, which used underwater video analysis in addition to angling as a method to quantify the fish stock, puts these former results into doubt. The reason for this: clever fishes that escape the pursuit of the anglers without a corresponding decline in fish stock levels.
More anglers means less painted comber on the hook
The research team investigated two fish species popular among recreational anglers along the Mediterranean Sea. Both have the same size and the same habitat but differ in their eating habits. The painted comber (Serranus scriba) show a carnivorous foraging mode and feeds on fish and small crustaceans while the annular sea bream (Diplodus annularis) lives on mobile algae and bivalves. The sea bream can afford to carefully examine the potential prey and takes its time moving around the baits, inspecting them and is generally less vulnerable to capture in comparison with the comber. By contrast, the comber evolved a carnivorous life-style: too much hesitation and the mobile prey is gone. As a result of this, the painted comber is much more aggressive towards baits than the annular sea bream in their natural habitats where fishing pressure is low, which makes the comber much more vulnerable to be harvested by the anglers.
The recent study by the researchers has now shown a starkly different behavior in sites where the fishing pressures is high. The researchers studied the behavioral responses towards baits in 54 different locations with the same habitat characteristics but different angling pressures. An autonomous underwater video recording was used to measure the behavior of the fish when they were exposed to baited hooks.
The researchers were amazed when finding a strong correlation between high fishing intensity and hook-avoidance behavior of painted comber: this species had starkly changed the behavior from aggressively attacking the baited hooks in the natural environments with low fishing pressure to being shy in exploited sites where they were able to recognize the fishing gear and avoid hooking. No such response was detected in the sea bream. The explanation may involve both genetic change towards increased shyness and learning to avoid future capture.
Less fish on the hooks does not necessarily mean less fish in the sea
Although the catch rates of comber in areas with high fishing intensity were half of those in low exploited and marine protected areas both sites showed similar fish densities as recorded by underwater video. Therefore, the benefits of marine protected areas previously determined by the same authors in 2013 were not supported by underwater video footage now. “These results suggest that recreational angling may contribute to patterns of hyper depletion in catch rates without a corresponding change in the fish population where catch rates declines stronger than the abundance of fishes,” the first author of the study, Josep Alós, comments. And further: “Reports on the dramatic decline of fish populations in the ocean which were only based on fishery-dependent data, for example data from the long-line fishery of tuna, cod or swordfish, could also have their cause in enhanced gear-avoidance behavior of those fishes. We have to rethink our monitoring of fish stocks and take the behavioral changes into account. Maybe some areas with high fishing intensity host more fish than we believe,” concludes study leader Robert Arlinghaus.
Story Source: Forschungsverbund Berlin e.V. (FVB)
Originally published here: www.sciencedaily.com/releases/2015/05/150520083129.htm
Favosipora purpurea, one of the new species of bryozoans discovered on the island of Madeira.
Credit: Javier Souto et al.
The Portuguese island of Madeira is considered a diversity hotspot for bryozoans, which are colonial, principally marine, organisms. However, the fauna of these small animals only started being documented a short while ago. A team of Spanish and Portuguese scientists have now discovered two new species of bryozoans, as well as another that had previously only been found in the waters of Rio de Janeiro (Brazil).
To date, some 140 species of bryozoans have been identified in Madeira, which is why some authors consider the island to be a diversity hotspot for the zoological group. However, most of the knowledge they have of the region’s animals is from studies carried out by English researchers at the end of the 19th and beginning of the 20th centuries.
Over the last few years, the application of more modern study techniques, together with electron microscopy, has enabled the diversity of these organisms to be analysed in greater detail, meaning greater distinctions between species can be made. This technology, in the majority of cases, allows researchers to compare the material collected now with what was gathered previously.
Thanks to these new methods, scientists from various Spanish and Portuguese centres have analysed samples of rocks colonised by the organisms at a depth of 11 metres, which were collected from the south of the island in August 2013. The results, published in the journal Zootaxa, reveal the discovery of two new species: Favosipora purpurea and Rhynchozoon papuliferum.
“This study not only describes two species of bryozoans which are new to science, but six documented species from the island of Madeira and a species considered endemic to Brazil which was found outside those waters for the first time are also described again,” Javier Souto, a researcher affiliated with the University of Vienna and the department of Zoology and Biological Anthropology of the University of Santiago de Compostela (USC), said.
In order to draw these conclusions, the team studied material gathered by the researchers themselves and samples collected at the end of the 19th century held in the Manchester Museum (UK). “In doing this we were able to confirm that all this material corresponded to a species that had never been discovered before, which we named Rhynchozoon papuliferum,” said Souto.
According to the biologist, the name is related to the papilla-esque morphology of avicularians (zooids that are specialists in defence), “a fact that British scientist A. W. Waters (who gives his name to the collection of bryozoans in the English museum) had noticed as early as 1909, but the characteristic did not lead him to discover a new species,” explained the Spanish researcher.
However, Favosipora purpurea, which takes its name from the colour of its colonies, is the first species belonging to this genus to be observed in the Atlantic Ocean, and it had previously only been known to inhabit the Pacific and Indian Oceans. As for its characteristics, it is more or less circular with a two-centimetre diameter.
Rediscovering the bryozoans
“The bryozoans are one of the most important fouling organisms of the marine benthos and often go unnoticed because of their small size,” underlined the author. Around 6,000 species are currently known around the world, but the actual figure is believed to be in the region of 11,000.
These animals form colonies that range from a few millimetres to large colonies almost a metre in size and they can consist of a mere few zooids right up to thousands of them, with morphologies and functions within the group varying from one species to another.
“This morphological variation is what distinguishes one species from another. In order to observe this variation, a scanning electron microscope, which enables accurate identification, is required,” noted Souto. The study also enabled six previously recorded species to be re-observed on the Portuguese island, with the technology providing new data and images of said species.
The study was carried out within the framework of a species monitoring project whose objective is to recognise diversity and detect species introduced by human activity on the island of Madeira. The initiative was started in 2013 by Joao Canning Clode, a researcher at, among other centres, the Marine Biology Station of Funchal (Maderia).
Story Source: Plataforma SINC
Originally published here: www.sciencedaily.com/releases/2015/05/150519083546.htm
Brain coral (Diploria labyrinthiformis) overgrown and smothered by the lavender branching sponge Aplysina cauliformis.
Joseph Pawlik, UNCW
It sounds like the plot of a B-movie, but researchers have determined that sponges in over-fished areas are using deadly tactics — such as smothering and toxic mucus — to kill coral colonies so that the sponges can grow on what’s left: skeletons.
The discovery shows how disruption of even just a few members of an ecosystem — in this case, tasty fish — can hurt many other organisms that live in the same area.
The problem, highlighted in the latest issue of the journal PeerJ, is particularly evident at Caribbean coral reefs, where the combined effects of warming seawater temperatures, storms, and diseases have already decimated populations of corals.
While coral looks sort of like an undersea plant, groupings actually consist of tiny marine creatures that live together within compact colonies. They usually grow slowly. Sponges, on the other hand, grow either quickly or more slowly, depending on the species.
“If the goal is to save the corals that build Caribbean reefs, we have to protect the angelfishes and parrotfishes that eat sponges,” lead author Tse-Lynn Loh, now a Postdoctoral Research Associate at the Haerther Center for Conservation and Research at Chicago’s Shedd Aquarium, said in a press release.
Loh and colleagues surveyed reefs from 12 countries across the Caribbean. The scientists compared 25 sites where fish abundance is very low (because of decades of intensive fish trapping) with 44 sites where fishes are plentiful (because they’ve been protected from fishermen).
Both fast and slow-growing sponges tended to dominate coral colonies at overfished sites, adversely impacting at least 25 percent of them. The damage was more than double the incidence of this seen at less-fished reefs. At the latter, angelfishes and parrotfishes munched on the sponges, helping to keep their dominant ways in check.
Even when the fish were around, slower-growing sponges still made a dent in coral colonies, since these sponges can unleash their arsenal of “weapons” that allow them to compete aggressively for reef real estate. In addition to the smothering tactics and toxic mucus, the sponges can kill coral by releasing other toxins and by shading out light.
In past studies, seaweed was also found to hurt coral, but the new research led to the surprising discovery that seaweeds were more abundant on reefs with greater numbers of fish. The outcome is contrary to the conventional wisdom that fishes eat seaweeds and keep them in check. It now looks like the relationship between seaweeds and fishes is more complicated than previously imagined.
Conservationists in earlier years based some of their claims about needed regulation of fishing at reefs on the idea that fish kept damaging seaweed under control. Now, there is convincing evidence that sponges, and perhaps not so much seaweed, are heavily impacted by over-fishing, which sets the stage for the sponges to kill and take over coral reefs.
“Caribbean nations can now base their fishing policy decisions on the clear connection between overfishing and sponge-smothered corals,” said co-author Joseph Pawlik of the University of North Carolina at Wilmington. “Coral conservation requires a healthy population of reef fishes.”
Author: Jennifer Viegas
Originally published here: http://news.discovery.com/earth/oceans/deadly-sponges-are-snuffing-out-coral-colonies-150427.htm
NOAA Fisheries biologist Nick Wegner holds an opah caught during a research survey off the California coast. Researchers say the opah is the first fish known to be fully warm-blooded, circulating heated blood throughout its body.
Over decades of studying the oceans’ fishes, some species have been found to have partial warm-bloodedness. But scientists say the opah, or moonfish, circulates heated blood — and puts it to a competitive advantage.
“Nature has a way of surprising us with clever strategies where you least expect them,” according to NOAA Fisheries biologist Nicholas Wegner, who works in the Southwest Fisheries Science Center in La Jolla, Calif. In a news release about finding, Wegner said, “It’s hard to stay warm when you’re surrounded by cold water but the opah has figured it out.”
The opah is not a small animal; it’s roughly the size of a car tire and often weighs more than 100 pounds. In the past, it was often viewed as a fairly complacent dweller of water that’s hundreds of feet deep.
Now researchers say the opah also uses internal warmth to help it move quickly and efficiently — and kill prey such as squids and smaller fish. As the researchers describe in the journal Science, the fish relies on an internal heating system that seems to have been developed in frigid waters.
From the National Oceanic and Atmospheric Administration Fisheries:
“Satellite tracking showed opah spend most of their time at depths of 150 to 1,300 feet, without regularly surfacing. Their higher body temperature should increase their muscle output and capacity, boost their eye and brain function and help them resist the effects of cold on the heart and other organs, Wegner said.
“Fatty tissue surrounds the gills, heart and muscle tissue where the opah generates much of its internal heat, insulating them from the frigid water.”
Heat is generated from the opah’s large wing-like pectoral fins, which were previously thought only to help it swim fast enough to catch prey.
The agency’s researchers say they found an unexpected design tweak in the opah’s gills that sets it apart from other fish: a counter-current heat exchange in which blood vessels carrying warm blood are twined around vessels that are bringing oxygen — and cold temperatures — from the gills. The design helps the opah maintain endothermy (warm-bloodedness).
“The fish had an average muscle temperature about 5 degrees C (roughly 9 degrees Fahrenheit) above the surrounding water while swimming about 150 to 1,000 feet below the surface,” NOAA says.
Revelations about the opah’s blood temperature come after a moonfish was captured in a striking photograph off the California coast earlier this year, an encounter that was seen as part of a surge in opah sightings off the western U.S. coast.
Opah have more commonly been spotted in Hawaii — including at fish auctions.
Of the flavor, National Geographic has reported:
“Opah are unusual in that different parts of their body look and taste different, the biologist explains. The upper part of the fish looks like tuna and tastes like a cross between tuna and salmon, he says. But their pectoral muscles — the ones that power the fins on the side of the body — look and taste a bit like beef.”
Originally published here: http://www.npr.org/sections/thetwo-way/2015/05/15/407072979/first-in-fish-fully-warm-blooded-moonfish-prowls-the-deep-seas
Author: Bill Chappell
Neolamprologus pulcher (N. pulcher) is the breed of cichlid used in the study.
Credit: Dario Josi
A new study shows that cichlid fish reared in larger social groups from birth display a greater and more extensive range of social interactions, which continues into the later life of the fish. Researchers say this indicates the fish develop more attuned social behavior as a result of early environments.
The researchers also found that those fish raised in a more complex social environment have a different brain structure to those who experienced fewer group members in early life. If fish experienced the complex social environment for 2 month they had a larger hypothalamus: the area that contains most of the brain nodes of the ‘social behavior network’. They also had a larger ‘optic tectum’, which processes visual stimuli and could be related to the need to process more visual stimuli in larger groups, say researchers.
The brains of fish with enhanced social skills were not bigger overall than those reared in small groups; however, the ‘architecture’ within the brain was different.
“Our data suggests that, during development, relative brain parts change their size in response to environmental cues without affecting overall brain size: increasing certain parts forces others to decrease concurrently. These ‘plastic’ adjustments of brain architecture were still present long after the early stages of social interaction,” said study author Dr. Stefan Fischer, from Cambridge University’s Department of Zoology.
“Social animals need to develop social skills, which regulate social interactions, aggression and hierarchy formations within groups. Such skills are difficult and costly to develop, and only beneficial if the early social environment predicts a high number of social interactions continues to be critically important later in life,” he said.
For the study, published this week in the journal The American Naturalist, researchers used the Neolamprologus pulcher (N. Pulcher) breed of cichlid, primarily found in Lake Tanganyika — the great African freshwater lake that feeds into the Congo River.
N. Pulcher lives in family groups with up to 25 individuals, with one breeder pair and several helpers participating in territory defense and raising of offspring — known as ‘cooperative breeding’. To test for social skills, the researchers reared juvenile fish over two months with either three or nine adult group members, and observed all social behaviors at key experimental points.
These interactions included ‘lateral display’ — when one fish interrupts another by displaying their body side-on, sometimes as a mating ritual — as well as ramming, tail quivering, and ‘mouth fighting': a social display in which fish lock mouths to challenge each other over everything from food to mates.
Six month after this test phase, individual fish brains were measured to investigate the long term consequences of early group size on brain morphology, revealing differences in brain architecture.
The researchers say that one of the effects on social behavior in larger groups might be the perception of environmental risk. “In the wild, larger social groups of N. Pulcher represent a low-risk environment with enhanced juvenile survival. Being part of a larger, safer group may increase the motivation of juveniles to interact socially with siblings, enhancing the opportunities to acquire social skills,” said Fischer.
As perhaps with any social creature, Fischer points out that higher social competence and the ability to conform to social hierarchies may well stand the cichlids in good stead in later life:
“Group size for these fish stays relatively stable across the years, they have delayed dispersal. Remaining in a larger group means a better chance of survival. Fish reared in large groups showed more submissive and less aggressive behavior to big fish in the group, social behavior which greatly enhances the survival chances of smaller fish.”
Fischer added: “In highly social animals, such as cooperative breeders, almost all activities involve social interactions, where individuals need to adequately respond to social partners. In larger groups, these interactions are more common and individuals developing sophisticated social skills during childhood might highly benefit from them later in life.”
Source: University of Cambridge
Originally published here: www.sciencedaily.com/releases/2015/05/150507114048.htm