Fish

Love written in light and sound

Sea horses are famous for one extraordinary fact: the male becomes pregnant. How did it happen that in seahorses, the roles are reversed? No one knows. 

But this biological wonder is only the beginning. Before mating, pairs perform elaborate daily courtship dances. They change colour together, entwine tails, and rise through the water in slow spirals. Hidden within these dances are tiny clicking sounds—soft snaps made by rubbing bones in their heads. 

Coral reef fisheries provide essential food and income for millions of people across the tropics. New research shows that most reefs are currently fished below the level that allows maximum sustainable production. 

While this represents a loss of potential food and livelihoods, it also highlights a significant opportunity: rebuilding reef fish stocks can deliver wide-ranging ecological and social benefits.

Scientists have unveiled a breakthrough tool that lets them identify fish by the sounds they make. By pairing spatial audio with 360° video, researchers have published the most extensive collection of fish sounds ever recorded, capturing a chorus that had remained largely unknown until now.

For the first time, scientists have decoded years of underwater “grunts” made by groupers to reveal how and when they spawn. The study, spanning more than a decade of recordings in the Gulf of Mexico and Western Atlantic, shows that fish sounds can provide vital clues for monitoring populations and detecting changes linked to climate and fishing pressure. 

Clown anemonefish, iconic residents of coral reefs, are now known to physically shrink to survive. A new study in Science Advances monitored 134 clownfish in Papua New Guinea during a 2023 marine heatwave and found that over 70 percent of individuals shrank at least once during the five-month event.

The Marine Conservation Society (MCS) has downgraded mackerel from a sustainable seafood choice to a cautionary amber rating, urging consumers to switch to herring or Cornish sardines instead. 

This groundbreaking research documents the behaviour in several oceanic fish species spanning three oceans. It describes the first recorded instances of fish using sharks and other fish to brush and scrape against, with the goal of freeing themselves of parasites.

The Hades’ snake moray (Uropterygius hades) is a slender, dark brown eel which stands out for its unique adaptations to and preference for dim, turbid environments.

Unlike most of its marine relatives, which thrive in coral reefs, it is at home in estuarine habitats, a characteristic that is unusual among the 230 known species of moray eels. It is distributed across the Central Indo-Pacific, and has been found in southern Japan, Taiwan, the Philippines, southern Java, and Fiji.

In a recent study, researchers investigated how sardines that find themselves on a predator's radar collectively employ collective evasive manoeuvres and how their predators respond to outsmart them.

Using computational modelling and aerial video footage, the team from the Cluster of Excellence “Science of Intelligence” (SCIol), the Humboldt-Universität zu Berlin, the Leibniz Institute of Freshwater Ecology and Inland Fisheries, and Cambridge University focussed on the predator-prey behaviour of striped marlins and sardine shoals in the open ocean. 

When it comes to making its grand entrance into the world, fish embryos do not leave things to chance.

Researchers, led by Dr. Matan Golan of the Hebrew University of Jerusalem and the Agricultural Research Organization-Volcani Institute, have discovered that the hatching process of fish embryos is not a passive process.