Steven G. Johnson via Wikimedia Commons // CC BY-SA 3.0
Steven G. Johnson via Wikimedia Commons // CC BY-SA 3.0

Invasive Comb Jellies Crowd the Adriatic Sea

Steven G. Johnson via Wikimedia Commons // CC BY-SA 3.0
Steven G. Johnson via Wikimedia Commons // CC BY-SA 3.0

In 1982, an unwelcome visitor arrived in the Black Sea. An oil tanker traveling from the American Atlantic dumped its ballast water into the sea, releasing a flood of warty comb jelly stowaways along with it. The alien invaders have since ravaged the area’s native fish populations, and now New Scientist reports that they’ve become a threat along the northern Adriatic coast.

Warty comb jellies (Mnemiopsis leidyi) have been seen in the Adriatic sea since 2005, but this summer marked the first time they’ve been present in such great numbers. Davor Lučić of the Institute for Marine and Coastal Research in Dubrovnik, Croatia told New Scientist that the clusters get as dense as 500 jellies per square meter in some spots. That estimate is based on fully-matured specimens—the number of juveniles is likely even higher.

The swarms have been documented along the Adriatic coast from Slovenia to Pesaro, Italy. Lagoons in northern Italy have been clogged with the creatures since July. The animals pose no direct threat to people, but their appetite has already proven disastrous to whatever ecosystem they invade.

A few of the warty comb jelly's meals of choice include fish eggs, fish larvae, and zooplankton. Zooplankton also happens to be the main food source for many commercial fish in the area. Less than a decade after the introduction of the comb jelly into the Black Sea, local anchovy and sardine fisheries were devastated. The seafood industry had lost billions by the mid-'90s.

Now, there’s threat of a repeat catastrophe in the Adriatic Sea. The mass emergence of the species coincides with anchovy spawning season, a crucial time for one of the sea’s most commercially significant fish. Some scientists are looking on the bright side: the Adriatic is more open and less polluted than the Black Sea, and its local fauna is more diverse. This makes the native populations better equipped to survive the invasion. Additionally, Mnemiopsis leidyi isn’t the sea’s only uninvited guest. Another comb jelly, Beroe ctenophore, has also invaded the waters, and scientists hope the aliens might contribute to one another’s demise.

Mnemiopsis likely entered the Adriatic through a ship’s ballast, the same Trojan horse it rode into the Black Sea. This problem isn’t limited to invasive jellies: A list of destructive species from ants to mussels have been introduced to new environments this way. A global treaty that aims to put an end to the issue will go into effect next year.

[h/t New Scientist]

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Whale Sharks Can Live for More Than a Century, Study Finds
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Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

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Animal Welfare Groups Are Building a Database of Every Cat in Washington, D.C.
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There are a lot of cats in Washington, D.C. They live in parks, backyards, side streets, and people's homes. Exactly how many there are is the question a new conservation project wants to answer. DC Cat Count, a collaboration between Humane Rescue Alliance, the Humane Society, PetSmart Charities, and the Smithsonian Conservation Biology Institute, aims to tally every cat in the city—even house pets, The New York Times reports.

Cities tend to support thriving feral cat populations, and that's a problem for animal conservationists. If a feline is born and grows up without human contact, it will never be a suitable house cat. The only options animal control officials have are to euthanize strays or trap and sterilize them, and release them back where they were found. If neither action is taken, it's the smaller animals that belong in the wild who suffer. Cats are invasive predators, and each year they kill billions of birds in the U.S. alone.

Before animal welfare experts and wildlife scientists can tackle this problem, they need to understand how big it is. Over the next three years, DC Cat Count will use various methods to track D.C.'s cats and build a feline database for the city. Sixty outdoor camera traps will capture images of passing cats, relying on infrared technology to sense them most of the time.

Citizens are being asked to help as well. An app is currently being developed that will allow users to snap photos of any cats they see, including their own pets. The team also plans to study the different ways these cats interact with their environments, like how much time pets spend indoors versus outdoors, for example. The initiative has a $1.5 million budget to spend on collecting data.

By the end of the project, the team hopes to have the tools both conservationists and animal welfare groups need to better control the local cat population.

Lisa LaFontaine, president and CEO of the Humane Rescue Alliance, said in a statement, “The reality is that those in the fields of welfare, ecology, conservation, and sheltering have a common long-term goal of fewer free-roaming cats on the landscape. This joint effort will provide scientific management programs to help achieve that goal, locally and nationally."

[h/t The New York Times]

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