A difficult youth is a good thing for a fish

A tough early life turns out to be a good thing for a fish, according to scientists at the University of California, Santa Barbara. They discovered that fish larvae that survive a long, rough, offshore journey eventually arrive at a near shore reef in good condition, and that they thrive afterwards.

In contrast, locally produced young have a relatively easy life and they arrive on the reef (near the area where they were spawned) in a variety of conditions –– from poor to good. Only the young that are in good condition survive after a month on the reef.

“This research delves into one of the major questions of how populations are connected through dispersal,” said Scott Hamilton, a postdoctoral fellow in the Department of Ecology, Evolution, and Marine Biology (EEMB) at UC Santa Barbara. “We want to know where the young of many marine organisms are coming from and going to, and what factors determine whether they survive.”

Hamilton is the first author of the report on the team’s findings, published in this week’s on-line version of the Proceedings of the National Academies of Science (PNAS). The results point to significant policy implications for the planning of marine protected areas, a topic of worldwide concern.

“It turns out that not all settlers arrive equally prepared for the rigors of the reef, and the probability that a new recruit will grow up to reproduce successfully may depend on where it came from,” said Robert Warner, a professor of ecology, evolution, and marine biology.

The scientists used a powerful tool to detect this information: chemical analysis of the ear bone of the fish. The ear bones, also called otoliths, are hard calcium carbonate structures located behind the eyes and below the brain of the fish. The otoliths grow a ring every day from birth, and these rings, like tree rings, hold vast amounts of information about the life of the fish. For example, the spacing of the rings indicates how quickly the fish grew at different periods in its life.

The otolith serves as an internal tag, or tracking device, that reveals the history and location of the fish during its travels. The chemical composition of the ring indicates the type of water in which the fish is located on any particular day.

A fish that is traveling near a populated shoreline collects a higher amount of trace metals, such as lead, in the rings of its otolith. The scientists explain that water near urban areas has higher concentrations of lead due to the run-off from human activities.

Each ocean area has a particular chemical “signature” or “fingerprint” that is incorporated into the ring of the otolith as the fish pass through. Thus scientists are able to map the history of the travels of the fish by chemical analysis of the otolith.

The results surprised the scientists. “This information went against our expectation,” said Hamilton. “We expected near shore fish to get back and do well, particularly because they are in nutrient-rich waters, which is a good place to be.”

As natural resource managers plan for marine protected areas and marine reserves, they need to know the source of the fish living there.

“We have been measuring ‘connectivity’ –– the proportional contribution of different sources to the population in any particular place –– by the numbers arriving,” said Warner. Survival may depend on where the fish originated, he explained.

It is generally agreed that a good knowledge of connectivity between marine populations is critical to spatial management of marine resources, including marine reserves.

The authors point out that connectivity measured by the numbers may be very different from “realized connectivity,” which is determined in part by differing survival rates of the young recruits.

The fish that the scientists analyzed in this study is the bluehead Wrasse, a fish that is common in the Caribbean Sea. Warner has studied the bluehead Wrasse since the late 1970s.

Source: University of California - Santa Barbara

Related stories:

Expeditions reveal gulf of California's deep sea secrets, as well as human imprints
Scientists from Scripps Institution of Oceanography at UC San Diego returning from research expeditions in Mexico have captured unprecedented details of vibrant sea life and ecosystems in the Gulf of California, including documentations of new species and marine animals previously never seen alive. Yet the expeditions, which included surveys at unexplored depths, have revealed disturbing declines in sea-life populations and evidence that human impacts have stretched down deeply in the gulf.
No place like home: New theory for how salmon, sea turtles find their birthplace
How marine animals find their way back to their birthplace to reproduce after migrating across thousands of miles of open ocean has mystified scientists for more than a century. But marine biologists at the University of North Carolina at Chapel Hill think they might finally have unraveled the secret.
Endangered sawfish focus of national collection and recovery efforts
The University of Florida, keeper of the world's shark attack records, is also now overseeing a national records collection for another toothy marine predator: the sawfish.
Salmon-tracking network challenges conventional wisdom
They were two of the 1,000 juvenile salmon implanted with almond-sized transmitters as they headed out of the Rocky Mountains, down the Snake River bound for the sea.
Keep big fish in their small ponds -- or in the ocean, says research
(PhysOrg.com) -- Scientists at the University of Toronto analysed Canadian fisheries data to determine the effect of the "keep the large ones" policy that is typical of fisheries. What they found is that the effect of this policy is an unsustainable fishery.
Science teacher delivers lesson from under the sea
Sixty-three feet below the ocean's surface, the science teacher was giving his morning lesson. "Hi, and welcome to Aquarius for our third and final broadcast from this mission," Mark Tohulka told his third-period marine biology students, watching via webcam from their classroom at MAST Academy in Key Biscayne.
'Gray's Paradox' solved: Researchers discover secret of speedy dolphins
(PhysOrg.com) -- There was something peculiar about dolphins that stumped prolific British zoologist Sir James Gray in 1936. He had observed the sea mammals swimming at a swift rate of more than 20 miles per hour, but his studies had concluded that the muscles of dolphins simply weren't strong enough to support those kinds of speeds. The conundrum came to be known as "Gray's Paradox."
'Fish technology' draws renewable energy from slow water currents
(PhysOrg.com) -- Slow-moving ocean and river currents could be a new, reliable and affordable alternative energy source. A University of Michigan engineer has made a machine that works like a fish to turn potentially destructive vibrations in fluid flows into clean, renewable power.

News discussion:

General Science news