A difficult youth is a good thing, at least for a fish.
Researchers in the United States have carried out a study and found that fish larvae which survive a long, rough and offshore journey eventually arrive at a near shore reef in good condition, and 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.
According to lead researcher Scott Hamilton of the University of California, "This research delves into one of the major questions of how populations are connected through dispersal."
"We want to know where the young of many marine organisms are coming from and going to, and what factors determine whether they survive."
The researchers came to the conclusion after they did a chemical analysis of the ear bone of a fish -- the bluehead Wrasse that is common in the Caribbean Sea -- by using a tool.
The ear bones or otoliths are actually hard calcium carbonate structures located behind the eyes and below the brain of the fish.
A fish that is travelling near a populated shoreline collects a higher amount of trace metals, such as lead, in the rings of its otolith. Water near urban areas has higher concentrations of lead due to 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 the researchers are able to map the history of the travels of the fish by chemical analysis of the otolith.
The results surprised them. "This information went against our expectation. 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," the
quoted Hamilton as saying.
The results of the study have been published in the 'Proceedings of the National Academies of Science' journal.