Scientists usually assume that in large oceans, fish can travel far, and as a result, different populations of a species would mix freely. However, according to a new study led by the University of Connecticut (UConn), this does not appear to be the case for a vital forage fish called sand lance, a species of small schooling fish that is impressively rich in lipids, which which are an important food source for over 70 different species, from whales and sharks to seabirds.
The experts were interested to see if the sand lance constitutes a massive and homogeneous population, or if there are genetically distinct groups among them. These are crucial questions to ask when it comes to the conservation and sustainable management of this species, because due to climate change, the regions where sand lances live are warming faster than many other places in the world. earth
By sequencing and analyzing nearly 300 samples from different locations across this species’ range using a technique called “low-coverage whole-genome sequencing,” the scientists found an area on the Scotian Shelf (offshore of Nova Scotia), where a It appeared that a genetic break occurred between two different populations of sand lance.
Genomic analyzes helped distinguish two distinct groups, one north and one south of the divide, with parts of their genomes diverging quite dramatically. Without clear physical barriers, such as a mountain range, for example, separating sand lance populations, the existence of these genetic differences represents a scientific conundrum. However, according to the researchers, the answer may lie in the movement of ocean currents.
“When northern fish breed and move south, they’re genetically less adapted to the warmer southern waters, even if it’s five or six degrees warmer in the winter, they just don’t survive,” he said lead study author Hannes Baumann, associate professor. of Marine Sciences at UConn.
“These populations may be linked by ocean currents, but the realized connectivity is basically zero. Example after example shows that the ocean is not as homogeneous a place as expected, and there are all kinds of things that prevent this constant mixing. We found another amazing example of this.”
Knowing that there are genetic and ecological barriers on the Scotian Shelf is important because, due to climate change, this barrier could move north and create problems, especially for southern sand lance populations. Fortunately, the fact that there are only two genetically distinct populations, rather than smaller population groups, could make their management and conservation less difficult.
“We want to make sure that this fish is productive and resilient, despite climate change, so we have to make sure that these areas where they are produced are protected. Those decisions should include experts to make sure that if there there is a very critical area for the sand lance, that any disturbance is temporary,” concluded Baumann.
The study is published in the ICES Journal of Marine Science.
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By Andrei Ionescu, Earth.com staff writer
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