14 DAY TRIAL // A new scientific study, aimed at understanding the effect that temperature climbs will have on marine species, has shown that species that live shorter lives and have a more varied gene pool are most likely to survive drastic shifts in their regular temperatures, while other, larger fish could face serious problems trying to adapt, because of their longer lifespan.
Apparently, this happens because fish species that are smaller in size benefit from wider "thermal windows," meaning that the temperature ranges between which they can breed and feed are much larger than those bigger fish need to do the same things. The scientists in charge of the study said that, though they haven't tested it yet, their discovery could apply to land animals as well.
"Each species covers a certain range. The ranges overlap, but their windows are not the same. In the Japan Sea, different thermal windows between sardines and anchovies (…) caused a regime shift to anchovies in the late 1990s," explained Hans-Otto Pörtner of the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, one of the authors of the current study.
Some of the largest fish, such as cod, are moving northwards in the Atlantic Ocean, following the temperatures they are accustomed to. But this migration dries them of their energy, and they can lag behind, which implies that females will deposits their eggs in waters that are too warm for their offspring to hatch. Over time, this could lead to a disastrous decline in their population. This also applies to numerous other aquatic species.
All of this is happening because global warming is constantly changing the water temperatures at all latitudes. Around the poles, the water becomes warmer, causing the ice to melt and fish species that depend on the ice are endangered. The same applies to tropical and equatorial zones, where fish are forced to move north.