Wednesday, 6 July 2016

Capelin and Climate Change

Capelin are what is known as an r-selected species, which means that their strategy as a species is focused on quantity or high growth rate, instead of investing heavily into any single member of their species (such as humans, whales, etc). As such, finding ideal conditions to reproduce in are fundamental in the same sense that education is fundamental to people, as a strategy.

El Niño is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific and this can affect global climates in a variety of ways. Its impact on the Atlantic is generally considered negligible as far as Newfoundland itself is concerned when we are specifically looking at surface ocean temperatures. However it does have the effect of heating up waters to the south such as in the Gulf of Mexico.

This may be important because capelin are pelagic fishes, "pelagic" is derived from Greek πέλαγος (pélagos), meaning "open sea". These are essentially fish that live near the surface of the sea but not around the coast. Therefore, climatatic events such as El Niño affect them adversely because surface ocean temperatures are the most susceptible to change.

As one could imagine, the bottom of the ocean is the most impervious to light for example, in fact it is fairly resistant to any particular variable because the surface is there to absorb most of the impact (although the species that live below the surface are heavily dependant on the surface). The surface ocean temperature has been heating up over the last hundred years or so in general, but climatic events such as El Niño could have potentially altered conditions further.

To add to the complexity of these conditions, the pelagic or "open sea" areas off the coast of Newfoundland and Labrador are either one of or perhaps the only location in the entire world that has been experiencing cooling. Fish like capelin actively seek cooler waters. Locations such as this area of water that is approximately 500 kilometers off the coast of Newfoundland allow these capelin the opportunity to avoid the adverse effects that El Niño and global climate change could have upon them.

Why might this area be cooling when the rest of the world is almost positively heating up? It is thought that the melting glacier water from Greenland, which is fresh water, is entering the Atlantic. This cold, fresh water - which has a tendency to rise above the warmer salt water - is weakening the warm Gulf current. These factors may have been involved in the weakening of the cod fishery in Newfoundland. The heart rate of cod fish can change drastically with temperature change of a few degrees. Cod tend to go deep into the water during the day and closer to the surface at night.

It may also perhaps affect capelin in some way. It remains to be seen how. Perhaps it is not a negative situation as far as capelin are concerned, but it is just important to understand what the unique conditions are out there so if we notice sigificant increases or decreases within this species, then we may be able to attribute these quantity changes to a particular event. This is especially important to consider as we are actually inside an event known as "La Niña", which more often than not, tends to follow El Niño. La Niña generally means cooler temperatures in the Pacific, but warmer in the Atlantic. We are in a La Niña event right now.

La Niña 

Written by Andrew Young


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