Dashboard Week: Friday

by Valerija Kirjackaja

Today is the final day of Dashboard Week for DS21. Our last dataset is looking at the crab distribution in the Eastern Bering Sea over the last 40 years. The data did not require any significant cleaning, so I was able to start exploring it in Tableau almost straightway.

The data shows that the crab population has been very uneven recently. To stabilise the situation, in 2005, The Bering Sea and Aleutian Islands (BSAI) Crab Rationalization Program was implemented, and although it appears that the total crab population has become much more stable since, looking closer at different crab species, we can see that each species had a spike in a different year.

Apart from that, I noticed that the percentage of legal crab only constitutes a small percentage of all crab caught, and that proportion has generally been getting even smaller in the last two decades.

As with any environmental topic, the rise of global temperatures is often suggested as a potential cause of many problems. After plotting the crab population and location data on a map and highlighting locations with lower temperatures with a darker colour, it seemed that of the larger circles, more of them were darker, which suggested there might be a correlation between water temperature and crab population. However, the scatterplot comparing those two metrics did not show any clear relationship, and neither could I find any evidence of water temperature in the Bering Sea getting warmer over the recent years. In fact, I came across several articles which stated that the water temperature in the Southeastern Bering Sea has actually decreased despite the global warming, but I did not find any good downloadable data to include that in my analysis.

I did find a more apparent correlation between the average depth where the crab are caught and the CPUE (Catch per Unit Effort), which implies that the deeper you go, the more likely you might be to encounter a larger crab population.

Finally, I decided to look at what happens when crab season isn’t particularly fruitful. A Wikipedia article mentioned that with the decline of crab abundance, many fishermen have been forced to diversify and start catching other species. I found some data on cod CPUE in the same area, and my analysis showed that there was indeed an interesting relationship between the two species, whereby a drop in crab CPUE was often followed by an increase in cod CPUE the following year.


Valerija Kirjackaja

Thu 26 Nov 2020

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