This is a fascinating article, but I'm bookmarking it for the unreadable graphs. It will be a great example for future presentations.
Can you explain your issues with the second graph, it seems perfect fine to me.
The first graph is merely "meh" ... the two key data points for this article are readily apparent: over all harvesting of tuna is increasing and the percentage of shipjack in that harvest is also increasing. What message was this graph supposed to communicate that it did not?
Can you share some specifics about how these graphs are unreadable, and how they can be improved?
The second graph is a little better but even in that one the very similarly coloured blue lines cross each other so you have to really look closely to figure out which is which.
I tried one of datawrapper's sample data sets, "Gender pay gap" and added a couple of extra columns. The resulting line graph has four shades of blue.
https://datawrapper.dwcdn.net/g98Jd/1/
(There are "base color" and "customize colors" buttons so the author could have changed this. Seems like a nice little app).
I guess the point is ... I've seen many, many examples of worse graphs, graphs where the point was obscured or graphs that were deliberately misleading; so I'm trying to figure out how these two are worthy of appearing in a presentation.
That still doesn't cut it: there are 18 fish in the graph key but at first glance the graph has around half that number. The others can be seen if you zoom right in but it's still not easy to hover over the pixel-wide slivers of similar blue.
That said I don't think the tonnage details are the point of this graph but rather a more general message: "Tuna fishing increased 6-fold over 65 years, skipjack makes up most of the increase". I think it communicates this message well. Perhaps more "infographic" than "graph"?