Ed Yong reports for Phenomena (a National Geographic blog) that a team of scientists has published a paper on the subject of how large marine animals grow. Not having to work against gravity, marine fauna can attain sizes that are beyond the reach of the largest land animals. There is, however, a tendency among those who make a living from the sea to – shall we say – exaggerate the dimensions of the creatures they catch, watch or photograph. Tony and I chuckle to ourselves about accounts (on facebook, unsurprisingly) of nearly six metre white sharks being spotted weekly in False Bay. In reality a great white shark of that size is uncommon.
The authors did exhaustive research to come up with best estimates for the maximum sizes of a range of creatures from whale sharks to giant isopods. They trawled museum collections, the scientific literature, newspaper archives, and even eBay to get hold of verifiable, accurate measurements for each creature. For some species the researchers were able to produce a size distribution – useful because, as Yong points out, “life mostly plays out in the middle.” The average-sized specimens (including False Bay’s white sharks) are the ones most likely to be seen. For some species, including white sharks, evidence suggests that their average size has been decreasing through time, which is a cause for concern.