There was an error published in J. Exp. Biol. 219, .
Eqn 1 was presented incorrectly. A ‘−1’ was missing after the ratio of densities, and the subscript of the first instance of the density of seawater (ρsw) was given incorrectly as ‘w’ instead of ‘sw’.
The original equation was: 
(1)
where: 
The correct equation is as follows: 
(1)
where: 
This error was corrected on 21 September 2016 in the full-text and PDF versions of this article. The Advance Article and print version of the article remain unchanged.
The authors apologise to the readers for any inconvenience this may have caused.
