I've never heard of gribbles before, & did wonder if they were in some way related to tribbles (or a certain US politician's hair...). But no, it turns out that gribbles are small, wood-boring crustaceans. And they look rather cute:
Image by Prof Simon McQueen-Mason & Dr Simon Cragg
However, their cuteness should not obscure the fact that gribbles (and their partners-in-crime, the molluscan shipworms & crustacean pillbugs) do a significant amount of damage to the wood of piers, jetties, & vessels. For this reason (Powell, 2012: 326)
Even in today's more ecologically oriented society, a motion to conserve the 'gribble' would receive little support along the world's waterfronts
And how did I find out about gribbles? Well, a good friend & colleague is a co-author on a just-published paper on the environmental history of marine woodborers (Rayes, Beattie & Duggan, 2015). The authors begin by saying that
While depictions of mariners fighting fearsome sea monsters or battling terrifying storms entertain us to this day, it is perhaps ironic that one of the main threats to commerce over the last millennium or more has come from a series of very small organisms whose history has been submerged in historical accounts.
The depredations of marine woodborers on these structures created headaches for governments, shipping companies and export industries alike, as authorities and companies grappled with the need to repair crumbling infrastructure and ships (ibid).
between 1995 and 1997, New York experienced severe woodborer damage, resulting in a 21-metre wharf section dropping into the East River and a six-metre section plunging from the Brooklyn pier (ibid).
the effects of gribbles [on the Timaru wharf] were compared to 'the suckling of a sugar stick by a sweet-toothed infant' (ibid).
Woodborers provide important ecological services within mangrove ecosystems and along coastlines by removing the build-up of dead woody debris, through increasing their rate of decomposition (ibid).
There is nothing remotely heroic about fighting a minute-sized shipworm when one could be grappling with a terrifying octopus ... [Marine woodborers] can offer neither the mystery nor appeal of a whale, still less the terror of a Great White Shark, or the cuteness of a dolphin. They have all the appeal of a snail or a slug, and probably induce the same inclinations ...Yet the fact that gribbles don't sell books or invite the same warm feeling or terror as larger creatures of the sea should not stop us from attempting to rescue them from the enormous condescension of posterity [that ignores their significant role in maritime history].
Powell, C.E. Jnr (2012) Isopods other than Cyathura. pp325 - 343 in Hart, C.W.Jnr (Ed) Pollution Ecology of Estuarine Invertebrates. pub Elsevier.
Rayes, C.A, Beattie, J., & Duggan, I.C. (2015) Boring through history: an environmental history of the extent, impact and management of marine woodborers in a global and local context, 500 BCE to 1930s CE. Environment and History 21(4): 477 - 512. doi: 10.3197/096734015X14414683716163