Nest building isn’ t just for the birds, says Paul Naylor, who looks upon the works of a small but mighty fish
CRITTERCONFIDENTIAL
Fifteen-spined( or sea)
stickleback
Spinachia spinachia
Nest building isn’ t just for the birds, says Paul Naylor, who looks upon the works of a small but mighty fish
It’ s around this time of year that divers and snorkellers can enjoy the spectacle of fish building or guarding their nests, an aspect of their behaviour that people not familiar with our underwater wildlife find so surprising. The most abundant and obvious of the builders is the corkwing wrasse, a fish I think of as‘ the colourful craftsman’, in recognition of the courting male’ s
The colourful craftsman, a Corkwing Wrasse with a mouthful of building material
16 glamorous orange and turquoise uniform, as well as his construction expertise. On a shallow rocky reef, I often spot one of these busy builders rushing past with a mouthful of pink seaweed, even if it takes a little more detective work to locate the nest itself.
With more patience and luck, a more rarely seen nest builder can also be observed in shallow water. The fifteenspined stickleback is slender and unobtrusive but has a very distinctive outline with an ultra-slim tail stem and an elongated snout that is reminiscent of pipefish and seahorses, to which it is related. The‘ Fifteen …’ name comes from a row of small spines in front of the single dorsal fin but don’ t worry, you don’ t need to count them to be sure of identification and the number varies anyway so perhaps the‘ Sea …’ name is more suitable.
Whatever the name, the fish’ s brownish colour, coupled with that slender shape and tendency to hang around clumps of tall seaweed or in seagrass can make it extremely easy to overlook. Their nests are even more unobtrusive but, if you look carefully at tall seaweed close to where one is hovering, you might spot some thin glossy threads wrapped around a clump of weed. These threads of protein are secreted by the male’ s kidneys and are what he uses to tie pieces of seaweed together to make his nest. This is usually well clear of the seabed and is where he invites a female to lay her eggs, which he fans and guards for a few weeks until they hatch.