Breeding pattern and nest guarding in Sicyopterus lagocephalus, a widespread amphidromous Gobiidae.

Amphidromous gobies are usually nest spawners.
Females lay a large number of small eggs under stones
or onto plant stems, leaves or roots while males take care of
the clutch until hatching. This study investigates the breeding
pattern and paternal investment of Sicyopterus lagocephalus
in a stream on Reunion Island. In February 2007
and January 2010, a total of 170 nests were found and the
presence of a goby was recorded at 61 of them. The number
of eggs in the nests ranged from 5,424 to 112,000 with an
average number of 28,629. We showed that males accepted a
single female spawning in the nest and cared for the eggs
until hatching. The probability for a nest to be guarded
increased with the number of eggs within it, suggesting that
paternal investment depends on a trade-off between the
reproductive value of the current reproduction and future
nesting events. We showed that large nest stones were
occupied by large males (TL [80 mm), whereas smaller
males (TL \50 mm) were found under smaller cobbles,
probably because of male–male competition for available
nests. Our results suggest that the male’s choice relies upon a
similarity to the female size, while the female’s choice was
based on both body and nest stone sizes.