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Zoology Publications from Victoria University of Wellington—Nos. 54 to 57

Spawning and Development

Spawning and Development

In the Lyall Bay and Island Bay areas near Wellington T. melobesia spawns from early September to late December. Egg masses are found beneath smooth stones which remain covered with water at low-tide. The egg clusters range from 0.5 cm in diameter, containing as few as three eggs, to about 8 cm in diameter and containing several hundred eggs. The eggs are laid close together forming flat, irregular-shaped masses.

The larger egg clusters always contain groups of eggs which differ in colour, ranging from bright crimson to pale pink. This variation in colour represents the progressive depletion of the yolk supply in the eggs of each group as development advances. It is strongly suggested therefore that the eggs are laid at different times on the same stone. The pale yolked eggs, being the most advanced in development, are found mainly in the middle of the egg masses. However, the difference in development of eggs of some adjacent groups is relatively very small, indicating that these egg groups are laid no more than one to two days apart.

The absolute fecundity of T. melobesia is apparently very low, as determined from 10 gravid females each of which was found to contain only 20–30 ripe eggs. Considering the apparent low fecundity and the close development of the adjacent groups within a cluster it is concluded that more than one female is responsible for egg clusters that contain several hundred eggs.

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Approximately 60 egg clusters were examined in rock pools in the Wellington area, of which about 80% had an adult T. melobesia in attendance. In these cases it was not clear whether this was a male or an immature female. When two adults were found close to the eggs the female could be distinguished by her characteristic pink and distended belly (the condition of a gravid female). Parental vigilance occurs commonly in littoral fish. Gibson (1969: 385) observes that predation on the eggs is prevented by the guardian activities of one of the parents, usually the male. Runyan (1961: 118) also states that "...eggs in good condition were usually accompanied by a male Gobiesox strumosus, that kept them constantly aerated by fanning anal and caudal fins...."