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Zoology Publications from Victoria University of Wellington—Nos. 63 and 64

Spawning and Development of T. Pinnulatus

Spawning and Development of T. Pinnulatus

In the Lyall Bay area T. pinnulatus begins spawning early in July and continues through to mid-October. South of Cook Strait spawning occurs later. Along the Canterbury coast north of Christchurch the "Earliest records of spawning in the field were made late in August in both 1962 and 1963" (Coakley 1964). Egg masses are found beneath large and small stones, Haliotis shells and other debris which offer secure shelter and remain covered with water at low tide. The egg mass from which this description is made was small (4 × 1.5cm) and contained 198 eggs. Typically, however, egg masses are large (up to 10 × 7cm) and contain as many as 1500 eggs. Coakley (1964) observed that the earliest spent females were the largest, indicating that the larger fish spawn early in the season.

The eggs are laid close together forming flat, irregular-shaped masses. The larger egg clusters always contain groups of eggs which differ appreciably in colour, that is white, orange, pale pink, crimson-red, or pale yellow. There is little intergrading of these colours. Egg sub-groups differing in colour in this way may be at similar stages of development. The variation in colour, unlike that of D. puniceus, does not represent the progressive depletion of the yolk supply in the eggs as development advances, although as time proceeds there is a paling of page 6the colour of each sub-group. It suggests, rather, that the different coloured sub-groups are laid on the same substrate by different females, and that the variation in yolk colour is due to some biochemical difference between each contributing female.

The male T. pinnulatus found with the eggs in the aquarium remained close to them even when alternative shelter was provided. It lay over the eggs, fanning the pectoral and caudal fins, thus maintaining a constant flow of water over the surface of the egg cluster. This current again helped to prevent the accumulation of detritus on the egg membrane. Well over 90% of the egg masses observed on the shore had an adult T. pinnulatus in attendance. Coakley (1964) showed, by dissection, that the majority of adults found close to the egg clusters were males, but only one attendant adult was sexed in the present study.