Studies on the ichthyoplankton of Wellington Harbour, New Zealand

Abstract

Wellington Harbour was sampled twice monthly from April 1977 to November 1978 at five stations. A 0.60 m Bongo net having parallel 0.500 mm and 0.300 mm nylon monofilament mesh cylindrical conical nets was used horizontally at the surface and at 8 m; a 0.96 m rectangular sledge net with 0.500 m nylon monofilament mesh was used on the bottom. Hauls were made both during the day and at night; a 24-hour station was also occupied. From the resultant 297 samples 335,819 teleost eggs and 24,786 larvae were removed, belonging to 25 families and 52 species. These are described and illustrated. Spotty (Labridae), flatfish (Pleuronectidae), and blennies (Tripterygiidae) contribute most to the ichthyoplankton. Overall ichthyoplankton abundance is greater in late winter to late spring, following closely the period of lower and higher harbour temperature. There are considerable differences in distribution and abundance of the various species, indicating that most of the species spawn in spring; 39 spawn within the Harbour; the remainder spawn outside, their eggs and larvae entering with the tide. Eggs are found throughout the water column but they are more abundant at the surface. Larvae of different species have different vertical distributions. Some species move from their day habitat during the night. In general larvae can avoid the net during the day after the development of fin rays. The 0.500 mm mesh net is inappropriate for general sampling in Wellington Harbour because larvae of some species are lost through the meshes. A 0.300 mm mesh is recommended for future similar studies.