Distribution of hoki (Macruronus novaezelandiae) eggs and larvae in relation to hydrography in eastern Cook Strait, September 1987

Abstract

A detailed survey in September 1987 determined the distribution of hoki eggs and larvae, and the hydrography of eastern Cook Strait. The hydrographic structure was complex, and appeared to be a response to local winds. South Taranaki Bight water occupied much of northern and ceniral Cook Strait. The coastal waters of Cloudy Bay were diluted by river outflows, and plumed offshore, apparently as a result of the same wind conditions that forced water within the Cook Strait Canyon to upwell into Clifford Bay and nearshore regions south of Cape Campbell. East Cape Current water occurred deeper than 200 m in the Cook Strait Canyon, and beyond the shelf edge. Deep mixing south of Cape Palliser indicated the presence of an anticyclonic eddy. Chlorophyll a concentrations were related to the mixed‐layer depth and were highest in vertically stratified1, surface waters. Hoki eggs were most abundant over the Cook Strait Canyon, an area known to be a hoki spawning site. Numbers of small hoki larvae (2,0–3.9 mm) were greatest in areas of high egg abundance and near Cape Campbell, whereas larger larvae (>10 mm) were most abundant in nearshore areas. The distribution of newly hatched larvae suggested that hoki eggs were advected from the Cook Strait Canyon into the nearshore region off Cape Campbell as a result of local upwelling.

Keywords:

• hydrography
• hoki
• Macruronus novaezelandiae
• eggs
• larvae
• chlorophyll
• Cook Strait
• New Zealand