Catchability and sampling of three species of juvenile penaeid prawns in the Embley River, Gulf of Carpentaria, Australia

Abstract

Tidal, diurnal, lunar and seasonal cycles of catchability of juvenile Penaeus merguiensis, P. esculentus and Metapenaeus endeavouri were investigated. P. merguiensis catches were primarily influenced by the tidal cycle and secondarily by the day-night cycle. Largest catches were usually on the last stage of the ebb tide which had the greater range of the daily tides. When the two ebb tides were of equal amplitude more prawns were caught during the night tide. Catches of M. endeavouri were most strongly influenced by the day-night cycle; virtually no prawns were caught during the day. P. esculentus catches were least influenced by the tide and day-night cycles although, in general, more were caught at night and towards low tide. All species were more active near high tide and catches were lowest at this time. Towards low tide, activity decreased and catches increased. However, when water levels were very low, P. esculentus and M. endeavouri buried in the substrate and, therefore, were not catchable by trawling. P. merguiensis did not bury, but concentrated near the shallow water's edge at low tide, and catches were highest then. -from Authors