Biological observations during rearing experiments with the garfish Belone belone

Abstract

The garpike Belone belone enters the Wadden Sea in April, to spawn in May and June. The large eggs (3mm) bear numerous, long hair-like filaments. Embryonic and larval development were investigated during rearing experiments in 1970 and 1971. The development of the embryo is described, with special reference to the circulatory system and “Kupffer's vesicles”. The embryos display ventilation with pectoral fins and gill opercula when still in the egg. They hatch after 2 or 3 weeks at 20° and 16°C, respectively. Newly hatched larvae accept a wide variety of prey, including dry, aquarium fish food. Growth, feeding behaviour, swimming performance, and survival of the juveniles were investigated in the laboratory and in a small outdoor pond. Young garpikes (1 to 3 cm standard length) survive at temperatures ranging from 13° to 25°C, and salinities from 7 to 50%. They may reach 12 to 15 cm in their first summer. Their cruising speed is estimated to be 1 to 2 body lengths/sec. Garpikes disappear from The Wadden Sea in October, and probably migrate offshore. Observations on the behaviour of adults (40 to 70 cm total length) in a large indoor tank, indicate that they avoid high light intensities in winter. Adults display panic reactions when the water temperature drops below 6° to 7°C; this indicates that garpikes probably migrate in winter to greater depth (lower light intensity), to avoid water temperatures below 6°C and rough weather conditions in the upper water layers.