Irish Pike Investigations

Abstract

The spawning of pike was studied in 1965 and 1966 in five large Irish limestone lakes-Loughs Sheelin, Ennell, Mask, Corrib and Arrow. The spawning period was found to be February to April. Spawning took place in shallow, sheltered situations where there was a carpet of dead or living vegetation on the bottom at a depth of 20 to 60 cm. Spawning took place by day, at a water temperature of at least 9-1O C, when lake levels were high or rising. Gill-net catches reached a peak during periods of spawning. Weather conditions in February and March were much milder in 1966 than in 1965, and spawning began about a month earlier than in 1965. The eggs of Irish pike are 2.7 to 3.0 cm in diameter. They are golden to honey coloured, with a great many minute oil-globules distributed through the yolk in numerous tiny clusters. The incubation period in the field is probably 8-14 days, and the newly hatched larva is 8.0-9.0 mm long. For the first 10 days or so, the larvae hang vertically from the vegetation by means of adhesive glands on the head. They then become free-swimming, and soon afterwards begin to feed. At this stage they measure 13.0-13.5 mm. Their first food consists of small cladocera and copepods. Later, they feed on larger cladocera, amphipods, isopods, young stages of aquatic insects, and fish fry.