Periodic swimming behaviour of amphipods in Wellington Harbour

Abstract

Twenty-four hour, lunar-month, and seasonal, samples of amphipods were taken using a light trap from Karaka Wharf, Wellington Harbour, New Zealand (41° 16'S, 174° 51'E). Average number of amphipods for the 31 night samples was 255 per 30-min sample; few amphipods were caught in daylight samples. Algae-dwelling species formed 80.6%, infaunal species 16.6%, and pelagic species 2.8% of the total amphipods caught. Infaunal species appear early in the dark period and numbers decline during the night; numbers of algae-dwelling species build up during the night and reach a peak before dawn. Numbers of infaunal species increase on days 1 and 20 of the lunar month, whereas algae-dwelling species show no lunar rhythmicity but numbers increase in turbulent sea conditions. Seasonal sample numbers were erratic, greatest numbers being taken in early August and small peaks coinciding with spring and autumn sea temperature changes.Peak, swimming activity by adults of the infaunal lysianassid Parawaldeckia stephenseni was on the early ebb tide; juveniles continued to swim until dawn. Ovigerous females were present in the swimming population from days 1 to 12 of the lunar month; non-ovigerous females are mated by day 24 and disappear from the swimming population. Males swim throughout the lunar month. Average number of eggs carried is 12, females mature at 3.6 mm, and numbers of eggs carried increase after each successive moult.

MBACI sampling of an episodic disturbance: Stormwater effects on algal epifauna

“…Night time sampling of dispersing amphipods in algal beds found greater numbers in the water column during heavy seas than calm conditions, suggesting dislodgement of amphipods from seaweeds by strong currents and large waves (Fincham, 1974). In addition, the abundance of epifauna is frequently lower on algae at exposed sites than the same algal habitat in protected areas (Sánchez-Moyano et al, 2000, Tararam and Wakabara, 1981, Yassini et al, 1995.…”

Importance of wave and current exposure to fauna communities in Laminaria hyperborea kelp forests

“…A rich and abundant mobile macrofauna, dominated by crustaceans and gastropods, is associated with kelp, and the largest abundances are found in association with epiphytic algae on kelp stipes (Norderhaug et al 2002). Wave forces may result in a considerable loss of fauna due to physical dislodgement from the kelp (Fincham 1974, Fenwick 1976. Wave exposure has also been found to increase diversity of macrofauna associated with epiphytic algae in kelp forests on the Norwegian coast (Christie et al 2003).…”

Sediment Transport and Disturbance on an Intertidal Sandflat: infaunal Distribution and Recolonization

“…Amphipods and other crustaceans are important prey for fishes (Fincham, 1974;Beukema, 1976) and are more subject to predation without the protection of the infaunal habitat (Nelson, 1979). This flow to planktonic predators may b e particularly significant when juvenile amphipods are abundant in the water column.…”