New Zealand Journal of Marine and Freshwater Research abstracts

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Distribution, body size, and brood characteristics of four species of mysids (Crustacea: Peracarida) in the Avon-Heathcote Estuary, New Zealand

MALCOLM B.JONES

Department of Zoology University of Canterbury Christchurch, New Zealand

Present address: Department of Biological Sciences, Plymouth Polytechnic, Drake Circus, Plymouth PL4 8AA, U.K.

JACK G. GREENWOOD

JOAN GREENWOOD

Department of Zoology University of Queensland St. Lucia, Brisbane, Australia

Abstract Four species of mysids are resident in the Avon-Heathcote Estuary, Christchurch. Tenago-mysis macropsis is by far the most abundant daytime species and has a wide distribution, not linearly correlated with salinity. Tenagomysis novae-zealandiae and T. chiltoni are much less abundant, increase in number toward the upper estuarine region, and (especially T. chiltoni) have distributions significantly correlated with salinity (P < 0.05-0.001). T. chiltoni has a spring/summer population maximum. Gastrosaccus australis appears to be an obligate nocturnal plankter and its; distribution in the system is unresolved. The largest mysid was T. chiltoni and the smallest T. novae-zealandiae, although there was considerable intraspecific size variation. For all 3 Tenagomysis species, males were mature at a smaller size than females, whereas the opposite was true for G. australis. For each species, ovigerous females generally achieved the maximum size recorded. Embryo numbers carried in the marsupium ranged from 4 to 25 for T. macropsis, from 6 to 19 for T. novae-zealandiae, and from 22 to 39 for T. chiltoni. Embryo sizes for the New Zealand species are in accord with the range found generally for coastal mysids.

Keywords Estuarine mysids; Tenagomysis macropsis; T. novae-zealandiae; T. chiltoni; Gastrosaccus australis; spatial distribution; salinity; body lengths; embryo numbers; embryo sizes; New Zealand east coast

New Zealand Journal of Marine and Freshwater Research, 1989, Vol. 23: 195-199 0028-8330/2302-0195$2.50/0 © Crown copyright 1989 Received 15 June 1988; accepted 7 October 1988

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