Life history and reproduction of two abundant mysids (Mysidacea: Mysidae) in an intermittently open New Zealand estuary

Abstract

Mysids typically form a large proportion of the hyperbenthic faunal biomass in estuaries and are central to the functioning of estuarine food webs. The population dynamics, annual life histories and reproductive effort of two common temperate estuarine mysids, Tenagomysis chiltoni and T. novae-zealandiae, are described in the intermittently open Kaikorai Lagoon, New Zealand. Mysids were sampled by night, monthly from September 2003 to September 2004. Both species completed their life cycles in the lagoon. There was an apparent spatial separation of breeding populations, with T. chiltoni prevalent in the upper lagoon and T. novae-zealandiae dominating the lower lagoon. Densities were lowest in late winter and peaked in late summer/early autumn for both species. Both species exhibited multivoltine life cycles, with breeding peaks occurring in T. chiltoni. Breeding strategy for both species varied over the year with the adult size, brood size and the reproductive effort of both T. novae-zealandiae and T. chiltoni all being highest in spring. The life histories of both T. novae-zealandiae and T. chiltoni in the Kaikorai Lagoon are comparable to life histories described for other temperate estuarine mysid species in large open estuaries, and were not significantly modified to cope with the unpredictable demands of life in an intermittent estuary.

Late summer hyperbenthic estuarine communities: comparing permanently open and intermittently closed systems along the Otago coastline

“…Mysids were recorded from all estuarine types; four species were present in open estuaries, whereas only T. chiltoni and T. novae-zealandiae were recorded from intermittently closed estuaries. The occurrence of only these two species in intermittently closed systems is consistent with records of mysid abundance collected over one annual cycle in the intermittently closed Kaikorai Lagoon, where only T. chiltoni and T. novaezealandiae were abundant and observed to reproduce during 2004 (Lill et al 2010). …”

Impact of Berm Breaching on Hyperbenthic Macroinvertebrate Communities in Intermittently Closed Estuaries

“…The loss of cohorts or significant numbers of breeding individuals at certain times of the year could have a significant impact on the breeding populations of many invertebrates resulting in altered communities later in the season (Chase 2003;Petraitis et al 2009). This may explain the distinctiveness of communities in individual, intermittently closed estuaries at the regional scale (Griffiths 1999;Lill et al 2010) A key factor determining the magnitude of community disturbance may be the interval between successive breaches. Where breaching occurs less frequently, larger impacts on community structure and taxon richness may occur (e.g.…”

“…Care was taken to collect all samples in new locations, with comparable effort, intensity and to ensure a representative sample of the entire water column across all available depths (e.g. Lill et al 2010Lill et al , 2011aLill et al , 2011b. For the MBAI-2007 study, triplicate invertebrate samples were taken weekly, whereas five replicate samples were taken daily during the BACI-2008 study.…”

“…Lill et al 2010Lill et al , 2011a from the impact of berm breaching, a more intensive controlled design was used (BACI-2008), taking advantage of an artificial breaching of the Kaikorai Lagoon by the ORC. As both artificial and natural openings produce similar physicochemical changes (Dye 2005;Dye and Barros 2005a,b), it is assumed that differences between natural and artificial openings would be minimal.…”