Abstract
Mysids form a large biomass and mediate the benthic–pelagic coupling of numerous estuaries in southern New Zealand. An intra‐annual (2011–2012) field survey in the breeding seasons (i.e. austral spring followed by summer) of mysids Tenagomysis chiltoni and Tenagomysis novaezealandiae , examining the body and brood sizes, was conducted. Samples were collected from six open and eight intermittently open/closed estuaries along the Otago coastline. Brood size of gravid females of T. chiltoni was not significantly related to their body size. Brood size of gravid females of T. novaezealandiae showed a significantly positive relationship with body size in spring but not in summer. It appears that brood size of gravid mysids do not always necessarily depend on body size, but may be influenced by breeding season (e.g. spring) and estuarine typology (e.g. intermittently open/closed).