Abstract
The blue swimmer crab (BSC, Portunus armatus) is an economically and culturally important species distributed throughout the coastal waters of the Indo-Pacific region. Reproduction of BSC is poorly understood in south-eastern Australia, a region that is experiencing substantial tropicalisation from global warming. We examined gonadal development, egg–mass relationships, and the influence of temperature on gonadal development and egg production within five different estuaries spanning ~2.5° of latitude. A negative correlation between the gonadosomatic index (GSI, an index of gonadal development and reproductive investment) and hepatosomatic index (HSI, an index of energy storage) was observed in only the final stages of ovarian development. The weight of the egg mass increased logarithmically with body mass, accounting for up to 55% of total body mass, which was significantly larger than observed in other studies. Thermal performance curves showed a peak in individual reproductive output at a mean monthly temperature of ~24°C, at which the individual egg mass weight reached a maximum and the HSI reached a minimum. Environmentally driven variation in BSC reproduction has implications for population productivity and inter-annual variation in recruitment.
Highlights
Portunidae is the family of swimming crabs, characterised by the modified pair of posterior thoracic limbs that are flattened into paddles for swimming (Stephenson and Campbell 1959)
High fishing pressure coupled with declines in recruitment arising from adverse environmental conditions have contributed to declines in several portunid fisheries globally (Tweedley et al 2017), including blue swimmer crabs (Portunus spp. complex) in Western Australia (Johnston et al 2011; Chandrapavan et al 2019) and Callinectes sapidus in Chesapeake Bay, USA (Lipcius and Stockhausen 2002; Zohar et al 2008)
1904 adult female (1538 mature; 366 egg-bearing) blue swimmer crab (BSC) were caught across five estuaries during the 5-month sampling period
Summary
Portunidae is the family of swimming crabs, characterised by the modified pair of posterior thoracic limbs that are flattened into paddles for swimming (Stephenson and Campbell 1959). High fishing pressure coupled with declines in recruitment arising from adverse environmental conditions have contributed to declines in several portunid fisheries globally (Tweedley et al 2017), including blue swimmer crabs (Portunus spp. complex) in Western Australia (Johnston et al 2011; Chandrapavan et al 2019) and Callinectes sapidus in Chesapeake Bay, USA (Lipcius and Stockhausen 2002; Zohar et al 2008). The C. sapidus fishery in Chesapeake Bay is still recovering (Huang et al 2015), and only one of the major P. armatus fisheries in Western Australia, Shark Bay, has rebounded to historic levels (Chandrapavan et al 2019), whereas other fisheries such as Cockburn Sound are showing minimal signs of recovery (Johnston et al 2021a). Measuring the links between environmental variability and recruitment will aid data-driven management of portunid fisheries (Caputi et al 2014; Tweedley et al 2017)
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