Before the bloom: How pre-winter conditions influence jellyfish production

Jellyfish are being increasingly targeted by fisheries, but their complex life cycles make it difficult to predict stock availability. The seasonal recruitment of juvenile jellyfish (ephyrae) is regulated by the reproductive output of the benthic polyp life stage. Within temperate environments, polyps typically undergo strobilation and produce ephyrae in spring. While previous works have documented how winter conditions can influence strobilation success, the potential role of pre-winter environmental conditions on ephyra production remains unknown. This research investigated a well-studied jellyfish species of bioresource interest ( Aurelia aurita ) in a multi-phase experiment designed to a) quantify the effects of temperature and food availability on polyp development, and b) determine how the environmental conditions in which polyps were reared in influence ephyra production and size following a controlled winter simulation. The results demonstrated that warmer pre-winter conditions not only enhanced initial somatic growth rates and bud production, but also increased the likelihood of mature polyps strobilating after temperatures had been reduced. Although polyps grew larger and subsequently produced more ephyrae when pre-winter food availability was increased, the likelihood of strobilation and total ephyra production of polyp populations was unaffected by previous feeding regimes. There was also no relationship between the diameter of parent polyps prior to winter simulation and the mean diameter of their ephyra progeny. Warmer pre-winter conditions could promote strobilation by increasing development rates or strengthening the environmental stimulus when temperatures decrease. These results demonstrate the potential value of considering pre-winter temperature when forecasting the recruitment of jellyfish stocks during summer. • Pre-winter conditions significantly influenced post-winter jellyfish production. • Polyp populations produced more jellyfish when conditioned to higher temperatures. • Food availability had opposite effects on metamorphosis and reproductive output. • Accounting for full seasonal cycles may improve predictions of jellyfish blooms.