Abstract

Despite the worldwide distribution, toxicity and commercial, industrial and medical impacts jellyfish present, many aspects of their ecology remain poorly understood. Quantified here are important ecological parameters of Chironex fleckeri medusae, contributing not only to the understanding of an understudied taxon, the cubozoa, but also to the broader understanding of jellyfish ecology. C. fleckeri medusae were collected across seven seasons (1999, 2000, 2003, 2005–07 and 2010), with growth rates, temporal variation in the medusae season onset and differences in population structure between estuarine and coastal habitats quantified. With a mean of 2 September ±2 d (mean ±95% confidence limits), the earliest date of metamorphosis was temporally constrained between seasons, varying by only 7 d (30 August to 5 September). Juvenile medusae appeared to be added over an extended period, suggesting polyp metamorphosis was an ongoing process once it commenced. At a maximum of 3±0.2 mm d−1 IPD, medusae growth to an asymptotic size of ∼190 mm IPD was rapid, yet, with the oldest medusae estimated to be ∼78 d in age, medusae did not appear to accumulate along the coastline. Furthermore, a greater proportion of juveniles were observed along the coastline, with estuarine populations typified by larger medusae. With key aspects of C. fleckeri's ecology now quantified, medusae season management protocols can be further developed.

Highlights

  • The occurrence of jellyfish, in blooms, negatively affects a range of recreational, industrial and commercial activities

  • For the Australian tropics, it is the seasonal occurrence of Chironex fleckeri Southcott that significantly impacts the way in which coastal areas are utilised, yet many of the currently favoured theories relating to the temporal variation in medusae occurrence, medusae growth and development as well as population structure are based on sting records or qualitative data

  • A significant and positive relationship was established between the number of tentacles per pedalium and inter pedalia distance (F = 1201.176, df = 16420, n = 422, P,0.001, R2 = 0.740) whereby medusae size (IPD in mm) increased as did the number of tentacles per pedalium (Figure 3)

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Summary

Introduction

The occurrence of jellyfish, in blooms, negatively affects a range of recreational, industrial and commercial activities. Serious industrial issues have been attributed to increased jellyfish abundances, with power station shut down necessary when water intake pipes have become clogged with medusae [4,5,6]. It is the medical liability that jellyfish represent that continues to adversely affect the tourism industry which is often integral to local and regional economies [7]. Despite these significant issues, quantitative data documenting key aspects of jellyfish ecology are, in general, lacking. For the Australian tropics, it is the seasonal occurrence of Chironex fleckeri Southcott that significantly impacts the way in which coastal areas are utilised, yet many of the currently favoured theories relating to the temporal variation in medusae occurrence, medusae growth and development as well as population structure are based on sting records or qualitative data

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