Balancing fishery and conservation: a case study of the barrel jellyfish Rhizostoma octopus in South Wales

Abstract

In Wales, the barrel jellyfish Rhizostoma octopus is commercially harvested to produce high-value medical grade collagen. Although the fishery is presently not regulated, there are concerns how it may affect the leatherback turtle (Dermochelys coriacea), which preys on R. octopus in local waters. We combined monitoring data and morphometric and weight measurements in models to estimate the potential impact of R. octopus fishery on foraging turtles. We found a significant quadratic relationship between bell diameter and wet weight of R. octopus, with bell diameter explaining 88% of the variability in wet weight. R. octopus biomass in the Carmarthen Bay varied inter-annually between 38.9 and 594.2 tonnes y−1. The amount of R. octopus needed to satisfy a leatherback turtle’s daily energetic requirements was estimated at 85.1–319.1 kg. Using leatherback turtle sighting data, our models show that during a jellyfish ‘low year”, the R. octopus population could be completely depleted by an average of two foraging turtles along with the current level of commercial harvesting (4.3 tonnes). During a jellyfish “high year”, the current level of commercial harvesting is predicted to have relatively little impact on food supply for even the maximum number of foraging leatherback turtle reported in the area. However, uncertainties related to the jellyfish’s life cycle in the local waters need to be resolved for proper management of this emerging fishery.

Jellyfishing in Europe: Current Status, Knowledge Gaps, and Future Directions towards a Sustainable Practice

“…Operations using suction to extract jellyfish from the water into ship hulls were attempted recently in China [70] and Mexico (D. Edelist, personal communications), but such endeavors are still mostly in the experimental phases [70]. As both food and non-food use emerge and proliferate [2,11,15,60], problems such as "scarring" of jellyfish bells by trawl or other nets cutting into the flesh may be overcome by using thicker netting material, or by division of the catch into edible and non-edible phases.…”

“…Today, main non-food uses of jellyfish include (1) pharmaceutical applications, e.g., purified collagen [60], anticoagulants, mucins, antimicrobiotics, and antihypertensive peptides [10] and therein, as well as bioactive compounds [8] and antioxidant peptides [22]; (2) cosmetics based on moisturizing [61], anti-aging, and UV protection properties of jellyfish extracts [20,62,63]; (3) agriculture as organic fertilizers and pesticides [17,64,65] and seed germination agents for sand dune restoration [15]; (4) animal and aquaculture feeds [10] and therein [66,67]; (5) biotech, with Nobel Prize-winning green fluorescent protein (GFP) hailed as "one of the most useful tools in modern medicine" [7]; and (6) decontamination development using coagulative properties of jellyfish mucus for capturing nano-and microparticles [23,68,69].…”

“…In the only other semi-commercial scale fishery in Europe [60], the barrel jellyfish Rhizostoma octopus is commercially harvested from the Bay of Biscay and Wales (Atlantic), respectively, to produce medical-grade collagen. In 2015, a total of 4.3 tons (wet weight) of R. octopus was collected for this purpose [60].…”

“…Ecosystem stability, minimizing bycatch, and competition with other species are the prime environmental concerns for managers [10,27,60]. Further, overexploitation of jellyfish has been shown to create risks to ecosystem stability [11].…”

Life Cycle of Edible Jellyfish Acromitus hardenbergi Stiasny, 1934 (Scyphozoa: Rhizostomeae) Inhabiting a Brackish-Water Environment

“…In the 1990s, owing to an increasing demand for jellyfish in Asia, edible jellyfish catches increased to larger than those of scallops or lobsters [1]. Recently, jellyfish demand has drastically increased, leading to expanded jellyfish expanded jellyfish fisheries worldwide [2][3][4][5]. Southeast Asia is the center of jellyfish exports; exportation of edible rhizostomes from this region account for the majority of the world jellyfish trade [1,[6][7][8][9], and they are an important commodity for the fisheries industry in this area.…”