MTN 17:5-7 Plastic Jellyfish

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Plastic Jellyfish

N. Mrosovsky
Departments of Zoology and Psychology, University of Toronto, Toronto, M5S 1A1, Canada
(temporary address: Department of Zoology, ABRG, South Parks Road, Oxford, U.K.)

There are several reports of the occurrence of plastic in the stomachs of sea turtles (Brongersma, 1968, Proe. Koninkl. Nederl. Akad. van Wetenschappen Ser C 71, 128-136; Hirth, 1971, Fisheries Synopsis 85, FAO, Rome; Hughes, 1974, Investigational Rep. 35 & 36, Oceanogr. Res. Inst., Durban, S. Africa; Carr and Stancyk, 1975, Biol. Conserv. 8, 161-172). The suggestion that turtles mistake plastic for jellyfish is not new but no one has attempted a quantitative assessment. This note presents evidence on leatherback turtles, Dermochelys coriacea, showing that ingestion of plastic is common.

Stomach contents of leatherbacks have been admirably reviewed by Brongersma in 1969 (Proc. Koninkl. Nederl. Akad. van Wetenschappen Ser C 72, 76-102); he concluded that jellyfish are a major food item. While working on a monograph on this species, I have assembled more recent data; Drs. Marx, Rhodin, Shoop and Threlfall kindly provided information. Listed below are all the cases since Brongersma's review that I am aware of where stomachs of leatherbacks have been examined, excluding data from a juvenile (Brongersma, 1970, Proc. Koninkl. Nederl, Akad, van Wetenschappen, Ser C 73, 323-335) and from an adult found dead on the beach in French Guiana (Mrosovsky and Pritchard, unpublished). Of course some reports may have been missed and other dissections may have gone unreported. Nevertheless the sample is sufficient to show that the eating of plastic is not just a rarity: 7 out of 16 cases, that is 44% of the leatherbacks examined had plastic (or cellophane) in their stomachs.

With plastic, or cellophane (other stomach contents not listed here).
cellophane sandwich bag (Marx H. pers. comm. 1970)
plastic bags, specimen De 49bis (Brongersma, 1972, Zool. Verhand. 121)
heavy plastic sheet, 3 x 4 m (Hughes, 1974, op.cit.)
several pieces of plastic (Rhodin, A.G.J. pers. comm. 1980; see Figure 1)
plastic and plastic spoon (Rhodin, A.G.J. pers. comm. 1980; see Fig. 1)
small pieces of plastic (Rhodin, A.G.J. pers. comm. 1980)
pieces of plastic bags (Duguy et al. 1980, Ann. Soc. Sci. Nat. Charente-Maritime 6, 681-691)

Figure 1: Plastic from stomachs of 2 leatherback turtles.

Without plastic (other stomach contents not listed here)
Montoya, A.E. (pers. comm. to Pritchard, 1971, IUCN Monogr. 1, Switzerland)
specimen De 63bis in Brongersma (1972, op. cit.)
2 cases, Glüsing (1973, Salamnndra, 9, 77-80)
2 cases, Threlfall, W. (pers. comm. 1979)
2 cases, Shoop, C.R. (pers. comm. 1979, 1980)
Duguy et al. (1980, op. cit.)

For a number of animals the immediate cause of death was becoming entangled in fishing lines; death cannot be attributed directly to the plastic. However, in one case the plastic was so large, 3 x 4 m (Hughes, 1974, op. cit.) and in another (Duguy et al. 1980 op. cit.) the turtle was in such an emaciated state with stomach pathology consistent with an obstruction, that it seems highly probable that the plastic had been harmful. Even the smaller amounts of plastic in the other cases could have made the turtles less healthy by decreasing absorption from the gut.

On the basis of the data given, 44% of adult non-breeding leatherbacks have plastic in their stomachs. An animal that can gulp down a Portuguese man-of-war does not necessarily survive eating an inert plastic bag.

Note added in proof. A recent article reports that 7 out of 8 leatherbacks found in the summer months near La Rochelle, France, had swallowed plastic (Duron, M & Duron, P. 1980. Courrier de la Nature 69, 37-41).