Introduction

Aquatic debris of anthropogenic origin has been paid attention internationally for some time (Miranda et al., 2016), and the aquatic environment has shown to be severely affected by the impact of these materials (Lusher et al., 2013).

Since the second half of the 20th century, there are many reports on ingestion of aquatic debris by different organisms all over the word (e.g. Kühnet al., 2015). Ingestion of aquatic debris can cause wounds, ulcerating sores, blockage of the digestive tract leading to starvation and death, reproductive inability, and failure to avoid predators (Oehlmann, 2009; Wright et al., 2013). In nature, fish are likely to come in contact with debris and get affected, but the likelihood is lower if compared with seabirds or turtles, where the prevalence of plastic ingestion is high (Van Franeker et al., 2011). So far, there are 18 species of rays/sharks, and 74 other fish species that have been found to ingest marine debris (Kühn et al., 2015). In the family Gadiedae, there are report on ingestion of marine debris (e.g. Foekema et al., 2013), and plastics (Rummel et al., 2015), such as plastic cups (Hoss and Settle, 1990).

Plastic materials are the most common debris that is ingested by fish and other aquatic animals (Van Franeker et al., 2011). Other materials with different sizes such as fishing net scraps, and pieces of wood and ropes have also been reported to be ingested by fish (Laist, 1997; Possatto et al., 2011). Much of the marine debris stems from consumer goods, and beverage cans, bottles and alike are one of the commonest marine debris found (Sheavly and Register, 2007). In Norway, there are several newspaper reports on different debris, including beverage cans in the stomach of Atlantic cod (Gadus morhua, Linnaeus, 1758), a commercially important species.

Except for the historical record by Gudger (1949) on a shark that had ingested a tin, there are no reports on such incidence. The aim of the present study is to report on this subject, which is an important aspect of sea pollution by debris, and its effect on marine organisms. It is about an unusual incident of a cod individual ingesting a beverage can and its potential impact.

1 Material and Methods

The 680mm (TL) and 2888g specimen used in this study was caught at depth of 4 meters in a fyke net in the inner part of Masfjorden, a narrow fjord in Western Norway, which is a relatively undisturbed area, with few people living there and very little boat traffic. The fyke net is a traditional fishing gear for costal cod in Norway, which consist of a leader connected to a funnel shaped trap. The fyke net was put out on 15th November 2013. The fyke net was collected on 21st November 2013. In total, 14 cod were caught. On the day of collection, the fish was radiographed with a Porta 100 HF (Eickemeyer Medizintechnik für Tierärzte KG, Tuttlingen, Germany) at 40kV and 10 mAs onto a 35x43cm image plate in a rigid cassette (Dürr Medical, Bietigheim-Bissingen, Germany) from 70cm above. The image plate was subsequently scanned with a CR 35 VET, Dürr Medical and converted into a digital TIFF file with Vet-Exam plus Software, version 4.14.0. The images were further processed using Adobe Photoshop, version CS2. During evaluation of the radiographs we detected the cod with the can inside the stomach. After the radiological examination all 14 fish were put at 40 meters depth inside a pot to study barotrauma effects in a separate study (Humborstad et al., 2016).

2 Results and Discussion

At the same day as the specimen was caught it was put at 40 meters depth inside a pot with 13 other cod. At this stage the fish was alive and active. Four days later a video record showed a motionless cod inside the trap. On 2nd December 2013, when the pot was brought to the surface, the fish was found dead inside the pot.

The fish had decomposed to a state where dissection was no longer possible. Neither had the radiographs been analyzed, so we did not know the presence of the can at this stage, and it was for that reason not retrieved. The can observed inside the stomach of the cod was not a full length can (344 mm), only the top of the can with a diameter of 67 mm was left, and it looked from the radiograph that the lower part was eroded away or chopped off (Figure 1).

The presence of undigested bone in the front of the can (Figure 1) may suggest that the can was blocking the normal passage through the digestive tract. When trapped in fyke nets, cod often eat smaller fish that are also trapped inside the net (authors own observation). The cod in the present study may have had a reduced feeding capacity due to the ingestion of the relatively big can; being able to feed on easily caught prey inside the trap, the cod may have ingested more than it could handle with a blocked digestive tract. In addition to the blockage of the intestine by the beverage can, there might have been other factors that caused the death of this fish. Damage of the internal organs or tissues by the piece of litter such as can, the possible infection by germs transferred to the fish by the can, and the stress condition that the fish was in is all plausible reasons for the death of this fish.

The present finding of a tin can inside the stomach of a cod along with several newspaper reports on similar cases in Norway, especially in urban areas, sheds light on the ability of fish to ingest such hard and large materials on one hand, and it conveys a message to the decision makers to take extra measures to limit the amount of debris that finds its way to the aquatic environment.

The works of Van Franeker et al. (2011), Foekema et al. (2013) Trevail et al. (2015) and Herzke et al. (2016) showed that the coasts of Norway have different levels of pollution by marine debris, which in turn have impacts on the marine organisms in this part of the world.

Though significant advances in degradable materials are being developed, the preventive actions of avoiding marine debris in the first step should be strengthened. Prevention, reduction and control of marine debris should be obtained through an effective collaboration of education, legislation and innovation (Sheavly and Register, 2007).

References

Barnes D.K.A., Galgani F., Thompson R.C. and Barlaz M., 2009, Accumulation and fragmentation of plastic debris in global environments. Philosophical Transaction of the Royal Society B: Biological Sciences 364, 1985-1998.

http://dx.doi.org/10.1098/rstb.2008.0205 PMid:19528051 PMCid:PMC2873009

Boerger C.M., Lattin G.L., Moore S.L. and Moore C.J., 2010, Plastic ingestion by planktivorous fishes in the North Pacific Central Gyre. Marine Pollution Bulletin 60, 2275–2278. 

http://dx.doi.org/10.1016/j.marpolbul.2010.08.007 PMid:21067782

Carpenter E.J., Anderson S.J., Harvey G.R., Miklas H.P. and Peck B.B., 1972. Polystyrene spherules in coastal waters. Science 178, 749–750.

http://dx.doi.org/10.1126/science.178.4062.749 PMid:4628343

Foekema E.M., De Gruijter C., Mergia M.T., van Franeker J.A., Murk A.J. and Koelmans A.A., 2013, Plastic in North Sea Fish. Environmental Science and Technology 47, 8818-8824.

http://dx.doi.org/10.1021/es400931b PMid:23777286

Gudger E. W. 1949, Natural history notes on tiger sharks, Galeocerdo tigrinus, caught at Key West, Florida, with emphasis on food and feeding habits. Copeia 1, 39-47.

http://dx.doi.org/10.2307/1437661

Herzke D., Anker-Nilssen T., Nøst T. H., Götsch A., Christensen-Dalsgaard S., Langset M. and Koelmans A. A. 2016, Negligible Impact of ingested microplastics on tissue concentrations of persistent organic pollutants in Northern Fulmars off coastal Norway. Environmental Science and Technology 50, 1924-1933.

Hoss D.E. and Settle L.R., 1990, Ingestion of plastics by teleost fishes. In: Proceedings of the Second International Conference on Marine Debris (Shomura, R.S. and Codfrey, H.L., eds.), 2–7 April 1989, Honolulu, Hawaii, 1990. US Department of Commerce, NOAA Technical Memorandum NMFS, Washington, DC, USA, pp. 693–709.

Humborstad O.B., Ferter K., Kryvi H. And Fjelldal P.G. 2016, Exophthalmia in wild-caught cod (Gadus morhua L.): development of a secondary barotrauma effect in captivity. Journal of Fish Diseases DOI: 10.1111/jfd.12484 (On line version).

http://dx.doi.org/10.1111/jfd.12484

Kühn S., Bravo Rebolledo E.L. and van Franeker J.A., 2015, Deleterious effects of litter on marine life. In M. Bergmann, L. Gutow and M. Klages (Eds.) Marine Anthropogenic Litter. pp.75-116.

http://dx.doi.org/10.1007/978-3-319-16510-3_4

Laist D.W., 1997, Impacts of marine debris: entanglement of marine life in marine debris including a comprehensive list of species with entanglement and ingestion records. In: Marine Debris: Sources. Impacts and Solutions (Coe, J.M. & Rogers, D.B., eds.) pp. 99–139. Frankfurt, Germany: Springer.

http://dx.doi.org/10.1007/978-1-4613-8486-1_10

Lusher, A., McHugh, M. and Thompson, R. (2013). Occurrence of microplastics in the gastrointestinal tract of pelagic and demersal fish from the English Channel. Marine Pollution Bulletin 67, 94-99.

http://dx.doi.org/10.1016/j.marpolbul.2012.11.028 PMid:23273934  

Miranda D.d.A. and de Carvalho-Souza G.F. 2016, Are we eating plastic-ingesting fish? Marine Pollution Bulletin 103, 109-114.

http://dx.doi.org/10.1016/j.marpolbul.2015.12.035 PMid:26763323

Neves D., Sobral P., Ferreira J.L. and Pereira T., 2015, Ingestion of microplastics by commercial fish off the Portuguese coast. Marine Pollution Bulletin 101, 119-126.

http://dx.doi.org/10.1016/j.marpolbul.2015.11.008 PMid:26608506

Oehlmann J., Schulte-Oehlmann U., Kloas W., Jagnytsch O., Lutz I., Kusk K.O., Wollenberger L., Santos M., Paull G.C., Van Look K.J.W. and Tyler C.R., 2009, A critical analysis of the biological impacts of plasticizers on wildlife. Philosophical Transaction of the Royal Society B: Biological Sciences 364, 2047–2062.

http://dx.doi.org/10.1098/rstb.2008.0242 PMid:19528055 PMCid:PMC2873012

Possatto F.E., Barletta M., Costa M.F., Ivar do Sul J.A. and Dantas D.V., 2011, Plastic debris ingestion by marine catfish: An unexpected fisheries impact. Marine Pollution Bulletin 62, 1098-1102.

http://dx.doi.org/10.1016/j.marpolbul.2011.01.036 PMid:21354578

Sheavly S.B. and Register K.M., 2007, Marine debris and plastics: environmental concerns, sources, impacts and solutions. Journal of the Polymers and the Environment 15, 301-305.

http://dx.doi.org/10.1007/s10924-007-0074-3

Trevail A. M., Gabrielsen G. W., Kühn S. and Van Franeker J. A. 2015, Elevated levels of ingested plastic in a high Arctic seabird, the northern fulmar (Fulmarus glacialis). Polar Biology 38, 975-981.

http://dx.doi.org/10.1007/s00300-015-1657-4

Van Franeker J. A., Blaize C., Danielsen J., Fairclough K., Gollan J., Guse, N. and Turner D. M. 2011, Monitoring plastic ingestion by the northern fulmar Fulmarus glacialis in the North Sea. Environtal Pollution 159, 2609-2615.

http://dx.doi.org/10.1016/j.envpol.2011.06.008 PMid:21737191

Wright S.L., Thompson R.C. and Galloway T.S., 2013, The physical impacts of microplastics on marine organisms: a review. Environmental Pollution 178, 483-492.

http://dx.doi.org/10.1016/j.envpol.2013.02.031 PMid:23545014