This is a pre-publication notice of scientific findings.
Marine microplastics are a contaminant of concern because their small size allows ingestion by a wide range of marine life. Using citizen science during the Newfoundland recreational cod fishery, we sampled 205 Atlantic cod (Gadus morhua) destined for human consumption and found that 5 had eaten plastic, an ingestion prevalence rate of 2.4%. Compared to other studies, this ingestion rate for Atlantic cod is the second lowest recorded rate in the reviewed published literature (the lowest is 1.4%), and the lowest for any fish in the North Atlantic. We hypothesize that this is because Arctic waters feed the east coast of Newfoundland where samples were collected, and that even though nearly half of the plastics ingested appear to be of local origin, the relatively low population of Newfoundland and Labrador means that local plastic pollution rates are lower than other areas.
Highlights of the study
- Plastic ingestion rate of 2.4% for Atlantic Cod (n=205)
- First recorded baseline for fish in Newfoundland, Canada
- This plastic ingestion prevalence rate is among the lowest recorded to date
- Used citizen science to collect GI tracts from fish destined for human consumption
Details and Background
The accumulation of plastics and their associated toxicants within marine life is of special concern in Newfoundland and other areas where people rely extensively on marine life for food sustenance. This study joins an emerging trend in plastic pollution research that evaluates the plastic ingestion by marine life that is destined for human consumption. In Newfoundland, Atlantic cod (Gadus morhua) is an important species to consider because of its cultural and culinary significance. Up to 82% of households along the west coast of Newfoundland report consuming local seafood more than once a week, of which cod is the preferred food choice (Lowitt 2013). While commercial harvesting of Atlantic cod is strictly controlled (Bavington 2011) people in Newfoundland and Labrador are able to fish for Atlantic cod during the seasonal recreational cod fishery. Individuals are permitted to catch five fish per person per day, with a maximum of fifteen fish per boat outing (Fisheries and Oceans Canada 2015). This takes place during two one-week periods in the summer and early fall (Schrank and Roy 2013; Fisheries and Oceans Canada 2015). During the September 2015 food fishery, we obtained the gastrointestinal (GI) tracts from citizen scientists (both commercial and recreational fish harvesters) fishing on the east coast of Newfoundland to monitor the rate of plastic ingestion in fish destined for human consumption. All fish were Atlantic cod (Gadus morhua). Data were used to determine the rate of ingestion between recreational and commercially caught fish, geographical locations where fish had been caught, and types and characteristics of ingested plastics, including their possible origins.
Of the 205 of cod collected, 5 had ingested 7 pieces of plastic between them (range 0 – 2), an ingestion prevalence rate of 2.4%. However, because our collection method involved local fishermen and women, 27 samples contained only part of the GI tract (usually just the stomach). Because other studies have found that some plastics are excreted by animals that ingest them (Ryan 2015), our protocol called for investigating the entire GI tract of fish. If we omit the samples that were missing the lower GI tract from our analysis, we had 177 of fish, 4 of which ingested plastics, an ingestion prevalence rate of 2.3%. Omitting fish whose entire GI tract was not sampled led to a very small underestimation of plastics and a slightly lower rate of prevalence. Given the small difference in results, we have decided to include fish with only part of the GI tract, which confirms a 2.4% baseline ingestion rate.
Plastics found in the stomachs were of a variety of types: 2 were film/sheet plastic, 2 were threads, and 3 were fragments.
Fish that had ingested plastics came from a variety of locations. Two were from Petty Harbour, three from Portugal Cove, one from Quidi Vidi, and one from Bell Island. This distribution is wide given that the vast majority of fish sampled were from Petty Harbour (32.2%) and Portugal Cove (40.5%), with only 11 (5.4%) fish from Belle Island and 3 (1.5%) from Quidi Vidi. Other locations account for the remaining 20.4% of catch. All samples were collected on wharves at Petty Harbour and St. Phillips, which accounts for the higher prevalence in samples from those locations. Fish harvesters are required by law to gut their fish onshore rather than at sea, making wharves the ideal locations for gathering samples.
Most fish sampled (n=188) were from the recreational cod fishery, while 17 were from the commercial fishery, all of which were destined for human consumption. All plastics were found in fish from the recreational fishery. The recreational fishery uses rods and lines to catch fish and stays close to shore (Protected Areas Association of Newfoundland and Labrador 1996). The commercial fishery, which contained no fish that ingested plastic, used bottom trawls further offshore (this is not true of all commercial fisheries in Petty Harbour, but was the case for the fishery we received samples from).
These results were presented at a public meeting in Petty Harbour, Newfoundland, in Feb 2015, and we were granted permission to publish the results in academic papers. These results have also been disseminated via radio (particularly CBC’s Fisheries Broadcast), and television. For more information, or to obtain the academic publication of these results, please contact project leader Max Liboiron, firstname.lastname@example.org.