Larval fish off the western coast of Hawaii Island are eating plastic within weeks of hatching, according to a recent study from NOAA's Pacific Islands Fisheries Science Center.
Researchers dissected 658 baby fish and found plastic particles in the stomachs of 42 of them. Some of the affected fish belong to species that people eat, including swordfish and mahi-mahi. Flying fish, another species that had consumed plastic, are an important food source for tuna. This is particularly concerning because plastics ingested by larval fish can potentially travel up the food chain when these animals are eaten by larger fish or birds.
The scientific literature shows that plastics harm a wide array of ocean animals, from sea turtles to crabs to corals. However, NOAA’s study is believed to be the first to focus on plastic ingestion among larval fish in tropical marine ecosystems.
It also highlighted the disproportionate presence of plastics in Hawaii’s surface slicks – long, narrow strips of water that were shown to contain fish nurseries and high densities of larval fish, phytoplankton, and zooplankton. Researchers discovered that the median plastic density in these slicks was 126 times higher than that of surrounding waters.
“To put this into context, median and maximum plastic densities in slicks along West Hawaii were 8.0- and 12.7-fold higher than the respective plastic densities recently sampled in the Great Pacific Garbage Patch,” the authors wrote in their study.
Here, plastics outnumber larval fish seven to one – and as a result, the fish are becoming a little more plastic themselves.
Faux fish food
Larval fish typically eat food that’s smaller than 1 mm, and much of the plastic found in these slicks fell into that category. Researchers suggested that the fish might be confusing plastic filaments for the antennae of the copepods they prey on.
In the context of this study, “microplastics” is too broad of a label for the types of plastics the fish had ingested, co-lead researcher Dr. Jamison Gove told Oceana. The term generally refers to plastics that measure about 5 mm or smaller, but the greatest threat to larval fish could be pieces that are even tinier, at less than 1 mm.
“It's the plastics that we don't see that are potentially the most harmful to the marine food web, and a lot of plastics are broken down from bigger pieces,” Gove said. “They look like they're weathered and fragmented. It's likely that these were once bigger pieces of plastic, like a water bottle, and break down smaller and smaller.”
In addition to larger plastics that break down over time, the types of microbeads that are found in some personal hygiene products are another source of miniscule plastics. And once these foreign objects enter the ocean, they are practically impossible to remove.
“There's not a whole lot that can be done about small plastics less than 1 mm,” Gove said. “I don't know if a technology exists that can clean it up.”
With about 17.6 billion pounds of plastic ending up in marine environments each year, the amount of “prey-size plastics” in ocean slicks is likely to increase as our plastic trash fragments and degrades, the study’s authors noted.
A “death sentence” for baby fish?
In other experiments, some species of plankton, marine worm, and adult fish consumed their food less efficiently after ingesting plastic. Studies have also shown that crabs have difficulty breathing after consuming plastic, and microplastics affect the growth of sea urchins.
But when it comes to baby fish, there’s lots of uncertainty. There has been plenty of research on plastic ingestion among adult fish, but hardly any studies examining ingestion among larval fish.
“Is plastic ingestion a death sentence for baby fish? And if so, what does it mean for adult fish? … (These are) unanswered questions that we hope to answer,” Gove said.
Gove plans to continue researching this topic and is currently looking for funding options. In the meantime, Gove stressed the need to “turn off the tap” and address the root of the problem: the production, sale, and use of single-use plastics.
“Most people would agree it makes little sense to make something that lasts for hundreds of years that we only use for minutes, at most,” Gove said.
He added, “We have every ability as society to take steps as necessary to reduce plastics going into the ocean and, more importantly, to reduce the sale and use of plastics.”
What Oceana is doing to help
Oceana is leading a multipronged, international plastics campaign to stem the tide of single-use plastics. One way of tackling this issue is by targeting the packaging sector, which is responsible for the largest chunk of plastic products. Oceana believes that consumers should be given more plastic-free options, and our campaigners are working to ensure that major companies rise to meet this demand.
On the policy side, Oceana supports mandates at all levels of government, from the local to the national level, that limit or ban single-use plastics. Following campaigning by Oceana and our allies, Peru passed a law in December 2018 that bans plastic bags and reduces the use of plastics in protected areas.
You can help, too. Visit our plastics campaign page to take the #BreakFreeFromPlastic pledge and join us in securing a plastic-free future for baby fish.