Texas A&M Researchers Improve Methods To Measure Contaminants, Like Mercury, In Fish
Story by Rachel Knight, VMBS Communications
Texas A&M University-led research is filling in data gaps and developing new tools to improve trace elements monitoring of fish and their consumers – including both people and wildlife – in the state of Alaska. Alaska fisheries provide about 60% of total U.S. seafood harvests, according to Alaska’s Resource Development Council, and are key foods for subsistence users.
As examples of these efforts, Dr. Todd O’Hara, a professor in the Department of Veterinary Integrative Biosciences in the Texas A&M School of Veterinary Medicine & Biomedical Sciences, recently published on two Alaskan fisheries-related projects with Dr. Andrew Cyr. Cyr is an Alaska Department of Health environmental toxicologist, studying mercury levels in fish consumed as a delicacy and aiming to improve current sampling and chemical analysis methods.
Contaminants like mercury are a major concern in the fisheries industry and, for some consumers, plays a key role in what seafood they choose to harvest or purchase to eat. Through their research, O’Hara and Cyr are improving Alaska’s ability to monitor fish and strategically advise consumers.
You Are What You Eat
Photo by Trent Sutton, University of Alaska Fairbanks
In their examination of the feeding ecology, or diet patterns, of Arctic lamprey, a delicacy and important food and commercial resource for parts of Alaska with cultural significance to some Native peoples, O’Hara and Cyr found that these fish contain relatively low concentrations of mercury.
“It’s important to recognize that mercury, and several other contaminants in fish, are elements,” Cyr said. “For fish, most of the mercury comes from diet. The same is true for most human exposures. The difference is that fish don’t offload mercury very well. Humans and mammals can offload, or excrete, mercury, but fish have less of an ability to do that, allowing mercury to accumulate in their bodies over time.”
Determining that, unlike other lamprey species, Arctic lamprey contain relatively low mercury concentrations is significant considering that there was no information about mercury or any other contaminants in Arctic lamprey prior to this study. As O’Hara pointed out before this study, one could have assumed similar concentrations occurred in Arctic lamprey, but we now know that would have been erroneous.
“They’re a very sought-after fish and have been for thousands of years,” Cyr said. “They’re also considered a delicacy because of their taste, nutritional content, and oil concentration. We needed to provide information about the level of mercury in these fish because it was a giant unknown.”
The research also concluded that the saying “you are what you eat” is especially true for Arctic lamprey.
Previously, Arctic lamprey were assumed to be parasitic carnivores, but O’Hara and Cyr’s work highlighted they consume fish in a more predatory capacity, targeting fish with high oil content.
“Fat is king in the Arctic. Everything in the Arctic is lipid-dependent, or fat-dependent, because our bodies use more energy and need additional fats to produce energy in the cold,” O’Hara explained. “The fact that these lampreys seem to be sophisticated in how they seek out fat-rich fish means that the fishing and scientific communities still have a lot to learn about them.”
The study also provided evidence that supports a previous hypothesis that the Arctic lamprey diet changes midway through its life cycle, as they documented diet percentage compositions shifted based on size class (i.e., medium versus large).
“In a previous study, a researcher mentioned her suspicion that these fish were changing their diet halfway through life, but there wasn’t enough data to draw a clear conclusion,” Cyr shared. “In this study, we were able to demonstrate that these fish actually do change their diet as they grow larger and more lipid rich, and it makes sense because they are a migrating species.”
Arctic lamprey start inland in muddy, freshwater sediment. They spend their first couple of years in the freshwater environment maturing and eating bacteria and detritus (decomposing organic material) before swimming to the ocean where they spend the next two to five years. Eventually, Arctic lamprey start consuming fish with higher fat content in preparation for their journey back upstream to the muddy, inland waters where they spawn.
“Thanks to this project, there’s very compelling evidence that there’s a shift in their diet as they get larger,” O’Hara said. “Research has traditionally ignored Arctic lamprey, but we’ve proven that it shouldn’t. Thousands of pounds of Arctic lamprey are consumed each year, so it’s important that we start learning more about them. There are conservation and human food needs to consider.”
Punching Up Fish Monitoring Efforts
Photo by Randy J. Brown, U.S. Fish and Wildlife Service
The researchers’ second project determined the effectiveness of a sampling method for mercury measures in fish using a biopsy punch. Biopsy punches – normally a diagnostic testing tool provides a small but deep sample of flesh – can be used to make mercury testing easier by eliminating the need for significant sample preparation as well as faster and cheaper with only limited drawbacks.
The biopsy punch collects a sample about the diameter of a pencil that can be analyzed for certain elements – like mercury, arsenic, cadmium, and lead – that in high amounts can be toxic to consumers. This is accomplished without taking a full filet from the fish like other collection methods that are commonly used in Alaska. O’Hara pointed out that the smaller sample means that relatively larger fish can be released after sampling, thus opening the door for biopsy punch testing to be used for conservation work on species whose numbers are threatened or endangered and to allow fishers to retain most of the edible portion of the fish they catch.
“What we’ve demonstrated is that biopsy punch samples are effective and are ideal for remote communities, resource managers, local health departments, and tribal entities that want to perform their own mercury analysis but may not have a lot of space or financial resources for more costly testing methods and laboratory infrastructure,” Cyr said. “The paper validated the accuracy was sufficient for many applications.”
O’Hara and Cyr explained that the most widely used mercury testing methods in Alaska currently require a full, or near full, filet from a fish, which makes testing a costly endeavor for fishers looking to sell or use their catch. State entities collect and sample the most consumed fish species from bodies of water in their territory to measure contaminants and advise the public on consumption.
Proving the mercury measurement efficacy of the biopsy punch method has the potential to increase sample donation participation and cooperation from fishers and biologists across the state.
“We think biopsy punch testing will enhance participation of fishers in monitoring elements in fish because we’re only taking a very small sample and not walking away with their food,” O’Hara shared. “We really do not like taking food away from people, and we’ve proven that the biopsy punch test is a good alternative that keeps us from having to do that.”
Casting A Net For New Discoveries
According to O’Hara, the two recently published projects are important steps forward in terms of monitoring and addressing fish contaminants. He and Cyr continue working together to improve our understanding of contaminants in fish and determine how best to approach them.
“Both projects improved our capabilities for our fish monitoring program. We took an underrepresented species, got data on it, and developed a new technique that will allow us to expand monitoring into areas where people may have been hesitant to work with a sampling program in the past,” O’Hara said.
“I also conduct research in Mexico, where we’ve been able to prove that some species, like sharks, store mercury in the muscle, while others store it in the liver,” he said. “Andrew and I will be working on determining how that translates to species in Alaska, because that could alter how we think about mercury moving through the food web and how we give consumption advice. There are always interesting questions when it comes to the exciting work of feeding ecology of contaminants in fish up and down the west coast of North America.”
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