Do scientists and fishermen collect the same size fish? Possible implications for exposure assessment

Recreational and subsistence fishing plays a major role in the lives of many people, although most Americans obtain their fish from supermarkets or other commercial sources. Fish consumption has generally increased in recent years, largely because of the nutritional benefits. Recent concerns about contaminants in fish have prompted federal and state agencies to analyze fish (especially freshwater fish targeted by recreational anglers) for contaminants, such as mercury and polychlorinated biphenyls (PCBs), and to issue fish consumption advisories to help reduce the public health risks, where warranted. Scientists engaged in environmental sampling collect fish by a variety of means, and analyze the contaminants in those fish. Risk assessors use these levels as the basis for their advisories. Two assumptions of this methodology are that scientists collect the same size (and types) of fish that fishermen catch, and that, for some contaminants (such as methylmercury and PCBs), levels increase with the size and age of the fish. While many studies demonstrate a positive relationship between size and mercury levels in a wide range of different species of fish, the assumption that scientists collect the same size fish as fishermen has not been examined. The assumption that scientists collect the same size fish as those caught (and eaten) by recreationalists or subsistence fishermen is extremely important because contaminant levels are different in different size fish. In this article, we test the null hypothesis that there are no differences in the sizes of fish collected by Aleut fishermen, scientists (including divers), and commercial trawlers in the Bering Sea from Adak to Kiska. Aleut fishermen caught fish using rod-and-reel (fishing rods, hook, and fresh bait) from boats, as they would in their Aleutian villages. The scientists collected fish using rod-and-reel, as well as by scuba divers using spears up to 90 ft depths. A fisheries biologist collected fish from a research/commercial trawler operated under charter to the National Oceanographic and Atmospheric Administration (NOAA). The fish selected for sampling, including those caught commercially in the Bering Sea, represented different trophic levels, and are species regularly caught by Aleuts while fishing near their villages. Not all fish were caught by all three groups. There were no significant differences in length and weight for five species of fish caught by Aleuts, scientists, and fisheries trawls, and for an additional 3 species caught only by the Aleut and scientist teams. There were small, but significant, differences in the sizes of rock greenling (Hexagrammos lagocephalus) and red Irish lord (Hemilepidotus hemilepidotus) caught by the scientist and Aleut fishermen. No scientists caught rock greenling using poles; those speared by the divers were significantly smaller than those caught by the Aleuts. Further, there were no differences in the percent of males in the samples as a function of fishing method or type of fishermen, except for rockfish and red Irish lord. These data suggest that if scientists collect fish in the same manner as subsistence fishermen (in this case, using fishing rods from boats), they can collect the same-sized fish. The implications for exposure and risk assessment are that scientists should either engage subsistence and recreational fishermen to collect fish for analysis, or mimic their fishing methods to ensure that the fish collected are similar in size and weight to those being caught and consumed by these groups. Further, total length, standard length, and weight were highly correlated for all species of fish, suggesting that risk assessors could rely on recreational and commercial fishermen to measure total lengths for the purpose of correlating mercury levels with known size/mercury level relationships. Our data generally demonstrate that the scientists and trawlers can collect the same size fish as those caught by Aleuts, making contaminant analysis, and subsequent contaminant analysis, representative of the risks to fish consumers.