Once mercury enters a lake, it works its way up the food chain. First, it infuses with plants and aquatic life like plankton and crayfish, which are then consumed by small fish, which are then eaten by even larger, predatory fish.<\/p>\n
Older, larger predatory fish, through this process of \u201cbioaccumulation,\u201d pose the greatest risk to human health, if consumed. These same fish may be safe to eat when they are younger and smaller.<\/p>\n
People who eat fish with high levels of mercury may have issues with developing nervous systems. Children and pregnant women are especially at risk.<\/p>\n
Safe for consumption?<\/div>\n
The Colorado Department of Public Health and Environment issues consumption advisories if levels of mercury from a sample of 10 fish exceed a concentration level of 0.3 parts per million. Guidelines for eating fish, which can be found on the department\u2019s website, hold recommendations for different types of fish and how many times to eat them.<\/p>\n
At Vallecito Lake, for instance, consumption advisories are placed on northern pike and walleye fish. Women who are pregnant, nursing or plan on being pregnant are advised not to eat any walleye. Children 6 or younger are recommended to eat only one meal of northern pike a month.<\/p>\n
At Lake Nighthorse, however, it\u2019s somewhat of a different story.<\/p>\n
Rainbow trout and kokanee salmon from Lake Nighthorse tested in 2012-13 had an average level of mercury at 0.1 ppm, well below the state standard, said Kristy Richardson, a toxicologist for CDPHE.<\/p>\n
More concerning, though, is that samples from 10 rainbow trout taken in 2015 showed mercury levels increased to 0.2 ppm \u2013 a sign that fish at Lake Nighthorse may be bioaccumulating mercury.<\/p>\n
Canoes, kayaks and inflatable boats were being used during the \u201cFirst to Fish\u201d kids-only fishing event at Lake Nighthorse. Fish in Lake Nighthorse are tested for mercury, but so far, levels have not exceeded the threshold that would require consumption advisories.<\/span>Jerry McBride\/Durango Herald file<\/span><\/figcaption><\/figure>\n<\/p>The Federal Drug Administration in 2012, for reference, found the average level of mercury in canned tuna was 0.35 ppm.<\/p>\n
\u201cIt\u2019s possible we\u2019re seeing that accumulation,\u201d Richardson said. \u201cEventually, if mercury levels were high enough, we\u2019d issue that site-specific advisory.\u201d<\/p>\n
The fish in Nighthorse<\/div>\n
A little backstory goes a long way in understanding the issue.<\/p>\n
Water started filling up what would be Lake Nighthorse in 2008, with the reservoir considered full around 2011. It\u2019s possible the fish in the lake haven\u2019t been there long enough to absorb mercury, Richardson said.<\/p>\n
CPW\u2019s White said the type of fish stocked at Lake Nighthorse \u2013 brown and rainbow trout and kokanee salmon \u2013 are rather low on the food chain and less at risk for mercury contamination, as opposed to northern pike and walleye.<\/p>\n
Plus, the fish that are put into the lake don\u2019t live there all that long \u2013 about seven years at the most, White said. And, because trout and kokanee salmon need flowing water and a gravel substrate, the fish aren\u2019t able to reproduce.<\/p>\n
Northern pike, on the other hand, feed on smaller fish and tend to live in lakes for about 20 years. It\u2019s that combination of a long life and accumulating smaller species that make it prone to mercury contamination.<\/p>\n
About 50,000 rainbow trout, 20,000 brown trout and 120,000 kokanee salmon are stocked each year at Lake Nighthorse, White said. Though non-native species, such as white suckers, fathead minnows and johnny darters, have entered through the pump from the Animas River.<\/p>\n
While many anglers have pushed for CPW to pursue a trophy trout fishery for Lake Nighthorse, White said the lake isn\u2019t supportive of such a designation. The lake has to be stocked to support fish.<\/p>\n
One other rumor to dispel: Lake Nighthorse is not affected by the uranium tailings that \u2013 while close by \u2013 do not drain into the waterway. The tailings are from the old uranium processing plant, not a uranium mine.<\/p>\n
Nicole Gordon, a spokeswoman for the U.S. Department of Energy, which oversees the Durango disposal site, said samples have proven the uranium tailings do not affect groundwater or surface water in regard to the lake.<\/p>\n
Gordon said samples are taken on a yearly basis.<\/p>\n
Positive reviews<\/div>\n
Cathy Metz, the city of Durango\u2019s Parks and Recreation director, said she has heard positive reviews from anglers eating the fish at Lake Nighthorse since it opened on a weekend basis April 1.<\/p>\n
Damien Davin of Redmesa holds one a rainbow trout caught during the \u201cFirst to Fish\u201d kids-only fishing event at Lake Nighthorse. Damien is the son of Robert and Sasha Davin. Fish are unable to reproduce in Lake Nighthorse\u2019s water, so they must be stocked on a yearly basis.<\/span>Jerry McBride\/Durango Herald file<\/span><\/figcaption><\/figure>\n<\/p>The lake is now open seven days a week and will allow motorized boats beginning Saturday.<\/p>\n
\u201cI\u2019ve heard good news from the fisherman that the fish are large and taste good,\u201d Metz said. \u201cI even saw people come up with a little grill and cook the fish right there.\u201d<\/p>\n
Local anglers are taking a more cautionary approach.<\/p>\n
\u201cMost of the fish there are planted, so I don\u2019t see any reason why you shouldn\u2019t eat those fish,\u201d said John Flock, owner of Duranglers. \u201cBut when people say, \u2018I want to keep a fish out of the Animas,\u2019 I say I wouldn\u2019t feed it to my kids.<\/p>\n
\u201cAgain, I wouldn\u2019t. But there\u2019s people that do, for sure.\u201d<\/p>\n
jromeo@durangoherald.com<\/a><\/em><\/p>\n","protected":false},"excerpt":{"rendered":"tell how mercury affects aquatic life<\/p>\n","protected":false},"author":1,"featured_media":99738,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[5736,5735],"tags":[13],"naviga_topic":[],"class_list":["post-99737","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-local-news","category-news","tag-frontpage-lead"],"acf":[],"author_name":"dh_admin","_links":{"self":[{"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/posts\/99737","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/comments?post=99737"}],"version-history":[{"count":0,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/posts\/99737\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/media\/99738"}],"wp:attachment":[{"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/media?parent=99737"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/categories?post=99737"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/tags?post=99737"},{"taxonomy":"naviga_topic","embeddable":true,"href":"https:\/\/dh.durangoherald.com\/tj\/wp-json\/wp\/v2\/naviga_topic?post=99737"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}