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Sport Fishes and Food Safety

Few things are quite as satisfying as frying up a fish you've caught yourself. But could eating that keeper pulled from the river be dangerous to your health? This question is at the heart of a study recently released by the Surface Water Ambient Monitoring Program (SWAMP), which is part of the State Water Resources Control Board. The group conducted the first statewide study of contaminants in sport fishes from rivers and streams across California. The good news is that contaminants such as pesticides, PCBs, and selenium rarely reached levels of safety concern in freshwater fish fillets. However, the report does raise a notable red flag: the level of methylmercury is alarmingly high in sport fishes from the Sacramento-San Joaquin Delta region, in keeping with the Delta's mercury legacy.


This survey of California's rivers and streams follows two previous SWAMP contamination studies: one of lakes and reservoirs in 2007 and 2008, and one of the coast, bays and estuaries in 2009 and 2010 (see Are your fish safe to eat?). For the most recent study, researchers collected 16 species of fishes from 63 rivers and streams throughout the state. They compared the concentration of contaminants in fish tissue to thresholds set by the California Office of Environmental Health Hazard Assessment. Eight survey locations had average methylmercury concentrations exceeding a threshold of 0.44 parts per million (ppm). This is the level where frequent consumption is considered dangerous to children and women of childbearing age because methylmercury can impair development of the nervous system. Seven of these eight hotspots occurred in the Delta and nearby tributaries. Similar to patterns found in previous surveys, the highest concentrations occurred around edges of the Delta, with lower concentrations in the center.


Fish species also differ in their levels of contamination, with Chinook salmon, rainbow trout, brook trout, and yellow perch generally exhibiting low levels of methylmercury. In contrast, high-level predators are known to accumulate more metals in their tissues (see Heavy metal). Sacramento Pikeminnow, smallmouth bass, largemouth bass, and striped bass frequently exceeded the methylmercury safety standards. Although the Delta jumps out as a mercury problem spot, about half of the 63 locations sampled around the state exhibited low concentrations of methylmercury (<0.07 ppm). This is partially because rainbow trout, which are low in mercury, were often the only one of the study's target species that could be collected in many high altitude streams. While this report provides good geographic information about locations of contamination concern, the study authors point out that long-term trends at these sites are currently unknown. They recommend establishing monitoring stations where a contamination time series can be generated through regular sampling. It's worth our while to pay attention to contaminants in waterways, which not only affect the health of fishes, but also travel up the food chain to enter our own bodies through the fish we eat.

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IN THE NEWS: Recent stories you might have missed...
Study finds unsafe mercury levels in fish from Delta watershed
Sacramento Bee 

The first comprehensive study of rivers and streams in California has found that sport fish in the Sacramento-San Joaquin Delta watershed have higher concentrations of mercury and PCBs than anywhere else in the state.
The survey adds to the history of high mercury levels in sport fish in the Sacramento region and dovetails with recent research that found consumption of sport fish from certain Delta region streams remains high... Read more> 

California's biggest dam removal project in history begins in Carmel Valley 

San Jose Mercury News  

For nine decades, the 10-story-high concrete dam with its rusted pipes, railings and valves has stood in the wooded canyons between the Big Sur hills and the picturesque town of Carmel, blocking the natural flows of the Carmel River. When San Clemente Dam was built in 1921, the curved arch structure was a key source of water for growing Monterey Peninsula towns. But now it's obsolete and at risk of collapsing in an earthquake. And its reservoir is so silted... Read more > 

San Joaquin Valley farmers get bleak report on water supply
Fresno Bee

Growers jammed into the Westlands Water District field shop Tuesday to hear bad news: Expect a zero percent water allocation next February if winter doesn't start out stormy. A leader with the U.S. Bureau of Reclamation, which sells water to the farmers, described a bleak situation, but stopped short of predicting zero next year. Westlands general manager Tom Birmingham didn't hesitate. "When we look at these dry conditions and low storage in reservoirs later this year, it's difficult to see how the initial allocation could be anything but zero... Read more > 

The decline of the world's most abundant fisheries
Scientific American
East Asia and the Northwestern Pacific are home to some of the world's biggest and most productive fisheries, with average yearly yields in the 20-24 million ton range (Ahlenius 2004). The region is home to many coral reefs and these fisheries provide food for a large percentage of the world's population. The coral reefs are also some of the most important ecological sites in the world, home to thousands of marine species. These biologically diverse marine habitats these reefs continue to add ecological and economical value... Read more >  
BC's Skeena River once supported more than 50 times more chum salmon
Market Wired

A new study published this week provides strong evidence that Skeena River chum salmon were in the past up to 52 times more abundant than at present.The study reported that on average each year from 1916 to 1919, between 268,000 and 471,000 chum salmon returned to the Skeena. That compares to fewer than 9,000 chum salmon that have returned each year since 2007. Researchers with SkeenaWild Conservation Trust, Wild Fish Conservancy, and The University of Montana's Flathead Lake Biological Station wrote the article... Read more >