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California Coastal Creeks and Salmonid Survival

A pair of salmonid species is fighting for survival in the quiet waters of Scott Creek. Tucked up in the hills of Santa Cruz County, Scott Creek is a typical California coastal stream that flows through redwood groves and meanders past stands of alder and willow on its way to meet the Pacific Ocean. The shady stream is home to populations of steelhead (Oncorhynchus mykiss) and coho salmon (O. kisutch), which are federally listed as threatened and endangered, respectively. To better conserve these populations, scientists have taken a keen interest in how the fish use their habitat. They've found that the estuary at the mouth of Scott Creek, while making up just 5% of the total stream area, plays an oversized role in contributing to steelhead survival, and may have historically benefited coho as well.


A steelhead smolt's shot at survival to adulthood is in large part predetermined by its body size when it enters the ocean -- and a fish's choice of nursery habitat can make all the difference. In summer, a seasonal sandbar forms at the mouth of the Scott Creek, trapping fresh water in a lagoon that usually persists through the fall.  Fish that rear in this lagoon, where the water is warm and the feeding is good, bulk up much faster than their counterparts that rear upstream in the watershed (Hayes et al. 2008). Estuary fish nearly double in size during their summer in the lagoon, and enter the ocean at a larger size than upstream-reared fish, giving them an edge in the ocean's fish-eat-fish world. Although less than half of the steelhead juveniles migrating downstream take advantage of the estuary for rearing, these fish make up the vast majority (87-95%) of the survivors that return to the watershed as adults (Bond et al. 2008). 


Although coho salmon have been relatively unstudied in the creek due to their depressed populations, supplementation efforts are allowing National Marine Fisheries Service (NMFS) scientists to turn their focus to coho use of coastal estuaries. New, yet-to-be published data from Sean Hayes and NMFS suggest coho salmon may also benefit from spring-time growth opportunities in the lagoon under hydrological conditions that support earlier formation of the seasonal sandbar. While research clearly outlines the crucial role that the estuary plays in salmonid life cycles, lagoons suitable for rearing have often been absent at Scott Creek over the past two decades due to drought, as well as people artificially breaching the sandbar.


To keep a close eye on the salmon and steelhead populations, the Fisheries Ecology Division of the NMFS Southwest Fisheries Science Center has operated a life-cycle monitoring station on Scott Creek since 2003. Such stations gather annual census data at multiple times during the salmonid life cycle (by surveying both adults and juveniles), and provide important information for long-term population modeling (see Going coastal). FISHBIO is currently partnering with the National Marine Fisheries Service and the Resource Conservation District of Santa Cruz County to create a decision-making tool to help researchers evaluate and update the current life-cycle monitoring station at Scott Creek. This tool compares potential salmonid survey techniques -- everything from fish traps to aerial counts -- which vary considerably in their complexity and cost. The forthcoming document will assist researchers in designing a sampling program for juvenile and adult salmonids tailored to the specific characteristics of their study site -- not only on Scott Creek, but for any salmonid population throughout the Central California Coastal region. 

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Climate change in the Mekong Delta

As biologists, we often think

about climate change in terms of its effects on wildlife and the environment (see Warming oceans alter fish catchesAlpine snorkeling). However, there is a human element in this equation as well. Climate change can potentially devastate the livelihoods of millions of people and the socio-economic stability of entire societies. Vietnam, for instance, is at particularly high risk. According to policy and climate experts, Vietnam's Mekong Delta-one of the most fertile areas of Southeast Asia-faces a grim future as a direct consequence of climate change.


Vietnam is no stranger to destructive weather events, such as tropical storms, flooding, and drought, but climate change would make these hazards worse. The region's low-lying elevation and complex set of tributaries make it highly vulnerable to rising sea-levels and salt water intrusion. According to an assessment by the United Nations, CARE, and the Center for International Earth Science Information Network at Columbia University, a 1 m sea-level rise could displace more than seven million residents of the Mekong Delta, and a 2 m sea-level rise could double that number (Warner et al. 2009). The Center for a New American Security, a U.S. public policy think tank, claims that a 2 m sea-level might even threaten densely populated urban areas, like Ho Chi Minh City (Burke et al. 2008). 


Sea-level rise poses a serious threat to the livelihoods of millions of Vietnamese because the Mekong Delta is incredibly productive...  Read more > 

IN THE NEWS: Recent stories you might have missed...

Floating fish collector helps salmon, steelhead

The Columbian

Mark Ferraiolo gently grabbed the slightly anesthetized young salmon, identified its species, measured it, and returned it to the water at PacifiCorp's new $63-million fish collection facility on Swift Reservoir. After a tanker truck ride of a bit more than an hour, the little coho was released with 104 others in the lower Lewis River at Woodland, free to continue its journey via the Columbia to the Pacific Ocean.It's a scenario that hopefully will be replicated a half million times a year eventually as the long process to re-establish salmon and steelhead runs... Read more > 

Old-style dam faces last days in Eastern Oregon  

Seattle Post Intelligencer   

A diversion dam blocking nearly 50 miles of prime fish spawning habitat on the Walla Walla River isslated for removal by September as part of a decades-long effort to rid the waterways of so-called gravel push-up dams. Excavators have lifted heavy basalt boulders into the river at Zell Ditch, raising the stream bed to continue redirecting water for farms and pastures. The structure's design mimics natural rapids and allows for passage of native salmon and steelhead, the East Oregonian reported. Without diversion dams, fish can move more easily... Read more > 

New bluefin tuna rules proposed in Atlantic, Gulf 
San Francisco Chronicle

Boats using surface fishing lines with miles of baited hooks would get individual yearly limits for bluefin tuna bycatch under rules proposed to end the practice of dumping dead bluefin caught on hooks meant for other species. Bluefin tuna, which can weigh 500 pounds and sell for thousands of dollars - the record is $736,000 - have been severely overfished to feed a worldwide market for sushi. Groups specifically fishing for bluefin, from anglers to general fishing boats, would lose nearly 69 tons of their current total quotas... Read more > 

Sterile farmed salmon can reduce genetic impact on wild fish

Phys Org

Interbreeding between escaped farmed salmon and their wild counterparts is a major headache for the aquaculture industry. Now Norwegian fish farming companies are raising one million sterile salmon in sea cages - for the purpose of research that may help to get the upper hand on this problem.

These sterile fish are triploids, a genetic condition induced by a non-GMO method developed through long-term Norwegian research efforts funded in part by the Research Council of Norway in close cooperation with the aquaculture...  Read more > 

Boat carrying hundreds of gallons of fuel sinks in Columbia River

The Daily News

An aging 75-foot boat with several hundred gallons of diesel fuel on board sunk off Willow Grove on Tuesday morning, and the Coast Guard and other agencies worked into the evening to clean up the leaking fuel. The Granby, a wood-hulled work crew vessel built in 1929, sank in 24 to 30 feet of water where it was moored at a dock in Fisher Island Slough, a Columbia River side channel just upriver from Willow Grove County Park. As of Tuesday, state Department of Ecology officials estimated that 50 to 100 gallons of diesel had leaked... Read more >