Last week we had the opportunity to observe spring-run Chinook salmon ascending the Parrot-Phelan diversion dam on Butte Creek near Chico. Currently the largest naturally spawning spring-run Chinook population in California, adult returns in Butte Creek have increased tenfold over the past decade. The increase has been attributed to habitat restoration, including the removal of four dams, the addition of eight adult passage ways and the installation of screened barriers to prevent juvenile fish from being diverted with water destined for irrigation.

April and May are peak months for upstream migration of spring-run Chinook salmon in the Central Valley. The migration typically coincides with runoff from snow melt, often allowing them to ascend farther upstream than would be possible during lower flows in late summer and early fall, when their fall-run conspecifics arrive back at their natal spawning grounds. Unlike fall-run fish, which arrive on the spawning grounds with fully developed eggs, spring-run Chinook enter tributaries reproductively immature and spend the summer in cold, deep pools without feeding. They rely exclusively on fat reserves they accumulated while feeding in the ocean to sustain survival and gonad development until they complete migration to their spawning grounds once water temperatures decline in early fall.  Since they are spawning earlier than fall-run Chinook, their fry will typically emerge from the gravel in December. A fraction of juveniles will out-migrate soon after emergence (December) while some will reside in freshwater for up to a year prior to migrating to the ocean. 

Spring-run Chinook are genetically distinguishable from the other runs of Chinook in the Central Valley (CV), though some interbreeding does occur. Interestingly, spring-run Chinook within each stream are more genetically similar to fall-run Chinook from the same stream than to spring-run Chinook from other streams, suggesting that multiple stocks have adapted this special life history independently of one another (Waples et al. 2004).

Despite recent population increases in some Sacramento River tributaries, spring-run Chinook in the CV are still listed as “Threatened” under state and federal legislation. Similar to other anadromous salmonids within the CV, their habitats have been highly impacted by the construction of dams and are currently found in a small fraction of CV watersheds they once occupied, including the Yuba and Feather Rivers, Big Chico, Deer, Mill, and Clear Creeks and, of course, Butte Creek.

Predation is a natural part of maintaining a healthy ecosystem. But when predation by one species on another increases because of human changes to the environment, it can have a negative impact on the ecosystem. Northern pikeminnow, Ptychocheilus oregonensis (formerly known as northern squawfish), are indigenous to the Columbia River, but they were not prevalent before the construction of the hydroelectric Federal Columbia River Power System. Reservoirs created by the hydropower system provided excellent slack water habitat for pikeminnow, and as a result their population in the lower Columbia and Snake Rivers flourished. They are voracious predators and salmonid smolts comprise a large portion of their diet (Sauter et al 2004). Northern pikeminnow prey on millions of salmon and steelhead each year in the lower Columbia and Snake River systems.

The Northern Pikeminnow Management Program (NPMP) was established in 1990 in an effort to reduce predation by northern pikeminnow on juvenile salmon and steelhead as they emigrate from the lower Columbia and Snake Rivers to the ocean. The goal of the program is not to eliminate northern pikeminnow, but to reduce the average size and decrease the number of larger, older fish that are known to be highly predacious. Since 1990, the Bonneville Power Administration (BPA) has sponsored the Northern Pikeminnow Sport Reward Fishery Program in the lower Columbia River and a portion of the Snake River (from the mouth to Hells Canyon), offering cash to registered anglers for each northern pikeminnow they catch measuring nine inches or longer. Site-specific gill netting and dam angling were also part of the NPMP, but were less efficient than the sport reward program and were discontinued in 2002 and 2006, respectively.

Each year thousands of anglers fish the Columbia and Snake Rivers for northern pikeminnow. The program runs annually from May 1 through September 30. While most anglers bring in just a few dollars, the top angler in 2011 earned $66,478 and the second place angler took home $60,742. This informative video describes how you can earn $20,000-50,000 annually while fishing for northern pikeminnow. The 2012 Sport Reward payment schedule is as follows:

• 1-100 fish pays $4 per fish
• 101-400 fish pays $5 per fish
• 401 and above pays $8 per fish
• Tagged fish rewards are $500 per tagged fish

Since 1990, the BPA has paid anglers to remove more than 3.9 million northern pikeminnow from the Columbia and Snake Rivers (annual average of 175,000), reducing predation on juvenile salmon by an estimated 40 percent. This equates to 4 to 6 million salmon smolts that would have otherwise been eaten by this predator.

This type of sport reward program could be successful in other systems to suppress populations of key predators of juvenile salmon and steelhead as they make their way out to the ocean. It is a win-win situation; the anglers get paid for their efforts while benefiting the survival of a salmon and trout.

The Freshwater Fish Specialist Group (FFSG) of the World Conservation Union (IUCN) Species Survival Commission has just held its annual meeting in Chester, UK. With diverse attendance, the meeting was a great opportunity to learn about efforts to conserve freshwater fish, from Africa to Australia, and many regions in between. The Mekong was also represented, as FISHBIO’s Conservation Director gave a talk on our work to establish the Mekong Fish Monitoring Network. With generous support from the Chester Zoo, the meeting was a chance to connect with other researchers, learn about different conservation approaches, and devise plans for future initiatives of the FFSG. One of the new goals of the group is to collate metadata for long-term data sets on freshwater fish into one searchable database. So if anyone out there would like to contribute to this effort just drop us a line. Such a resource would be extremely useful for students, researchers, anglers, and resource managers around the world. Historic data can help us to understand how fish populations have changed over time, recognizing that yesteryear’s “status quo” may seem like a myth to us today. In the historic British city of Chester, many things have changed, yet the past was visible all around us. Chester was established over 2,000 years ago, and is home to one of the oldest Roman walls in Britain, which still encircles the city center. In the midst of efforts to understand where we are today, it’s important to remember where we’ve been, recognizing shifting baselines.

 What do you do when your electrofishing boat breaks down in the middle of a time sensitive research project and it’s going to take a week to get the parts needed for repairs? Build a replacement. That’s exactly what we did. With a little technical help from our friends at Smith-Root, we retrofitted one of our smaller boats with a Streambank Generator Powered Pulsator. Working well beyond normal hours, our master fabricators were able to construct a guardrail, mount fiberglass poles to suspend the electrode arrays, install floodlights, and wire-up all the electronics that make an electrofishing boat operate. Thanks to a dedicated team of people we were back on the water in less than 24-hours, catching the fish needed to complete our study.

We know we’ve posted on lamprey in the past, but we think it’s worth sharing this close-up photo of a Pacific lamprey’s gill ducts. Lamprey are different from most fishes that respire by taking water in through their mouth, passing it over their gills arches and expelling it out through gill slits. Because lamprey spend most of their adult lives attached by their mouths to a host organism, they must respire by pumping water in and out of their gill pouches. By contracting extensive musculature surrounding the gill pouches they can pump water in and out of their 7 pairs of external gill ducts, allowing respiration to occur while they are latched onto their next meal.

The diets of juvenile Chinook salmon rearing in freshwater tend to vary between river basins and over time since they are opportunistic feeders consuming a wide variety of terrestrial and aquatic insects. Early in their development, as fry and parr, their diet typically consists of small prey items such as zooplankton and insect larvae, but as they grow larger and develop into smolts their larger mouth gape makes them capable of consuming prey such as fish larvae and adult insects. As juvenile salmon continue to grow and enter the ocean they become even more voracious predators, feeding on pelagic planktivore fish like herring, anchovies and sardines. This little salmon has a long way to go before getting to the ocean, but with such a full belly it seems to be well prepared for the trip.

What could be more appetizing than “crispy Mekong River weed”? We found a street vendor selling these packages while searching for fish at the morning market in Luang Prabang, Laos. Feeling a bit adventurous we tried the unusual snack at a nearby restaurant and found it quite tasty. The locals call this filamentous algae khai paen, which literally means “skin of the stone,” since it grows along the banks of the Mekong River. Villagers seasonally gather the river weed, combine it with garlic, tomato and sesame seeds, press it into sheets, and dry it in the sun. The dried sheets are eventually cut into squares and fried to make the popular crispy snack. It makes a person wonder what delicious treats might be growing locally right under their own nose.

As word spreads of the abundance of Chinook salmon being caught off the coast of California, anglers are eager to make their way to the sea in hopes that they are as fortunate. The extended fishing season and forecast of an unprecedented salmon rebound have only added to the excitement, which is predicted to bring greater profits to coastal communities. Rumors have been floating around that anglers are limiting out and are back at the docks by 9 am and salmon fever is now full-bore. This is a great sign for the communities that have fallen on hard times due to low salmon abundances and the restrictions placed on sport fishing over the last few years.

The Pacific Fishery Management Council (PFMC) pre-season report predicted that most areas along the West Coast around recreational fishing communities would see an increase in the amount of tourist traffic and money this year compared to recent years. In 2011, folks along the West Coast made an estimated total of 211,200 angler trips and that number is projected to increase by 123,300 trips in 2012. Furthermore, the additional activity is estimated to be valued at almost $10 million more than the 2011 estimate of $17 million. In a down economy, this is great news for the California charter fishing industry, which took a hit after the 2007 season and the collapse of the Sacramento River Fall Chinook (SRFC) salmon fishery. However, the fishing frenzy caused by the increase in abundance could have negative effects on the recovery of the salmon. PFMC stated in the Review of 2011 Ocean Salmon Fisheries that SRFC are currently overfished based on the fact that the three-year geometric mean for escapement is below 91,500 fish. In times when abundance is still recovering and there is a lot of excitement around the fishing community it is important that we remain cautious about the future of Chinook salmon.

This year, the salmon fishing season is long and there will likely be a lot of fish captured during the next few months. Depending on your location the recreational fishing season started as early as April 7 and is expected to go through early November, while the commercial fishing season will begin May 1 and end September 30. Catch totals for recreational and commercial fishing are projected to be around 215,000 and 555,000, respectively, along the West Coast with almost half of the catch occurring south of Horse Mountain (Fort Bragg). Due to the overestimate of salmon abundance in recent years the catch of SRFC has actually been lower than predicted (23% lower in 2011) in years past, but if the fish continue to bite then there will be a lot of salmon harvested.

When most of us think of a trawl fishery what comes to mind are the large, sea-going vessels dragging huge nets 200 ft. wide along the sea floor, but in the Mekong Delta of Vietnam the fishery operates on a much smaller scale. The most common method of fishing in the Mekong Delta is the trawl, and it has been reported that 70% of the fishing boats in Vietnam are small-scale trawlers in the Delta (Sinh and Long 2011). The Vietnamese trawlers are a more simplified version of the mid-water trawlers used for monitoring in the San Francisco Bay-Delta. The nets have a large, open front end that reduces down to the back of the net, or the ‘cod end’, where the catch is collected as the net is hand-pulled into the boat. In the Mekong Delta fishers attach the mouth of the net to a heavy pipe, which is dragged along the bottom of the channel. Watch our YouTube video to see a small-scale trawler in action.

We took a tour with researchers from Cantho University to see how they acquire fish samples working with fishermen in the Mekong Delta. Rather than operating their own trawl vessels, it is more efficient for the researchers to hire local fishers to operate the trawl for them. In this case, the researchers are conducting monthly trawl sampling at specific locations in the Hau River, a distributary of the Mekong, to assess the seasonal differences in fish species composition and abundance.