Fisheries research, monitoring, and conservation
A handy feature of the VAKI Riverwatcher system is that it allows us to record video clips of each fish that passes through our fish counting weirs. In addition to identifying the fish species, length, and passage date when we review the video, we also document the condition of each fish. We look for abrasions, lacerations, fungal infections, lamprey scars, hook scars—and in this case the actual hook! In this video you can see the shiny fishing lure dangling from a Chinook salmon’s dorsal fin. The angler is probably disappointed that he or she foul-hooked this salmon and lost not only the catch, but the lure to boot—although it does make for a flashy fish accessory.
Archive for Vaki Riverwatcher
If you’re having trouble viewing the presentation, you can also download it.
FISHBIO and VAKI Aquaculture Systems conducted a seminar this week in California to introduce fisheries biologists to the Riverwatcher fish monitoring system. We were pleased with the turnout and the interest in the Riverwatcher’s capabilities. Magnús Þór Ásgeirsson from the VAKI Corporation in Iceland provided a fantastic overview of the evolution of the system and demonstrated the operation of the equipment and software. Ryan Cuthbert from FISHBIO shared his 10 years of experience using Riverwatchers to enumerate instream fish migrations and demonstrated various data analysis possibilities. The seminar also included a fieldtrip to the Tuolumne River fish counting weir to see the system in action during the fall-run Chinook salmon migration. Participants showed great interest in the integration of the Riverwatcher system with resistance board weirs and other fish ways. A good example of this was our recent post on the integrated Riverwatcher/PIT tag antenna used by Casitas Municipal Water District to monitor steelhead in Southern California.
Adding a little humor to an otherwise routine task, this crewmember shows off his dance moves after cleaning algae from the viewing window of a fish counting weir. Using high tech electronic fish counting systems, like the Vaki Riverwatcher, to record fish passage provides highly accurate results; but like most things in life (here comes the cliché), you only get out what you put into it. Field technicians regularly visit our fish counting weirs to clean the camera lens, lights and glass that monitor the fish passage chute (or in this case the dance floor).
The 141st annual meeting of the American Fisheries Society is currently underway in Seattle, Washington and the theme for the event is “New Frontiers in Fisheries Management and Ecology: Leading the Way in a Changing World.” This year is expected to surpass all others, with an estimated 4,000 in attendance. Fisheries biologists from FISHBIO, along with others from around the world, are presenting their research findings and sharing ideas for new and innovative technologies. For example, this year we are demonstrating the VAKI Riverwatcher in the Trade Show. By fabricating a mechanical carousel that passes a fiberglass fish though the Riverwatcher, we can show observers first-hand how the device detects passing fish and records data.
We’re always looking for better ways to showcase the easy setup and use of the VAKI Riverwatcher fish counter. We’ve had great success over our 8 years of using it, and get asked a lot of questions about installation and how it works. So, it only made sense to put our technicians to the task of fabricating a portable display in the FABLAB to demo it.
Because the system is made up of 4 key components, they’re easy to put together and easily adaptable to various applications, such as resistance board weirs, fish traps, fish ladders, fykes, flumes and many others. Our own Scott Wucherer demonstrates how the system works.
Preliminary estimates of adult fall-run Chinook salmon escapement (that is, the number of adults returning to spawn) in the Central Valley in 2010 have been posted in the “GrandTab” by the California Department of Fish and Game. A summary table is provided below.
The number of Sacramento River fall-run Chinook salmon (SRFC) is 152,831 and for the San Joaquin River basin is 10,350. Although numbers are up from previous years, SRFC numbers are still below the 2010 conservation objective of 180,000 recommended by the Pacific Fishery Management Council, and adult returns are likely to be lower in 2011 considering that the number of parents and associated juvenile production contributing to adult returns in 2011 will be substantially less than 2010. In fact, the 2011 SRFC escapement will be comprised of adults produced from the three lowest adult return years on record for SRFC – 2007, 2008, and 2009. As such, the parental stock (brood years 2007, 2008, and 2009) for adult fish returning to spawn in 2011 is 212,089, which is 52.3% less than the parental stock abundance for 2010 escapement.
Additionally, abundance is only part of the story because the “GrandTab” only provides the numbers of fish observed in each location, not their origins. That is, the numbers reported for “Hatcheries” in the “GrandTab” are the number of salmon entering the hatcheries to spawn (which may consist of both hatchery-origin and natural-origin fish) and the numbers reported for “In-river” are the estimated number of salmon spawning in the rivers (which also may consist of both hatchery-origin and natural-origin fish). In 2010, a considerable portion of adult in-river returns was likely composed of hatchery-origin salmon, particularly in San Joaquin Basin tributaries where increased numbers of ad-clipped fish were observed at the Stanislaus River weir (24.7% as of 12/6/10) and the Tuolumne River weir (29.0% as of 11/30/10) (See FISHBIO Update 2 for more details). Most ad-clipped fish are of hatchery origin. Since neither of these two tributaries have hatcheries and no ad-clipped fish have been released into them since 2006, the observed numbers of marked fish indicates that a tremendous amount of straying has occurred, and that hatchery fish probably make up a much larger percentage of CV escapement than previously thought.
High straying rates of hatchery-origin salmon is generally attributed to Central Valley hatchery practices and straying, in part, has led to the genetic homogenization of Central Valley fall-run Chinook salmon populations. In 2005, a genetic study of Central Valley Chinook salmon (Williamson and May 2005) did not observe genetic separation of any natural or hatchery Central Valley populations, even between populations of the Sacramento and San Joaquin Basin, which is in contrast to other major Pacific salmon regions (Alaska, British Columbia, and the Pacific Northwest), where basin scale genetic diversity has been demonstrated. A decrease in genetic diversity may result in reduced fitness and lower productivity of natural populations, leading Central Valley fall-run Chinook salmon to be more susceptible to environmental stressors.
Photo source: FISHBIO
This post is the last in a “how to” series on the basic components of building a fish counting weir. A weir can have many uses, in some cases this fence-like structure might be built to exclude fish from a certain location, but the majority of weirs are used to enumerate migrating species or to trap fish in order to collect biological data or brood stock for a hatchery program
For fish counting weirs, an opening must be created in order for fish to be counted as they pass through. This can be achieved by removing one or more resistance weir panels, but is better accomplished by modifying a panel to create a passing chute. Fish migrating upriver encounter the weir and move sideways from bank to bank until they locate the opening. For salmonid monitoring, the passing chute is located near the thalweg where there is ample flow for fish to cue in on. Passing chutes can be fitted with electronic monitoring equipment (VAKI Riverwatcher, Video recorder, PIT tag antenna, etc.) and/or a livebox fish trap.
Fish traps can be as large and sophisticated, or as small and simplified as need for a particular application. A livebox fish tap typically consists of a rectangular cage fabricated from aluminum or galvanized steel to prevent corrosion. One or more fykes are located at the entrance to help guide the fish into the box, and to reduce the likelihood of fish escaping or moving back downstream. Liveboxes may also include a crowder gate that can guide trapped fish to one side of the trap or facilitate removal. Resistance board weirs are gaining recognition as a respected device in fisheries management and we hope that after reading our posts you have better understanding of the process of weir fabrication.
See the other posts from this how to series:
Fish counting weir: how to series
Fish counting weir: substrate rail
Fish counting weir: resistance weir panels
Fish counting weir: rigid weir and bulkhead
Photo source: FISHBIO
Resistance board weir panels are designed for use in the main river channel and adjust to changing flow and debris conditions, but they are not intended for sloped river banks. Instead, rigid weir panels are used on either side of the resistance panels to extend the weir out to the bank. Rigid panels are simply galvanized steel pipes welded to iron cross members, held in place by A-frame supports. We usually make the panels 3 ft. wide and 5 to 10 ft. tall, depending on the expected range of channel depths. Large vertical panels (5 ft. x 20 ft.) called bulkheads serve as an interface between the stationary and movable parts of the weir, moving up and down with the resistance board panels. Bulkheads consist of a welded aluminum frame with PVC conduit pickets spaced 2 in. apart, and are fastened to long stakes driven into the substrate.
Photo source: FISHBIO
Fall-run Chinook adults are still trickling into various tributaries along the West Coast, leading to even higher numbers than were observed in 2009. Since higher numbers are good news, we are providing updated counts for comparison. For an explanation of the ocean conditions that contributed to these recent increases in returning salmon, see our previous Year-to-date post.
Although salmon numbers are up, people have been asking ‘What is going on with all the adipose fin-clipped (ad-clip) Chinook salmon observed in the San Joaquin Basin this year?’ To answer this question, we’ve put together some information regarding ad-clipped fish and present some possible explanations in a section following our updated adult return numbers.
San Joaquin Basin
On the Stanislaus River, 1,346 adult Chinook salmon have been counted at the weir so far this year (as of 12/12/10), which is similar to 2009 (Figure 1). On the Tuolumne and Mokelumne Rivers, counts of adult Chinook salmon during 2010 have substantially exceeded counts from 2009 (Figure 2, Figure 3). Net passage through the end of sampling (11/30/10) on the Tuolumne River was 766, and the net passage to-date (as of 12/7/10) on the Mokelumne River is 6,982 adults.
Figure 1. Cumulative Chinook Passage at the Stanislaus River Weir, 2003-2010.
Figure 2. Cumulative Chinook passage at the Tuolumne River weir, 2009 and 2010.
Figure 3. Cumulative Chinook Passage at Woodbridge Dam, Mokelumne River, 2009-2010.
Other West Coast Basins
In the Sacramento River Basin, the count on the Yuba River is up at 3,024 adults (as of 11/29/10), representing a continuing, steady increase in annual abundance over the past four years (Figure 4). Battle Creek fall-run Chinook passages are on the rise as well with 10,967 passages (as of 11/15/10), exceeding last year’s total of 8,268, but still several thousand shy of exceeding passages from years prior (Figure 5).
Figure 4. Fall-run Chinook Passage at Daguerre Point Dam, Yuba River, 2007-2010.
Figure 5. Cumulative Chinook salmon passage in Battle Creek, 2003-2010.
In California’s Russian River, adult Fall-run Chinook abundance has been on the rise in the last couple of years and has reached 2,414 as of 11/28/10 (Figure 6).
Further north, at Bonneville Dam on the Columbia River, the count is up to 467,765 as of December 13 and passage has surpassed totals from each of the past five (5) years (Figure 7).
Figure 6. Fall-run Chinook passage at Mirabel Rubber Dam on the Russian River, 2000-2010.
Figure 7. Fall-run salmon passage at Bonneville Dam on the Columbia River, 2000-2010.
Adipose Fin-Clipped (Ad-clipped) Chinook Salmon
Adipose fins (the small fin behind the dorsal fin) are removed from Chinook salmon to indicate the presence of a coded-wire-tag (CWT) in their snout. CWTs are pieces of stainless steel wire 0.5 to 1 mm long that are injected into the snouts of salmon and contain specific information about the fish such as brood year, release date, and whether the fish is wild or came from a hatchery.
Many of the tributaries within the San Joaquin River Basin are seeing an unusually high percentage of ad-clipped Chinook salmon (>25%) compared with previous years (Table 1). Ad-clip passages recorded at the Stanislaus River weir (24.7% as of 12/6/10) have exceeded previous years and at the Tuolumne River weir (29.0% as of 11/30/10) have increased compared to our first sampling year (Table 1). Since neither of these two tributaries have hatcheries and no hatchery releases have been conducted into these tributaries since 2006, it is apparent that a tremendous amount of straying is occurring. Given that roughly 75% of hatchery fish are not clipped and assuming that un-clipped and clipped hatchery fish are equally likely to stray, it is likely that quite a few un-clipped hatchery fish also entered these two rivers in 2010. In previous years, straying of fish released off-site into San Pablo Bay has been estimated to be as high as 70% (CDFG & NMFS 2001) and may be found to be even greater once analysis of CWT data for the most recent years are completed.
Unlike the other two San Joaquin Basin tributaries, the Mokelumne River has a hatchery and a proportion of fish that are released have CWT’s. As such, we expect to observe ad-clipped fish in this river and ad-clipped passage at the Mokelumne River (51.6%) is much higher than the tributaries without hatcheries. However, similar to the other two tributaries, ad-clip passages are still higher in the Mokelumne River compared to the previous year (Table 1).
Table 1. Central Valley ad-clip Chinook passage, 2007-2010.
We suspect that higher percentages of ad-clipped salmon in the San Joaquin Basin this year are due to a combination of factors including the implementation of a Constant Fractional Marking (CFM) program beginning in brood year 2007; the acclimation and release of a greater number of salmon smolts in San Pablo Bay in 2008; and low San Joaquin River Basin tributary juvenile abundance combined with low juvenile migrant survival through the lower San Joaquin River and Delta in 2008.
The CFM program is a goal that was set to consistently tag and mark at least 25% of all juvenile hatchery Chinook salmon that are released, in order to better evaluate the relative contribution of hatchery and wilds Chinook salmon populations within the Central Valley. Prior to 2007, there was no CFM for Central Valley hatcheries and relatively low numbers of juvenile hatchery fish were marked with coded-wire-tags (CWT) before being released. In 2007, Central Valley hatcheries purchased automated trailers (stations capable of tagging and clipping fish at a faster rate) and adopted the CFM program. Therefore, if an ad-clipped Chinook is spotted during an adult counting (i.e., adult escapement) survey, the fish will be checked for a CWT, which can be read back at the lab to determine from which hatchery the fish originated. Based on the life cycle of salmon, a Chinook that was tagged and released in 2008 would likely return to the Central Valley in 2010 to spawn. Thus explaining, at least in part, the increase in ad-clipped salmon.
In most years since 1993, a proportion of Chinook salmon smolts from three State Hatcheries (Nimbus-American River, Feather River, and Mokelumne River Hatcheries) have been released off-site into San Pablo Bay to improve survival. In recent years, 4-10 million juveniles have been released into the Bay. However, due to drastic declines of fall run Chinook salmon in the Central Valley system, the California Department of Fish and Game doubled the number of acclimation fish in 2008 resulting in about 20 million fish released into San Pablo Bay. Also in 2008, for the first time in over a decade, Coleman National Fish Hatchery acclimated and released 1.4 million smolts into San Pablo Bay.
Another factor to consider is that the San Joaquin Basin experienced some of the lowest fall-run Chinook adult salmon returns on record in the fall of 2007, and thus juvenile abundance was extremely low the following year (SJRGA 2009). In addition, survival of juveniles migrating through the lower San Joaquin River and Delta in 2008 was estimated to be low (USGS 2009). As such, low juvenile abundance combined with low survival in 2008 has likely contributed to the proportionally lower abundance of naturally spawned Chinook salmon observed in 2010.
Special thanks to Matt Saldate with East Bay Municipal Utility District and Alice Low with CDFG for providing data to us directly. Also, we thank the hosts of various websites where other data has been obtained.
Photo source: FISHBIO
One of the advantages of a resistance board weir over a rigid weir is the ability to withstand higher flows. Rigid weirs have a tendency to get blown-out when increased velocity and debris put excessive force against the weir, whereas resistance board weirs have flexibility and can shed debris over the top. This type of weir is made up of an array of resistance panels that span the majority of the river channel. Each panel consists of evenly spaced PVC conduit pickets held together by UHMW polyethylene (high density plastic) stringers. The upstream end of the panel is attached to a cable and rail system (i.e. substrate rail) that is anchored to the channel bottom, and the downstream end is lifted above the water surface by a 2 ft. x 3 ft. resistance board that planes upward in flowing water.
The resistance board weir is comprised of more than 35 unique pieces of hardware, some of which are readily available, but others are individually fabricated prior to assembly. There are 5 different types of stringers that are constructed for each panel. Three inch wide stringers are fabricated out of ½-in. thick UHMW polyethylene sheets and the edges are rounded with a router to reduce water resistance. Hole locations are marked with a template and drilled (see photo above); there are 130 holes in 10 stringers (3-21 holes per stringer) for each panel.
Not surprisingly, resistance boards are the key feature in the function of a resistance board weir (aka fish counting weir, floating weir, Alaskan weir). A resistance board is fabricated out of ½ in. pieces of marine grade plywood, which are primed and painted with marine grade paint. A polystyrene board is laminated between two sheets of the painted plywood, to improve buoyancy, and is secured with stainless steel hardware. The resistance board it is attached to the panel with hinges to allow the user to adjust the angle. This is one of the many ways that the resistance board weirs can be customized to fit each unique location and situation.
Photo source: FISHBIO
