They return to spawn in the Columbia by the gazillion, comprising as much as 90 percent of all upstream-migrating fish some years, and have a future as “bright” as their scales, yet surprisingly little is known about the species.
But a new report is cracking the door open on shad, as well as recommending more research and monitoring of the East Coast imports and whether they’re affecting far more prized – and troubled – Chinook, coho, A- and B-run steelhead and other native stocks in the big river.
It seems intuitive that the now massive annual returns of shad would be impacting the Columbia’s ecosystem, competing for forage with young salmonids – but also possibly benefiting them – jostling springers and sockeye in the fish ladders on those epic 500,000-fish days at Bonneville and carpet bombing reservoirs with decaying carcasses.
But a science panel essentially shrugged its shoulders in an 89-page report issued late last month to the watershed’s hydropower and fish and wildlife overseers who tasked them with gathering what’s known about the species and answering nine key questions.
“Given their abundance and biomass, it is surprising how little we know about them. Their sheer numbers suggest there should be interactions with other fishes and with the birds and mammals that prey on them. However, the limited studies available do not identify clear interactions between shad and salmon or the role of shad in major ecosystem processes,” wrote the 11-member Independent Scientific Advisory Board.
They recommended a “systematic, multiyear research program” because “potential risks for the ecosystem and anadromous salmonids warrant caution and continued attention.”
Where that was about as definitive as ISAB got in their assessment to the Northwest Power and Conservation Council, Columbia River Basin Indian Tribes and National Marine Fisheries Service, a council summary expressed a bit more alarm.
“The opposing general trends for shad (increasing) and salmonids (decreasing) point to an ongoing, and perhaps accelerating, disruption of ecosystem health in the basin. Furthermore, the growth of shad populations risks straining the management and operational infrastructure aimed at stabilizing or recovering anadromous salmonid communities,” the organization wrote on its website.
For watchers of all things Columbia fish run, the paper is interesting as a summation of what’s known about a fish that the ISAB authors note had people scratching their heads in the 1890s and again in the 1990s.
For a 2019 blog, I quoted an ODFW official who called them “an interesting puzzle.”
It shares more information on how shad got here, what led to “dramatically increased” returns in the 1960s, the stocks’ “uncommonly genetically diverse” population and evolution of “mini-shad,” decreased size over the decades, tribal disinterest in the species, and growth rate that averages “4.7 percent per year, with no indication that the population has reached an abundance limit.”
While many stories accurately trace the West Coast origin of settlers’ beloved East Coast foodstuff to 1871 introductions in California’s Sacramento River, from which they rapidly colonized the Columbia, the report also notes that in 1885 a United States Fish Commission shipment of 900,000 fry meant for Puget Sound was rerouted due to a bridge collapse, and while most died en route, 50,000 were released into the Willamette and 10,000 into the Snake near today’s Tri-Cities.
The next year, the commission released 550,000 fry into the Willamette at Albany and 300,000 into the Columbia just above the Wallula Gap.
But it wasn’t the late 1950s that shad did much of much in the Columbia.
That was when The Dalles Dam came online, drowning the frothing torrent that was Celilo Falls. With the dam’s fish passage facilities, shad were easily able to extend their range deeper into the Columbia Basin. They’re now found up to Priest Rapids Dam on the mainstem Columbia and past Lower Granite Dam on the Snake.
By the mid-1960s their numbers began to rival the entire salmon and steelhead run at Bonneville, and by the late 1970s started routinely surpassing it as more and more shad tapped into all the new upstream habitat.
Sharp spikes in the late 1980s, early 2000s and late 2010s – a record 7.5 million in 2018 – chart an upward trajectory that salmonid managers and recovery advocates can only drool over.
“The future of shad right now looks bright in the Columbia River Basin which should continue to provide near-optimal habitat for shad spawning and rearing in the chain of flow-through reservoirs,” the ISAB report states. “A warmer climate will likely favor shad over salmonids, although much depends on the continued productivity of the river and reservoirs, the estuary, and, above all, the ocean. The winds and currents that create this productivity are likely to become even more erratic, so populations of shad and other fishes (and of everything that preys on them) are likely to show wide and unpredictable fluctuations.”
As for why they’re doing so well, there are five hypotheses.
Besides the creation of fish ladders and reservoirs that provide “near-optimal conditions for shad spawning and rearing,” the others include: the species’ tolerance to a wide range of freshwater conditions; anadromy predisposing them to colonization (some were caught in Lake Washington this spring); broadcast spawning instead of digging redds; and largely beneficial ocean conditions.
Shad are probably also being aided by general disinterest in harvesting them – though not necessarily by sport anglers, who creeled a quarter million of the hard-pulling battlers in 2018 for pickling and use as sturgeon and crab bait.
While recent years have seen some of the highest marine landings reported on the Oregon and Washington coasts, they’re only caught “incidental” to other fish. Inriver commercial fisheries have tailed off to nothing due to low market value – “they are no longer preferred by consumers to any significant extent given the wide availability and variety of other food fish,” the council writeup states – and the difficulty in accessing a run that overlaps Endangered Species Act-listed salmon stocks.
(Of note, NMFS recently tweeted that a Northwest Fisheries Science Center researcher is looking into “the potential of Columbia River American shad meal to replace sardine meal as feed for growing commercially-valuable sablefish.”)
ISAB’s report also collects the thoughts of a treaty fisherman and a treaty fisheries manager.
“Overall, there seems to be little interest in shad for Tribal fisheries, despite their abundance. This appears to be the result of poor markets for shad, the difficulty of getting them to the markets, and by-catch of salmon in shad fisheries. Further, as a non-native species with no cultural importance, shad and their potential impacts to salmon and other native fishes remain a large concern for Tribes,” it summarizes.
On the genetic side, Columbia shad have also become quite diverse “for a population founded with a small number of colonists.”
“Moreover, the presence of genetic differentiation across Pacific Coast populations suggests that some metapopulation structure has developed in the 150 years since founding,” the report states.
Just as most salmon and steelhead have different life histories, so too with shad. After they hatch, most head for the saltwater in fall and then feed at sea for several years before returning to spawn, mostly as 4- and 5-year-olds. Unlike the East Coast, most Columbia spawners are first-time spawners.
But some shad exhibit an extended freshwater residency. Known as mini-shad, these 1- to 2-year-old males and females are bigger than fellow year-class fish but smaller than adults. Some shad don’t even go out into the Pacific, according to the report.
What they eat at sea has “received little attention,” but is probably similar to what young coho and Chinook forage on, with analysis of isotopes showing they feed over the continental shelf and at water depths you would expect to see young salmon at.
“Thus, trophic competition at sea is possible, although the prey base is shared with many other fishes such as Pacific herring that are much more numerous than shad,” the report states.
Their spawning is linked to water temperatures and the question of whether the river ecosystem might benefit from their carcasses is complex, given that as much as a third actually live to spawn again, and any nutrients they do add would likely be concentrated more in the estuary than upper watershed tributaries where most salmon go.
And while shad fry might compete with young salmon for forage, juvenile Chinook may get a boost by feeding on juvenile shad when they become more abundant in midsummer, though it’s not known if they’re a dietary benefit or sugar. Then there are questions of whether they buffer young salmonids from predation, or lead to increased sea lion presence in the Columbia.
Indeed, much more needs to be sussed out about shad and this report presents some good starting points for researchers to build on what’s known, namely deeper dives centered around their biology, effects on the ecosystem, population modeling, and management.
“Research and monitoring to better understand shad may not be the most important management issue for the [Northwest Power and Conservation Council’s] Fish and Wildlife Program, but continuing to ignore the role of shad in the Columbia River increases future uncertainties. Strategic assessment and evaluation could provide critical information for decision makers and managers in the future if shad populations continue to increase,” ISAB concludes.