Fisheries at Risk if More Delta Water Diverted

Important fishing grounds in Northern California are dwindling to insignificance because water is being diverted from the Sacramento and San Joaquin rivers, worsening water quality from the Delta to the Golden Gate. The State Water Resources Control Board, in hearings begun last year and continuing until 1989, will determine if even more water should be diverted from the estuary. The hearings are vastly important to the entire state, because they will decide how to divide--among competing factions--nearly half of all the flowing water in California. The remaining water is supposed to support the fisheries.

When the hearings are over, it is likely that the water contractors will get their way; more water will be sent south, some to urban areas but most to a few huge corporate farms in the San Joaquin Valley. This increased diversion of water will cause the environmental quality of the Sacramento-San Joaquin estuary to decline even more rapidly.

If diversions increase, we will lose much of our wild salmon, striped bass, steelhead, American shad and sturgeon populations, and eliminate a number of unique fish and invertebrate species. The declines of these species are already under way; to reverse the trends we will need more water, not less, flowing through the estuary.

For the estuary to support its important fisheries, there must be extensive shallow areas where salt water mixes with freshwater. Such areas are immensely productive of the small organisms that form the base of the food chains leading to fish. Most important, they are the nursery areas for the small, helpless larvae of many fishes. In the first three weeks of life, these tiny larvae must live in a soup of food organisms; they must literally bump into their food in order to find it. If the larvae do not bump into enough food, they die of starvation.

The main place where there is enough shallow area for a productive mixing zone is Suisun Bay, below the Delta and above San Pablo Bay, in the middle reaches of the estuary. To keep the mixing zone in Suisun Bay requires large amounts of water from mid-March through July. High spring flows are also necessary to move young salmon out to sea and to provide the flooded areas some fish need for spawning. Higher flows may be needed through September as well, to bolster growth rates and survival of young fish. The exact amount of water needed for these purposes is hotly debated but there is little doubt that more is needed than is currently required by law.

What will happen to various fish species if higher outflows are not provided?

--Salmon and steelhead. The runs of salmon and steelhead in central California used to number in the millions. Today the runs are numbered in the thousands and two runs of chinook salmon are being considered for endangered status. One major factor contributing to this decline is the loss of young salmon as they pass through the estuary. When outflows are high, the salmon move through quickly and thereby avoid predators, such as striped bass. When outflows are low, most of the young salmon do not make it out to sea, so fewer are harvested or make it back to spawn.

If adequate flow standards are not adopted, salmon and steelhead will dwindle to small remnant runs maintained by hatcheries at considerable expense.

--Striped bass. These East Coast fish became established in 1871 when a few hundred were thrown into the Sacramento River. Within a few years, more than 1 million pounds were being harvested annually; it became one of California’s most popular sport fisheries.

As water development proceeded, however, the bass populations declined. Recently the decline has been drastic. The exact cause has been much debated but it is clearly tied to reduced outflows. If current trends continue, a limited fishery for striped bass will depend on rearing bass in hatcheries for their first year of life. Natural reproduction will cease to be a significant contributor to the fishery.

--American shad. These fish were introduced about the same time as striped bass and their history and requirements are very similar. There is a strong relationship between the success of shad reproduction and the amount of outflow.

--White sturgeon. Sturgeon complete their entire life cycle in the estuary, moving up into the main rivers only for spawning. In the past they have suffered severe declines from overfishing and perhaps accumulation of toxins. In recent years, however, they appear to have increased in numbers and catches of 100-to-200-pound fish are common.

Sturgeon may have bucked the declining trends of other fishes because they live so long that they can take advantage of good spawning conditions, even if they only occur once in a decade. Sturgeon populations will take a long time to respond to changes in the estuary, but eventually they will decline, as successful spawning becomes less frequent. Hatchery rearing may become necessary.

--Native non-game fishes. California has a rich heritage of unique native fish. Many occur in the Sacramento-San Joaquin estuary; two occur only there: Delta smelt and Sacramento splittail.

The Delta smelt are small fish that feed on plankton throughout their lives. Like striped bass, they depend on high outflows to provide sufficient food for their young. Smelt live only one or two years, spawn and die. In recent years, their numbers have declined precipitously and there is a possibility of having them declared an endangered species.

Splittail are not in such immediate danger, but their success also depends on high outflows, in part because they spawn on flooded vegetation.

--Opossum shrimp. This small shrimp is the most important food in the estuary for fishes 4 to 10 inches long, including striped bass, splittail and sturgeon. Its populations are highest when outflows keep the mixing zone in Suisun Bay for extended periods, where the shrimp feeds on smaller organisms.

Under a regime of consistently low outflows, the populations of opossum shrimp will decline to insignificance, hastening the decline of fishes that depend on them. Low shrimp populations will limit the success of hatchery programs that release small fish.

This scenario of decline and extinction may seem oversimplified and unduly pessimistic, but it is realistic. History is on our side: Virtually every major water project in the West has been justified in part by its benefits to fisheries; with a few notable exceptions, they have had just the opposite effect.

Millions have been spent attempting to mitigate the effects of dams on salmon populations in California and yet the populations continue to decline. California contains more endangered or extinct fishes than any other state, mostly because water projects have taken or altered the water the fish needed to survive.

It is too late to undo much of the damage to our fisheries, but before we continue with further water development, we should know its real costs, both biological and economic. In the Sacramento-San Joaquin estuary, expanded water exports means elimination of major fisheries and unique native species. There is more than enough water available now to satisfy California’s agricultural, industrial and urban needs without devastating fish and fisheries--provided we are willing to alter drastically the ways we use, deliver and market water.

California’s leaders and voters must become wise enough to realize this and not let another large--and valuable--piece of our natural heritage disappear.